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Myth - The earth has a very small and limited supply of available uranium.

1. The worlds present measured resource of uranium in the cost category, and used in conventional reactors is enough to last for another 90 years. This is a higher level of assured resource than most materials. (https://world-nuclear.org/information-library/nuclear-fuel-cycle/uranium-resources/supply-of-uranium.aspx#:~:text=The%20world's%20present%20measured%20resources,is%20normal%20for%20most%20minerals.)

2. The world's known uranium resources has increased by at least one-quarter in the last decade due to mineral exploration. (Link above)

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Uranium is a relatively common metal, found in rocks and seawater. Economic concentrations of it are not uncommon.

Quantities of mineral resources are greater than commonly perceived, and are relative to both market prices and cost of extraction.

The world's known uranium resources increased by at least one-quarter in the last decade due to increased mineral exploration.

Uranium is a relatively common element in the crust of the Earth (very much more than in the mantle). It is a metal approximately as common as tin or zinc, and it is a constituent of most rocks and even of the sea.
Table 1: Typical natural uranium concentrations ppm = parts per million
* Where uranium is at low levels in rock or sands (certainly less than 1000 ppm) it needs to be in a form which is easily separated for those concentrations to be called 'ore' - that is, implying that the uranium can be recovered economically. This means that it needs to be in a mineral form that can easily be dissolved by sulfuric acid or sodium carbonate leaching.
Total world resources of uranium, as with any other mineral or metal, are not known exactly. The only meaningful measure of long-term security of supply is the known reserves in the ground capable of being mined.

An orebody is, by definition, an occurrence of mineralisation from which the metal is economically recoverable. Orebodies, and thus measured resources - the amount known to be economically recoverable from orebodies - are therefore relative to both costs of extraction and market prices. For example, at present neither the oceans nor any granites are orebodies, but conceivably either could become so if prices were to rise sufficiently. At ten times the current price*, seawater, for example, might become a potential source of vast amounts of uranium. Thus, any predictions of the future availability of any mineral, including uranium, which are based on current cost and price data, as well as current geological knowledge, are likely to prove extremely conservative. Factors affecting the supply of resources are discussed further and illustrated in Appendix 2.
* US DOE-funded work using polymer absorbent strips suggest $610/kgU in 2014. Japanese (JAERI) research in 2002 using a polymeric absorbent in a nonwoven fabric containing an amidoxime group that was capable of forming a complex with uranyl tricarbonate ions, suggested about $300/kgU.
Uranium availability
Table 2: Identified resources recoverable (reasonably assured resources plus inferred resources), to $130/kg U, 1/1/21, from OECD NEA & IAEA, Uranium 2022: Resources, Production and Demand ('Red Book'). The total recoverable identified resources to $260/kg U is 7.918 million tonnes U. Uranium resources by country in 2021

Historical uranium production
Table 3: Historical uranium production, 1945-2022
Uranium has been successfully mined since the 1940s. Historical uranium production is generally well known, though uncertainties remain about the amount mined in the Soviet Union between 1945 and 1990. Table 3 summarises historical production. World Nuclear Association has estimated production in countries where data is unavailable.

* Until 1991 USSR comprised the uranium produced in Russia, Kazakhstan, Uzbekistan, Ukraine and other former Soviet Union republics.

Uranium production over the period 1945-2022 can be divided into four distinct phases:

A military era, from 1945 to the mid-1960s. The generation of electricity from nuclear fuel was incidental to the nuclear arms race. Production rose rapidly in the 1950s to satisfy the requirement for highly enriched uranium and plutonium. Uranium demand fell sharply in the 1960s and, in response, production halved by the mid-1960s.

Mid-1960s to mid-1980s. A period of rapidly expanding civil nuclear power saw uranium production pick up as reactor orders expanded. Many new mines were brought into production, often underwritten by long-term contracts agreed with electricity utilities in North America, Japan and Western Europe. Western production peaked in 1980 and stayed above annual reactor requirements until 1985.

Mid-1980s to about 2002. By 1985, the nuclear construction programme had been cut back severely. Many utilities had signed uranium contracts in anticipation of building more plants. Honouring these created a significant overhang. As mines were being run down, many cut production or closed. Utilities satisfied requirements by drawing down their significant inventories, without recourse to new production. The supply overhang was extended due to the arrival on the Western market of uranium from the former Soviet Union starting in 1993.

Early 2000s to present. There was a strong market reaction to the perception that new primary production would be needed to facilitate an anticipated renaissance in nuclear growth. This took place in the context of a uranium mining sector that had faced unfavourable economic conditions for many years and needed to offset declining and finite secondary supplies. This reaction started in 2003 with a strong upward movement in world uranium prices that continued into 2007 (the spot market price increased by a factor of 13 between early 2003 and mid-2007), but went into a downward correction, accentuated by the Fukushima accident in 2011. Since the accident, uranium prices have fallen to one of the lowest inflation-adjusted levels ever experienced.

Reactor fuel requirements

The world's power reactors, with combined capacity of about 400 GWe, require some 67,500 tonnes of uranium from mines or elsewhere each year. While this capacity is being run more productively, with higher capacity factors and reactor power levels, the uranium fuel requirement is increasing, but not necessarily at the same rate. The factors increasing fuel demand are offset by a trend for higher burn-up of fuel and other efficiencies, so demand is steady. (Over the years 1980 to 2008 the electricity generated by nuclear power increased 3.6-fold while uranium used increased by a factor of only 2.5.)

The world's present measured resources of uranium (6.1 Mt) in the cost category less than three times present spot prices and used only in conventional reactors, are enough to last for about 90 years. This represents a higher level of assured resources than is normal for most minerals. Further exploration and higher prices will certainly, on the basis of present geological knowledge, yield further resources as present ones are used up.

Reducing the tails assay in enrichment reduces the amount of natural uranium required for a given amount of fuel. Reprocessing of used fuel from conventional light water reactors also utilises present resources more efficiently, by a factor of about 1.3 overall. The 2016 and 2018 editions of the Red Book recognised these trends, along with more efficient plant operation, and as a result of which, the report's generic reactor fuel consumption was reduced from 175 tU per GWe per year at 0.30% tails assay (2012 report) to 160 tU per GWe per year at 0.25% tails assay (2016, 2018 and 2020 reports). The corresponding U ₃O ₈ figures are 206 tonnes and 189 tonnes. Note that these figures are generalisations across the industry and across many different reactor types.

Today's reactor fuel requirements are met from primary supply and secondary sources: commercial stockpiles, nuclear weapons stockpiles, recycled plutonium and uranium from reprocessing used fuel, and some from re-enrichment of depleted uranium tails (left over from original enrichment). These various secondary sources make uranium unique among energy minerals.

Secondary sources of uranium

The most obvious secondary source is civil stockpiles held by utilities and governments. The amount held here is difficult to quantify, due to commercial confidentiality. At the end of 2020 some 282,000 tU total inventory was estimated for utilities - USA 41,000 t, EU 42,000 t, China 129,000 t, India 9600 t, other East Asia 60,000 t. Chinese inventory is estimated to be 129,000 tU and India 9600 tU at the end of 2020 ( The Nuclear Fuel Report 2021, World Nuclear Association). These reserves are expected to be maintained at a fairly high level to provide energy security for utilities and governments.

Military warheads have been an important source of nuclear fuel since 1987. The USA and countries of the former USSR signed a series of disarmament treaties to reduce the nuclear arsenals of the signatory countries by approximately 80%.

The weapons contained a great deal of uranium enriched to over 90% U-235 ( i.e. up to 25 times the proportion in reactor fuel). For two decades, up to 10% of electricity produced in the USA was generated from fuel fabricated using uranium that had been converted from bomb-grade material under the so-called "Megatons to Megawatts" programme. Under the programme, enough bomb-grade material for 20,000 nuclear warheads was eliminated.

Worldwide, until 2013, the conversion of military high-enriched uranium was providing about 15% of the world's reactor requirements.

For more information, see information page on Military warheads as a source of nuclear fuel.

Recycled uranium and plutonium is another source, and currently saves about 2000 tU per year of primary supply, depending on whether just the plutonium or also the uranium is considered. In fact, plutonium is quickly recycled as MOX fuel, whereas the reprocessed uranium (RepU) is mostly stockpiled, but some 16,000 tonnes of RepU from Magnox reactors in the UK has been used to make about 1650 tonnes of enriched AGR fuel. In Belgium, France, Germany and Switzerland over 8000 tonnes of RepU has been recycled into nuclear power plants. For more information, see information page on Processing of Used Nuclear Fuel.

Re-enrichment of depleted uranium (DU, enrichment tails) is another secondary source. There is about 1.2 million tonnes of depleted uranium available, from both military and civil enrichment activity since the 1940s, most at tails assay of 0.25-0.35% U-235 (though the USA had about 114,000 tU assaying 0.34% or more in 2013). Non-nuclear uses of DU are very minor relative to annual arisings of over 40,000 tU per year. This leaves most DU available for mixing with recycled plutonium on MOX fuel or as a future fuel resource for fast neutron reactors.

However, some DU that has relatively high assay can be fed through under-utilised enrichment plants to produce natural uranium equivalent, or even enriched uranium ready for fuel fabrication. Russian enrichment plants have treated 10-15,000 tonnes per year of DU assaying over 0.3% U-235, stripping it down to 0.1% and producing a few thousand tonnes per year of natural uranium equivalent. This Russian programme treating Western tails has now finished, but a new US one is expected to start when surplus capacity is available, treating about 140,000 tonnes of old DU assaying 0.4% U-235.

Underfeeding at enrichment plants is a significant source of secondary supply, especially since the Fukushima accident reduced enrichment demand for several years. This is where the operational tails assay is lower than the contracted/transactional assay, and the enricher sets aside some surplus natural uranium, which it is free to sell (either as natural uranium or as enriched uranium product) on its own account. This source will provide an estimated 3500-7000 tU/yr to the mid-2020s.

International fuel reserves

There have been three major initiatives to set up international reserves of enriched fuel, two of them multilateral ones, with fuel to be available under International Atomic Energy Agency (IAEA) auspices despite any political interruptions which might affect countries needing them. The third is under US auspices, and also to meet needs arising from supply disruptions.

Russian LEU reserve

Russia opened an international fuel bank at its Angarsk enrichment facility in December 2010. The fuel bank is under IAEA control and holds 123 tU as LEU enriched to between 2.0% and 4.95% U-235 representing two full fuel loads for a typical 1000 MWe LWR reactor. The fuel is available to any IAEA member state in good standing, which is unable to procure LEU or its components for political reasons. However, the fuel bank does not cover any fabrication of fuel assemblies.

IAEA LEU bank
* 'LEU IAEA' is defined as LEU owned by the IAEA in the form of uranium hexafluoride (UF6) with a nominal enrichment of U-235 to 4.95%. It comprises up to 60 full containers of the 30B type or later versions. Type 30B cylinders each hold 2.27 t UF6 (1.54 tU), hence about 92 tU. The IAEA bears the costs of the purchase and delivery (import-export) of LEU, the purchase of equipment and its operation, technical resources and other goods and services required. Kazakhstan will meet the costs of LEU storage, including payment of electricity, heating, office space and staff costs. The agreement allows for the possible transfer of the LEU fuel bank to another site from the Ulba Metallurgical Plant, and it has a ten-year duration with automatic renewal at the end of this period.
In December 2010 the IAEA board resolved to establish a similar guaranteed reserve of low-enriched uranium, the IAEA LEU Bank*. It comprises a physical stock of UF ₆ owned by the IAEA, which shall "be responsible for storing and protecting" it. According to international norms, such a 'fuel bank' must be located in a country with no nuclear weapons and be fully open to IAEA inspectors. The fuel bank will be a potential supply of 90 tonnes LEU (as UF ₆) for the production of fuel assemblies for nuclear power plants. The Kazakh government in April 2015 approved a draft agreement with the IAEA for this. In June 2015 the IAEA board approved plans for the IAEA LEU Bank to be located at the Ulba Metallurgical Plant (UMP) at Ust-Kamenogorsk (aka Oskemen) and operated by Kazakhstan. A formal agreement with Kazakhstan to establish the legal framework was signed in August. A transit agreement with Russia for shipping LEU was also approved. An agreement between the IAEA and UMP was signed in May 2016. The facility was formally opened at the end of August 2017. In October 2019 the facility became operational, taking delivery of the first shipment of LEU, and in November it awarded contracts to Orano and Kazatomprom to supply it.

The IAEA LEU Bank is fully funded by voluntary contributions including $50 million from the US-based Nuclear Threat Initiative (NTI) organization, $49 million from the USA, up to $25 million from the European Union, $10 million each from Kuwait and the United Arab Emirates, and $5 million from Norway.

American assured fuel supply

In 2005 the US government announced plans for the establishment of a mechanism to ensure fuel supply for use in commercial reactors in foreign countries where there has been supply disruption. The fuel would come from downblending 17.4 tonnes of high-enriched uranium (HEU). In August 2011 US Department of Energy announced an expanded scope for the programme so it would also serve US utility needs, and now be called the American Assured Fuel Supply (AFS). At that point most of the downblending of the HEU had been completed, and the scheme was ready to operate. The AFS comprises 286 tonnes of low-enriched uranium (with another 60t from downblending being sold on the market to pay for the work). Additionally, the USA has completed the process of downblending another 20.1 tonnes of HEU. The AFS programme is administered by the US National Nuclear Safety Administration, foreign access must be through a US entity, and the fuel will be sold at current market prices. The 286 t amount is equivalent to about six reloads for a 1000 MWe reactor.

Unconventional resources

In addition to the over 6 million tonnes of uranium in the world's known recoverable resources, there are substantial amounts comprising what is known as 'unconventional resources'. Such unconventional resources, from which uranium can be produced in conjunction with other metals, as by-product, have accounted for over 11% of historical uranium production.

The main unconventional resource for uranium is rock phosphate, or phosphorite, and some 20,000 tU has been recovered as a by-product of agricultural phosphate production to the 1990s, but it then became uneconomic. Estimates of the amount available range from 9 to 22 million tonnes of uranium, though the 2022 edition of the Red Book tabulates only about 9.3 million tonnes.

With uranium as a minor by-product of phosphates, the potential supply is tied to the economics of phosphate production, as well as the uranium price, coupled with the environmental benefits of removing uranium from the waste stream and/or product. World phosphorous pentoxide (P ₂O ₅) production capacity from about 250 Mt of rock phosphate is about 50 million tonnes per year. From 1981 to 1992 US production from central Florida's phosphate deposits as by-product averaged just over 1000 tU per year, comprising up to 20% of US total, then fell away sharply and finished in 1998. Morocco has by far the largest known resources of uranium in phosphate rock.

Rare earth element (REE) deposits are another such unconventional resource. REEs have unique catalytic, metallurgical, nuclear, electrical, magnetic and luminescent properties, and play a critical role in the application of many modern technologies, including magnetic resonance imaging (MRI) machines, satellites, batteries, LED screens and solar panels. China is the leading supplier of REEs, giving rise to commercial pressure for development of deposits elsewhere.

REEs are a set of 17 chemical elements in the periodic table, specifically the 15 contiguous lanthanides plus the lighter scandium and yttrium. Scandium and yttrium are considered REEs since they tend to occur in the same ore deposits as the lanthanides and exhibit similar physical and chemical properties. REEs are in fact relatively abundant in the Earth's crust, but are rarely found in concentrations that are economically exploitable. REE resources occur in four primary geological settings: carbonatites, ion-absorption clay deposits, igneous systems and monzanite-xenotime placer deposits. REE resources are usually reported as rare earth oxides (REO).

Kvanefjeld in Greenland is the main REE deposit with major potential for uranium production, with Sorensen, Zone 3 and Steenstrupfjeld orebodies in the same Ilimaussac intrusive complex. Those four deposits have a total of 228,000 tU (May 2015, JORC-compliant), nearly half of it measured and indicated resources. Greenland Minerals has an agreement with Chinese company Shenghe Resources which would enable development to proceed.

Black (Alum) shales are another unconventional resource with some attempts being made to exploit them. The 2018 Red Book tabulates about 300,000 tU in Sweden and the 2022 Red Book tabulates 25,500 tU in Finland at the Sotkamo mine of Terrafame Oy, for which the government granted a permit in 2020 for uranium recovery by heap leaching.

Thorium as a nuclear fuel

Today uranium is the only fuel supplied for nuclear reactors. However, thorium can also be utilised as a fuel for CANDU reactors or in reactors specially designed for this purpose. Neutron efficient reactors, such as CANDU, are capable of operating on a thorium fuel cycle, once they are started using a fissile material such as U-235 or Pu-239. Then the thorium (Th-232) atom captures a neutron in the reactor to become fissile uranium (U-233), which continues the reaction. Some advanced reactor designs are likely to be able to make use of thorium on a substantial scale.

The thorium fuel cycle has some attractive features, though it is not yet in commercial use. Thorium is reported to be about three times as abundant in the Earth's crust as uranium. The 2009 IAEA-NEA Red Book listed 3.6 million tonnes of known and estimated resources as reported, but points out that this excludes data from much of the world, and estimates about 6 million tonnes overall. For more information, see paper on Thorium.

Notes & references

General sources

OECD NEA & IAEA, Uranium 2020: Resources, Production and Demand
OECD NEA & IAEA, Uranium 2018: Resources, Production and Demand
World Nuclear Association, 2019, The Nuclear Fuel Report - Global Scenarios for Demand and Supply Availability 2019-2040
World Nuclear Association, 2019, The Nuclear Fuel Report - Global Scenarios for Demand and Supply Availability 2021-2040
UN Institute for Disarmament Research, Yury Yudin (ed) 2011, Multilateralization of the Nuclear Fuel Cycle - The First Practical Steps
A. Monnet, CEA, Uranium from Coal Ash: Resource assessment and outlook, IAEA URAM 2014

Appendices

Appendix 1: Mineral resources and reserves

The following are internationally-recognised categories based on Australia's JORC code, which the Canadian NI 43-101 code follows.

A 'mineral resource' is a known concentration of minerals in the Earth's crust with reasonable prospects for eventual economic extraction. Mineral resources are sub-divided, in order of increasing geological confidence, into inferred, indicated and measured categories.

An 'inferred' mineral resource is that part of a mineral resource for which tonnage, grade and mineral content can be estimated with only a low level of confidence. The information on which it is based is limited, or of uncertain quality and reliability.

An 'indicated' mineral resource is that part of a mineral resource for which tonnage, grade and mineral content can be estimated with a reasonable level of confidence. It is based on exploration, sampling and testing information which is adequate to assume but not confirm geological and/or grade continuity.

A 'measured' mineral resource is that part of a mineral resource for which tonnage, physical characteristics, grade and mineral content can be estimated with a high level of confidence. It is based on detailed and reliable exploration, sampling and testing information with locations spaced closely enough to confirm geological and grade continuity.

A 'mineral' reserve (or ore reserve) is the economically mineable part of a measured and/or indicated mineral resource. It allows for dilution and losses which may occur when the material is mined. Appropriate assessments and studies will have been carried out, and include consideration of realistically assumed mining, metallurgical, economic, marketing, legal, environmental, social and governmental factors. Mineral or ore reserves are sub-divided in order of increasing confidence into probable mineral/ore reserves and proved mineral/ore reserves.

A 'probable' mineral reserve (or probable ore reserve) is the economically mineable part of an indicated mineral resource. Studies to at least pre-feasibility level will have been carried out, demonstrating that extraction could reasonably be justified.

A 'proved' mineral reserve (or proved ore reserve) is the economically mineable part of a measured mineral resource. Studies to at least pre-feasibility level will have been carried out, demonstrating that extraction is justified.

Appendix 2: The Sustainability of Mineral Resources (September 2005)

Substantially derived from 2003 WNA Symposium paper by Colin MacDonald, Uranium: Sustainable Resource or Limit to Growth? - supplemented by his 2005 WNA Symposium paper and including a model Economic adjustments in the supply of a 'non-renewable' resource from Ian Hore-Lacy.

It is commonly asserted that because "the resources of the earth are finite", therefore we must face some day of reckoning, and will need to plan for "negative growth". All this, it is pointed out, is because these resources are being consumed at an increasing rate to support our western lifestyle and to cater for the increasing demands of developing nations. The assertion that we are likely to run out of resources is a re-run of the "Limits to Growth" argument (Club of Rome 1972 popularised by Meadows et al in Limits of Growth at that time. (A useful counter to it is W Berckerman, In Defence of Economic Growth, also Singer, M, Passage to a Human World, Hudson Inst. 1987). In the decade following its publication world bauxite reserves increased 35%, copper 25%, nickel 25%, uranium and coal doubled, gas increased 70% and even oil increased 6%.) fashionable in the early 1970s, which was substantially disowned by its originators, the Club of Rome, and shown up as nonsense with the passing of time. It also echoes similar concerns raised by economists in the 1930s, and by Malthus at the end of the 18th Century.

In recent years there has been persistent misunderstanding and misrepresentation of the abundance of mineral resources, with the assertion that the world is in danger of actually running out of many mineral resources. While congenial to common sense if the scale of the Earth's crust is ignored, it lacks empirical support in the trend of practically all mineral commodity prices and published resource figures over the long term. In recent years some have promoted the view that limited supplies of natural uranium are the Achilles heel of nuclear power as the sector contemplates a larger contribution to future clean energy, notwithstanding the small amount of it required to provide very large amounts of energy.

Uranium supply news is usually framed within a short-term perspective. It concerns who is producing with what resources, who might produce or sell, and how does this balance with demand? However, long-term supply analysis enters the realm of resource economics. This discipline has as a central concern the understanding of not just supply/demand/price dynamics for known resources, but also the mechanisms for replacing resources with new ones presently unknown. Such a focus on sustainability of supply is unique to the long view. Normally-functioning metals markets and technology change provide the drivers to ensure that supply at costs affordable to consumers is continuously replenished, both through the discovery of new resources and the re-definition (in economic terms) of known ones.

Of course the resources of the earth are indeed finite, but three observations need to be made: first, the limits of the supply of resources are so far away that the truism has no practical meaning. Second, many of the resources concerned are either renewable or recyclable (energy minerals and zinc are the main exceptions, though the recycling potential of many materials is limited in practice by the energy and other costs involved). Third, available reserves of 'non-renewable' resources are constantly being renewed, mostly faster than they are used.

There are three principal areas where resource predictions have faltered:

predictions have not accounted for gains in geological knowledge and understanding of mineral deposits;

they have not accounted for technologies utilised to discover, process and use them;

economic principles have not been taken into account, which means that resources are thought of only in present terms, not in terms of what will be economic through time, nor with concepts of substitution in mind.

What then does sustainability in relation to mineral resources mean? The answer lies in the interaction of these three things which enable usable resources (Some licence is taken in the use of this word in the following, strictly it is reserves of minerals which are created) effectively to be created. They are brought together in the diagram below.

Numerous economists have studied resource trends to determine which measures should best reflect resource scarcity (Tilton, J. On Borrowed Time? Assessing the threat of mineral depletion, Resources for the Future, Washington DC 2002). Their consensus view is that costs and prices, properly adjusted for inflation, provide a better early warning system for long-run resource scarcity than do physical measures such as resource quantities.

Historic data show that the most commonly used metals have declined in both their costs and real commodity prices over the past century. Such price trends are the most telling evidence of lack of scarcity. Uranium has been a case in point, relative to its late 1970s price of US$ 40/lb U ₃O ₈.

An anecdote underlines this basic truth: In 1980 two eminent professors, fierce critics of one another, made a bet regarding the real market price of five metal commodities over the next decade. Paul Ehrlich, a world-famous ecologist, bet that because the world was exceeding its carrying capacity, food and commodities would start to run out in the 1980s and prices in real terms would therefore rise. Julian Simon, an economist, said that resources were effectively so abundant, and becoming effectively more so, that prices would fall in real terms. He invited Ehrlich to nominate which commodities would be used to test the matter, and they settled on these (chrome, copper, nickel, tin and tungsten). In 1990 Ehrlich paid up - all the prices had fallen.

However, quantities of known resources tell a similar and consistent story. To cite one example, world copper reserves in the 1970s represented only 30 years of then-current production (6.4 Mt/yr). Many analysts questioned whether this resource base could satisfy the large expected requirements of the telecommunications industry by 2000. But by 1994, world production of copper had doubled (12 Mt/yr) and the available reserves were still enough for another 30 years. The reserve multiple of current production remained the same.

Another way to understand resource sustainability is in terms of economics and capital conservation. Under this perspective, mineral resources are not so much rare or scarce as they are simply too expensive to discover if you cannot realise the profits from your discovery fairly soon. Simple economic considerations therefore discourage companies from discovering much more than society needs through messages of reduced commodity prices during times of oversupply. Economically rational players will only invest in finding these new reserves when they are most confident of gaining a return from them, which usually requires positive price messages caused by undersupply trends. If the economic system is working correctly and maximizing capital efficiency, there should never be more than a few decades of any resource commodity in reserves at any point in time.

The fact that many commodities have more resources available than efficient economic theory might suggest may be partly explained by two characteristics of mineral exploration cycles. First, the exploration sector tends to over-respond to the positive price signals through rapid increases in worldwide expenditures (which increases the rate of discoveries), in particular through the important role of more speculatively-funded junior exploration companies. Exploration also tends to make discoveries in clusters that have more to do with new geological knowledge than with efficient capital allocation theory. As an example, once diamonds were known to exist in northern Canada, the small exploration boom that accompanied this resulted in several large discoveries - more than the market may have demanded at this time. These patterns are part of the dynamics that lead to commodity price cycles. New resource discoveries are very difficult to precisely match with far-off future demand, and the historic evidence suggests that the exploration process over-compensates for every small hint of scarcity that the markets provide.

Another important element in resource economics is the possibility of substitution of commodities. Many commodity uses are not exclusive - should they become too expensive they can be substituted with other materials. Even if they become cheaper they may be replaced, as technology gains have the potential to change the style and cost of material usage. For example, copper, despite being less expensive in real terms than 30 years ago, is still being replaced by fibre optics in many communication applications. These changes to materials usage and commodity demand provide yet another dimension to the simple notion of depleting resources and higher prices.
Geological knowledge
In summary, historic metals price trends, when examined in the light of social and economic change through time, demonstrate that resource scarcity is a double-edged sword. The same societal trends that have increased metals consumption, tending to increase prices, have also increased the available wealth to invest in price-reducing knowledge and technology. These insights provide the basis for the economic sustainability of metals, including uranium.

Whatever minerals are in the earth, they cannot be considered usable resources unless they are known. There must be a constant input of time, money and effort to find out what is there. This mineral exploration endeavour is not merely fossicking or doing aerial magnetic surveys, but must eventually extend to comprehensive investigation of orebodies so that they can reliably be defined in terms of location, quantity and grade. Finally, they must be technically and economically quantified as mineral reserves. That is the first aspect of creating a resource. See section in paper for mineral resource and reserve categories.

For reasons outlined above, measured resources of many minerals are increasing much faster than they are being used, due to exploration expenditure by mining companies and their investment in research. Simply on geological grounds, there is no reason to suppose that this trend will not continue. Today, proven mineral resources worldwide are more than we inherited in the 1970s, and this is especially so for uranium.

Simply put, metals which are more abundant in the Earth's crust are more likely to occur as the economic concentrations we call mineral deposits. They also need to be reasonably extractable from their host minerals. By these measures, uranium compares very well with base and precious metals. Its average crustal abundance of 2.7 ppm is comparable with that of many other metals such as tin, tungsten, and molybdenum. Many common rocks such as granite and shales contain even higher uranium concentrations of 5 to 25 ppm. Also, uranium is predominantly bound in minerals which are not difficult to break down in processing.

As with crustal abundance, metals which occur in many different kinds of deposits are easier to replenish economically, since exploration discoveries are not constrained to only a few geological settings. Currently, at least 14 different types of uranium deposits are known, occurring in rocks of wide range of geological age and geographic distribution. There are several fundamental geological reasons why uranium deposits are not rare, but the principal reason is that uranium is relatively easy both to place into solution over geological time, and to precipitate out of solution in chemically reducing conditions. This chemical characteristic alone allows many geological settings to provide the required hosting conditions for uranium resources. Related to this diversity of settings is another supply advantage ?the wide range in the geological ages of host rocks ensures that many geopolitical regions are likely to host uranium resources of some quality.

Unlike the metals which have been in demand for centuries, society has barely begun to utilise uranium. As serious non-military demand did not materialise until significant nuclear generation was built by the late 1970s, there has been only one cycle of exploration-discovery-production, driven in large part by late 1970s price peaks (MacDonald, C, Rocks to reactors: Uranium exploration and the market. Proceedings of WNA Symposium 2001). This initial cycle has provided more than enough uranium for the last three decades and several more to come. Clearly, it is premature to speak about long-term uranium scarcity when the entire nuclear industry is so young that only one cycle of resource replenishment has been required. It is instead a reassurance that this first cycle of exploration was capable of meeting the needs of more than half a century of nuclear energy demand.

Related to the youthfulness of nuclear energy demand is the early stage that global exploration had reached before declining uranium prices stifled exploration in the mid-1980s. The significant investment in uranium exploration during the 1970-82 exploration cycle would have been fairly efficient in discovering exposed uranium deposits, due to the ease of detecting radioactivity. Still, very few prospective regions in the world have seen the kind of intensive knowledge and technology-driven exploration that the Athabasca Basin of Canada has seen since 1975. This fact has huge positive implications for future uranium discoveries, because the Athabasca Basin history suggests that the largest proportion of future resources will be as deposits discovered in the more advanced phases of exploration. Specifically, only 25% of the 635,000 tonnes of U ₃O ₈ discovered so far in the Athabasca Basin could be discovered during the first phase of surface-based exploration. A sustained second phase, based on advances in deep penetrating geophysics and geological models, was required to discover the remaining 75%.
Technology
Another dimension to the immaturity of uranium exploration is that it is by no means certain that all possible deposit types have even been identified. Any estimate of world uranium potential made only 30 years ago would have missed the entire deposit class of unconformity deposits that have driven production since then, simply because geologists did not know this class existed.

It is meaningless to speak of a resource until someone has thought of a way to use any particular material. In this sense, human ingenuity quite literally creates new resources, historically, currently and prospectively. That is the most fundamental level at which technology creates resources, by making particular minerals usable in new ways. Often these then substitute to some degree for others which are becoming scarcer, as indicated by rising prices. Uranium was not a resource in any meaningful sense before 1940.

More particularly, if a known mineral deposit cannot be mined, processed and marketed economically, it does not constitute a resource in any practical sense. Many factors determine whether a particular mineral deposit can be considered a usable resource - the scale of mining and processing, the technological expertise involved, its location in relation to markets, and so on. The application of human ingenuity, through technology, alters the significance of all these factors and is thus a second means of 'creating' resources. In effect, portions of the earth's crust are reclassified as resources. A further aspect of this is at the manufacturing and consumer level, where technology can make a given amount of resources go further through more efficient use.(aluminium can mass was reduced by 21% 1972-88, and motor cars each use about 30% less steel than 30 years ago)

An excellent example of this application of technology to create resources is in the Pilbara region of Western Australia. Until the 1960s the vast iron ore deposits there were simply geological curiosities, despite their very high grade. Australia had been perceived as short of iron ore. With modern large-scale mining technology and the advent of heavy duty railways and bulk shipping which could economically get the iron ore from the mine (well inland) through the ports of Dampier and Port Hedland to Japan, these became one of the nation's main mineral resources. For the last 45 years Hamersley Iron (Rio Tinto), Mount Newman (BHP-Billiton) and others have been at the forefront of Australia's mineral exporters, drawing upon these 'new' orebodies.

Just over a hundred years ago aluminium was a precious metal, not because it was scarce, but because it was almost impossible to reduce the oxide to the metal, which was therefore fantastically expensive. With the discovery of the Hall-Heroult process in 1886, the cost of producing aluminium plummeted to about one twentieth of what it had been and that metal has steadily become more commonplace. It now competes with iron in many applications, and copper in others, as well as having its own widespread uses in every aspect of our lives. Not only was a virtually new material provided for people's use by this technological breakthrough, but enormous quantities of bauxite world-wide progressively became a valuable resource. Without the technological breakthrough, they would have remained a geological curiosity.

Incremental improvements in processing technology at all plants are less obvious but nevertheless very significant also. Over many years they are probably as important as the historic technological breakthroughs.
Economics
To achieve sustainability, the combined effects of mineral exploration and the development of technology need to be creating resources at least as fast as they are being used. There is no question that in respect to the minerals industry this is generally so, and with uranium it is also demonstrable. Recycling also helps, though generally its effect is not great.

Whether a particular mineral deposit is sensibly available as a resource will depend on the market price of the mineral concerned. If it costs more to get it out of the ground than its value warrants, it can hardly be classified as a resource (unless there is some major market distortion due to government subsidies of some kind). Therefore, the resources available will depend on the market price, which in turn depends on world demand for the particular mineral and the costs of supplying that demand. The dynamic equilibrium between supply and demand also gives rise to substitution of other materials when scarcity looms (or the price is artificially elevated). This then is the third aspect of creating resources.

The best known example of the interaction of markets with resource availability is in the oil industry. When in 1972 OPEC suddenly increased the price of oil fourfold, several things happened at both producer and consumer levels.

The producers dramatically increased their exploration effort, and applied ways to boost oil recovery from previously 'exhausted' or uneconomic wells. At the consumer end, increased prices meant massive substitution of other fuels and greatly increased capital expenditure in more efficient plant. As a result of the former activities, oil resources increased dramatically. As a result of the latter, oil use fell slightly to 1975 and in the longer perspective did not increase globally from 1973 to 1986. Forecasts in 1972, which had generally predicted a doubling of oil consumption in ten years, proved quite wrong.

Oil will certainly become scarce one day, probably before most other mineral resources, which will continue to drive its price up. As in the 1970s, this will in turn cause increased substitution for oil and bring about greater efficiencies in its use as equilibrium between supply and demand is maintained by the market mechanism. Certainly oil will never run out in any absolute sense - it will simply become too expensive to use as liberally as we now do.

Another example is provided by aluminium. During World War II, Germany and Japan recovered aluminium from kaolinite, a common clay, at slightly greater cost than it could be obtained from bauxite.
Replacement of uranium
Due to the operation of these three factors the world's economically demonstrated resources of most minerals have risen faster than the increased rate of usage over the last 50 years, so that more are available now, notwithstanding liberal usage. This is largely due to the effects of mineral exploration and the fact that new discoveries have exceeded consumption.

A characteristic of metals resource replacement is that the mineral discovery process itself adds a small cost relative to the value of the discovered metals. As an example, the huge uranium reserves of Canada's Athabasca Basin were discovered for about US$1.00/kgU (2003 dollars, including unsuccessful exploration). Similar estimates for world uranium resources, based on published IAEA exploration expenditure data and assuming that these expenditures yielded only the past uranium produced plus the present known economic resources categories at up to US$80/kg ( Uranium 2003: Resources, Production and demand. Nuclear Energy Agency and IAEA, OECD Publications 2004) yields slightly higher costs of about US$1.50/kgU. This may reflect the higher component of State-driven exploration globally, some of which had national self-sufficiency objectives that may not have aligned with industry economic standards.

From an economic perspective, these exploration costs are essentially equivalent to capital investment costs, albeit spread over a longer time period. It is, however, this time lag between the exploration expense and the start of production that confounds attempts to analyse exploration economics using strict discounted cash flow methods. The positive cash flows from production occur at least 10-15 years into the future, so that their present values are obviously greatly reduced, especially if one treats the present as the start of exploration. This creates a paradox, since large resource companies must place a real value on simply surviving and being profitable for many decades into the future; and, without exploration discoveries, all mining companies must expire with their reserves. Recent advances in the use of real options and similar methods are providing new ways to understand this apparent paradox. A key insight is that time, rather than destroying value through discounting, actually adds to the option value, as does the potential of price volatility. Under this perspective, resource companies create value by obtaining future resources which can be exploited optimally under a range of possible economic conditions. Techniques such as these are beginning to add analytical support to what have always been intuitive understandings by resource company leaders - that successful exploration creates profitable mines and adds value to company shares.

Since uranium is part of the energy sector, another way to look at exploration costs is on the basis of energy value. This allows comparisons with the energy investment cost for other energy fuels, especially fossil fuels which will have analogous costs related to the discovery of the resources. From numerous published sources, the finding costs of crude oil have averaged around US$ 6/bbl over at least the past three decades. Uranium's finding costs make up only 2% of the recent spot price of US$ 30/lb ($78/kgU), while the oil finding costs are 12% of a recent spot price of US$ 50/bbl.
Forecasting replenishment
By these measures, uranium is a very inexpensive energy source to replenish, as society has accepted far higher energy replacement costs to sustain oil resources. This low basic energy resource cost is one argument in favour of a nuclear-hydrogen solution to long-term replacement of oil as a transportation fuel.

Supply forecasters are often reluctant to consider the additive impacts of exploration on new supply, arguing that assuming discoveries is as risky and speculative as the exploration business itself. Trying to predict any single discovery certainly is speculative. However, as long as the goal is merely to account for the estimated total discovery rate at a global level, a proxy such as estimated exploration expenditures can be used. Since expenditures correlate with discovery rate, the historic (or adjusted) resources discovered per unit of expenditure will provide a reasonable estimate of resource gains to be expected. As long as the time lag between discovery and production is accounted for, this kind of dynamic forecasting is more likely to provide a basis for both price increases and decreases, which metals markets have historically demonstrated.

Without these estimates of uranium resource replenishment through exploration cycles, long-term supply-demand analyses will tend to have a built-in pessimistic bias (i.e. towards scarcity and higher prices), that will not reflect reality. Not only will these forecasts tend to overestimate the price required to meet long-term demand, but the opponents of nuclear power use them to bolster arguments that nuclear power is unsustainable even in the short term. In a similar fashion, these finite-resources analyses also lead observers of the industry to conclude that fast breeder reactor technology will soon be required. This may indeed make a gradual appearance, but if uranium follows the price trends we see in other metals, its development will be due to strategic policy decisions more than uranium becoming too expensive.

The resource economics perspective tells us that new exploration cycles should be expected to add uranium resources to the world inventory, and to the extent that some of these may be of higher quality and involve lower operating cost than resources previously identified, this will tend to mitigate price increases. This is precisely what has happened in uranium, as the low-cost discoveries in Canada's Athabasca Basin have displaced higher-cost production from many other regions, lowering the cost curve and contributing to lower prices. Secondary uranium supplies, to the extent that they can be considered as a very low-cost mine, have simply extended this price trend.

The first exploration and mining cycle for uranium occurred about 1970 to 1985. It provided enough uranium to meet world demand for some 80 years, if we view present known resources as arising from it. With the rise in uranium prices to September 2005 and the concomitant increase (boom?) in mineral exploration activity, it is clear that we have the start of a second such cycle, mid-2003 to ??. The price increase was brought about by diminution of secondary supplies coupled with a realization that primary supplies needed to increase substantially.
Depletion and sustainability
Several significant decisions on mine development and increased exploration by major producers will enable this expansion of supply, coupled with smaller producers coming on line. The plethora of junior exploration companies at the other end of the spectrum which are finding no difficulty whatever in raising capital are also a positive sign that a vigorous new exploration and mining cycle is cranking up. From lows of around US$ 55 million per year in 2000, world uranium exploration expenditure rose to about US$ 110 million in 2004 and is expected to be US$ 185 million in 2005, half of this being from the junior exploration sector. The new cycle is also showing considerable regional diversification. Measured from 1990, cycle 2 totals US$ 1.5 billion to 2005, compared with a total of about three times this figure (uncorrected) for the whole of the first cycle.

Conversely, the exhaustion of mineral resources during mining is real. Resource economists do not deny the fact of depletion, nor its long-term impact - that in the absence of other factors, depletion will tend to drive commodity prices up. But as we have seen, mineral commodities can become more available or less scarce over time if the cost-reducing effects of new technology and exploration are greater than the cost-increasing effects of depletion.

One development that would appear to argue against economic sustainability is the growing awareness of the global depletion of oil, and in some regions such as North America, natural gas. But oil is a fundamentally different material. This starts with geology, where key differences include the fact that oil and gas were formed by only one process: the breakdown of plant life on Earth. Compared with the immense volumes of rock-forming minerals in the Earth? crust, living organisms on top of it have always been a very tiny proportion. But a more important fact is that the world has consumed oil, and recently natural gas as well, in a trajectory of rapid growth virtually unmatched by any other commodity. Consumption growth rates of up to 10% annually over the past 50 years are much higher than we see for other commodities, and support the contention that oil is a special depletion case for several reasons: its geological occurrence is limited, it has been inexpensive to extract, its energy utility has been impossible to duplicate for the price, and its resulting depletion rates have been incredibly high.

This focus on rates of depletion suggests that one of the dimensions of economic sustainability of metals has to do with their relative rates of depletion. Specifically, it suggests that economic sustainability will hold indefinitely as long as the rate of depletion of mineral resources is slower than the rate at which it is offset. This offsetting force will be the sum of individual factors that work against depletion, and include cost-reducing technology and knowledge, lower cost resources through exploration advances, and demand shifting through substitution of materials.

An economic sustainability balance of this type also contemplates that, at some future point, the offsetting factors may not be sufficient to prevent irreversible depletion-induced price increases, and it is at this point that substituting materials and technologies must come into play to take away demand. In the case of rapid oil depletion, that substitute appears to be hydrogen as a transport fuel. Which raises the question of how the hydrogen is produced, and nuclear energy seems the most likely means of that, using high-temperature reactors.

From a detached viewpoint all this may look like mere technological optimism. But to anyone closely involved it is obvious and demonstrable. Furthermore, it is illustrated by the longer history of human use of the Earth's mineral resources. Abundance, scarcity, substitution, increasing efficiency of use, technological breakthroughs in discovery, recovery and use, sustained incremental improvements in mineral recovery and energy efficiency - all these comprise the history of minerals and humankind.

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Uranium is ubiquitous on the Earth. It is a metal approximately as common as tin or zinc, and it is a constituent of most rocks and even of the sea.

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Myth: Being exposed to radiation from nuclear energy will make a person glow green.

Evidence 1: Our bodies do not have sensors or special ways in which they can detect alpha-particles, beta-particles, or gamma rays, which are all components of radioactive waves. Essentially, radioactivity is invisible to us (from link above).

Evidence 2: Some people may argue that some things, like watches or other tools from the 1900s, had radium in them that glowed green. However, the radium in them itself doesn't give off a glow and instead does because it was mixed with a chemical called a phosphor (from link above).

Evidence 3: The simple fact of something being radioactive means that the energy of the emission is so high that it becomes invisible to the human eye (which can be explained through the electromagnetic spectrum). - source: https://rinconeducativo.org/en/recursos-educativos/do-radioactive-substances-glow/

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Green glow of radiation › Dr Karl’s Great Moments In Science (ABC Science)

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myth-spent or used uranium from nuclear power plants can be turned into weapons.

Evidence #1:"Military plutonium can blended with uranium oxide to form mixed oxide (MOX) fuel.After LEU or MOX is burned in power reactors, the spent fuel is not suitable for weapons manufacture."

Evidence #2:"DU is not usable for nuclear weapons as it does not contain enough fissile material to sustain a nuclear chain reaction."

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(Updated February 2017)

Weapons-grade uranium and plutonium surplus to military requirements in the USA and Russia is being made available for use as civil fuel.

Weapons-grade uranium is highly enriched, to over 90% U-235 (the fissile isotope). Weapons-grade plutonium has over 93% Pu-239 and can be used, like reactor-grade plutonium, in fuel for electricity production.

Highly-enriched uranium from weapons stockpiles has been displacing some 8850 tonnes of U₃O₈ production from mines each year, and met about 13% to 19% of world reactor requirements through to 2013.

For more than five decades, concern has centred on the possibility that uranium intended for commercial nuclear power might be diverted for use in weapons. This gave way to a focus on the role of military uranium as a major source of fuel for commercial nuclear power.

Since 1987 the United States and countries of the former USSR have signed a series of disarmament treaties to reduce the nuclear arsenals by about 80%.

Nuclear materials declared surplus to military requirements by the USA and Russia have been converted into fuel for commercial nuclear reactors. This continues. With the disintegration of the Soviet Union, a unique opportunity arose to deploy military weapons material for making electricity. A 1993 agreement covered essentially the enrichment component of this material, but left unresolved the question of feed from mines, and a 1999 agreement dealt with what happened to the feed material.

The main weapons material is highly enriched uranium (HEU), containing at least 20% uranium-235 (U-235) and usually about 90% U-235. HEU can be blended down with uranium containing low levels of U-235 to produce low-enriched uranium (LEU), less than 5% U-235, fuel for power reactors. It is blended with depleted uranium (mostly U-238), natural uranium (0.7% U-235), or partially-enriched uranium.

Highly-enriched uranium in US and Russian weapons and other military stockpiles amounts to about 1500 tonnes*, equivalent to about seven times annual world mine production.

World stockpiles of weapons-grade plutonium are reported to be some 260 tonnes, which if used in mixed oxide fuel in conventional reactors would be equivalent to a little over one year's world uranium production. Military plutonium can blended with uranium oxide to form mixed oxide (MOX) fuel.

After LEU or MOX is burned in power reactors, the spent fuel is not suitable for weapons manufacture.

Megatons to Megawatts, the Russian HEU deal

Commitments by the USA and Russia to convert nuclear weapons into fuel for electricity production was known as the Megatons to Megawatts program.

Surplus weapons-grade HEU resulting from the various disarmament agreements led in 1993 to an agreement between the US and Russian governments. Under this Russia would convert 500 tonnes of HEU from warheads and military stockpiles (equivalent to around 20,000 bombs) to LEU to be bought by the USA for use in civil nuclear reactors.

In 1994, a US$13 billion implementing contract was signed between the US Enrichment Corporation (now USEC Inc) and Russia's Techsnabexport (Tenex) as executive agents for the US and Russian governments. USEC purchased 500 tonnes of weapons-grade HEU over 20 years to 2013, at a rate of up to 30 tonnes/year from 1999. The HEU was progressively blended down to 14,446 t of LEU in Russia, using 1.5% U-235 (re-enriched depleted uranium tails), to restrict levels of U-234 and U-236 in the final product to western specifications.* USEC then sold the LEU to its utility customers as fuel. The LEU enrichment levels specified in the agreement were 3.6%, 4.0%, 4.4% and 4.95%, though it is understood that 4.4% was typical, and possibly that used in the later years of the agreement.

It was essentially an enrichment deal totalling about 90 million SWU. About 150,000 t of natural uranium was exchanged for the LEU, of which 112,000 t sold on the market under the terms of the 1999 feed agreement and 38,000 t sent to Russia. This is equivalent to an average of 8850 t/yr of U ₃O ₈ from mines over the 20 years. In the latter years it supplied about 13% of world uranium demand.

Overall the blending down of 500 tonnes of Russian HEU resulted in about 14,446 tonnes of LEU over 20 years. This is equivalent to about 150,000 tonnes of natural U (177,000 t U ₃O ₈), about 2.5 times annual world demand.

In 1999 a supplementary agreement addressed what should happen to the uranium feed from mines, against which the blended down LEU was supplied to customers. See section below on the 1999 Agreement.

The last of the 500 tonnes of HEU was downblended in August 2013 by Russia's ElectroChemical Plant (ECP) at Zelenogorsk and shipped in November. Other plants involved in the project were Urals Electrochemical Combine at Novouralsk, Siberian Chemical Combine at Seversk, Angarsk Electrolysis & Chemical Combine, and PA Mayak at Ozersk. The whole deal is equivalent to 20,000 nuclear warheads and 89 million SWU. According to Tenex, total revenue was US$17 billion, including hard currency gains and the cost of natural uranium component.

Russia has other military HEU which it may blend down for its own use, using simply depleted uranium (giving a satisfactory grade of LEU for use in Russian reactors).

US HEU disposition

For its part, the US government initially declared just over 174 tonnes of HEU (of various enrichments) to be surplus from military stockpiles. Of this, USEC took delivery of 14.2 tonnes in the form of uranium hexafluoride (UF ₆) containing around 75% U-235, and 50 tonnes as uranium oxide or metal containing around 40% U-235. Downblending of the UF ₆ was completed in 1998, to produce 387 tonnes of LEU. Some 13.5 tonnes of the HEU oxide or metal had been processed by September 2001 to produce 140.3 tonnes of LEU. In 2004 the Nuclear Regulatory Commission issued a licence for downblending 33 tonnes HEU by Nuclear Fuel Services in Tennessee and in 2005 the first delivery was made to a TVA power plant.

DOE's National Nuclear Security Administration (NNSA)* in 2005 announced plans to remove a further 200 tonnes of HEU from military stockpiles. Of this, 160 tonnes was retained for naval propulsion, thus postponing the need for building a new uranium high-enrichment facility for at least 50 years. An additional 20 tonnes was reserved for space missions and for research reactors. The final 20 tonnes was to be downblended to LEU for research reactors, power generation and for 17 tonnes, the new reliable fuel supply initiative (see below).

Also in 2005, NNSA said that it was committing about 40 tonnes of off-specification HEU (with elevated levels of U-236) to the Blended Low-Enriched Uranium (BLEU) program. This material would be used by TVA. In 2008 NNSA was negotiating with TVA to release a further 21 tonnes of HEU under the program, which would yield about 250 tonnes of LEU, some of which might be sold to other utilities.

In mid-2007 the NNSA awarded contracts to Nuclear Fuel Services and Wesdyne International to downblend 17.4 tonnes of HEU from dismantled warheads to be part of a new international fuel reserve. NFS downblended the material in Tennessee to yield some 290 tonnes of LEU (4.95% U-235) by early 2012. Wesdyne, the prime contractor, is then storing 230 tonnes of the LEU at the Westinghouse fuel fabrication plant in South Carolina to be available for the American Assured Fuel Supply (AFS) program. It will take about 60 tonnes as payment in kind, to be sold on the market over a three to four year period. This first batch of LEU will be available for use in civilian reactors by nations in good standing with the International Atomic Energy Agency that have good nonproliferation credentials and are not pursuing uranium enrichment and reprocessing technologies. It will also now be available to domestic utilities. The fuel - worth some $500 million - will be sold at the current market price.

In June 2009 NNSA awarded a further contract ($209 million) to NFS and Wesdyne for 12.1 tonnes of HEU which will yield some 220 tonnes of LEU by 2012. This second batch of LEU is to provide fuel supply assurance for utilities which participate in DOE's mixed-oxide fuel program utilising surplus plutonium from US weapons. (The AFS scheme is consistent with international concerns to limit the spread of enrichment technology to countries without well-established nuclear fuel cycles. Russia has agreed to join the initiative.)

In the short term most US military HEU is likely to be blended down to 20% U-235, then stored. In this form it is not useable for weapons.

How the Market Works

Normally, a utility buys natural uranium from a mining company as "yellowcake" (U ₃O ₈) and has it converted to UF ₆. It then supplies this feed to USEC, paying them for the enrichment component. USEC runs its energy-intensive enrichment plant to separate an appropriate amount of enriched uranium (eg at 3.5 - 5.0% U-235, leaving a lot of depleted uranium). USEC then returns the enriched uranium to the utility for its reactor.

A different, and somewhat complicated, system is used for the Russian material. The utility supplies the feed component of natural uranium as before and pays USEC for the enrichment component. But instead of running their plant, USEC pays the Russians for some blended-down weapons uranium and passes this on to the customer utility as "enriched" uranium fuel. The customers receive the blended-down Russian material, paid for as if it were their own uranium which had been enriched.

USEC pays Russia for the enrichment services component (basically energy) of the low-enriched product it receives. This amounts to about 5.5 million SWU per year. Russia takes ownership of the corresponding amount of natural uranium "feed" provided to USEC by its utility customers for toll enrichment services. Under the 1999 agreement (below) at least 72% of the feed is sold to Cameco, Areva and Nukem in the proportion 45/45/10, and the remainder is sent to Russia for domestic use there. In 2009 Rosatom said that its portion of the natural uranium feed to date - worth US$ 2.7 billion - had been received in Russia.

1999 Market Agreement re natural uranium feed to USEC

After years of stalled negotiations on this matter, a major agreement was approved early in 1999 by the US and Russian governments. It involved 163,000 tonnes of natural U ₃O ₈ feed to be supplied over the remaining 15 years of the US-Russian HEU agreement.

Cameco, Cogema (now Areva), and Nukem signed the commercial agreement with Tenex of Russia, giving them "exclusive options to purchase" 118,000 tonnes of this (nominally 70%), leaving the remainder "available to Tenex". One important stipulation was that stockpiles, each of some 26,000 tonnes U3O8, would be held by both Russian and US governments for ten years, to 2009. The US stockpile already existed, Russia's was built up over the next few years from all feed not purchased by Tenex or an associate, and Russia was free to sell only what exceeded this.

The new agreement did not change the overall supply and demand situation, but it removed some major uncertainties over how the material would be released to the market.

The 1993 agreement significantly depressed uranium exploration activities and the uranium price, which took until about 2003 to recover.

Plutonium and MOX

Disarmament will also give rise to some 150-200 tonnes of weapons-grade plutonium (Pu). Weapons-grade plutonium has over 93% of the fissile isotope, Pu-239, and can be used, like reactor-grade Pu, in fuel for electricity production. Options considered for it included:

Immobilisation with high-level waste - treating plutonium as waste,

Fabrication with uranium oxide as a MOX fuel for burning in existing reactors,

Fabrication with thorium as a fuel for existing Russian reactors,

Fuelling fast-neutron reactors.

In 1994 the USA announced that about half of its military plutonium stockpile was surplus to military requirements. This included non-pit material, and about 20 tonnes of it was of such quality that it might not be possible to utilise it for MOX. In 2012 the US DOE plutonium inventory was announced as being 95.4 tonnes as of 2009, after some transuranic wastes containing 4.8 t of plutonium had been disposed of at the Waste Isolation Pilot Plant (WIPP) in New Mexico. The 95.4 t was composed of 81.3 t weapons grade, 12.7 t fuel grade, and 1.4 t reactor grade plutonium. Since 1944, 103.4 tonnes has been produced, and a further 8.0 t had come from industry, foreign countries and research reactors. Some 3.4 tonnes had been used in tests, 7.8 t discarded as waste and 2.8 t otherwise removed. Russia's inventory of weapons-grade plutonium is unknown, but is assumed to be of the same order as USA's.

In June 2000, the USA and Russia agreed to dispose of at least 34 tonnes each of weapons-grade plutonium by 2014. The USA undertook to pursue a dual track program (immobilisation and MOX), self-funded, while the G-7 nations were to provide some US$ 2.5 billion to set up Russia's program. The latter was initially MOX-oriented for VVER reactors, the high cost being because this was not part of Russia's fuel cycle policy. The USA agreed to allow the Russian plutonium to be used in BN-600 and BN-800 fast neutron reactors, and the timeline stretched to 2018. However, the G7 funding was not available on this basis and Russia is funding most of the program, with the USA contributing $400 million. The 68 tonnes of weapons-grade plutonium in both countries is equivalent to about 12,000 tonnes of natural uranium.

In 2011 an amending protocol to the 2000 agreement came into force, confirming the Russian use of fast reactors and specifying a weapons plutonium disposition rate of 1.3 t/yr in each country from 2018. However, after the Russian MOX plant had been built and the US project stalled, Russia unilaterally cancelled the agreement in October 2016. A bill was introduced to Russia's parliament, with an explanatory note saying that there were both political and technical reasons to cancel the deal, even though it could be renewed under certain conditions related to relaxing US sanctions. The presidential decree said the main reason for cancellation is "the emergence of a threat to strategic stability as a result of US hostile actions against Russia."

Weapons-grade plutonium entering the civil fuel cycle needs to be kept under very tight security, and there are some technical measures needed to achieve this. MOX fuel made from it should degrade it so that Pu-239 cannot be extracted. As it became clear that this could be achieved, the USA dropped its immobilisation plans for most military plutonium,* and this is reflected in the April 2010 agreement with Russia.

USA projects

After environmental and safety reviews, the US Nuclear Regulatory Commission authorised construction of a MOX fuel fabrication plant (MFFF) at the DOE Savannah River site in South Carolina by Duke, Cogema, Stone & Webster. Construction started in August 2007, by Shaw Areva MOX Services. It would make about 1700 civil MOX fuel assemblies from depleted uranium and at least 34 tonnes of weapons-grade plutonium, unlike other MOX plants which use fresh reactor-grade plutonium having around one third non-fissile plutonium isotopes. US reactors using MOX fuel will need to licensed for it. The MFFF is designed to turn 3.5 t/yr of weapons-grade plutonium into about 150 MOX fuel assemblies, both PWR and BWR. The project includes a facility for plutonium pits dismantlement and metallic plutonium conversion to oxide which is complex and has delayed progress.

Shaw Areva MOX Services is under contract to the National Nuclear Security Administration (NNSA), which will own the plant, originally expected to be in operation from 2016, then 2019. The high cost of the plant - $3.5 billion plus $1.3 billion contingency and $183 million per year to operate - is justified on non-proliferation grounds. Annual cost would be offset by revenue.* However, early in 2014 the project was excluded from the DOE budget request for NNSA due to cost escalation, so faced being shut down while 60% complete. This would leave the USA in default on the 2000 bilateral agreement, while Russia has fulfilled its side.

* The following is a comment on this US situation from Dr C. Wolfe, former chairman of the Technical Advisory Panel to the Department of Energy's Plutonium Focus Area, whose task had been to advise on technology to enable the disposition of the excess plutonium: In discussion with Russia "the USA often emphasized elaborate technology schemes to immobilize the plutonium in a proliferation-resistant state. These included grouts, synthetic rock, glass and co-disposal with spent nuclear fuel. The Russians were astounded. They couldn't believe that we were willing to take this material, which we had spent billions of dollars producing, and just throw it away. Not only throw it away, but spend a lot of additional money to get rid of it. The Russians saw it for what it was: a tremendous energy resource. The US eventually came to the same conclusion and opted for converting 34 metric tons of weapons-grade plutonium into MOX fuel to provide electrical energy for the US economy." (Aiken Standard 10/8/09)

In June 2005 the first four fuel assemblies with mixed oxide fuel made from US military plutonium (plus depleted uranium) started generating electricity in Duke Power's Catawba-1 nuclear power plant in South Carolina, on a trial basis. They incorporated 140 kg of weapons-grade plutonium. The plutonium was made into 2 tonnes of pellets at the Cadrache plant and then fabricated into fuel assemblies at the Melox plant in France. This trial was concluded satisfactorily.

DOE was moving all its surplus non-pit weapons plutonium - reported to be 12.8 tonnes - to Savannah River by 2010. Once the material is consolidated there, the Department's plans for disposing of it involve the use of three Savannah River site facilities: the MOX Fuel Fabrication Facility (MFFF, under construction) for 7.8 tonnes, the existing H-Canyon processing plant followed by a proposed new small-scale plutonium vitrification plant for the balance of 5.0 tonnes. The H-Canyon facility* is the last such US plant able to treat used HEU fuel and similar materials still operational.

Following DOE's September 2007 addition of 9 tonnes of plutonium from dismantled weapons to the MOX program, making 43.4 tonnes surplus to defence needs and designated for MOX, NNSA decided that the Savannah River plant might also produce starter fuel for advanced fast reactors, part of the advanced fuel cycle initiative (AFCI) program.

Meanwhile the US has developed a "spent fuel standard". This specifies that plutonium should never be more accessible than if it were incorporated in spent fuel and thus protected from interference by strong gamma radiation. The plutonium immobilisation plant, if and when it is eventually built, would thus incorporate the plutonium in a version of Synroc ( artificial rock), and encase small discs of this in canisters of vitrified high-level radioactive waste. Alternatively, plutonium would be mixed with fission products and vitrified at the small plant proposed for Savannah River.

Europe's well-developed MOX capacity suggests that weapons plutonium could be disposed of relatively quickly. Input weapons-grade plutonium might need to be mixed with reactor grade material or blended with Pu-238, but using such MOX as 30% of the fuel in one third of the world's reactor capacity would remove about 15 tonnes of warhead plutonium per year. This would amount to burning 3000 warheads per year to produce 110 billion kWh of electricity.

About 40 reactors in Europe are licensed to use MOX fuel, and 30 French reactors are licensed to use it as 30% of their fuel.

Russian projects

Russia is using its plutonium to fuel fast neutron reactors such as its BN-600 and BN-800, and later BREST at Beloyarsk. The USA earlier insisted that it duplicate US plans to make it into MOX fuel for late-model conventional reactors, and for this Russia insisted that the USA pay all costs. But after announcement of the Global Nuclear Energy Partnership in 2006 with its proposals for use of fast reactors, US objection to Russian plans disappeared. The 34 tonnes of plutonium initially available for MOX would have been enough for 1350 fuel assemblies for light-water reactors, but instead is going into MOX fuel for BN-600 and BN-800 fast reactors - the former with one-third MOX core and the latter with full MOX core, and accounting for most of the usage. The USA has agreed to contribute US$ 400 million towards the cost of this - much less than for the MOX option in VVER reactors. The BN-600 will be run without a breeding blanket and the BN-800 at conversion ratio of less than 1.

A small pelletised MOX fuel fabrication plant has operated at the Mayak Production Association facility at Ozersk since 1993, for BN-600 fuel (40 fuel assemblies per year), and it supplied some initial pelletised MOX fuel for BN-800 start-up.

The 60 t/yr commercial MOX Fuel Fabrication Facility (MFFF) commenced operation at Zheleznogorsk in 2015, operated by the Mining & Chemical Combine (MCC). It represents the first industrial-scale use of plutonium in the Russian civil fuel cycle. It makes pelletised MOX fuel assemblies for the BN-800 and future BN-1200 fast reactors. The MOX can have up to 30% plutonium. The Research Institute of Atomic Reactors (RIAR or NIIAR) at Dimitrovgrad, has a small MOX fuel fabrication plant producing vibropacked fuel which is more readily recycled.

In collaboration with TVEL, the Siberian Chemical Combine (SCC) at Seversk is making test batches of dense mixed nitride uranium-plutonium (MNUP) fuel for fast reactors, essentially prototype fuel for BREST fast reactors which are being developed. Burning SCC's test batch MNUP fuel in the BN-600 fast reactor commenced in 2015. The BN-800 reactor has a uranium blanket but will operate as a net plutonium consumer for the life of the disposition project. Jointly the two BN reactors are expected to burn 1.5 tonnes of this weapons plutonium per year.

The USA and Russia earlier intended to continue cooperative development of a gas-cooled high-temperature reactor (GT-MHR) in Russia which was to "create additional possibilities for speeding up plutonium disposition" from about 2015. This plan has lapsed.

The 2000 US-Russian agreement precludes the reprocessing of MOX fuel using military plutonium if the plutonium is separated out, so such reprocessing will be either to give plutonium plus uranium or plus actinides. Russia is said to have 40 tonnes of separated reactor-grade plutonium already from reprocessed fuel.

UK plans

In 1998 the UK held an estimated 7.6 tonnes of military plutonium, of which 3.5 tonnes was weapons-grade. A total of 4.4 tonnes was subsequently declared surplus to military needs. (The UK also holds about 100 tonnes of reactor-grade plutonium for which uses are being evaluated.)

Thorium-plutonium fuel project

Since the early 1990s Russia has had a program to develop a thorium-uranium fuel, which then moved to have a particular emphasis on utilisation of weapons-grade plutonium in a thorium-plutonium fuel. The program was based at Moscow's Kurchatov Institute and involved the US company Lightbridge Corporation (formerly Thorium Power) and US government funding to design fuel for Russian VVER-1000 reactors.

Whereas normal fuel uses enriched uranium oxide throughout the fuel assembly, the new design has a demountable centre portion and blanket arrangement, with plutonium-zirconium metal fuel rods in the centre and uranium-thorium oxide pellets in conventional fuel rods around it*. The Th-232 in the blanket captures neutrons to become U-233, which is fissile - as is the core Pu-239. Blanket material remains in the reactor for nine years but the centre portion is burned for only three years (as in a normal VVER). Design of the seed fuel rods in the centre portion draws on extensive experience of Russian navy reactors.

The thorium-plutonium fuel claims four advantages over MOX: proliferation resistance, compatibility with existing reactors - which will need minimal modification to be able to burn it, and the fuel can be made in existing plants in Russia. In addition, a lot more plutonium can be put into a single fuel assembly than with MOX, so that three times as much can be disposed of as when using MOX. The spent fuel amounts to about half the volume of MOX and is even less likely to allow recovery of weapons-useable material than spent MOX fuel, since less fissile plutonium remains in it. With an estimated 150 tonnes of weapons Pu in Russia, the thorium-plutonium project would not necessarily cut across existing plans to make MOX and mixed nitride fuel. However, the program appears to have lapsed.
See also information papers: Plutonium, Mixed Oxide Fuel, Fuel Fabrication and Synroc.
Sources:
Ivanov, 2000, paper in Proceedings of 25th UI Symposium.
NATO ASI series, 1994, Managing the Plutonium Surplus: Applications and Technical Options.
Underhill, D H, 1998, paper to U'98 Conference, Adelaide.
NNSA, US-Russia Partnership Reaches Key Milestone in Converting Russian Nuclear Weapons into US Nuclear Fuel, 24 June 2013.
Thorium Power 2003, Weapons-grade Plutonium Burning Fuel for Russian VVER-1000 Nuclear Power Plants.
Morozov et al, Thorium fuel as a superior approach to disposing of excess weapons-grade plutonium in Russian VVER-1000 reactors, Nuclear Future, Vol 1 No. 1 (2005).

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Military Warheads as a Source of Nuclear Fuel

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Weapons-grade uranium and plutonium surplus to military requirements can be used as civil fuel. Weapons-grade uranium is highly enriched. Weapons-grade plutonium has over 93% Pu-239 and can be used in fuel for electricity production.

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Fact - Nuclear Waste is the most environmentally impactful aspect of nuclear energy production

Evidence - Nuclear energy can create radioactive waste, these radioactive wastes don't degrade at a fast pace and can remain radioactive and dangerous for thousands of years. Radiation can make all aspects of the environment contaminated.

Evidence - Radioactive waste is hazardous because it contains or emits radioactive particles, which if not properly managed can be a risk to human health and the environment. epa.gov

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Nuclear power and the environment - U.S. Energy Information Administration (EIA)

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Environmental issues, effects, and impacts of nuclear energy and uranium production.

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Fact - 'Using and producing nuclear power is less expensive than using oil or coal'

While the initial construction of the plants is comparable to traditional oil and coal plants, the operation of the plants and production of the nuclear energy is way lower.

Based on world-nuclear.org the cost of nuclear energy is about a third of that for coal-fired plants and a fifth of those for gas cycle plants.

Based on the world nuclear association claims existing plants function well with a high degree of predictability and the operation costs of the factories have low risks of operating cost inflation. This means that nuclear energy is economical longterm and will most likely stay this way, while oil and coal have highly fluctuating prices especially with the political insecurity of contries with oil.

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The statement that 1 pound of uranium is the same energy as 50 tons of coal is a MYTH.

According to the Union of the Concerned Scientists "One pound of uranium has as much energy as three million pounds of coal" three million pounds is equivilant to 500 tons which would be ten times more than the statment declared when it said 50 tons.

Additionally according to EuroNuclear, in order to generate 45,000 kWh of electricity it only requires 1 kg of natural uranium where it would require 14,0000 kg of coal.

Meaning that for the same amount of energy 14,000X more coal is required than uranium.

This once again iterates that this statement is a myth.

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At a basic level, nuclear power is the practice of splitting atoms to boil water, turn turbines, and generate electricity.

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Fact - Nuclear power plants in the United States cannot explode like an atomic bomb

E1 - “A thermal explosion cannot occur because our [MIT] reactor is designed to want to shut down on its own as temperature increases (i.e., it has a negative temperature coefficient).”

E2 - “It is impossible for a reactor to explode like a nuclear weapon; these weapons contain very special materials in very particular configurations, neither of which are present in a nuclear reactor.”

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[Yucca Mountain] Myth- Yucca Mountain was proposed as a Nuclear Waste storage site but was only used for a very small amount of time. There are 80 nuclear waste storage facilities all over the country.

"Political and legal opposition to the project has delayed the licensing, construction, and operation of the proposed Yucca Mountain repository. NWPA authorized DOE to enter into agreements with nuclear utilities and other reactor owners to collect fees to pay for DOE’s disposal of the SNF. However, due to the delay in operation of a permanent repository, the federal government has paid roughly $7.4 billion from the Judgment Fund to nuclear utilities and other reactor owners pursuant to court settlements and final judgments through FY2018,"

"The Department of Energy (DOE) oversees the treatment and disposal of radioactive waste from the nation’s nuclear weapons program; it is also responsible for siting, building, and operating a geologic repository to dispose of nuclear waste. There are a number of ways that DOE could improve how it stores, treats, and disposes of this waste," [https://www.gao.gov/nuclear-waste-disposal]

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Fact- Nuclear power plants are targets for terrorism

Evidence #1- "The Energy Department’s nine national laboratories have begun an extensive review of counterterrorism, including the vulnerability of U.S. nuclear sites and materials." (https://www.brookings.edu/articles/terrorism-and-nuclear-energy-understanding-the-risks/)

Evidence #2- "The principal attraction of civil nuclear-energy facilities as terrorist targets lies in the potential for creating a release of radioactivity large enough to produce significant casualties and land contamination."

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Chapter: 7 Threats to Civil Nuclear-energy Facilities

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Science and Technology to Counter Terrorism: Proceedings of an Indo-U.S. Workshop Get This Book

This volume presents the papers and summarizes the discussions of a workshop held in Goa, India, in January 2004, organized by the Indian National Institute of Advanced Science (NIAS) and the U.S. Committee on International Security and Arms Control (CISAC). During the workshop, Indian and U.S. experts examined the terrorist threat faced in both countries and elsewhere in the world, and explored opportunities for the U.S. and India to work together. Bringing together scientists and experts with common scientific and technical backgrounds from different cultures provided a unique opportunity to explore possible means of preventing or mitigating future terrorist attacks.

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Read chapter 7 Threats to Civil Nuclear-energy Facilities: This volume presents the papers and summarizes the discussions of a workshop held in Goa, India...

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The only air pollutant that is given off by the production of nuclear energy is steam. MYTH!

According to energy.gov "The heat released by fission is used to create steam that spins a turbine to generate electricity without the harmful byproducts emitted by fossil fuels" meaning not only is steam the only pollutant being produced through nuclear energy, but it's actually beneficial in the process of creating nuclear power. nationalgrid.com backs this up with their statement noting that "Nuclear energy also avoids producing air pollutants that are often associated with burning fossil fuels for energy"

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Myth - There is no safe dose of exposure to radiation

1.) Although radiation exposure is extremely dangerous, low-dose radiation is used for medical purposes and there are many natural sources of radiation that we are all exposed to every day.

2.) Routine radiation doses to patients, medical staff, and industrial radiation workers are below 100 mGy. If these doses are spread out over time, instead of being delivered all at once, their effects tend to be less severe.

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Abstract

The "no dose is safe" linear no-threshold (LNT) model forms the basis for radiation safety in radiology practice. This model has its origins in observations of germline mutations in fruit flies exposed to X-rays. After World War II, quantitative risk estimates of radiation injury are primarily derived from the atomic bomb survivor Life Span Study. Current understanding of tissue response to radiation has raised doubts about the validity of LNT model at low doses encountered in the practice of diagnostic radiology. This article traces the evolution of basic radiation safety concepts and provides a bird's eye view of the Life Span Study and other studies which throw light on the matter. The arguments for an alternative, threshold, or even hermetic models of dose response are examined. The relevance of these developments to the nuclear power industry is also outlined.

Keywords: radiation, dose, radiology, safety, history

Introduction

"Nothing in life is to be feared, it is only to be understood"-Marie Curie

The risks of radiation have been an ever-present concern for radiation workers since the discovery of X-rays and radioactivity at the end of the 19th century. After the atomic bombing of Hiroshima and Nagasaki, this concern flooded the public conscience and as a consequence, governments and regulatory agencies adopted a sort of zero tolerance to radiation risks in the form of the Linear no-threshold (LNT) model. Since then, meticulous follow-up of the atom bomb survivors, early radiobiological studies, and the sensational nuclear accidents in Chernobyl and Fukushima had reinforced this concern and the desire for absolute safety. Routine radiation doses to patients, medical staff, and industrial radiation workers are below 100 mGy. With rare exceptions, populations exposed to high environmental radiation from natural sources or contamination following accidents also fall in this dose range. In other words, risks of low dose radiation, encountered in the process of peaceful application of radiation, are more relevant to society. Incontrovertible evidence exists for stochastic effects at doses above 0.5 to 1 Gy. The LNT model, however, extrapolates this risk linearly into the low dose range all the way to zero. Paradoxically recent data from these very same sources-population studies and radiobiology-which established and validated the LNT model over the years, have yielded evidence which casts doubt on this assumption. These developments have great import to both the future of radiology practice and nuclear power. Recently studies claiming increased risk of cancer from CT scanners have created a furore both among the public as well as within the medical community. It is vital that radiologists are aware of the origin and evolution of concepts of radiation risk and the emerging evidence indicating safety of low dose radiation.

The discovery of X-rays in 1895 was followed by its wide and rapid adoption for various applications ranging from research in the physical sciences to medical diagnosis to cosmetic skin treatments and even shoe-fitting fluoroscopes. Radioactivity discovered a year later was also subject to intense investigation by scientists and found early commercial applications like radium dials in watches. Along with this enthusiasm and the obvious benefits, the risks of radiation also became apparent within a few years. The tragic story of Clarence Dally, Thomas Alva Edison's assistant, is a case in point. Dally was involved in developing an improved X-ray tube which involved long hours of exposure to radiation to his hands without any protection. He developed radiation burns on both hands which subsequently became cancerous and had to undergo a series of amputations of both upper limbs before succumbing to metastatic disease. 1 Subsequently many physicists and medical imaging pioneers in the western world also suffered injuries and some of them, unfortunately, became radiation "martyrs." Though the mechanism of injury was not known, knowledge of the physics of X-rays and gamma rays itself led to early protection measures based on time of exposure, distance, and shielding. However, up until the middle of the 20 th century, radiation effects on the body remained largely in the domain of experts and was not a cause for public concern.

In 1927, Herman J. Mueller, discovered that X-rays produce mutations in the germ cells of Drosophila fruit fly by observing anomalies in the progeny. 2 The discovery, apart from illuminating and opening new avenues in the field of genetics, marked the first step in the study of biologic effects of radiation. In 1928, the International X-ray and Radium Protection Committee (IXRPC) was established with Rolf Maximilian Sievert as chairman. The organization was renamed International Committee for Radiological Protection (ICRP) in 1950.3 The Americans constituted the National Council on Radiation Protection & Measurements (NCRP) in 1929. In 1934 IXRPC recommended a "tolerance" dose of 0.2 Roentgens per day (approximately 730 mSv/y) for radiation workers. The term "tolerance" implies that there are no risks below that threshold dose. In 1951, amidst mounting concerns about effects of radiation this was revised down to 0.3 Roentgens per week (approximately 154 mSv/y) and the term "maximum permissible" dose was applied implying uncertainty about absolute safety below this level.4

The atom bombing of Hiroshima and Nagasaki in August 1945 and its immediate aftermath shocked the scientific world and the general public, forcefully bringing into center stage the danger posed by nuclear weapons and more importantly, the hazards of radiation to public health. Herman Mueller in his Nobel Prize acceptance speech in 1946 stated that dose-injury relationship for mutations was linear and that no dose, however, small, is safe. 5 In the 1950s the United States (U.S.), Britain and Union of Soviet Socialist Republics (USSR) conducted hundreds of surface-based and high atmosphere nuclear tests leading to significant radioactive fallout. Despite government secrecy and official assurances that the radiation levels were within safe limits, there was great public anxiety and scientists like Linus Pauling campaigned for banning atmospheric nuclear tests. It is important to understand that germline genetic modification by radiation-induced mutations which could potentially harm millions of unborn children was the dominant concern of this era. Somatic effects like cancer were thought to have a different mechanism.4 5 The geneticists argued that the same risk of radiation-induced mutations in germ cells must apply to somatic cells and further that these mutations could lead to cancer. Thus, the basis of carcinogenesis that we today accept as fact was first expressed in the nuclear safety debate of the 1950s. The deoxyribonucleic acid (DNA) structure had just been discovered by Watson and Crick in 1953 and it would take many years to unravel the gene as a physical entity and understand its function in cells. The "no safe dose" was proposed based on germline mutations for which the geneticists apparently had direct evidence. This also made the gonads appear to be the most critical targets of radiation, a fact that was to have a very long-lasting impact on regulatory policy and the perceptions of generations of doctors and patients.

Linear No-Threshold Model

Recent research has shown that there were other dose response studies at that time that suggested a linear relationship only at high doses raising the possibility of a threshold effect. But these studies were overlooked by dominant voices including Mueller, due, perhaps, to their strong moral indignation at the use of atomic science for war and their desire to protect future generations from potential harm. 5 In view of the raging controversy playing out in the media and scientific circles the U.S. National Academy of Sciences constituted a Biological Effects of Atomic Radiation (BEAR) committee to study the issue and provide recommendations. The 1 st BEAR report submitted in 1956 recommended reductions in permissible dose and adoption of LNT model for guiding regulatory policy. Later the committee was renamed Biological Effects of Ionizing Radiation (BEIR) and it has continued to submit its recommendations periodically, the latest being the BEIR VII report in 2006. By the early 1970s the LNT model was firmly established and adopted by ICRP and all other national regulatory bodies. The recommendation of the ICRP Publication No: 26 adopted in 1977 was a watershed in radiation safety history.6 It outlined for the first time the ALARA (as low as reasonably achievable) principle which follows directly from the LNT concept and became central to the practice of Radiology. The publication also, for the first time, assigned tissue weighting factors for various organs based on their estimated sensitivity to radiation injury.

The linear no threshold model underpins the radiation safety recommendations and cancer risk predictions of international and national radiation safety authorities-ICRP, NCRP, Atomic Energy Regulatory Board (AERB), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), etc. The model is based on a "single-hit" hypothesis which assumes that a photon or particle of ionizing radiation directly damages a random part of the DNA molecule leading to a point mutation or strand break which can turn into cancer later on or, in the case germ cells, cause congenital anomalies in the progeny. LNT implies that even the smallest incremental dose above background increases the relative risk for oncogenesis by a proportional amount and that damage is cumulative ( Fig. 1 ). The LNT model and the ALARA principle find application not only in medical procedures but also directs the design, construction, and operation of nuclear power plants. Nuclear waste disposal and government policy related to the evacuation of public and environmental clean ups following nuclear accidents are also guided by this concept.

Is LNT Model Reliable for Low Dose Exposures?

While the link between radiation and cancer at high doses above 1 Gy (1,000 mGy) is unquestionable, at lower doses there is room for skepticism. By convention "Low Dose" refers to doses below 100 mSv. This is the range which concerns patients undergoing diagnostic radiology procedures, radiation workers, and populations exposed to natural radiation or contamination of environment. Though the model is universally accepted and applied for regulatory purposes, many physicists and even some scientific bodies have questioned its validity in recent times. The reasons for this shift in thinking have arisen from different parts of the world and in different fields of study. It is necessary for radiologists to be acquainted with these issues to have a holistic and updated understanding of radiation safety in their practice. There are five distinct "stories": (1) Data from the atom bomb survivor Life Span study; (2) The recent CT radiation dose controversy; (3) Molecular biological studies on the response of cell and DNA to radiation; (4) Studies of populations exposed to high levels of natural and background radiation in India, China, Brazil, and Iran and (5) Studies of the local population and environment in Chernobyl and Fukushima. We will examine each one in turn.

The Life Span Study

After the atomic bombing of Hiroshima and Nagasaki, the Japanese and the U.S. governments collaborated to study the effects of radiation on the surviving population in these cities. In 1947, the Atom Bomb Casualty Commission was created to oversee and coordinate the effort to identify survivors, conduct clinical examinations, and collect data. In 1955 ABCC launched the Life Span Study (LSS) which is a multicohort lifelong follow-up of atom bomb survivors and controls. In 1975, the commission was renamed as the Radiation Effects Research Foundation (RERF). The LSS remains, to this day, the most important source for our understanding the effects of radiation on humans. All the radiation risk assessment and safety recommendations of the ICRP and the various national organizations derive from the LSS results which are published from time to time.

The main cohort of the LSS was the carefully selected 120,000 residents of Hiroshima and Nagasaki, 96,000 of whom were exposed to the bomb and 24,000 were controls who were "not in city" at the time of the bombing. The dose to each survivor was estimated by ascertaining the distance from the center to the spot where the person found herself at the time of bombing and the shielding present, i.e., whether the person was in the open or inside a wooden/metal/concrete building or underground in a shelter. It is noteworthy that though the mean dose was 200 mSv, 80% of subjects in the study received doses less than 100 mSv and only 7% received doses above 500 mSv. The second cohort was 3,600 women pregnant and exposed at the time of bombing and followed up to study the effect of radiation in utero. The third cohort was 77,000 children whose one parent or both parents were survivors of the bombing.

The risk for cancer is expressed as excess relative risk (ERR). Relative risk is the ratio of occurrence rate in exposed population to that in controls, i.e., number of cancers in exposed individuals/number of exposed individuals divided by number of cancers in nonexposed/number of nonexposed individuals. ERR is this value minus 1.

Increased risk for leukemia became evident by the early 1950s in subjects who received more than approximately 200 mSv. The incidence peaked early and reduced over the years with the majority of excess deaths occurring before 1975. There were 45% excess deaths in those exposed to more than 5 mGy and 86% more for those exposed to 1 Gy. However, leukemia is a rare disease, and the absolute number of excess deaths was only 98 and it was seen predominantly in persons exposed at a young age.

To put it in perspective an acute exposure of 1,000 mGy to a population of 100 people would lead to one excess cancer over and above the 42 persons who would have cancer from other causes. 11 The natural background rate of cancer in humans is very high-around 40% in males and 29% in females. Detecting a very small increase, if any, of cancer in a population exposed to low doses of radiation is a big epidemiological challenge. There is, thus, reason to doubt the validity of extrapolating risks at high doses to doses below 200 or 100 mGy12 ( Fig. 2 ).

The third LSS cohort of children born to exposed parents was carefully selected to address the most important question the scientific community was facing in the 1950s-the effect of radiation on germ cells and thereby the next generation. The surprising finding was that irrespective of the amount of radiation received by one or both parents, there was no excess incidence of congenital anomalies, mental retardation, or childhood leukemia. Some of these individuals are in their 7th decade of life now and there has also been no increase in adult cancers compared with controls. Even direct tests for chromosomal aberrations in peripheral leukocytes do not show any difference. 7 The relative radio-resistance of human germ cells, evident by the 1990s, upturned a long-held dogma and effectively took the gonads out of the center of the radiation safety debate. However, "gonad centricity" continues to cast a shadow over training in radiodiagnosis and our choice of subspecialty practice! Comparing the relative weights assigned to various organs in the ICRP tissue weighting tables over the years is very instructive ( Table 1 ). In the very first publication (ICRP 26 in 1977), the gonads were assigned 25% of the total risk to all tissues. This was reduced to 20% in the second publication (ICRP 60 in 1990) and dramatically scaled down to 8% in the latest update (ICRP 103 in 2007).6 14

Table 1

Organs

ICRP 26

ICRP 60

ICRP 103

Recent Radiation Controversies in Diagnostic Radiology

High Background Radiation Areas

Radiobiology, DNA Repair, Adaptive Response and Hormesis

Since the body is 65% water and the DNA itself is compacted into a small part of the cell, direct "hit" by a photon is an exception rather than the rule. Most of the radiation damage is mediated through reactive oxygen species (RSOs) generated by hydrolysis of water molecules by the radiation. The subsequent injury is thus chemically mediated. The number of RSOs produced per day in a single human cell from normal metabolism has been estimated to be around 1 billion (10 ⁹ )! An efficient detoxifying system consisting of antioxidants, catalases, superoxide dismutase, etc., limits the number of DNA alterations to around one million (10 ⁶ ). DNA alterations can be single strand breaks, base change, or double strand breaks (DSBs). While single strand breaks and base changes are normally repaired efficiently within minutes, DSBs are uncommon, and the repair is more complex and carries the risk of lasting damage. In a normal nonradiated cell, DSBs have been estimated to occur at the rate of 0.1/cell/d. A 1 mGy dose to a mammalian cell has been estimated to produce only 5 × 10 −3 DNA alterations per cell compared with the huge 10 ⁶ changes occurring per day in a nonradiated cell. The dose of 1 mGy is expected to produce only 1/1,000th number of DSBs compared with that produced by the normal endogenous metabolism. However, the proportion of DSB out of the total DNA alterations produced is 1,000 times more for ionizing radiation compared with endogenously induced DNA alterations. At high doses above 1 Gy the DSB proportion increases further and at lethal doses of 2.5 Gy and above it becomes the dominant effect causing widespread loss of cell function leading to the multiorgan failure of acute radiation syndrome.21

DSB repair is activated within seconds of damage and is achieved by enzymes in the nucleus, triggered and orchestrated by several genes. One of the first steps in the DNA repair process is to pause the cell cycle. The DNA replication is prevented during repair. If the repair is not successful, the abnormal cell is eliminated by triggering an immune response or taking it down the senescence pathway or by apoptosis. It has been observed in humans and mice models that, after exposure to low dose radiation, the activated defense system remains upregulated for days or even weeks and responds with even greater efficiency to a subsequent exposure. This adaptive response has been shown to disappear at higher doses beyond 300 mGy which indicates threshold dose response ( Fig. 1 ).17 Radiation hormesis is a related phenomenon whereby the repair systems primed by low dose radiation offers protection from all causes of DNA damage leading to a reduction in cancer risk compared with controls4 22 ( Fig. 1 ).

Lessons from Chernobyl and Fukushima and the Challenges of a Nuclear Renaissance

The Chernobyl nuclear plant accident in 1986 is a worst-case scenario in which poor design and operator error combined to blow up the reactor operating under full power. The explosion was a result of high-pressure hydrogen gas build up within the reactor and its subsequent violent reaction with atmospheric oxygen. The hazards are primarily, heat and radiation from the exposed reactor and secondarily, fall out of the radioactive material released into the atmosphere. Twenty-eight plant personnel and first response fire fighters died from burns and acute radiation sickness. Radiation fall out exposed the evacuees in the neighborhood to a whole-body dose (cumulative over two decades) of 30 mSv. Though from one perspective this is equivalent to only couple of abdomen CT scans, it is 15 times the maximum permissible dose for public from a regulatory perspective in most countries. In the fall out zone outside this core area, the 20-year cumulative dose for an individual was 9 mSv. In the years that followed, approximately 15 excess deaths due to thyroid cancer in children were attributed to radioactive iodine (I ¹³¹ ) intake through milk. Large number of thyroid cancers detected in this period is believed to have been due to intensive screening and vast majority of them were successfully treated. No other excess cancer incidence or deaths have been observed so far.23 Contrary to the general perception of a "disaster" only approximately 40 to 50 deaths can be directly linked to the incident. On the other hand, the large-scale evacuation and resettlement that followed, produced loss of livelihood, disruption of social bonds, and profound psychological stress. More than 1,200 suicides were recorded in this displaced population. Moreover, thousands of pregnancies were voluntarily aborted in countries as far away as Greece though the dose from fall out in these locations was infinitesimally small.24

In 2011, the Fukushima nuclear plant in northern Japan was hit by a massive tsunami. Unlike Chernobyl, the reactor was shut down in time. However, the residual heat (decay heat) could not be cooled down since the back-up generators for the cooling system were flooded. Not a single person was killed or injured by radiation in the plant. The tsunami itself killed more than 18,000 people and resulted in extensive damage to homes and infrastructure. Panic and hurried evacuation of 100,000 people from a 20 km radius followed. The fallout from the reactors was widespread; but the exposure to individuals was not more than 2 mSv in a year! Disruption of medication of chronically ill elderly people and accidents resulted in the deaths of at least 1,000 people during the evacuation. There has been no recorded incidence of excess cancer or any other health risks so far in this population which is being flowed up closely. 25

Is it justifiable to risk the lives of hundreds of people now for a very small probability of reduced cancer in the distant future? What will be the incremental cost of reducing already low doses to negligible levels be it a CT or a nuclear plant? Is there any tangible benefit for such costs to patients and public? The average nonexpert anywhere in the world today continues to have the same fear of radiation engendered by the atom bomb in 1945 and this anxiety has been institutionalized by regulatory policy.

It has become imperative to rapidly reduce CO ₂ emissions to offset climate change. Nuclear power is being increasingly recognized as the cleanest source for base power which can be supplemented by solar, wind, and other renewable sources to achieve emission targets. Safety in nuclear installations is also anchored in the LNT model. Unlike thermal or hydel power, a large proportion of nuclear power costs goes into maintaining safety right from construction, to dedicated systems, and personnel during operation. A zero dose, absolute safety approach will make nuclear energy financially unviable, is not practically achievable and is not necessary if the LNT model is not valid for low doses. The "15 country study," an almost 50 years follow up of over 400,000 nuclear plant workers, some of whom received up to 100 mSv cumulative personal doses, in its final analysis, did not show any increased rate of cancer or any other deleterious effect.26 27

Summary

A very stringent application of the ALARA principle has unfortunately resulted in doctors and patients preferring MR over CT even when it is not appropriate. Moreover, body CT scan, especially in children, are many times uninterpretable due to image noise, defeating the very purpose of the scan. The most commonly performed radiological investigation with a relatively high dose is a multiphase abdomen MDCT. A recent study using 256 slice CT and model-based iterative reconstruction algorithm showed that the dose for a four-phase abdominal scan of good diagnostic quality was between 17 and 25 mSv only. 29

Adaptive response of the DNA repair systems can be expected to mitigate even repeated radiological exposures which are typically fractionated and cumulative over time. Acute patient doses in the 100 mSv range are encountered only in complex interventional procedures. Current concepts can ameliorate some of the concerns of patients requiring such procedures. On the other hand, doses to IR personnel using appropriate protection gear and shielding are very low and any excess risk for cancer is very unlikely. Gonads are no longer considered the most radiosensitive organs and congenital anomalies or cancer in the next generation is extremely unlikely with doses in the diagnostic range. Similarly, for in utero exposure up to even 100 mSv, no anomalies or any other abnormality is expected over and above the normal incidence.

Conclusion

Limiting dose to patient will remain an important primary responsibility of the radiologist. However, as data from the LSS and other exposed populations around the world continues to accumulate, concepts will have to be continually reviewed and reshaped. Current state of evidence seems to indicate that doses below 100 mSv have negligible or no risks. Based on a more realistic estimate of risk we could move from "as low as reasonably achievable" to a "as low as diagnostically acceptable" paradigm. Apart from adopting best practices and using advanced technology it has become imperative for radiologists to keep in touch with developments in this field so that we can continuously engage with the rest of the medical fraternity and public and assume our true roles as counsellors and guardians at the forefront of medical radiation safety. Meanwhile on the regulatory side, a "no safe dose" approach is convenient to frame policies and ensure compliance. But changes in regulatory policy concerning permissible doses could be expected in the future based on new evidence.

Footnotes

Conflict of Interest None dseclared.

References

6. ICRP, 1977 Recommendations of the ICRP. ICRP Publication 261977 Ann. ICRP 1 (3)

11. NCR . National Research Council, Washington DC: National Academy Press; 2006. Health Risks from Exposures to Low Levels of Ionizing Radiation: BEIR VII Phase 2. [ Google Scholar]

13. Pregnancy and Medical RadiationICRP Publication 84. 2000; Ann ICRP;30(1) [ PubMed]

14. Recommendations of the International Commission on Radiological ProtectionICRP Publication 103. 2007 Ann. ICRP 37 (2-4) [ PubMed]

21. Pollycove M, Feinendegen L E.Radiation-induced versus endogenous DNA damage: possible effect of inducible protective responses in mitigating endogenous damage Hum Exp Toxicol 200322 06290-306., discussion 307, 315-317, 319-323 [[ PubMed] Google Scholar]

25. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013Sources, effects and risks of ionizing radiation. Vol I Scientific AnnexA: levels and effects of radiation exposure due to the nuclear accident after the 2011 Great East Japan earthquake and tsunamiAccessed December 24, 2020 at: https://www.unsear.org/docs/reports/2013/13-85418_Report_2013_Annexe_A.pdf

28. Tubiana M, Aurengo A, Averbeck D.Dose-Effect Relationships and the Estimation of the Carcinogenic Effects of Low Doses of Ionizing RadiationAcademy of Medicine (Paris) and Academy of Science (Paris) Joint Report No. 2, March 30;2005

29. Kulkarni C B, Pullara S K, Prabhu N K, Patel S, Suresh A, Moorthy S. Comparison of knowledge-based iterative model reconstruction (IMR) with hybrid iterative reconstruction (iDose [ ⁴ ) techniques for evaluation of hepatocellular carcinomas using computed tomography . Acad Radiol. 2020;S1076-6332(20):30483-30489. [ PubMed] Google Scholar]

Articles from The Indian Journal of Radiology & Imaging are provided here courtesy of Thieme Medical Publishers

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How Safe Are Radiation Doses in Diagnostic Radiology? A Historical Perspective and Review of Current Evidence

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The "no dose is safe" linear no-threshold (LNT) model forms the basis for radiation safety in radiology practice. This model has its origins in observations of germline mutations in fruit flies exposed to X-rays. After World War II, quantitative ...

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Myth - nuclear power plants emit higher amounts of pollutants into the atmosphere than fossil fuel plants.

Evidence - Nuclear power reactors do not produce air pollution while the are operating, unlike fossil fueled power plants.

Evidence - Deaths from fossil fueled energy is estimated to be more than 613 times higher than the amount caused involved with nuclear power. The amount of deaths are per unit of electricity and from accidents involving the supply of the power plants.

Source above

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Nuclear reactors and power plants have complex safety and security features

An uncontrolled nuclear reaction in a nuclear reactor could result in widespread contamination of air and water. The risk of this happening at nuclear power plants in the United States is small because of the diverse and redundant barriers and safety systems in place at nuclear power plants, the training and skills of the reactor operators, testing and maintenance activities, and the regulatory requirements and oversight of the U.S. Nuclear Regulatory Commission. A large area surrounding a nuclear power plant is restricted and guarded by armed security teams. U.S. reactors also have containment vessels that are designed to withstand extreme weather events and earthquakes.

A containment dome on a nuclear reactor

Source: Stock photography (copyrighted)

Nuclear power reactors do not produce direct carbon dioxide emissions

Unlike fossil fuel-fired power plants, nuclear reactors do not produce air pollution or carbon dioxide while operating. However, the processes for mining and refining uranium ore and making reactor fuel all require large amounts of energy. Nuclear power plants also have large amounts of metal and concrete, which require large amounts of energy to manufacture. If fossil fuels are used for mining and refining uranium ore, or if fossil fuels are used when constructing the nuclear power plant, then the emissions from burning those fuels could be associated with the electricity that nuclear power plants generate.

Nuclear energy produces radioactive waste

A major environmental concern related to nuclear power is the creation of radioactive wastes such as uranium mill tailings, spent (used) reactor fuel, and other radioactive wastes. These materials can remain radioactive and dangerous to human health for thousands of years. Radioactive wastes are subject to special regulations that govern their handling, transportation, storage, and disposal to protect human health and the environment. The U.S. Nuclear Regulatory Commission (NRC) regulates the operation of nuclear power plants.

Radioactive wastes are classified as low-level waste or high-level waste. The radioactivity of these wastes can range from a little higher than natural background levels, such as for uranium mill tailings, to the much higher radioactivity of used (spent) reactor fuel and parts of nuclear reactors. The radioactivity of nuclear waste decreases over time through a process called radioactive decay. The amount of time it takes for the radioactivity of radioactive material to decrease to half its original level is called the radioactive half-life. Radioactive waste with a short half-life is often stored temporarily before disposal to reduce potential radiation doses to workers who handle and transport the waste. This storage system also reduces the radiation levels at disposal sites.

By volume, most of the waste related to the nuclear power industry has a relatively low level of radioactivity. Uranium mill tailings contain the radioactive element radium, which decays to produce the radioactive gas radon. Most uranium mill tailings are placed near the processing facility, or mill, where they come from. Uranium mill tailings are covered with a sealing barrier of material such as clay to prevent radon from escaping into the atmosphere. The sealing barrier is covered by a layer of soil, rocks, or other materials to prevent erosion of the sealing barrier.

The other types of low-level radioactive waste are the tools, protective clothing, wiping cloths, and other disposable items that become contaminated with small amounts of radioactive dust or particles at nuclear fuel processing facilities and nuclear power plants. These materials are subject to special regulations for their handling, storage, and disposal so they will not come in contact with the outside environment.

High-level radioactive waste consists of irradiated, or spent, nuclear reactor fuel (fuel that is no longer useful for producing electricity). The spent reactor fuel is in a solid form, consisting of small fuel pellets in long metal tubes called rods.

Spent reactor fuel storage and reactor decommissioning

Spent reactor fuel assemblies are highly radioactive and, initially, must be stored in specially designed pools of water. The water cools the fuel and acts as a radiation shield. Spent reactor fuel assemblies can also be stored in specially designed dry storage containers. An increasing number of reactor operators now store their older spent fuel in dry storage facilities using special outdoor concrete or steel containers with air cooling. The United States does not currently have a permanent disposal facility for high-level nuclear waste.

When a nuclear reactor stops operating, it must be decommissioned. Decommissioning involves safely removing from service the reactor and all equipment that has become radioactive and reducing radioactivity to a level that permits other uses of the property. The U.S. Nuclear Regulatory Commission has strict rules governing nuclear power plant decommissioning that involve cleanup of radioactively contaminated power plant systems and structures and removing the radioactive fuel.

A dry storage cask for spent nuclear reactor fuel

Some spent fuel storage canisters are designed to be placed vertically in robust above-ground concrete or steel structures.

Source: U.S. Nuclear Regulatory Commission (Public Domain)
Last updated: November 7, 2022

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Nuclear power and the environment - U.S. Energy Information Administration (EIA)

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Environmental issues, effects, and impacts of nuclear energy and uranium production.

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Fact- Nuclear energy plants are safe for the communities they are located in and the people who work there.

Evidence- "Nuclear power plants maintain the highest standard for operational safety, security, cybersecurity and emergency preparedness. The industry’s comprehensive safety procedures and stringent federal regulations keep our plants and neighboring communities safe." https://www.nei.org/fundamentals/safety

Evidence- "The national regulator is responsible for ensuring the plants are operated safely by the licensee, and that the design is approved. A second important concept is that a regulator’s mission is to protect people and the environment."

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( Updated June 2019)

From the outset, there has been a strong awareness of the potential hazard of both nuclear criticality and release of radioactive materials from generating electricity with nuclear power.

As in other industries, the design and operation of nuclear power plants aims to minimise the likelihood of accidents, and avoid major human consequences when they occur.

There have been three major reactor accidents in the history of civil nuclear power - Three Mile Island, Chernobyl and Fukushima. One was contained without harm to anyone, the next involved an intense fire without provision for containment, and the third severely tested the containment, allowing some release of radioactivity.

These are the only major accidents to have occurred in over 17,000 cumulative reactor-years of commercial nuclear power operation in 33 countries.

The evidence over six decades shows that nuclear power is a safe means of generating electricity. The risk of accidents in nuclear power plants is low and declining. The consequences of an accident or terrorist attack are minimal compared with other commonly accepted risks. Radiological effects on people of any radioactive releases can be avoided.

Context

In relation to nuclear power, safety is closely linked with security, and in the nuclear field also with safeguards. Some distinctions apply:

Safety focuses on unintended conditions or events leading to radiological releases from authorised activities. It relates mainly to intrinsic problems or hazards.

Security focuses on the intentional misuse of nuclear or other radioactive materials by non-state elements to cause harm. It relates mainly to external threats to materials or facilities.

Safeguards focus on restraining activities by states that could lead to acquisition or development of nuclear weapons. It concerns mainly materials and equipment in relation to rogue governments. (See also information paper on Safeguards.)

No industry is immune from accidents, but all industries learn from them. In civil aviation, there are accidents every year and each is meticulously analysed. The lessons from nearly one hundred years' experience mean that reputable airlines are extremely safe. In the chemical industry and oil-gas industry, major accidents also lead to improved safety. There is wide public acceptance that the risks associated with these industries are an acceptable trade-off for our dependence on their products and services. With nuclear power, the high energy density makes the potential hazard obvious, and this has always been factored into the design of nuclear power plants. The few accidents have been spectacular and newsworthy, but of little consequence in terms of human fatalities. The novelty value and hence newsworthiness of nuclear power accidents remains high in contrast with other industrial accidents, which receive comparatively little news coverage.

Harnessing the world's most concentrated energy source

In the 1950s attention turned to harnessing the power of the atom in a controlled way, as demonstrated at Chicago in 1942 and subsequently for military research, and applying the steady heat yield to generate electricity. This naturally gave rise to concerns about accidents and their possible effects. However, with nuclear power, safety depends on much the same factors as in any comparable industry: intelligent planning, proper design with conservative margins and back-up systems, high-quality components and a well-developed safety culture in operations. The operating lives of reactors depend on maintaining their safety margin.

A particular nuclear scenario was loss of cooling which resulted in melting of the nuclear reactor core, and this motivated studies on both the physical and chemical possibilities as well as the biological effects of any dispersed radioactivity. Those responsible for nuclear power technology in the West devoted extraordinary effort to ensuring that a meltdown of the reactor core would not take place, since it was assumed that a meltdown of the core would create a major public hazard, and if uncontained, a tragic accident with likely multiple fatalities.

In avoiding such accidents the industry has been very successful. In over 17,000 cumulative reactor-years of commercial operation in 33 countries, there have been only three major accidents to nuclear power plants - Three Mile Island, Chernobyl, and Fukushima - the second being of little relevance to reactor designs outside the old Soviet bloc.

The three significant accidents in the 50-year history of civil nuclear power generation are:

Three Mile Island (USA 1979) where the reactor was severely damaged but radiation was contained and there were no adverse health or environmental consequences.

Chernobyl (Ukraine 1986) where the destruction of the reactor by steam explosion and fire killed two people initially plus a further 28 from radiation poisoning within three months, and had significant health and environmental consequences.

Fukushima (Japan 2011) where three old reactors (together with a fourth) were written off after the effects of loss of cooling due to a huge tsunami were inadequately contained. There were no deaths or serious injuries due to radioactivity, though about 19,000 people were killed by the tsunami.

Appendix 1: The Hazards of Using Energy contains a table showing all reactor accidents and a table listing some energy-related accidents with multiple fatalities.

These three significant accidents occurred during more than 17,000 reactor-years of civil operation. Of all the accidents and incidents, only the Chernobyl and Fukushima accidents resulted in radiation doses to the public greater than those resulting from the exposure to natural sources. The Fukushima accident resulted in some radiation exposure of workers at the plant, but not such as to threaten their health, unlike Chernobyl. Other incidents (and one 'accident') have been completely confined to the plant.

Apart from Chernobyl, no nuclear workers or members of the public have ever died as a result of exposure to radiation due to a commercial nuclear reactor incident. Most of the serious radiological injuries and deaths that occur each year (2-4 deaths and many more exposures above regulatory limits) are the result of large uncontrolled radiation sources, such as abandoned medical or industrial equipment. (There have also been a number of accidents in experimental reactors and in one military plutonium-producing pile - at Windscale, UK, in 1957 - but none of these resulted in loss of life outside the actual plant, or long-term environmental contamination.) See also Table in Appendix 2: Serious Nuclear Reactor Accidents.

It should be emphasised that a commercial-type power reactor simply cannot under any circumstances explode like a nuclear bomb - the fuel is not enriched beyond about 5%, and much higher enrichment is needed for explosives.

The International Atomic Energy Agency (IAEA) was set up by the United Nations in 1957. One of its functions was to act as an auditor of world nuclear safety, and this role was increased greatly following the Chernobyl accident. It prescribes safety procedures and the reporting of even minor incidents. Its role has been strengthened since 1996 (see later section). Every country which operates nuclear power plants has a nuclear safety inspectorate and all of these work closely with the IAEA.

While nuclear power plants are designed to be safe in their operation and safe in the event of any malfunction or accident, no industrial activity can be represented as entirely risk-free. Incidents and accidents may happen, and as in other industries, what is learned will lead to a progressive improvement in safety. Those improvements are both in new designs, and in upgrading of existing plants. The long-term operation (LTO) of established plants is established by significant investment in such upgrading.

The safety of operating staff is a prime concern in nuclear plants. Radiation exposure is minimised by the use of remote handling equipment for many operations in the core of the reactor. Other controls include physical shielding and limiting the time workers spend in areas with significant radiation levels. These are supported by continuous monitoring of individual doses and of the work environment to ensure very low radiation exposure compared with other industries.

The use of nuclear energy for electricity generation can be considered extremely safe. Every year several thousand people die in coal mines to provide this widely used fuel for electricity. There are also significant health and environmental effects arising from fossil fuel use. To date, even the Fukushima accident has caused no deaths, and the IAEA reported in June 2011: "to date, no health effects have been reported in any person as a result of radiation exposure." Subsequent WHO and UNSCEAR reports have supported this.

Achieving safety: the reactor core

Concerning possible accidents, up to the early 1970s, some extreme assumptions were made about the possible chain of consequences. These gave rise to a genre of dramatic fiction (e.g. The China Syndrome) in the public domain and also some solid conservative engineering including containment structures in the industry itself. Licensing regulations were framed accordingly.

It was not until the late 1970s that detailed analyses and large-scale testing, followed by the 1979 meltdown of the Three Mile Island reactor, began to make clear that even the worst possible accident in a conventional western nuclear power plant or its fuel would not be likely to cause dramatic public harm. The industry still works hard to minimize the probability of a meltdown accident, but it is now clear that no-one need fear a potential public health catastrophe simply because a fuel meltdown happens. Fukushima has made that clear, with a triple meltdown causing no fatalities or serious radiation doses to anyone, while over two hundred people continued working on the site to mitigate the accident's effects.

The decades-long test and analysis program showed that less radioactivity escapes from molten fuel than initially assumed, and that most of this radioactive material is not readily mobilized beyond the immediate internal structure. Thus, even if the containment structure that surrounds all modern nuclear plants were ruptured, as it has been with at least one of the Fukushima reactors, it is still very effective in preventing escape of most radioactivity.

A mandated safety indicator is the calculated probable frequency of degraded core or core melt accidents. The US Nuclear Regulatory Commission (NRC) specifies that reactor designs must meet a 1 in 10,000 year core damage frequency, but modern designs exceed this. US utility requirements are 1 in 100,000 years, the best currently operating plants are about 1 in 1 million and those likely to be built in the next decade are almost 1 in 10 million. While this calculated core damage frequency has been one of the main metrics to assess reactor safety, European safety authorities prefer a deterministic approach, focusing on actual provision of back-up hardware, though they also undertake probabilistic safety analysis (PSA) for core damage frequency, and require a 1 in 1 million core damage frequency for new designs.

Even months after the Three Mile Island (TMI) accident in 1979 it was assumed that there had been no core melt because there were no indications of severe radioactive release even inside the containment. It turned out that in fact about half the core had melted. Until 2011 this remained the only core melt in a reactor conforming to NRC safety criteria, and the effects were contained as designed, without radiological harm to anyone.* Greifswald 5 in East Germany had a partial core melt in November 1989, due to malfunctioning valves (root cause: shoddy manufacture) and was never restarted. At Fukushima in 2011 (a different reactor design with penetrations in the bottom of the pressure vessel) the three reactor cores evidently largely melted in the first two or three days, but this was not confirmed for about ten weeks. It is still not certain how much of the core material was not contained by the pressure vessels and ended up in the bottom of the drywell containments, though certainly there was considerable release of radionuclides to the atmosphere early on, and later to cooling water**.
* About this time there was alarmist talk of the so-called 'China Syndrome', a scenario where the core of such a reactor would melt, and due to continual heat generation, melt its way through the reactor pressure vessel and concrete foundations to keep going, perhaps until it reached China on the other side of the globe! The TMI accident proved the extent of truth in the proposition, and the molten core material got exactly 15 mm of the way to China as it froze on the bottom of the reactor pressure vessel. At Fukushima, cooling was maintained just long enough apparently to avoid testing the containment in this way. ** Ignoring isotopic differences, there are about one hundred different fission products in fuel which has been undergoing fission. A few of these are gases at normal temperatures, more are volatile at higher temperatures, and both will be released from the fuel if the cladding is damaged. The latter include iodine (easily volatilised, at 184°C) and caesium (671°C), which were the main radionuclides released at Fukushima, first into the reactor pressure vessel and then into the containment which in unit 2 apparently ruptured early on day 5. In addition, as cooling water was flushed through the hot core, soluble fission products such as caesium dissolved in it, which created the need for a large water treatment plant to remove them.
However apart from these accidents and the Chernobyl disaster there have been about ten core melt accidents - mostly in military or experimental reactors - Appendix 2 lists most of them. None resulted in any hazard outside the plant from the core melting, though in one case there was significant radiation release due to burning fuel in hot graphite (similar to Chernobyl but smaller scale). The Fukushima accident should also be considered in that context, since the fuel was badly damaged and there were significant off-site radiation releases.

Licensing approval for new plants today requires that the effects of any core-melt accident must be confined to the plant itself, without the need to evacuate nearby residents.

The main safety concern has always been the possibility of an uncontrolled release of radioactive material, leading to contamination and consequent radiation exposure off-site. Earlier assumptions were that this would be likely in the event of a major loss of cooling accident (LOCA) which resulted in a core melt. The TMI experience suggested otherwise, but at Fukushima this is exactly what happened. In the light of better understanding of the physics and chemistry of material in a reactor core under extreme conditions it became evident that even a severe core melt coupled with breach of containment would be unlikely to create a major radiological disaster from many Western reactor designs, but the Fukushima accident showed that this did not apply to all. Studies of the post-accident situation at TMI (where there was no breach of containment) supported the suggestion, and analysis of Fukushima will be incomplete until the reactors are dismantled.

Certainly the matter was severely tested with three reactors of the Fukushima Daiichi nuclear power plant in Japan in March 2011. Cooling was lost about an hour after a shutdown, and it proved impossible to restore it sufficiently to prevent severe damage to the fuel. The reactors, dating from 1971-75, were written off. A fourth is also written off due to damage from a hydrogen explosion.

Achieving optimum nuclear safety

A fundamental principle of nuclear power plant operation worldwide is that the operator is responsible for safety. The national regulator is responsible for ensuring the plants are operated safely by the licensee, and that the design is approved. A second important concept is that a regulator's mission is to protect people and the environment.

Design certification of reactors is also the responsibility of national regulators. There is international collaboration among these to varying degrees, and there are a number of sets of mechanical codes and standards related to quality and safety.

With new reactor designs being established on a more international basis since the 1990s, both industry and regulators are seeking greater design standardisation and also regulatory harmonization. The role of the World Nuclear Association's CORDEL Working Group and the OECD/NEA's MDEP group are described in the Cooperation paper.

An OECD/NEA report in 2010 pointed out that the theoretically-calculated frequency for a large release of radioactivity from a severe nuclear power plant accident has reduced by a factor of 1600 between the early Generation I reactors as originally built and the Generation III/III+ plants being built today. Earlier designs however have been progressively upgraded through their operating lives.

It has long been asserted that nuclear reactor accidents are the epitome of low-probability but high-consequence risks. Understandably, with this in mind, some people were disinclined to accept the risk, however low the probability. However, the physics and chemistry of a reactor core, coupled with but not wholly depending on the engineering, mean that the consequences of an accident are likely in fact be much less severe than those from other industrial and energy sources. Experience, including Fukushima, bears this out.

A 2009 US Department of Energy (DOE) Human Performance Handbook notes: "The aviation industry, medical industry, commercial nuclear power industry, U.S. Navy, DOE and its contractors, and other high-risk, technologically complex organizations have adopted human performance principles, concepts, and practices to consciously reduce human error and bolster controls in order to reduce accidents and events." "About 80 percent of all events are attributed to human error. In some industries, this number is closer to 90 percent. Roughly 20 percent of events involve equipment failures. When the 80 percent human error is broken down further, it reveals that the majority of errors associated with events stem from latent organizational weaknesses (perpetrated by humans in the past that lie dormant in the system), whereas about 30 percent are caused by the individual worker touching the equipment and systems in the facility. Clearly, focusing efforts on reducing human error will reduce the likelihood of events." Following the Fukushima accident the focus has been on the organisational weaknesses which increase the likelihood of human error.

In passing, it is relevant to note that the safety record of the US nuclear navy from 1955 on is excellent, this being attributed to a high level of standardisation in over one hundred naval power plants and in their maintenance, and the high quality of the Navy's training program. Until the 1980s, the Soviet naval record stood in marked contrast.

Defence in depth

To achieve optimum safety, nuclear plants in the western world operate using a 'defence-in-depth' approach, with multiple safety systems supplementing the natural features of the reactor core. Key aspects of the approach are:

high-quality design & construction,

equipment which prevents operational disturbances or human failures and errors developing into problems,

comprehensive monitoring and regular testing to detect equipment or operator failures,

redundant and diverse systems to control damage to the fuel and prevent significant radioactive releases,

provision to confine the effects of severe fuel damage (or any other problem) to the plant itself.

These can be summed up as: Prevention, Monitoring, and Action (to mitigate consequences of failures).

The safety provisions include a series of physical barriers between the radioactive reactor core and the environment, the provision of multiple safety systems, each with backup and designed to accommodate human error. Safety systems account for about one quarter of the capital cost of such reactors. As well as the physical aspects of safety, there are institutional aspects which are no less important - see following section on International Collaboration.

The barriers in a typical plant are: the fuel is in the form of solid ceramic (UO2) pellets, and radioactive fission products remain largely bound inside these pellets as the fuel is burned. The pellets are packed inside sealed zirconium alloy tubes to form fuel rods. These are confined inside a large steel pressure vessel with walls up to 30 cm thick - the associated primary water cooling pipework is also substantial. All this, in turn, is enclosed inside a robust reinforced concrete containment structure with walls at least one metre thick. This amounts to three significant barriers around the fuel, which itself is stable up to very high temperatures.

These barriers are monitored continually. The fuel cladding is monitored by measuring the amount of radioactivity in the cooling water. The high pressure cooling system is monitored by the leak rate of water, and the containment structure by periodically measuring the leak rate of air at about five times atmospheric pressure.

Looked at functionally, the three basic safety functions in a nuclear reactor are:

to control reactivity,

to cool the fuel and

to contain radioactive substances.

The main safety features of most reactors are inherent - negative temperature coefficient and negative void coefficient. The first means that beyond an optimal level, as the temperature increases the efficiency of the reaction decreases (this in fact is used to control power levels in some new designs). The second means that if any steam has formed in the cooling water there is a decrease in moderating effect so that fewer neutrons are able to cause fission and the reaction slows down automatically.

In the 1950s and 1960s some experimental reactors in Idaho were deliberately tested to destruction to verify that large reactivity excursions were self-limiting and would automatically shut down the fission reaction. These tests verified that this was the case.

Beyond the control rods which are inserted to absorb neutrons and regulate the fission process, the main engineered safety provisions are the back-up emergency core cooling system (ECCS) to remove excess heat (though it is more to prevent damage to the plant than for public safety) and the containment.

Traditional reactor safety systems are 'active' in the sense that they involve electrical or mechanical operation on command. Some engineered systems operate passively, e.g. pressure relief valves. Both require parallel redundant systems. Inherent or full passive safety design depends only on physical phenomena such as convection, gravity or resistance to high temperatures, not on functioning of engineered components. All reactors have some elements of inherent safety as mentioned above, but in some recent designs the passive or inherent features substitute for active systems in cooling etc. Such a design would have averted the Fukushima accident, where loss of electrical power resulted is loss of cooling function.

The basis of design assumes a threat where due to accident or malign intent (e.g. terrorism) there is core melting and a breach of containment. This double possibility has been well studied and provides the basis of exclusion zones and contingency plans. Apparently during the Cold War neither Russia nor the USA targeted the other's nuclear power plants because the likely damage would be modest.

Nuclear power plants are designed with sensors to shut them down automatically in an earthquake, and this is a vital consideration in many parts of the world. (See Nuclear Power Plants and Earthquakes paper)

Severe accident management

In both the TMI and Fukushima accidents the problems started after the reactors were shut down - immediately at TMI and after an hour at Fukushima, when the tsunami arrived. The need to remove decay heat from the fuel was not met in each case, so core melting started to occur within a few hours. Cooling requires water circulation and an external heat sink. If pumps cannot run due to lack of power, gravity must be relied upon, but this will not get water into a pressurised system - either reactor pressure vessel or containment. Hence there is provision for relieving pressure, sometimes with a vent system, but this must work and be controlled without power. There is a question of filters or scrubbers in the vent system: these need to be such that they do not block due to solids being carried. Ideally any vent system should deal with any large amounts of hydrogen, as at Fukushima, and have minimum potential to spread radioactivity outside the plant. Filtered containment ventilation systems (FCVSs) are being retrofitted to some reactors which did not already have them, or any of sufficient capacity, following the Fukushima accident. The basic premise of a FCVS is that, independent of the state of the reactor itself, the catastrophic failure of the containment structure can be avoided by discharging steam, air and incondensable gases like hydrogen to the atmosphere.

The Three Mile Island accident in 1979 demonstrated the importance of the inherent safety features. Despite the fact that about half of the reactor core melted, radionuclides released from the melted fuel mostly plated out on the inside of the plant or dissolved in condensing steam. The containment building which housed the reactor further prevented any significant release of radioactivity. The accident was attributed to mechanical failure and operator confusion. The reactor's other protection systems also functioned as designed. The emergency core cooling system would have prevented any damage to the reactor but for the intervention of the operators.

Investigations following the accident led to a new focus on the human factors in nuclear safety. No major design changes were called for in western reactors, but controls and instrumentation were improved significantly and operator training was overhauled.

At Fukushima Daiichi in March 2011 the three operating reactors shut down automatically, and were being cooled as designed by the normal residual heat removal system using power from the back-up generators, until the tsunami swamped them an hour later. The emergency core cooling systems then failed. Days later, a separate problem emerged as spent fuel ponds lost water. Analysis of the accident showed the need for more intelligent siting criteria than those used in the 1960s, and the need for better back-up power and post-shutdown cooling, as well as provision for venting the containment of that kind of reactor and other emergency management procedures.

Nuclear plants have Severe Accident Mitigation Guidelines (SAMG, or in Japan: SAG), and most of these, including all those in the USA, address what should be done for accidents beyond design basis, and where several systems may be disabled. See section below.

In 2007 the US NRC launched a research program to assess the possible consequences of a serious reactor accident. Its draft report was released nearly a year after the Fukushima accident had partly confirmed its findings. The State-of-the-Art Reactor Consequences Analysis (SOARCA) showed that a severe accident at a US nuclear power plant (PWR or BWR) would not be likely to cause any immediate deaths, and the risks of fatal cancers would be vastly less than the general risks of cancer. SOARCA's main conclusions fall into three areas: how a reactor accident progresses; how existing systems and emergency measures can affect an accident's outcome; and how an accident would affect the public's health. The principal conclusion is that existing resources and procedures can stop an accident, slow it down or reduce its impact before it can affect the public, but even if accidents proceed without such mitigation they take much longer to happen and release much less radioactive material than earlier analyses suggested. This was borne out at Fukushima, where there was ample time for evacuation - three days - before any significant radioactive releases.

In 2015 the Canadian Nuclear Safety Commission (CNSC) released its Study of Consequences of a Hypothetical Severe Nuclear Accident and Effectiveness of Mitigation Measures. This was the result of research and analysis undertaken to address concerns raised during public hearings in 2012 on the environmental assessment for the refurbishment of Ontario Power Generation's (OPG's) Darlington nuclear power plant. The study involved identifying and modelling a large atmospheric release of radionuclides from a hypothetical severe nuclear accident at the four-unit Darlington power plant; estimating the doses to individuals at various distances from the plant, after factoring in protective actions such as evacuation that would be undertaken in response to such an emergency; and, finally, determining human health and environmental consequences due to the resulting radiation exposure. It concluded that there would be no detectable health effects or increase in cancer risk. A fuller write-up of it is on the World Nuclear News website.

A different safety philosophy: Early Soviet-designed reactors

The April 1986 disaster at the Chernobyl nuclear power plant in Ukraine was the result of major design deficiencies in the RBMK type of reactor, the violation of operating procedures and the absence of a safety culture. One peculiar feature of the RBMK design was that coolant failure could lead to a strong increase in power output from the fission process ( positive void coefficient). However, this was not the prime cause of the Chernobyl accident. It once and for all vindicated the desirability of designing with inherent safety supplemented by robust secondary safety provisions. By way of contrast to western safety engineering, the Chernobyl reactor did not have a containment structure like those used in the West or in post-1980 Soviet designs.

The accident destroyed the reactor, and its burning contents dispersed radionuclides far and wide. This tragically meant that the results were severe, with 56 people killed, 28 of whom died within weeks from radiation exposure. It also caused radiation sickness in a further 200-300 staff and firefighters, and contaminated large areas of Belarus, Ukraine, Russia and beyond. It is estimated that at least 5% of the total radioactive material in the Chernobyl 4 reactor core was released from the plant, due to the lack of any containment structure. Most of this was deposited as dust close by. Some was carried by wind over a wide area.

About 130,000 people received significant radiation doses ( i.e. above internationally accepted ICRP limits) and continue to be monitored. According to an UNSCEAR report in 2018, about 20,000 cases of thyroid cancer were diagnosed in 1991-2015 in patients who were 18 and under at the time of the accident. The report states that a quarter of the cases in 2001-2008 were "probably" due to high doses of radiation, and that this fraction was likely to have been higher in earlier years, and lower in later years. However, it also states that the uncertainty around the attributed fraction is very significant - at least 0.07 to 0.5 - and that the influence of annual screenings and active follow-up make comparisons with the general population problematic. Thyroid cancer is usually not fatal if diagnosed and treated early; the report states that of the diagnoses made between 1991 and 2005 (6,848 cases), 15 proved to be fatal. No increase in leukaemia or other cancers have yet shown up, but some is expected. The World Health Organization is closely monitoring most of those affected.

The Chernobyl accident was a unique event and the only time in the history of commercial nuclear power that radiation-related fatalities occurred. The main positive outcome of this accident for the industry was the formation of the World Association of Nuclear Operators (WANO), building on the US precedent.

The destroyed unit 4 was enclosed in a concrete shelter, which was replaced by a more permanent structure in 2017.

An OECD expert report on the accident concluded: "The Chernobyl accident has not brought to light any new, previously unknown phenomena or safety issues that are not resolved or otherwise covered by current reactor safety programs for commercial power reactors in OECD member countries." In other words, the concept of 'defence in depth' was conspicuous by its absence, and tragically shown to be vitally important.

Apart from the RBMK reactor design, an early Russian PWR design, the VVER-440/V-230, gave rise to concerns in Europe, and a program was initiated to close these down as a condition of EU accession, along with Lithuania's two RBMK units. See related papers on Early Soviet Reactors and EU Accession, and RBMK Reactors.

However, after the US Atomic Energy Commission published General Design Criteria for Nuclear Power Plants in 1971, Russian PWR designs conformed, according to Rosatom. In particular, the VVER-440/V-213 Loviisa reactors in Finland were designed at that time and modified to conform. The first of these two came on line in 1977.

A broader picture - other past accidents

There have been a number of accidents in experimental reactors and in one military plutonium-producing reactor, including a number of core melts, but none of these has resulted in loss of life outside the actual plant, or long-term environmental contamination. Elsewhere (Safety of Nuclear Power info paper appendix) we tabulate these, along with the most serious commercial plant accidents. The list of ten probably corresponds to incidents rating 4 or higher on today's International Nuclear Event Scale (Table 4). All except Browns Ferry and Vandellos involved damage to or malfunction of the reactor core. At Browns Ferry a fire damaged control cables and resulted in an 18-month shutdown for repairs; at Vandellos a turbine fire made the 17-year old plant uneconomic to repair.

Mention should be made of the accident to the US Fermi 1 prototype fast breeder reactor near Detroit in 1966. Due to a blockage in coolant flow, some of the fuel melted. However no radiation was released off-site and no-one was injured. The reactor was repaired and restarted but closed down in 1972.

The well-publicized criticality accident at Tokai Mura, Japan, in 1999 was at a fuel preparation plant for experimental reactors, and killed two workers from radiation exposure. Many other such criticality accidents have occurred, some fatal, and practically all in military facilities prior to 1980. A review of these is listed in the References.

In an uncontained reactor accident such as at Windscale (a military facility) in 1957 and at Chernobyl in 1986, (and to some extent: Fukushima in 2011,) the principal health hazard is from the spread of radioactive materials, notably volatile fission products such as iodine-131 and caesium-137. These are biologically active, so that if consumed in food, they tend to stay in organs of the body. I-131 has a half-life of 8 days, so is a hazard for around the first month, (and apparently gave rise to the thyroid cancers after the Chernobyl accident). Caesium-137 has a half-life of 30 years, and is therefore potentially a long-term contaminant of pastures and crops. In addition to these, there is caesium-134 which has a half-life of about two years. While measures can be taken to limit human uptake of I-131, (evacuation of area for several weeks, iodide tablets), high levels of radioactive caesium can preclude food production from affected land for a long time. Other radioactive materials in a reactor core have been shown to be less of a problem because they are either not volatile (strontium, transuranic elements) or not biologically active (tellurium-132, xenon-133).

Accidents in any field of technology provide valuable knowledge enabling incremental improvement in safety beyond the original engineering. Cars and airliners are the most obvious examples of this, but the chemical and oil industries can provide even stronger evidence. Civil nuclear power has greatly improved its safety in both engineering and operation over its 55 years of experience with very few accidents and major incidents to spur that improvement. The Fukushima Daiichi accident is the first since TMI in 1979 which will have significant implications, at least for older plants.

Scrams, Seismic shutdowns

A scram is a sudden reactor shutdown. When a reactor is scrammed, automatically due to seismic activity, or due to some malfunction, or manually for whatever reason, the fission reaction generating the main heat stops. However, considerable heat continues to be generated by the radioactive decay of the fission products in the fuel. Initially, for a few minutes, this is great - about 7% of the pre-scram level. But it drops to about 1% of the normal heat output after two hours, to 0.5% after one day, and 0.2% after a week. Even then it must still be cooled, but simply being immersed in a lot of water does most of the job after some time. When the water temperature is below 100°C at atmospheric pressure the reactor is said to be in "cold shutdown".

European 'stress tests' and US response following Fukushima accident

Aspects of nuclear plant safety highlighted by the Fukushima accident were assessed in the 143 nuclear reactors in the EU's 27 member states, as well as those in any neighbouring states that decided to take part. These comprehensive and transparent nuclear risk and safety assessments, the so-called "stress tests", involved targeted reassessment of each power reactor's safety margins in the light of extreme natural events, such as earthquakes and flooding, as well as on loss of safety functions and severe accident management following any initiating event. They were conducted from June 2011 to April 2012. They mobilized considerable expertise in different countries (500 man-years) under the responsibility of each national Safety Authority within the framework of the European Nuclear Safety Regulators Group (ENSREG).

The Western European Nuclear Regulators' Association (WENRA) proposed these in response to a call from the European Council in March 2011, and developed specifications. WENRA is a network of Chief Regulators of EU countries with nuclear power plants and Switzerland, and has membership from 17 countries. It then negotiated the scope of the tests with the European Nuclear Safety Regulators Group (ENSREG), an independent, authoritative expert body created in 2007 by the European Commission comprising senior officials from the national nuclear safety, radioactive waste safety or radiation protection regulatory authorities from all 27 EU member states, and representatives of the European Commission.

In June 2011 the governments of seven non-EU countries agreed to conduct nuclear reactor stress tests using the EU model. Armenia, Belarus, Croatia, Russia, Switzerland, Turkey and Ukraine signed a declaration that they would conduct stress tests and agreed to peer reviews of the tests by outside experts. Russia had already undertaken extensive checks. (Croatia is co-owner in the Krsko PWR in Slovenia, and Belarus and Turkey plan to build nuclear plants but have none now.)

The reassessment of safety margins is based on the existing safety studies and engineering judgment to evaluate the behaviour of a nuclear power plant when facing a set of challenging situations. For a given plant, the reassessment reports on the most probable behaviour of the plant for each of the situations considered. The results of the reassessment were peer-reviewed and shared among regulators. WENRA noted that it remains a national responsibility to take or order any appropriate measures, such as additional technical or organisational safety provisions, resulting from the reassessment.

The scope of the assessment took into account the issues directly highlighted by the events in Fukushima and the possibility for combination of initiating events. Two 'initiating events' were covered in the scope: earthquake and flooding. The consequences of these - loss of electrical power and station blackout, loss of ultimate heat sink and the combination of both - were analysed, with the conclusions being applicable to other general emergency situations. In accident scenarios, regulators consider power plants' means to protect against and manage loss of core cooling as well as cooling of used fuel in storage. They also study means to protect against and manage loss of containment integrity and core melting, including consequential effects such as hydrogen accumulation.

Nuclear plant operators start by documenting each power plant site. This analysis of 'extreme scenarios' followed what ENSREG called a progressive approach "in which protective measures are sequentially assumed to be defeated" from starting conditions which "represent the most unfavourable operational states." The operators have to explain their means to maintain "the three fundamental safety functions (control of reactivity, fuel cooling confinement of radioactivity)" and support functions for these, "taking into account the probable damage done by the initiating event."

The documents had to cover provisions in the plant design basis for these events and the strength of the plant beyond its design basis. This means the "design margins, diversity, redundancy, structural protection and physical separation of the safety relevant systems, structures and components and the effectiveness of the defence-in-depth concept." This had to focus on 'cliff-edge' effects, e.g. when back-up batteries are exhausted and station blackout is inevitable. For severe accident management scenarios they must identify the time before fuel damage is unavoidable and the time before water begins boiling in used fuel ponds and before fuel damage occurs. Measures to prevent hydrogen explosions and fires are to be part of this.

Since the licensee has the prime responsibility for safety, they performed the reassessments, and the regulatory bodies then independently reviewed them. The exercise covered 147 nuclear plants in 15 EU countries - including Lithuania with only decommissioned plants - plus 15 reactors in Ukraine and five in Switzerland.

Operators reported to their regulators who then reported progress to the European Commission by the end of 2011. Information was shared among regulators throughout this process before the 17 final reports went to peer-review by teams comprising 80 experts appointed by ENSREG and the European Commission. The final documents were published in line with national law and international obligations, subject only to not jeopardising security - an area where each country could behave differently. The process was extended to June 2012 to allow more plant visits and to add more information on the potential effect of aircraft impacts.

The European Commission adopted, with ENSREG, the final stress tests Report on April 26, 2012 and issued the same day a joint statement underlining the quality of the exercise. The full report and a summary of the 45 recommendations were published on www.ensreg.eu. Drawing on the peer reviews, the EC and ENSREG cited four main areas for improving EU nuclear plant safety:

Guidance from WENRA for assessing natural hazards and margins beyond design basis.

Giving more importance to periodic safety reviews and evaluation of natural hazards.

Urgent measures to protect containment integrity.

Measures to prevent and mitigate accidents resulting from extreme natural hazards.

The results of the stress tests pointed out, in particular, that European nuclear power plants offered a sufficient safety level to require no shutdown of any of them. At the same time, improvements were needed to enhance their robustness to extreme situations. In France, for instance, they were imposed by ASN requirements, which took into account exchanges with its European counterparts. A follow-up European action plan was established by ENSREG from July 2012.

The EU process was completed at the end of September 2012, with the EU Energy Commissioner announcing that the stress tests had showed that the safety of European power reactors was generally satisfactory, but making some other comments and projections which departed from ENSREG. An EC report was presented to the EU Council in October 2012.

In the USA the Nuclear Regulatory Commission (NRC) in March 2012 made orders for immediate post-Fukushima safety enhancements, likely to cost about $100 million across the whole US fleet. The first order requires the addition of equipment at all plants to help respond to the loss of all electrical power and the loss of the ultimate heat sink for cooling, as well as maintaining containment integrity. Another requires improved water level and temperature instrumentation on used fuel ponds. The third order applies only to the 33 BWRs with early containment designs, and will require 'reliable hardened containment vents' which work under any circumstances. The industry association, NEI, told the NRC that licensees with these Mark I and Mark II containments "should have the capability to use various filtration strategies to mitigate radiological releases" during severe events, and that filtration "should be founded on scientific and factual analysis and should be performance-based to achieve the desired outcome." All the measures are supported by the industry association, which has also proposed setting up about six regional emergency response centres under NRC oversight with additional portable equipment.

In Japan similar stress tests were carried out in 2011 under the previous safety regulator, but then reactor restarts were delayed until the newly constituted Nuclear Regulatory Authority devised and published new safety guidelines, then applied them progressively through the fleet.

Severe Accident Management

In addition to engineering and procedures which reduce the risk and severity of accidents, all plants have guidelines for Severe Accident Management or Mitigation (SAM). These conspicuously came into play after the Fukushima accident, where staff had immense challenges in the absence of power and with disabled cooling systems following damage done by the tsunami. The experience following that accident is being applied not only in design but also in such guidelines, and peer reviews on nuclear plants will focus more on these than previously.

In mid-2011 the IAEA Incident and Emergency Centre launched a new secure web-based communications platform to unify and simplify information exchange during nuclear or radiological emergencies. The Unified System for Information Exchange on Incidents and Emergencies (USIE) has been under development since 2009 but was actually launched during the emergency response to the accident at Fukushima.

Earthquakes and Volcanoes

The International Atomic Energy Agency (IAEA) has a Safety Guide on Seismic Risks for Nuclear Power Plants, and the matter is dealt with in the WNA paper on Earthquakes and Nuclear Power Plants. Volcanic hazards are minimal for practically all nuclear plants, but the IAEA has developed a new Safety Guide on the matter. The Bataan plant in Philippines which has never operated, and the Armenian plant at Metsamor are two known to be in proximity to potential volcanic activity.

Flooding - storms, tides and tsunamis

Nuclear plants are usually built close to water bodies, for the sake of cooling. The site licence takes account of worst case flooding scenarios as well as other possible natural disasters and, more recently, the possible effects of climate change. As a result, all the buildings with safety-related equipment are situated on high enough platforms so that they stand above submerged areas in case of flooding events. As an example, French Safety Rules criteria for river sites define the safe level as above a flood level likely to be reached with one chance in one thousand years, plus 15%, and similar regarding tides for coastal sites.

Occasionally in the past some buildings have been sited too low, so that they are vulnerable to flood or tidal and storm surge, so engineered countermeasures have been built. EDF's Blayais nuclear plant in western France uses seawater for cooling and the plant itself is protected from storm surge by dykes. However, in 1999 a 2.5 m storm surge in the estuary overtopped the dykes - which were already identified as a weak point and scheduled for a later upgrade - and flooded one pumping station. For security reasons it was decided to shut down the three reactors then under power (the fourth was already stopped in the course of normal maintenance). This incident was rated 2 on the INES scale.

In 1994 the Kakrapar nuclear power plant near the west coast of India was flooded due to heavy rains together with failure of weir control for an adjoining water pond, inundating turbine building basement equipment. The back-up diesel generators on site enabled core cooling using fire water, a backup to process water, since the offsite power supply failed. Following this, multiple flood barriers were provided at all entry points, inlet openings below design flood level were sealed and emergency operating procedures were updated. In December 2004 the Madras NPP and Kalpakkam PFBR site on the east coast of India was flooded by a tsunami surge from Sumatra. Construction of the Kalpakkam plant was just beginning, but the Madras plant shut down safely and maintained cooling. However, recommendations including early warning system for tsunami and provision of additional cooling water sources for longer duration cooling were implemented.

In March 2011 the Fukushima Daiichi nuclear plant was affected seriously by a huge tsunami induced by the Great East Japan Earthquake. Three of the six reactors were operating at the time, and had shut down automatically due to the earthquake. The back-up diesel generators for those three units were then swamped by the tsunami. This cut power supply and led to weeks of drama and loss of the reactors. The design basis tsunami height was 5.7 m for Daiichi (and 5.2 m for adjacent Daini, which was actually set a bit higher above sea level). Tsunami heights coming ashore were about 14 metres for both plants. Unit 3 of Daini was undamaged and continued to cold shutdown status, but the other units suffered flooding to pump rooms where equipment transfers heat from the reactor circuit to the sea - the ultimate heat sink.

The maximum amplitude of this tsunami was 23 metres at point of origin, about 160 km from Fukushima. In the last century there had been eight tsunamis in the Japan region with maximum amplitudes above 10 metres (some much more), these having arisen from earthquakes of magnitude 7.7 to 8.4, on average one every 12 years. Those in 1983 and in 1993 were the most recent affecting Japan, with maximum heights 14.5 metres and 31 metres respectively, both induced by magnitude 7.7 earthquakes. This 2011 earthquake was magnitude 9.

For low-lying sites, civil engineering and other measures are normally taken to make nuclear plants resistant to flooding. Lessons from Blayais have fed into regulatory criteria since 2000, and those from Fukushima will certainly do so. Sea walls are being built or increased at Hamaoka, Shimane, Mihama, Ohi, Takahama, Onagawa, and Higashidori plants. However, few parts of the world have the same tsunami potential as Japan, and for the Atlantic and Mediterranean coasts of Europe the maximum amplitude is much less than Japan.

Hydrogen

In any light-water nuclear power reactor, hydrogen is formed by radiolytic decomposition of water. This needs to be dealt with to avoid the potential for explosion with oxygen present, and many reactors have been retrofitted with passive autocatalytic hydrogen recombiners in their containment, replacing external recombiners that needed to be connected and powered, isolated behind radiological barriers. Also in some kinds of reactors, particularly early boiling water types, the containment is rendered inert by injection of nitrogen. It was reported that WANO may require all operators to have hydrogen recombiners in PWRs. As of early 2012, a few in Spain and Japan did not have them.

In an accident situation such as at Fukushima where the fuel became very hot, a lot of hydrogen is formed by the oxidation of zirconium fuel cladding in steam at about 1300°C. This is beyond the capability of the normal hydrogen recombiners to deal with, and operators must rely on venting to atmosphere or inerting the containment with nitrogen.

International collaboration to improve safety

There is a lot of international collaboration, but it has evolved from the bottom, and only in 1990s has there been any real top-down initiative. In the aviation industry the Chicago Convention in the late 1940s initiated an international approach which brought about a high degree of design collaboration between countries, and the rapid universal uptake of lessons from accidents. There are cultural and political reasons for this which mean that even the much higher international safety collaboration since the 1990s is still less than in aviation. See also: paper on Cooperation in Nuclear Power Industry, especially for fuller description of WANO, focused on operation.

World Association of Nuclear Operators

There is a great deal of international cooperation on nuclear safety issues, in particular the exchange of operating experience under the auspices of the World Association of Nuclear Operators ( WANO) which was set up in 1989. In practical terms this is the most effective international means of achieving very high levels of safety through its four major programs: peer reviews; operating experience; technical support and exchange; and professional and technical development. WANO peer reviews are the main proactive way of sharing experience and expertise, and by the end of 2009 every one of the world's commercial nuclear power plants had been peer-reviewed at least once. Following the Fukushima accident these have been stepped up to one every four years at each plant, with follow-up visits in between, and the scope extended from operational safety to include plant design upgrades. Pre-startup reviews of new plants are being increased.

IAEA Convention on Nuclear Safety

The IAEA Convention on Nuclear Safety (CNS) was drawn up during a series of expert level meetings from 1992 to 1994 and was the result of considerable work by Governments, national nuclear safety authorities and the IAEA Secretariat. Its aim is to legally commit participating States operating land-based nuclear power plants to maintain a high level of safety by setting international benchmarks to which States would subscribe.

The obligations of the Parties are based to a large extent on the principles contained in the IAEA Safety Fundamentals document The Safety of Nuclear Installations. These obligations cover for instance, siting, design, construction, operation, the availability of adequate financial and human resources, the assessment and verification of safety, quality assurance and emergency preparedness.

The Convention is an incentive instrument. It is not designed to ensure fulfilment of obligations by Parties through control and sanction, but is based on their common interest to achieve higher levels of safety. These levels are defined by international benchmarks developed and promoted through regular meetings of the Parties. The Convention obliges Parties to report on the implementation of their obligations for international peer review. This mechanism is the main innovative and dynamic element of the Convention. Under the Operational Safety Review Team (OSART) program dating from 1982 international teams of experts conduct in-depth reviews of operational safety performance at a nuclear power plant. They review emergency planning, safety culture, radiation protection, and other areas. OSART missions are on request from the government, and involve staff from regulators, in these respects differing from WANO peer reviews.

The Convention entered into force in October 1996. As of September 2009, there were 79 signatories to the Convention, 66 of which are contracting parties, including all countries with operating nuclear power plants.

The IAEA General Conference in September 2011 unanimously endorsed the Action Plan on Nuclear Safety that Ministers requested in June. The plan arose from intensive consultations with Member States but not with industry, and was described as both a rallying point and a blueprint for strengthening nuclear safety worldwide. It contains suggestions to make nuclear safety more robust and effective than before, without removing the responsibility from national bodies and governments. It aims to ensure "adequate responses based on scientific knowledge and full transparency". Apart from strengthened and more frequent IAEA peer reviews (including those of regulatory systems), most of the 12 recommended actions are to be undertaken by individual countries and are likely to be well in hand already.

Following this, an extraordinary general meeting of 64 of the CNS parties in September 2012 gave a strong push to international collaboration in improving safety. National reports at future three-yearly CNS review meetings will cover a list of specific design, operational and organizational issues stemming from Fukushima lessons. They include further design features to avoid long-term offsite contamination and enhancement of emergency preparedness and response measures, including better definition of national responsibilities and improved international cooperation. Parties should also report on measures to "ensure the effective independence of the regulatory body from undue influence."

In February 2015 diplomats from 72 countries unanimously adopted the Vienna Declaration of Nuclear Safety, setting out "principles to guide them, as appropriate, in the implementation of the objective of the CNS to prevent accidents with radiological consequences and mitigate such consequences should they occur" but rejected Swiss amendments to the CNS as impractical. However, in line with Swiss and EU intentions, "comprehensive and systematic safety assessments are to be carried out periodically and regularly for existing installations throughout their lifetime in order to identify safety improvements... Reasonably practicable or achievable safety improvements are to be implemented in a timely manner."

IAEA Design Safety Reviews and Generic Reactor Safety Reviews

An IAEA Design Safety Review (DSR) is performed at the request of a member state organization to evaluate the completeness and comprehensiveness of a reactor's safety documentation by an international team of senior experts. It is based on IAEA published safety requirements. If the DSR is for a vendor's design at the pre-licensing stage, it is done using the Generic Reactor Safety Review (GRSR) module. IAEA Safety Standards applied in the DSR and GRSR at the fundamental and requirements level, are generic and apply to all nuclear installations. Therefore, it is neither intended nor possible to cover or substitute licensing activity, or to constitute any kind of design certification.

DSRs have been undertaken in Pakistan, Ukraine, Bulgaria and Armenia. GRSRs have been done on AP1000 (USA & UK), Atmea1, APR1400, ACPR-1000+, ACP1000, and AES-2006 and VVER-TOI.

Eastern Europe from 1980s

In relation to Eastern Europe particularly, since the late 1980s a major international program of assistance was carried out by the OECD, IAEA and Commission of the European Communities to bring early Soviet-designed reactors up to near western safety standards, or at least to effect significant improvements to the plants and their operation. The European Union also brought pressure to bear, particularly in countries which aspired to EU membership.

Modifications were made to overcome deficiencies in the 11 RBMK reactors still operating at the time in Russia. Among other things, these removed the danger of a positive void coefficient response. Automated inspection equipment has also been installed in these reactors.

The other class of reactors which has been the focus of international attention for safety upgrades is the first-generation of pressurised water VVER-440 reactors. The V-230 model was designed before formal safety standards were issued in the Soviet Union and they lack many basic safety features. Four are still operating in Russia and one in Armenia, under close inspection.

Later Soviet-designed reactors are very much safer and have Western control systems or the equivalent, along with containment structures.

Europe since 1999

The main European safety collaboration is through the European Nuclear Safety Regulators Group ( ENSREG), an independent, authoritative expert body created in 2007 by the European Commission to revive the EU nuclear safety directive, which was passed in June 2009. It comprises senior officials from the national nuclear safety, radioactive waste safety or radiation protection regulatory authorities from all 27 EU member states, and representatives of the European Commission. It was preceded in 1999 by the Western European Nuclear Regulators' Association ( WENRA), a network of Chief Regulators of EU countries with nuclear power plants and Switzerland, with membership from 17 countries.

Ageing of nuclear plants; knowledge management

Engineering

Several issues arise in prolonging the lives of nuclear plants which were originally designed for nominal 30- or 40-year operating lives. Systems, structures and components (SSC) whose characteristics change gradually with time or use are the subject of attention, which is applied with vastly greater scientific and technical knowledge than that available to the original designers many decades ago.

Some components simply wear out, corrode or degrade to a low level of efficiency. These need to be replaced. Steam generators are the most prominent and expensive of these, and many have been replaced after about 30 years where the reactor otherwise has the prospect of running for 60 years. This is essentially an economic decision. Lesser components are more straightforward to replace as they age, and some may be safety-related as well as economic.

In PHWR units, notably CANDU reactors, pressure tube replacement has been undertaken on some older plants, after some 30 years of operation. Fuel channel integrity is another limiting factor for Candu reactors, and mid-life inspection and analysis can extend the original 175,000 full-power operating hours design assumption to 300,000 hours.

A second issue is that of obsolescence. For instance, older reactors have analogue instrument and control systems, and a question must be faced regarding whether these are replaced with digital in a major mid-life overhaul, or simply maintained.

Thirdly, the properties of materials may degrade with age, particularly with heat and neutron irradiation. In some early Russian pressurized water reactors, the pressure vessel is relatively narrow and is thus subject to greater neutron bombardment that a wider one. This raises questions of embrittlement, and has had to be checked carefully before extending licences.

In some Russian and UK plants (RBMK, AGR), graphite is used as the moderator. The graphite blocks cannot be replaced during the operating life of the reactors. However, radiation damage changes the shape and size of the crystallites that comprise graphite, giving some dimensional change and degradation of the structural properties of the graphite. For continued operation, it is therefore necessary to demonstrate that the graphite can still perform its intended role irrespective of the degradation, or undergo some repair. In Russia, after dismantling the pressure tubes, longitudinal cutting of a limited number of deformed graphite columns returns the graphite stack geometry to a condition that meets the initial design requirements. Leningrad 1 was the first RBMK reactor to undergo this over 2012-13.

In respect to all these aspects, periodic safety reviews are undertaken on most older plants in line with the IAEA safety convention and WANO's safety culture principles to ensure that safety margins are maintained. The IAEA undertakes Safety Aspects of Long-Term Operation (SALTO) evaluations of reactors on request from member countries. These SALTO missions check both physical and organizational aspects, and function as an international peer review of the national regulator. They are backed up by the IAEA International Generic Ageing Lessons Learned (IGALL) program which is documented in databases and publications, in the form of downloadable safety guides and reports on ageing.

Equipment performance is constantly monitored to identify faults and failures of components. Preventative maintenance is adapted and scheduled in the light of this, to ensure that the overall availability of systems important for both safety and plant availability are within the design basis, or better than the original design basis. Collecting reliability and performance data is of the utmost importance, as well as analysing them, for tracking indicators that might be signs of ageing, or indicative of potential problems having been under-estimated, or of new problems. The results of this monitoring and analysis are often shared Industry-wide through INPO and WANO networks. The use of probabilistic safety analysis makes possible risk-informed decisions regarding maintenance and monitoring programs, so that adequate attention is given to the health of every piece of equipment in the plant. This process is similar to that in other industries where safety is paramount, e.g. aviation. Reliability Centered Maintenance was adapted from civil aviation in the 1980s for instance, and led to nuclear industry review of existing maintenance programs.

In the USA most of the one hundred reactors are expected to be granted licence extensions from 40 to 60 years. This justifies significant capital expenditure in upgrading systems and components, including building in extra performance margins. There is widespread agreement that further extensions may be justified, to 80 years, and this prospect is driving research on ageing to ensure both safety and reliability in older plants.

Knowledge management

The IAEA has a safety knowledge base for ageing and long-term operation of nuclear power plants (SKALTO) which aims to develop a framework for sharing information on ageing management and long term operation of nuclear power plants. It provides published documents and information related to this.

Knowledge management in relation to the original design basis of reactors becomes an issue with corporate reorganisation or demise of vendors, coupled with changes made over several decades. While operators usually have good records, some regulators do not. Design Basis Knowledge Management (DKM) is an issue receiving a lot of attention in the last ten years or so.

Nuclear DKM addresses the specific needs of nuclear plants and organizations. Its scope extends from research and development, through design and engineering, construction, commissioning, operations, maintenance, refurbishment and long-term operation (LTO), waste management, to decommissioning. Nuclear DKM issues and priorities are often unique to the particular circumstances of individual countries and their regulators as well as other nuclear industry organizations. Nuclear DKM may focus on knowledge creation, identification, sharing, transfer, protection, validation, storage, dissemination, preservation or utilization. Nuclear DKM practices may enhance and support traditional business functions and goals such as human resource management, training, planning, operations, maintenance, and much more.

There must always be a responsible owner of the DKM system for any plant. In most cases this will be the operator, however, based on a variety of changes such as market conditions, the responsible owner may change over time. An effective nuclear DKM system should be focused on strengthening and aligning the knowledge base in three primary knowledge domains in an organization: people, processes and technology, each of which must also be considered within the context of the organizational culture. Knowledge management policies and practices should help create a supportive organizational culture that recognizes the value of nuclear knowledge and promotes effective processes to maintain it.

In Canada, the Pickering A - Bruce A saga is a cautionary tale (and classic industry case study) regarding DKM. By the mid-1990s there was a divergence between drawings and modifications which had progressively been made, and also the operating company had not shared operating experience with the designer. Maintenance standards fell and costs rose. A detailed audit in 1997-98 showed that the design basis was not being maintained and that 4000 additional staff would be required to correct the situation at all Ontario Hydro plants, so the two A plants (eight units) were shut down so that staff could focus on the 12 units not needing so much attention. From 2003, six of the eight A units were returned to service with design basis corrected, having been shut down for several years - a significant loss of asset base for the owners.

Reporting nuclear incidents

The International Nuclear Event Scale (INES) was developed by the IAEA and OECD in 1990 to communicate and standardise the reporting of nuclear incidents or accidents to the public. The scale runs from a zero event with no safety significance to 7 for a "major accident" such as Chernobyl. TMI rated 5, as an "accident with off-site risks" though no harm to anyone, and a level 4 "accident mainly in installation" occurred in France in 1980, with little drama. Another accident rated at level 4 occurred in a fuel processing plant in Japan in September 1999. Other accidents have been in military plants .

The International Nuclear Event Scale
For prompt communication of safety significance

Level, Descriptor

Off-Site Impact, release of radioactive materials

On-Site Impact

Defence-in-Depth Degradation

Examples

Major Release:
Widespread health and environmental effects

Chernobyl, Ukraine, 1986 (fuel meltdown and fire);
Fukushima Daiichi 1-3, 2011 (fuel damage, radiation release and evacuation)

Significant Release:
Full implementation of local emergency plans

Mayak at Ozersk, Russia, 1957 'Kyshtym' (reprocessing plant criticality)

Limited Release:
Partial implementation of local emergency plans, or

Severe damage to reactor core or to radiological barriers

Three Mile Island, USA, 1979 (fuel melting);
Windscale, UK, 1957 (military)

4
Accident Mainly in Installation, with local consequences.
either of:

Minor Release:
Public exposure of the order of prescribed limits, or

Significant damage to reactor core or to radiological barriers; worker fatality

Saint-Laurent A1, France, 1969 (fuel rupture) & A2 1980 (graphite overheating);
Tokai-mura, Japan, 1999 (criticality in fuel plant for an experimental reactor).

Very Small Release:
Public exposure at a fraction of prescribed limits, or

Major contamination; Acute health effects to a worker, or

Near Accident:
Loss of Defence in Depth provisions - no safety layers remaining

Fukushima Daiichi 4, 2011 (fuel pond overheating);
Fukushima Daini 1, 2, 4, 2011 (interruption to cooling);
Vandellos, Spain, 1989 (turbine fire);
Davis-Besse, USA, 2002 (severe corrosion);
Paks, Hungary 2003 (fuel damage)

nil

Significant spread of contamination; Overexposure of worker, or

Incidents with significant failures in safety provisions

nil

nil

Anomaly beyond authorised operating regime

Source: International Atomic Energy Agency

Security - terrorism, etc.

Since the World Trade Centre attacks in New York in 2001 there has been increased concern about the consequences of a large aircraft being used to attack a nuclear facility with the purpose of releasing radioactive materials. Various studies have looked at similar attacks on nuclear power plants. They show that nuclear reactors would be more resistant to such attacks than virtually any other civil installations - see Appendix 3. A thorough study was undertaken by the US Electric Power Research Institute (EPRI) using specialist consultants and paid for by the US Dept. of Energy. It concludes that US reactor structures "are robust and (would) protect the fuel from impacts of large commercial aircraft".

The analyses used a fully-fuelled Boeing 767-400 of over 200 tonnes as the basis, at 560 km/h - the maximum speed for precision flying near the ground. The wingspan is greater than the diameter of reactor containment buildings and the 4.3 tonne engines are 15 metres apart. Hence analyses focused on single engine direct impact on the centreline - since this would be the most penetrating missile - and on the impact of the entire aircraft if the fuselage hit the centreline (in which case the engines would ricochet off the sides). In each case no part of the aircraft or its fuel would penetrate the containment. Other studies have confirmed these findings.

Penetrating (even relatively weak) reinforced concrete requires multiple hits by high speed artillery shells or specially-designed "bunker busting" ordnance - both of which are well beyond what terrorists are likely to deploy. Thin-walled, slow-moving, hollow aluminum aircraft, hitting containment-grade heavily-reinforced concrete disintegrate, with negligible penetration. But further (see Sept 2002 Science paper and Jan 2003 Response & Comments), realistic assessments from decades of analyses, lab work and testing, find that the consequence of even the worst realistic scenarios - core melting and containment failure - can cause few if any deaths to the public, regardless of the scenario that led to the core melt and containment failure. This conclusion was documented in a 1981 EPRI study, reported and widely circulated in many languages, by Levenson and Rahn in Nuclear Technology.

In 1988 Sandia National Laboratories in USA demonstrated the unequal distribution of energy absorption that occurs when an aircraft impacts a massive, hardened target. The test involved a rocket-propelled F4 Phantom jet (about 27 tonnes, with both engines close together in the fuselage) hitting a 3.7m thick slab of concrete at 765 km/h. This was to see whether a proposed Japanese nuclear power plant could withstand the impact of a heavy aircraft. It showed how most of the collision energy goes into the destruction of the aircraft itself - about 96% of the aircraft's kinetic energy went into the its destruction and some penetration of the concrete - while the remaining 4% was dissipated in accelerating the 700-tonne slab. The maximum penetration of the concrete in this experiment was 60 mm, but comparison with fixed reactor containment needs to take account of the 4% of energy transmitted to the slab. See also video clip.

As long ago as the late 1970s, the UK Central Electricity Generating Board considered the possibility of a fully-laden and fully-fuelled large passenger aircraft being hijacked and deliberately crashed into a nuclear reactor. The main conclusions were that an airliner would tend to break up as it hit various buildings such as the reactor hall, and that those pieces would have little effect on the concrete biological shield surrounding the reactor. Any kerosene fire would also have little effect on that shield. In the 1980s in the USA, at least some plants were designed to take a hit from a fully-laden large military transport aircraft and still be able to achieve and maintain cold shutdown.

The study of a 1970s US power plant in a highly-populated area is assessing the possible effects of a successful terrorist attack which causes both meltdown of the core and a large breach in the containment structure - both extremely unlikely. It shows that a large fraction of the most hazardous radioactive isotopes, like those of iodine and tellurium, would never leave the site.

Much of the radioactive material would stick to surfaces inside the containment or becomes soluble salts that remain in the damaged containment building. Some radioactive material would nonetheless enter the environment some hours after the attack in this extreme scenario and affect areas up to several kilometres away. The extent and timing of this means that with walking-pace evacuation inside this radius it would not be a major health risk. However it could leave areas contaminated and hence displace people in the same way as a natural disaster, giving rise to economic rather than health consequences.

Looking at spent fuel storage pools, similar analyses showed no breach. Dry storage and transport casks retained their integrity. "There would be no release of radionuclides to the environment".

Similarly, the massive structures mean that any terrorist attack even inside a plant (which are well defended) and causing loss of cooling, core melting and breach of containment would not result in any significant radioactive releases.

However, while the main structures are robust, the 2001 attacks did lead to increased security requirements and plants were required by NRC to install barriers, bulletproof security stations and other physical modifications which in the USA are estimated by the industry association to have cost some $2 billion across the country.

See also Science magazine article 2002 and Appendix 3.

Switzerland's Nuclear Safety Inspectorate studied a similar scenario and reported in 2003 that the danger of any radiation release from such a crash would be low for the older plants and extremely low for the newer ones.

The conservative design criteria which caused most power reactors to be shrouded by massive containment structures with biological shield has provided peace of mind in a suicide terrorist context. Ironically and as noted earlier, with better understanding of what happens in a core melt accident inside, they are now seen to be not nearly as necessary in that accident mitigation role as was originally assumed.

Advanced reactor designs

The designs for nuclear plants being developed for implementation in coming decades contain numerous safety improvements based on operational experience. The first two of these advanced reactors began operating in Japan in 1996.

One major feature they have in common (beyond safety engineering already standard in Western reactors) is passive safety systems, requiring no operator intervention in the event of a major malfunction.

The main metric used to assess reactor safety is the likelihood of the core melting due to loss of coolant. These new designs are one or two orders of magnitude less likely than older ones to suffer a core melt accident, but the significance of that is more for the owner and operator than the neighbours, who - as TMI and Fukushima showed - are safe also with older types. (As mentioned in the box above, studies related to the 1970s plant in USA show that even with a breach of containment as well, the consequences would not be catastrophic.)

Safety relative to other energy sources

Many occupational accident statistics have been generated over the last 40 years of nuclear reactor operations in the US and UK. These can be compared with those from coal-fired power generation. All show that nuclear is a distinctly safer way to produce electricity.
Deaths from energy-related accidents per unit of electricity Source: Paul Scherrer Institut 1998, considering 1943 accidents with more than five fatalities. One TW.yr is the amount of electricity used by the world in about five months.
Coal-fired power generation has chronic, rather than acute, safety implications for public health. It also has profound safety implications for the mining of coal, with thousands of workers killed each year in coal mines (see Appendix).

Hydro power generation has a record of few but very major events causing thousands of deaths. In 1975 when the Banqiao, Shimantan & other dams collapsed in Henan, China, at least 30,000 people were killed immediately and some 230,000 overall, with 18 GWe lost. In 1979 and 1980 in India some 3500 were killed by two hydro-electric dam failures, and in 2009 in Russia 75 were killed by a hydro power plant turbine disintegration. Early in 2017 nearly 200,000 people were evacuated due to the potential failure of the Oroville Dam in California.

Three simple sets of figures are quoted in the Tables below and that in the appendix. A major reason for coal's unfavourable showing is the huge amount which must be mined and transported to supply even a single large power station. Mining and multiple handling of so much material of any kind involves hazards, and these are reflected in the statistics.
Summary of severe* accidents in energy chains for electricity 1969-2000 Data from Paul Scherrer Institut, in OECD 2010. * severe = more than five fatalities
Comparison of accident statistics in primary energy production
(Electricity generation accounts for about 40% of total primary energy)
* Basis: per million MWe operating for one year, not including plant construction, based on historic data which is unlikely to represent current safety levels in any of the industries concerned.
Sources: Sources: Ball, Roberts & Simpson, 1994; Hirschberg et al, Paul Scherrer Institut 1996, in: IAEA 1997; Paul Scherrer Institut, 2001.
In the UK, Friends of the Earth commissioned a study by the Tyndall Centre, which drew primarily on peer-reviewed academic literature, supplemented by literature from credible government, consultancy and policy sources. It concluded in January 2013 that "Overall the safety risks associated with nuclear power appear to be more in line with lifecycle impacts from renewable energy technologies, and significantly lower than for coal and natural gas per MWh of supplied energy."

Notes & references

General sources

Ball, Roberts & Simpson, Research Report #20, Centre for Environmental & Risk Management, University of East Anglia, 1994
IAEA 2005, Chernobyl Forum report: Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts
IAEA 1997, Sustainable Development and Nuclear Power
Paul Scherrer Institut 2001, Severe Accidents in the Energy Sector
Twilley R C, Framatome ANP's SWR1000 reactor design, Nuclear News, Sept 2002
EPRI Dec 2002 report Deterring Terrorism: Aircraft Crash Impact Analyses Demonstrate Nuclear Power Plant's Structural Strength on NEI website
Chapin D.M., Levenson M., Pate Z.P., Rockwell T et al 2002, Nuclear Power Plants and their Fuel as terrorist Targets, Science, Sept 2002; with Letters & Response, Science 10 Jan 2003
Levenson, M. & Rahn, F. 1981, Realistic Estimates of the Consequences of Nuclear Accidents, Nuclear Technology 53:99-110, ANS, May 1981
Stoiber, Carl 2007, World Nuclear University Summer Institute
OECD Nuclear Energy Agency 2010, Comparing Nuclear Accident Risks with those from other energy sources. NEA No. 6861
Tyndall Centre report commissioned by Friends of the Earth, Jan 2013
Los Alamos report, 2000, A Review of Criticality Accidents, LA-1363
United Nations Scientific Committee on the Effects of Atomic Radiation, Evaluation of Data on Thyroid Cancer in Regions Affected by the Chernobyl Accident, A white paper to guide the Scientific Committee's future programme of work, 2018

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Safety of Nuclear Reactors - World Nuclear Association

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Safety of Nuclear Power Reactors. The risks from western nuclear power plants, in terms of the consequences of an accident or terrorist attack, are minimal compared with other commonly accepted risks. Nuclear power plants are very robust.

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Fact- Spent or used Uranium can be reprocessed or recycled and used again for energy production.

Approximately 97%[Of Nuclear Waste] – the vast majority (~94%) being uranium – of it could be used as fuel in certain types of reactor." (World Nuclear Association)

Spent nuclear fuel can be recycled to make new fuel and byproducts. More than 90% of its potential energy still remains in the fuel, even after five years of operation in a reactor. The United States does not currently recycle spent nuclear fuel but foreign countries, such as France, do. (Office of Nulcear Energy)

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1. Commercial spent nuclear fuel is a solid

Spent fuel refers to the nuclear fuel that has been used in a reactor.

The fuel used in today's commercial reactors is made up of small ceramic pellets of low-enriched uranium oxide. The fuel pellets are stacked vertically and encased in a metallic cladding to form a fuel rod. These fuel rods are bundled together into tall fuel assemblies that are then placed into the reactor.

The fuel is a solid when it goes into the reactor and a solid when it comes out.

Sorry "Simpsons."

2. The U.S. generates about 2,000 metric tons of spent fuel each year

This number may sound like a lot, but the volume of the spent fuel assemblies is actually quite small considering the amount of energy they produce.

The amount is roughly equivalent to less than half the volume of an Olympic-sized swimming pool.

And, the clean energy generated from this fuel would be enough to power more than 70 million homes -avoiding more than 400 million metrics tons of carbon dioxide emissions.

If we take that a step further, U.S. commercial reactors have generated about 90,000 metric tons of spent fuel since the 1950s. If all of it were able to be stacked together, it could fit on a single football field at a depth of less than 10 yards.

The nation's spent nuclear fuel is initially stored in steel-lined concrete pools surrounded by water. It's later removed from the pools and placed into dry storage casks that are made of steel and concrete or other materials used for protective shielding.

3. Spent fuel from U.S. commercial nuclear power reactors is stored at more than 70 sites in 35 states

Most of the nation's spent fuel is safely and securely stored  at more than 70 reactor sites across the country. Roughly a quarter of these sites no longer have a reactor in operation.

The U.S. Department of Energy is now exploring the possibility of consolidating this spent nuclear fuel at one or more federal interim storage facilities using a consent-based siting process.

For the foreseeable future, the spent fuel can safely stay at the reactor sites or a future consolidated interim storage facility until a permanent disposal solution is determined by the federal government.

4. Spent fuel is safely transported across the United States

Over the last 55 years,  more than 2,500 cask shipments  of spent fuel have been transported across the United States without any radiological releases to the environment or harm to the public.

The fuel is shipped in transportation casks that are designed to withstand more than 99 percent of vehicle accidents, including water immersion, impact, punctures and fires.

5. Spent fuel can be recycled

That's right!

Spent nuclear fuel can be recycled to make new fuel and byproducts.

More than 90% of its potential energy still remains in the fuel, even after five years of operation in a reactor.

The United States does not currently recycle spent nuclear fuel but foreign countries, such as France, do.

There are also some  advanced reactor designs in development  that could consume or run on spent nuclear fuel in the future.

Learn more about our work with spent nuclear fuel.

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Get up to speed with these five fast facts about spent nuclear fuel.

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fact - Nuclear "waste" is in constant motion around the country.

according to World Nuclear, globally, about 15 million packages of radioactive material are transported each year on public roads, railways, and ships.

According to Transporting Radioactive Waste in Virginia, from Virginia, low-level radioactive waste is hauled to Clive, Utah or Andrews, Texas by rail and by truck on the interstate highways. High-level radioactive waste is shipped across Virginia via CSX and Norfolk Southern tracks from Newport News, transporting used fuel assemblies from US Navy aircraft carriers.

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Radioactive material accounts for a very small proportion of all dangerous material shipped each year - just 1% in the USA, the world's largest producer of nuclear power.

Globally, about 20 million consignments of radioactive material are transported each year on public roads, railways, and ships.

Radioactive material is not unique to the nuclear fuel cycle. The significant majority - about 95% - of radioactive consignments are not related to nuclear power.

Transport is, however, an integral part of the nuclear fuel cycle; most countries that mine uranium do not produce nuclear power.

Though transport is a very minor cost in the nuclear fuel cycle, lack of harmonization and over-regulation in authorization creates problems for transport of all radioactive materials between countries.

Radioactive material constitutes only a very small proportion of all dangerous goods. In the USA - a country that operates over 20% of the world's civil nuclear power reactors - flammable, explosive, corrosive, or poisonous materials account for 99% of the dangerous material shipped each year. According to the US Department of Transportation, less than 0.5% of the total cost related to the shipping of dangerous materials each year in the USA is attributable to radioactive substances.

International regulations for the transport of radioactive material have been published by the International Atomic Energy Agency (IAEA) since 1961. The IAEA has regularly issued revisions to the transport regulations in order to keep them up-to-date. The latest edition of its Regulations for the Safe Transport of Radioactive Material was released in 2018. The IAEA regulations have been widely adopted into national policies, as well as by the International Civil Aviation Organization (ICAO), the International Maritime Organization (IMO), and regional transport organizations.

The objective of the regulations is to protect people and the environment from the effects of radiation during the transport of radioactive material, both routinely and when transport accidents occur. The fundamental principle is that the protection comes from the design of the package, regardless of how the material is transported. More specifically, protection is achieved by:

Containment of radioactive contents.

Control of external radiation levels.

Prevention of criticality.

Prevention of damage caused by heat.

Radioactive material (defined as Class 7 (see Notes) material in the UN Model Regulations on Dangerous Goods) is not unique to the nuclear fuel cycle. Radioactive substances are used extensively in medicine, agriculture, research, manufacturing, non-destructive testing, and minerals exploration (for further information, see information page on The Many Uses of Nuclear Technology), and it is estimated that just 5% of radioactive material shipped globally each year relates to nuclear power production. Regulatory control of shipments of radioactive material is independent of the material's intended application.

About 20 million consignments of radioactive material take place around the world each year. Since 1961, when the IAEA's safe transport regulations were first issued, it is likely that over one billion consignments have been safely completed. Of the approximately 3,000,000 packages containing radioactive material that are shipped each year in the USA, only about 250,000 contain waste from US nuclear power plants, and just 25 to 100 contain used fuel. The US Department of Transportation estimates that the average distance per shipment of radioactive material is about 55 kilometres, well below the 185 kilometre average across all hazardous materials.

For the generation of a given quantity of electricity, the amount of nuclear fuel required is very much smaller than the amount of any other fuel. Therefore, the conventional risks and environmental impacts associated with fuel transport are greatly reduced with nuclear power (for further information, see information page on Nuclear Energy and Sustainable Development). Nevertheless, whilst volumes of fuel required are modest, used fuel emits very high levels of heat and radioactivity. As such, consignments are transported in robust 125-tonne 'Type B' casks, each containing up to about 20 tonnes of used fuel (see below). The Nuclear Regulatory Commission notes: "Over the last 40 years, thousands of shipments of commercially generated spent nuclear fuel have been made throughout the USA without causing any radiological releases to the environment or harm to the public." Most of these shipments are between different power plants owned by the same utility, so as to share storage space for spent fuel.

Materials requiring transport

Transport is an integral part of the nuclear fuel cycle. There are about 450 operable nuclear power reactors in 31 countries, but uranium mining occurs in only about 30, with most production from countries without nuclear power. Furthermore, in the course of over 60 years of the nuclear power industry, a number of centralized facilities have been developed in various locations around the world to provide fuel cycle services.

Most material used in nuclear fuel is transported several times during its progress through the fuel cycle. Transport is frequently international and often over large distances, but is a very minor cost in the overall fuel cycle. Much of the material moved is similar to that from other industrial activities. However, fresh nuclear fuel, which is mildly radioactive, and some wastes that are significantly more so, are the focus of significant attention. Any substantial quantity of radioactive material is generally transported by specialized companies. (For further information on nuclear waste, see information page on Radioactive Waste Management).

The term 'transport' is used in this document to refer only to the movement of material between facilities ( i.e. through areas outside such facilities' boundaries). Most consignments of nuclear fuel material occur between different stages of the cycle, but occasionally material may be transported between similar facilities. When the stages are directly linked (such as mining and milling) the facilities for the different stages are usually on the same site, and no transport is required.

With very few exceptions, nuclear fuel cycle materials are transported in solid form. The following table shows the principal nuclear material transport activities.

Stages of nuclear transport
*Not yet taking place
Although some waste disposal facilities are located adjacent to the facilities that they serve, using one disposal site to manage the wastes from several facilities usually reduces environmental impacts and associated costs. When shared disposal is used, transport from individual facilities to the disposal site will be required. (For further information, see information paper on Storage and Disposal of Radioactive Wastes.)

Uranium oxide concentrate ('yellowcake')

​Uranium oxide concentrate, sometimes called yellowcake, is transported from mines to conversion plants. Transport takes place in 200-litre drums, each holding about 400 kg U ₃O ₈, packed into normal six-metre shipping containers. No radiation protection is required beyond having the steel drums clean and within the shipping container.

The importance of safe and secure yellowcake transport is evidenced by the fact that 80% of uranium is mined in just five countries, only one of which (Canada) uses uranium for nuclear power.

Every year around 50 shipments of 500 containers of Australian uranium are safely transported by road and rail to ports in Adelaide and Darwin where they are shipped, with no recorded incident affecting public health. Australia is the world's third largest miner of uranium.

Natural and enriched UF₆

To and from enrichment plants, uranium is in the form of uranium hexafluoride (UF ₆), which has low levels of radioactivity, but significant chemical toxicity. Natural uranium as hexafluoride is usually shipped to enrichment plants in Type 48Y cylinders, each 122 cm diameter and holding about 12.5 tonnes of UF ₆ (8.4 tU). These cylinders are then used for long-term storage of depleted uranium as hexafluoride, typically at the enrichment site. Enriched uranium is shipped to fuel fabricators in smaller Type 30B cylinders, each with a 76 cm diameter and holding 2.27 t UF ₆ (1.54 tU). High-assay LEU (HALEU) above 5% enriched will require new cylinders.

Fresh fuel

Uranium fuel assemblies are manufactured at fuel fabrication plants. The fuel assemblies are made up of ceramic pellets formed from pressed U ₃O ₈ that has been sintered at a high temperature (over 1400°C). The pellets are aligned within long, hollow metal rods, which in turn are arranged in the fuel assemblies, ready for introduction into the reactor.

Different types of reactor require different types of fuel assembly, so when the fuel assemblies are transported from the fuel fabrication facility to the nuclear power reactor, the contents of the shipment will vary depending on the type of reactor receiving it.

In Western Europe, Asia, and the USA, the most common means of transporting uranium fuel assemblies is by truck. A typical truckload supplying a light water reactor contains six tonnes of fuel. In Russia and Eastern Europe rail transport is most often used. Intercontinental transport is mostly by sea, though occasionally by air.

The annual operation of a 1000 MWe light water reactor requires an average fuel load of 27 tonnes of uranium dioxide, containing 24 tonnes of enriched uranium. The required annual fuel load can be transported in 4 or 5 trucks. The fuel assemblies are transported in packages specially constructed to protect them from damage during transport. Uranium fuel assemblies have a low radioactivity level and radiation shielding is not necessary.

Fuel assemblies contain fissile material and criticality is prevented by the design of the package, and the maximum number of packages carried in one shipment.

Used fuel

Used fuel from a nuclear power reactor contains 96% uranium, 3% fission products, and 1% plutonium as well as a small amount of other transuranics.

Used fuel emits high levels of both radiation and heat, and so is stored in water pools adjacent to the reactor to allow the initial heat and radiation levels to decrease. Typically, used fuel is stored onsite for at least five months before it can be transported, although it may be stored there long-term. From the reactor site, used fuel is transported by road, rail, or sea to either an interim storage site or a reprocessing plant.

Used fuel assemblies are shipped in Type B casks which are shielded with steel, or a combination of steel and lead. Since 1971 there have been at least 25,000 cargoes of used fuel transported, covering many millions of kilometres on both land and sea.In total some 300 sea voyages have been made in purpose built ships carrying used nuclear fuel over a cumulative distance of more than 8 million kilometres. The major company involved has completed about 200 sea voyages over 40 years, transporting more than 4000 casks, each of about 100 tonnes.

Shipments of spent fuel from Japan to Europe for reprocessing used 94-tonne Type B casks, each holding a number of fuel assemblies. More than 160 of these shipments took place from 1969 to the 1990s, involving more than 4000 casks, and moving several thousand tonnes of highly radioactive used fuel to the UK (4200 tonnes) and to France (2940 tonnes). (For further information see information paper on Japanese Waste and MOX Shipments From Europe.)

In Sweden, more than 80 large transport casks are transported annually to the CLAB central interim waste storage facility. Each 80-tonne cask has steel walls 30 cm thick and holds 17 BWR or 7 PWR fuel assemblies. The used fuel is shipped to CLAB after it has been stored for about a year at the reactor, during which time heat and radioactivity diminish considerably. Over 7000 tonnes of used fuel has been transported to CLAB, much of it around the coast by ship.

In the USA the Nuclear Regulatory Commission noted about 2013: "Over the last 40 years, thousands of shipments of commercially generated spent nuclear fuel have been made throughout the United States without causing any radiological releases to the environment or harm to the public." Most of these shipments are between different power plants owned by the same utility, so as to share storage space for used fuel.

Canada's Nuclear Waste Management Organization published a report in 2015 estimating spent nuclear fuel consignments worldwide:

Canada: five per year by road.

​USA: 3000 to 2015 by road, rail, and ship.

Sweden: 40 per year by ship.

UK: 300 per year by rail.

​France: 250 per year by rail.

Germany: 40 per year by rail.

​Japan: 200 to 2013 by ship.

(For further information, see information page on Storage and Disposal of Radioactive Wastes, since storage and transport often have a lot in common.)

Plutonium oxide

​Plutonium is separated during the reprocessing of used fuel. It is normally then made into mixed oxide (MOX) fuel.

Plutonium is transported, following reprocessing, as an oxide powder, since this is its most stable form. It is insoluble in water and only harmful to humans if it enters the lungs.

Plutonium oxide is transported in several different types of sealed package and each can contain several kilograms of material. Criticality is prevented by the design of the package, limitations on the amount of material contained within the package, and on the number of packages carried on a transport vessel. Special physical protection measures apply to plutonium consignments.

A typical consignment consists of one truck carrying one protected shipping container. The container holds a number of packages with a total weight varying from 80 to 200 kg of plutonium oxide.

Vitrified waste

​The highly radioactive wastes (especially fission products) created in the nuclear reactor are segregated and recovered during reprocessing. These wastes are incorporated in a glass matrix by a process known as 'vitrification', which stabilizes the radioactive material. The molten glass is poured into a stainless steel canister where it cools and solidifies. A lid is welded into place to seal the canister. The canisters are then placed inside a Type B cask, similar to those used for the transport of used fuel.

The quantity per shipment depends upon the capacity of the transport cask. Typically a vitrified waste transport cask contains up to 28 canisters of glass.

Return nuclear waste shipments from Europe to Japan since 1995 have been in vitrified form and contained within stainless steel canisters. Up to 28 canisters (total 14 tonnes) are packed in each 94-tonne steel transport cask, the same type used for the transport of spent fuel. Over 1995-2007 twelve shipments were made from France of vitrified HLW comprising 1310 canisters in total and containing almost 700 tonnes of glass. Return shipments from the UK commenced in 2010 to move about 900 canisters.

Waste materials

Low-level and intermediate-level wastes (LLW and ILW) are generated throughout the nuclear fuel cycle and from the production of radioisotopes used in medicine, industry, and other areas. The transport of these wastes to waste treatment facilities and storage sites is common.

LLW comprises a variety of materials that emit low levels of radiation slightly above normal background levels. It often consists of solid materials, such as clothing, tools, or contaminated soil. LLW is transported from its origin to waste treatment sites, or to an intermediate or final storage facility.

A variety of radionuclides give LLW its radioactive character. However, the radiation levels from these materials are very low and the packaging used for the transport of LLW does not require special shielding.

LLW is transported in drums, often after being compacted in order to reduce the total volume of waste. The drums commonly used contain up to 200 litres of material. LLW is moved by road, rail, and internationally by sea. However, most LLW is only transported within the country where it is produced, given the relative ease of storage and disposal of it.

The composition of ILW is broad, but unlike LLW it requires shielding due to radioactivity levels. Much ILW comes from nuclear power plants and reprocessing facilities.

ILW is taken from its source to an interim storage site, a final storage site (as is the case in Sweden), or a waste treatment facility. It is transported by road, rail, and sea.

In the USA the deep geological repository near Carlsbad, New Mexico, received its 10,000 road shipment of defence-related transuranic waste for permanent disposal in 2011. Almost half the shipments were from Idaho National Laboratory. The repository, known as the Waste Isolation Pilot Plant (WIPP), is about 700 m deep in a Permian salt formation.

Packaging of materials

When radioactive materials are transported, it is important to ensure that radiation exposure to the personnel involved in the transport and the general public along the transport routes is avoided. Packaging for radioactive materials includes, where appropriate, shielding to reduce potential radiation exposure. For some materials, such as fresh uranium fuel assemblies, the radiation levels are negligible and no shielding is required. Other materials, such as used fuel and HLW, are highly radioactive and purpose-designed containers with integral shielding are used. To limit the risk in handling of highly radioactive materials, dual-purpose containers (casks), which are appropriate for both storage and transport of used nuclear fuel, are often used. (For further information, see information page on Storage and Disposal of Radioactive Wastes.)
Arrival of Mox shipment from France to Japan (Image: Kansai Electric Power Company)
As with other hazardous materials being transported, packages of radioactive materials are labelled in accordance with the requirements of national and international regulations. These labels not only indicate that the material is radioactive by including a radiation symbol, but also give an indication of the radiation field in the vicinity of the package.

The principal assurance of safety in the transport of nuclear materials is the design of the packaging, which must allow for foreseeable accidents. The consignor bears primary responsibility for this as well as for the training of personnel directly involved in the transport. Many different radioactive materials are transported and the degree of potential hazard from these materials varies considerably. Conditions which packages are tested to withstand include: fire, impact, wetting, pressure, heat, and cold. Packages of radioactive material are checked prior to shipping and, when it is found to be necessary, cleaned to remove contamination.

Different packaging standards have been developed by the IAEA according to the characteristics and potential hazard posed by the different types of nuclear material. The IAEA's guidelines are complex, but identify five different categories of primary package based on the activity and physical form of the waste being transported. The categories are: Excepted, Industrial, Type A, Type B, and Type C.

Excepted

Excepted packages have radioactive content at such low levels that the potential hazards are insignificant and therefore no testing is required with regard to containment or shielding integrity.

Industrial

Ordinary industrial containers are used for low-activity material such as uranium oxide concentrate shipped from mines. They are also used for LLW transport within countries.

Type A

'Type A' packages are used for the transport of relatively small, but significant, quantities of radioactive material. They are designed to withstand accidents and are used for limited quantities of medium-activity materials, such as medical or industrial radioisotopes as well as some nuclear fuel materials.

Type B

Type B packages used for HLW, used fuel, and MOX fuel are robust and very secure casks. They range from drum-size to truck-size and maintain shielding from gamma and neutron radiation, even under extreme accident conditions. Designs are certified by national authorities. There are over 150 certified Type B packages, and the larger ones cost around $1.6 million each.

Type B casks for used fuel can weigh up to 110 tonnes when empty and hold from 6 to 20 tonnes of fuel, containing their highly radioactive payload safely during transport. The internal structure of transport casks (using multi-purpose canisters or not) is designed to maintain separation of fuel assemblies even in extreme accidents, and the external structure is designed to maintain safe containment in extreme accidents. Both features are tested before licensing.

An example of a Type B shipping package for used fuel is Holtec's HI-STAR 80 cask (STAR = storage, transport and repository), a multi-layered steel cylinder that holds 12 PWR or 32 BWR high burn-up used fuel assemblies (above 45 GWd/t), and which has had cooling times as short as 18 months.

Holtec's HI-STAR 100 is a high-capacity system which is engineered to accept one sealed multi-purpose canister (MPC) containing a 68-cell fuel basket for BWR fuel or a 32-cell fuel basket for PWR fuel. The MPC containing the fuel can be transferred to HI-STORM 100 storage systems on an independent spent fuel storage installation (ISFSI) pad or below ground surface, exchanging one overpack for another which is engineered for maximum shielding. The HI-STAR 190 cask has a 38 kW heat load capacity and is envisaged as the main used fuel transport to central storage or disposal sites in the USA. It is promoted as a universal transport cask.

Areva has a range of Type B transport casks for used fuel. Its TN12/2 cask designed for used fuel has been adapted for fresh MOX fuel, and holds 12 PWR fuel assemblies or 32 BWR ones. It is robust, with shock-absorbing covers at each end.

In France alone, there are some 750 shipments each year of Type B packages. This is in relation to 15 million shipments classified as 'dangerous goods', 300,000 of which are of radioactive materials of some kind.

In Russia, TUK (transportation packaging set) casks are used to transport used nuclear fuel. Several TUK-13 casks fit into a container or TK carrier for rail transport, each cask holding about 6 tonnes of fuel. A TUK-1410 cask has now been licensed to replace the older model for VVER-1000 fuel, both in Russia and from overseas. Each weighs over 100 tonnes, holds 18 VVER fuel assemblies weighing 9 tonnes in a removable canister, and is designed for hotter fuel - up to 36 kW heat load. (For further information see information page on Storage and Disposal of Radioactive Waste.)

A particular 'Type B' package is used for shipping uranium hexafluoride (UF ₆), where the main accident hazard is chemical rather than radiological. Natural uranium is usually shipped to enrichment plants in Type 48Y cylinders, 122 cm diameter and each holding about 12.5 tonnes of uranium hexafluoride. These cylinders are then used for long-term storage of depleted uranium as hexafluoride, typically at the enrichment site. Due to criticality considerations, enriched uranium is shipped to fuel fabricators in smaller Type 30B cylinders, 76 cm diameter and 2.1 m long, each holding 2.27 t UF ₆. These may be shipped with overpacks. Both kinds of uranium hexafluoride cylinder must withstand a pressure test of at least 1.4 MPa, a drop test, and survive a fire of 800°C for 30 minutes.

Type C

Smaller amounts of high-activity materials (including plutonium) transported by aircraft are in 'Type C' packages, which give even greater protection than Type B packages in accident scenarios. They can survive being dropped from an aircraft at cruising altitude.

Although not required by transport regulations, the nuclear industry chooses to undertake some shipments of nuclear material using dedicated, purpose-built transport vehicles or vessels.

Purpose-built transportation

In 1993, the International Maritime Organization (IMO) introduced the voluntary Code for the Safe Carriage of Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes in Flasks on Board Ships (INF Code), complementing the IAEA Regulations. These provisions mainly cover ship design, construction, and equipment. The INF Code came into force in January 2001 and introduced advanced safety features for ships carrying used fuel, MOX, or vitrified HLW.

There are at least five small purpose-built ships ranging from 1250 to 2200 DWT, and four purpose-built ships ranging from 3800 to 5000 DWT, able to carry Type B casks and other materials. They conform to all relevant international safety standards, notably INF-3 (Irradiated Nuclear Fuel class 3) set by the IMO, allowing them to carry highly radioactive materials such as HLW and used nuclear fuel, as well as mixed-oxide (MOX) fuel, and plutonium.

The three largest ships belong to a British-based company, Pacific Nuclear Transport Ltd (PNTL), a subsidiary of International Nuclear Services Ltd (INS)*. The three PNTL vessels currently in service, the Pacific Heron, Pacific Egret, and Pacific Grebe were launched in Japan in 2008, 2010, and 2010, respectively. All have double hulls separated by impact-resistant structures, together with duplication and separation of all essential systems to provide high reliability and significant contingency in the event of an accident. Twin engines operate independently. Each ship can carry up to 20 or 24 transport casks. Each ship is 4916 tonnes (DWT) and 104 metres long. Pacific Grebe carries mainly wastes, whilst the other two usually carry consignments of MOX fuel. Earlier ships in the PNTL fleet mainly carried Japanese used fuel to Europe for reprocessing. The PNTL fleet has completed more than 180 shipments with more than 2000 casks over some 40 years without any incident resulting in the release of radioactivity.
* PNTL is now owned by International Nuclear Services Ltd (INS, 68.75%), Japanese utilities (18.75%), and Areva (12.5%). INS is in turn owned by the UK's Nuclear Decommissioning Authority.
In 2013 Sweden's SKB commissioned the Sigrid, a slightly larger replacement for its 1982 vessel the Sigyn. Sigrid was built by Damen Shipyards and carried its first shipment in January 2014. It is used for moving used fuel from reactors to the CLAB interim waste storage facility. Sigrid is equipped with a double hull, four engines, and redundant systems for safety and security. Sigrid is 99.5 metres long and 18.6 metres wide, 1600 DWT and capable of carrying 12 nuclear waste casks. ( Sigyn was 1250 DWT and carried ten casks.)

Rosatomflot is operating the 1620 DWT Rossita, built in Italy and completed in 2011. It is designed for transporting spent nuclear fuel and materials of decommissioned nuclear submarines from Russian Navy bases in northwest Russia. It will be used on the Northern Sea Route, between Gremikha, Andreeva Bay, Saida Bay, Severodvinsk, and other places hosting facilities which dismantle nuclear submarines. Spent fuel is to be delivered to Murmansk for rail shipment to Mayak. Rosatomflot has the Serebryanka (1625 DWT, 102 metres long, built 1974) already in service. The Imandra (2186 DWT, 130 metres long, built 1980) is described as a floating technical base but is reported to be in service transporting used fuel and wastes from the Nerpa shipyard and Gremikha to Murmansk.

Rossita is an ice-class vessel and is designed to operate in the harsh conditions of the Arctic. The ship is 84 metres long and 14 m wide, has two engines, and two isolated cargo holds with a total capacity of 720 tonnes. The €70 million vessel was given to Russia as part of Italy's commitment to the G8 partnership program for cleaning up naval nuclear wastes, and is designed to cover all needs in spent nuclear fuel and radwaste shipments in northwest Russia throughout the entire period of cleaning up these territories.

Rosatomflot also operates a new vessel, the semi-submersible pontoon dock Itarus, built in Italy under a 2013 contract, and delivered in 2016. It is designed to transport three compartment units of dismantled Russian nuclear submarines for SevRAO in Saida Bay.
Road transport of used fuel, Japan (Image: Nuclear Fuel Transport Ltd.)
Accident scenarios

There has never been any accident in which a Type B transport cask containing radioactive materials has been breached or has leaked. A significant accident in the USA in 1971 demonstrated the integrity of a Type B cask, which was later returned to service.

The safety features built into Type B containers are very significant. For the radioactive material in a large Type B package in sea transit to become exposed, the ship's hold (inside double hulls) would need to rupture, the 25 cm thick steel cask would need to rupture, and the stainless steel flask or the fuel rods would need to be broken open. Either borosilicate glass (for reprocessed wastes) or ceramic fuel material would then be exposed, but in either case these materials are very insoluble.

The purpose-built transport ships described above are designed to withstand a side-on collision with a large oil tanker. If the ship did sink, the casks would remain sound for many years and would be relatively easy to recover since instrumentation including location beacons would activate and monitor the casks.

Challenges in radioactive material transport

The majority - over 95% - of radioactive material consignments relate to radioisotopes for medical and industrial use (for further information see information paper on The Many Uses of Nuclear Technology). A 2015 Euratom Supply Agency study identified lack of harmonization and over-regulation in transport authorization for radioactive materials, particularly between countries, as a significant risk from a security of supply perspective.

Multiple layers of regulation and a lack of international consistency are considerable disincentives, and may deter companies from executing shipments. Shipments are occasionally denied due to national competent authorities not being recognized by other countries.

Most reports of denial of shipment relate to non-fissile materials, either Type B packages (mainly cobalt-60) or tantalum-niobium concentrates. For uranium concentrates the main problem is the limited number of ports which handle them, and the relatively few marine carriers which accept them. For all radioactive materials, consignors are required to provide training to personnel handling the packages, creating significant cost and inconvenience to shippers.

Notes

Any goods that pose a risk to people, property and the environment are classified as dangerous goods, which range from paints, solvents and pesticides up to explosives, flammables, and fuming acids, and are assigned to different classes under the UN Recommendations on the Transport of Dangerous Goods, Model Regulations:

Class 1: Explosives.

Class 2: Gases.

Class 3: Flammable liquids.

Class 4: Flammable solids; substances liable to spontaneous combustion; substances which, on contact with water, emit flammable gases.

Class 5: Oxidizing substances and organic peroxides.

Class 6: Toxic and infectious substances.

Class 7: Radioactive material.

Class 8: Corrosive substances.

Class 9: Miscellaneous dangerous substances and articles, including environmentally hazardous substances.

When transported, these goods need to be packaged correctly, as laid out in the various international and national regulations for each mode of transport, to ensure that they are carried safely to minimize the risk of an incident.

The US Nuclear Regulatory Commission defines, for transport purposes only, radioactive materials as those with specific activity greater than 74 Bq per gram. This definition does not specify a quantity, only a concentration. As an example, pure cobalt-60 has a specific activity of 37 TBq per gram, which is about 500 billion times greater than the definition. However, uranium-238 has a specific activity of only 11 kBq per gram, which is only 150 times greater than the definition.

Sources

a. Radioactive Waste Management of Nuclear Power Plant, International Journal of Renewable Energy Technology Research (2014). [ Back]

b. Bureau of Transportation Statistics, US Department of Transportation (2017). [ Back]

c. Transportation of Radioactive Material, US Environmental Protection Agency. [ Back]

d. Transportation of Spent Nuclear Fuel, US Nuclear Regulatory Commission. [ Back]

e. Australia's Uranium Industry, Minerals Council of Australia. [ Back]

f. A Historical Review of the Safe Transport of Spent Nuclear Fuel, US Department of Energy (2016). [ Back]

g. 40 Years of PNTL, Pacific Nuclear Transport Limited (2015). [ Back]

h. Transport of MOX fuel from Europe to Japan, International Atomic Energy Agency (2002). [ Back]

i. SKB - Our Operations, SKB. [ Back]

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About twenty million packages of all sizes containing radioactive materials are routinely transported worldwide annually on public roads, railways and ships. These use robust and secure containers. At sea, they are generally carried in purpose-built ships. Since 1971 there have been more than 20 000 shipments of used fuel and high-level wastes (over 80 000 tonnes) over many million kilometres.

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#19) Myth- The Zion Nuclear power plant has been in operation for the past 20 years and just recently shut down.

Evidence 1) Zion Units 1 and 2 were permanently certified as shut down on February 13, 1998- 26 years ago. (nrc.gov)

Evidence 2) The Zion Nuclear Power Plant is on the southwestern shore of Lake Michigan, and was in operation from 1973 until 1998- 25 years running. (clui.org)

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1.0 Site Identification

2.0 Site Status Summary

Zion Units 1 and 2 were permanently certified as shut down on February 13, 1998. The fuel was transferred to the spent fuel pool, and the owner submitted the certification of fuel transfer on March 9, 1998. On September 1, 2010, the facility license was transferred from Exelon to ZionSolutions for the express purpose of expediting the decommissioning of the site. Decontamination and dismantlement began in 2011. Completion of spent fuel transfer to the ISFSI was completed in January 2015. Completion of spent fuel transfer to the ISFSI was completed in January 2015. Submittal of the license termination plan (LTP) license amendment request occurred in December 2014, and an NRC LTP public meeting was held in April 2015. The LTP was approved in September 2018.

Since this license transfer to ZionSolutions from Exelon occurred, one Direct License Transfer and two Indirect License Transfer Orders and associated conforming amendments were approved for the transfer of the Part 50 Facility Operating Licenses and generally icensed on-site Independent Spent Fuel Storage Installation (ISFSI) from ZionSolutions to Constellation Energy Generation; however, the Transfer Orders were conditioned that before transfer the decommissioning of the Zion site had to be completed. All above grade plant structures have been removed and the NRC found that the site met the unrestricted release criteria for the remaining survey units outside the boundary of the on-site ISFSI on November 8, 2023. On November 16, 2023, the NRC issued the confirming amendments that identify Constellation Energy Generation as the licensee. The licensed area now consists of the ISFSI, the ISFSI Support Building, and the ISFSI Warehouse and encompasses approximately 5 acres.

3.0 Major Technical or Regulatory Issues

None

4.0 Estimated Date for Closure

Part 50 License effectively terminated November 8, 2023. (Outside of remaining onsite ISFSI)

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Fact- Most Americans support the use and development of nuclear power for this county's energy needs.

According to the American Nuclear Society, as of 2023 76% of Americans favor using nuclear energy and only 24% of Americans oppose using it. This number has continued to increase from 1983 until 2023.

https://www.ans.org/news/article-5070/public-support-for-nuclear-stays-at-record-highs-but-misconceptions-remain-a-problem/

According to Grist.org, "55 percent of U.S. adults support the use of nuclear power. That’s up four percentage points from last year and reflects the highest level of public support for nuclear energy use in electricity since 2012. The survey found that Republicans are more likely to favor nuclear energy than Democrats, consistent with previous Gallup polls."

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At the same time, however, Americans continue to harbor negative attitudes toward nuclear energy that are associated with fears of radiation, and those attitudes and fears can be changed only with improved education and research. Ann Bisconti, president of Bisconti Research, explored this trend in a January 2023 review of her company's past survey findings, stretching back three decades. In certain ways, according to Bisconti, the public's understanding of radiation has seemingly degraded in recent years.

Major findings for 2023: The survey, which was conducted from April 28 to May 5, included 1,000 adults who were considered to be representative of the national population. Results had a margin of error of ±3 percentage points.

After a dip in the previous decade, the three-year trend of support for nuclear continues. In this year's survey, 76 percent of respondents said that they "strongly favor" or "somewhat favor" the use of nuclear energy as one of the sources of electricity in the United States.

Other pronuclear sentiments found in the survey include the following:

86 percent of respondents agreed that nuclear energy will continue to be important for meeting U.S. electricity needs in the coming years.

89 percent agreed that current nuclear plants should be relicensed if they meet federal safety standards.

87 percent agreed that preparations should be made now for advanced nuclear plants.

71 percent said that the United States should "definitely" build more nuclear plants.

Demographic differences: As in previous years, the 2023 survey found some striking differences in nuclear views among different demographic groups. When asked the question, "Overall, do you strongly favor, somewhat favor somewhat oppose, or strongly oppose the use of nuclear energy as one of the ways to provide electricity in the United States," the most pronuclear demographic group remained male college graduates (49 percent of whom strongly favored nuclear). Overall, 40 percent of men answered "strongly favor," compared with 19 percent of women (18 percent of college-educated women were strongly in favor). Most women (76 percent) were "fence-sitters," the survey found, neither strongly for or against nuclear.

Opinions among different generations were markedly varied. Gen Z respondents (generally considered to be those born between 1997 and 2012) were the weakest group, with only 16 percent being strong supporters and 80 percent being fence-sitters. Millennials (born between 1981 and 1996) were the strongest pronuclear age group, with 34 percent expressing strong support. Gen Xers (1965-1980) also strongly supported nuclear at a level of 27 percent, while 29 percent of Baby Boomers (1946-1964) were strongly pronuclear. The Silent Generation (1928-1945) rivaled the Millennials, with strong support at 32 percent. No demographic group had more than 6 percent expressing strong opposition to nuclear.

Political differences: The 2023 survey again found that self-identified Republicans (37 percent) and conservatives (39 percent) were the strongest pronuclear supporters. Comparatively, 26 percent of self-identified Democrats, 24 percent of independents, 22 percent of moderates, and 24 percent of liberals said they strongly favored nuclear.

Knowledge leads to support: One factor that holds down levels of support for nuclear energy is lack of information. According to the 2023 survey, only 14 percent of the American public felt like they were "very well informed" about nuclear energy. But among those very well-informed respondents, 74 percent strongly supported nuclear. Those who said they felt "not at all" informed (86 percent of respondents) were also the most opposed (50 percent).

Messaging matters: Bisconti, in her January blog post, discussed the types of messages that are effective and ineffective in educating the public about radiation and nuclear energy, based on eight messages about radiation from nuclear power plants that were tested in the 2022 survey. Four of the messages were framed as emotional appeals, and the other four as appeals to rational thinking.

Regardless of the framing, she said, "the best points communicated about how radiation is controlled and about the many beneficial uses of nuclear technologies." Bisconti added, "Talking about beneficial uses makes nuclear technologies more familiar and less threatening. Reminders of how radiation is used in medical and industrial technologies conveys that we know how to control these technologies."

Analogies were the least effective form of messaging, according to previous surveys. "Being told that one gets more radiation from another source such as a coal plant does not explain how the nuclear power plant radiation is controlled, measured, and contained so that the public is protected," she said.

Analysis: In an analysis of the survey respondents' pronuclear views, Bisconti wrote, "Why do people hold their opinions of nuclear energy? An open-ended question gathered these reasons without influencing answers. Favorable reasons are primarily about the need for this energy because it is affordable, reliable, and efficient and about environmental benefits relating to clean air and climate change. The themes of energy independence and energy security that have reemerged in policy discussions due to Russia's war in Ukraine are not yet cited as major reasons for opinions about nuclear energy."

Summing up the results: "Support for nuclear energy remains high in the context of concerns about energy and the environment," Bisconti summarized. "Nuclear energy's benefits are being mentioned in the public discourse and this information is being heard. The current survey shows, once again, the very close correlation between the level of feeling informed about nuclear energy and strong favorability. Also, it shows the value of information for strengthening public support. Most Americans do not feel very well informed about nuclear energy, so information makes a big difference."

Challenging misperceptions to change minds: The survey noted that the large middle ground occupied by respondents-the fence-sitters-is a sign that public opinion is changeable. Of some respondents' antinuclear views, Bisconti wrote, "Unfavorable opinions are primarily focused on danger, although some did mention that nuclear energy is becoming safer. In open-ended questions about reasons for opinions about nuclear energy, few even mention waste."

Positive messaging will remain ineffective if negative misperceptions are too strong, according to Bisconti. For example, at the beginning of the 2022 survey-before education on the matter was provided-64 percent of participants believed that that living near nuclear power plants exposes people to harmful levels of radiation. After this misperception was corrected by the survey, 51 percent of participants still believed it. "That's an improvement but hardly the shift one would hope for," Bisconti said. "The association of radiation with nuclear power plants is so strong that it persists with many people, even after they see persuasive messages."

Bisconti concluded from analyzing decades of surveys that "radiation remains an area in which words alone are helpful but not sufficient, and the research shows that more education is needed. Get out the Geiger counters! Show pictures and models that demonstrate containment and control. More research is needed too. Test ways to show radiation measurements, including safe levels. Test perceived value of the many ways that radiation technologies are used to benefit society. Continue to look for potential signs of change in the perspective of younger generations."

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Public support for nuclear stays at record highs, but misconceptions remain a problem

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At the same time, however, Americans continue to harbor negative attitudes toward nuclear energy that are associated with fears of radiation, and those attitudes and fears can be changed only with improved education and research. Ann Bisconti, president of Bisconti Research, explored this trend in a January 2023 review of her company's past survey findings, stretching back three decades.

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Myth- Nuclear energy is not necessary in the US because we have a 133 year supply of clean coal.

1. Our coal supply is decreasing more rapidly because we have to increase demand due to the cold winters.

2. 'Clean' coal is not actually as environmentally friendly as it is claimed to be. It still produces more carbon emmisons than nuclear power and more human health impacts. (World Nuclear Association)

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Electricity Monthly Update - U.S. Energy Information Administration (EIA)

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Energy Information Administration - EIA - Official Energy Statistics from the U.S. Government

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Myth- A nuclear power plant has a lifespan of 20 years

Evidence #1- Generally speaking, early nuclear plants were designed for a life of about 30 years, though with refurbishment, some have proved capable of continuing well beyond this. Newer plants are designed for a 40 to 60 year operating life. (world-nuclear.org (linked above))

Evidence #2- As the average age of American reactors approaches 40 years old, experts say there are no technical limits to these units churning out clean and reliable energy for an additional 40 years or longer. (energy.gov)

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About 200 commercial, experimental or prototype reactors, over 500 research reactors, and several fuel cycle facilities have been retired from operation. Some of these have been fully dismantled.

Most parts of a nuclear power plant do not become radioactive, or are contaminated at only very low levels. Most of the metal can be recycled.

Proven techniques and equipment are available to dismantle nuclear facilities safely and these have now been well demonstrated in several parts of the world.

Decommissioning costs for nuclear power plants, including disposal of associated wastes, are high relative to other industrial plants but are reducing, and contribute only a small fraction of the total cost of electricity generation.

All power plants, coal, gas and nuclear, have a finite life beyond which it is not economically feasible to operate them. Generally speaking, early nuclear plants were designed for a life of about 30 years, though with refurbishment, some have proved capable of continuing well beyond this. Newer plants are designed for a 40 to 60 year operating life. At the end of the life of any power plant, it needs to be decommissioned, cleaned up and demolished so that the site is made available for other uses.

For nuclear plants, the term decommissioning includes all clean-up of radioactivity and progressive dismantling of the plant. This may start with the owner's decision to write it off or declare that it is permanently removed from operation. For practical purposes it includes defueling and removal of coolant, though NRC at least defines it as strictly beginning only after fuel and coolant are removed. It concludes with licence termination after decontamination is verified and wastes removed.

A Table showing shutdown reactors is at the end of this paper. About 25 of these have completed the decommissioning process.

Decommissioning options for nuclear plants

The International Atomic Energy Agency (IAEA) has defined three options for decommissioning, the definitions of which have been internationally adopted:

Immediate Dismantling (or Early Site Release/'Decon' in the USA): This option allows for the facility to be removed from regulatory control relatively soon after shutdown or termination of regulated activities. Final dismantling or decontamination activities can begin within a few months, depending on the facility. Following removal from regulatory control, the site is then available for re-use within a decade.

Safe Enclosure ('Safstor') or deferred dismantling: This option postpones the final removal of controls for a longer period, usually in the order of 40 to 60 years. The facility is placed into a safe storage configuration until the eventual dismantling and decontamination activities occur after resudual radioactivity has decayed. There is a risk in this case of regulatory change which could increase costs unpredictably.

Entombment (or 'Entomb'): This option entails placing the facility into a condition that will allow the remaining on-site radioactive material to remain on-site without ever removing it totally. This option usually involves reducing the size of the area where the radioactive material is located and then encasing the facility in a long-lived structure such as concrete, that will last for a period of time to ensure the remaining radioactivity is no longer of concern.

Each approach has its benefits and disadvantages. National policy determines which approach or combination of approaches is adopted or allowed. In the case of immediate dismantling (or early site release), responsibility for completion of decommissioning is not transferred to future generations. The experience and skills of operating staff can also be utilised during the decommissioning programme, which may be undertaken by the utility or handed over to a specialist company, with transfer of licence and accumulated funds. Alternatively, Safe Enclosure (or Safstor) allows significant reduction in residual radioactivity, thus reducing radiation hazard during the eventual dismantling. The expected improvements in mechanical techniques should also lead to a reduction in the hazard and also costs.

In the case of nuclear reactors, about 99% of the radioactivity is associated with the fuel which is removed following permanent shutdown. Apart from some surface contamination of plant, the remaining radioactivity comes from "activation products" in steel which has long been exposed to neutron irradiation, notably the reactor pressure vessel. Stable atoms are changed into different isotopes such as iron-55, iron-59 and zinc-65. Several are highly radioactive, emitting gamma rays. However, their half life is such (2.7 years, 45 days, 5.3 years, 245 days respectively) after 50 years from closedown their radioactivity is much diminished and the occupational risk to workers largely gone.

Decommissioning experience

Considerable experience has been gained in decommissioning various types of nuclear facility. About 200 commercial, experimental or prototype power reactors, as well as over 500 research reactors have been retired from operation. About 25 reactors have been fully dismantled.

(Ships and numerous submarines have also been decommissioned but are not included in this paper.)

European reactors

To decommission its retired gas-cooled reactors at the Chinon, Bugey and St Laurent nuclear power stations, EDF chose partial dismantling and postponed final dismantling and demolition for 50 years. As other reactors will continue to operate at those sites, monitoring and surveillance do not add to the cost.

A recycling plant for steel from dismantled nuclear facilities is at Marcoule, in France. This metal will contain some activation products, but it can be recycled for other nuclear plants.

Decommissioning has begun at 33 UK reactors, 26 of them early Magnox types with graphite moderators.* One of the first was Berkeley nuclear power station (2 x 138 MWe), closed for economic reasons in 1989 after 27 years of operation, where defuelling was completed in 1992. The cooling ponds were then drained, cleaned and filled in and the turbine hall was dismantled and demolished. The reactor buildings are in an extended Safstor period. Ultimately they too will be dismantled, leaving the site to be leveled and landscaped. The same pattern is being followed at other UK reactor sites.

Spain's Vandellos 1, a 480 MWe gas-graphite reactor, was closed down in 1990 after 18 years operation, due to a turbine fire which made the plant uneconomic to repair. In 2003 ENRESA concluded phase 2 of the reactor decommissioning and dismantling project, which allowed much of the site to be released. After 30 years Safstor, when activity levels have diminished by 95%, the remainder of the plant will be removed. The cost of the 63-month project was €93 million.

Eleven of Germany's 19 shutdown units were subject to immediate dismantling. At Greifswald nuclear power station in the former East Germany, where five reactors had been operating, immediate dismantling was chosen. Similarly, the site of the 100 MWe Niederaichbach nuclear power plant in Bavaria was declared fit for unrestricted agricultural use in mid-1995. The 15 MWe Kahl experimental BWR was shut down in 1985, after 25 years of operation. After decontamination, the plant was completely dismantled and the site was cleared for unrestricted use. The 250 MWe Gundremmingen A unit was Germany's first commercial nuclear reactor, operating 1966-77. Decommissioning work started in 1983, and moved to the more contaminated parts in 1990, using underwater cutting techniques. This project demonstrated that decommissioning could be undertaken safely and economically without long delays, and recycling most of the metal.

Of the eight German units shut down in March 2011 for political reasons, most will be dismantled over about 15 years. The four operators had €38 billion set aside for decommissioning and waste disposal.

Japan's Tokai 1 reactor, a 160 MWe UK Magnox design, is being decommissioned after 32 years service to 1998. After 10 years storage, in Phase 2 (to 2011) the steam generators and turbines were removed, and in Phase 3 (to 2018) the reactor is being dismantled, the buildings demolished and the site left ready for re-use. The total cost will be JPY 93 billion (USD 1.04 billion) - 35 billion for dismantling and 58 billion for waste treatment which will include the graphite moderator (which escalates the cost significantly, see subsection below).

US reactors

Experience in the USA has varied, but about ten power reactors are using the Safstor approach, while about 20 - mostly single-unit plants - are using, or have used, Decon.

Early in 2017 a joint venture, Accelerated Decommissioning Partners, was set up under the leadership of NorthStar Group Services with Orano USA to acquire and decommission shutdown US nuclear reactor facilities and take over their used fuel. Another joint venture in the field is Comprehensive Decommissioning International (CDI), formed in 2018 between SNC-Lavalin and Holtec. Holtec Decommissioning International (HDI) functions as the licensed operator for Holtec-owned nuclear power plants and provides the licensee oversight of CDI. HDI additionally, manages the decommissioning trust fund and other owner interests, such as licensing strategy, insurance, land and government interface. EnergySolutions was already active in this kind of role.

Procedures are set by the Nuclear Regulatory Commission (NRC), and considerable experience has now been gained. A total of 32 power reactors have been closed and decommissioned. NRC requires that the operating licence of a closed reactor be terminated and decommissioning activities be completed within 60 years. Site release often excludes the onsite used fuel storage in an ISFSI (independent spent fuel storage installation), which usually remains, to await the Department of Energy taking away the used fuel (over which it has title) to a national repository sometime in the future.

Rancho Seco (single 913 MWe, PWR) was closed in 1989, and in 1995 NRC approved a Safstor plan for it. However, the utility subsequently decided upon incremental dismantling and this was completed in 2009, leaving about 3 ha still under NRC licence for waste storage. About 32 ha has been released for unrestricted use.

At multi-unit nuclear power stations, the choice has been to place the first closed unit into Safstor until the others end their operating lives, so that all can be decommissioned in sequence. This will optimise the use of staff and the specialised equipment required for cutting and remote operations, and achieve cost benefits.

Thus, after 14 years of comprehensive clean-up activities, including the removal of fuel, debris and water from the 1979 accident, Three Mile Island 2 was placed in post-defuelling monitored storage (Safstor) until unit 1 eventually closed down, so that both units could be dismantled together. EnergySolutions has a contract with FirstEnergy to decommission unit 2. Unit 1 is being placed in Safstor.

San Onofre 1 (436 MWe PWR), which closed in 1992, was put into Safstor until licences for units 2&3 expire in 2022-23. However, after NRC changes, dismantling was brought forward to 1999, so it became an active Decon project which was largely completed in 2008. A small amount of work remains to be completed with eventual dismantling of units 2&3 (each 1070 MWe PWR) on the site, which were shut down in May 2013. In April 2016 the California Public Utilities Commission approved $4.41 billion in decommissioning costs for them, from funds held in trust. Southern California Edison said that funds were then $3.37 billion. Used fuel will be removed from 2024 to an onsite ISFSI, and dismantling the plant is expected to be completed by 2030. SONGS Decommissioning Solutions - a joint venture between Aecom and EnergySolutions - was selected in December 2016 as the general contractor.

A US Decon project was the 60 MWe Shippingport reactor, which operated commercially from 1957 to 1982. It was used to demonstrate the safe and cost-effective dismantling of a commercial scale nuclear power plant and the early release of the site. Defuelling was completed in two years, and five years later the site was released for use without any restrictions. Because of its size, the pressure vessel could be removed and disposed of intact. For larger units, such components have to be cut up.

Immediate Decon also the option chosen for Fort St Vrain, a 330 MWe high temperature gas-cooled reactor which was closed in 1989. This took place on a fixed-price contract for US$ 195 million (hence costing less than 1 cent/kWh despite only a 16-year operating life) and the project proceeded on schedule to clear the site and relinquish its licence early in 1997 - the first US power reactor of this size to achieve this.

Shoreham BWR, on Long Island, generated very little power and never received a full operating licence, so the level of activation products was minimal. It was shut down in 1989 and became a Decon project, completed in 1994. The 59 MWe Pathfinder prototype BWR in South Dakota, shut down in 1967 after a very short life was also a Decon project, completed in 1992.

For Trojan (1180 MWe, PWR) in Oregon the dismantling was undertaken by the utility itself. The plant closed in 1993, steam generators were removed, transported and disposed of at Hanford in 1995, and the reactor vessel (with internals) was removed and transported to Hanford in 1999. Except for the used fuel storage, the site was released for unrestricted use in 2005. The cooling tower was demolished in 2006. This was a relatively low-cost operation - about $300 million.

Another US Decon project was Maine Yankee, a 860 MWe PWR plant which closed down in 1996 after 24 years operation. The containment structure was finally demolished in 2004 and except for 5 ha with the dry store for used fuel, the site was released for unrestricted public use in 2005, on budget (about $500 million) and on schedule.

Haddam Neck/Connecticut Yankee (560 MWe PWR) also shut down in 1996 after 29 years operation. Decommissioning work began in 1998 and demolition was concluded in 2006. The site was released for unrestricted public use in 2007, apart from 2 ha for dry cask used fuel storage. Residual contamination on the land is below the NRC's limit of 0.25 millisievert per year for maximum radiation dose.

In 2006 the site of 72 MWe Big Rock Point nuclear power plant in Michigan, shut down in 1997 after 35 years operation, was largely returned to greenfield status. In January 2007 most of the land was released for derestricted public use, though 43 hectares still has the dry cask storage facility where used fuel is stored pending transfer to the national repository. The total cost was $836 million.

Vermont Yankee (535 MWe BWR) was shut down in 2014 and is in Safstor and was expected to cost $577 million to decommission over many years. However, Entergy arranged to accelerate the process by transferring the licence and selling the whole site to a consortium of decommissioning companies headed by NorthStar Group Services, which expects to complete the process and sell the cleared site by 2030. Fuel was moved to dry storage in 2017. Areva Nuclear Materials, now Orano USA, is contracted to cut up and remove the reactor vessel and internals.

With Exelon's Zion 1&2 reactors (2 x 1098 MWe) closed down in 1998 and initially in Safstor, Exelon decided to accelerate the process and contracted a specialist company - EnergySolutions - to dismantle the plant, ship the waste to its disposal site in Utah, and return the site to greenfield status. To achieve this, in 2010 the plant's licence and decommissioning funds were transferred to EnergySolutions, which became owner and licensee, and the site should be returned to Exelon about 2022. In 12 months to January 2015 EnergySolutions transferred all 2226 used fuel assemblies to 61 Magnastor dry casks onsite - an ISFSI, where it will remain until taken to the future national repository. By September 2021 the site was clean and being vegetated. EnergySolutions had similarly decommissioned LaCrosse, a 50 MWe BWR, Big Rock Point, a 67 MWe BWR, and the small (20 MWt) SEFOR experimental reactor in Arkansas. It is signed up to decommission Three Mile Island 2, San Onofre (see above) and Fort Calhoun.

Exelon's Oyster Creek (619 MWe BWR) in New Jersey will be dismantled and cleaned up by Comprehensive Decommissioning International (CDI) - the SNC-Lavalin and Holtec JV - starting in 2019 and expected to take less than ten years. The licence was transferred from Exelon in July 2019. CDI will also be the decommissioning general contractor for the Pilgrim BWR shut down in 2019, and for Indian Point 1, 2&3 (1974, 2020, 2021) and Palisades from 2022.

Entergy's Indian Point plant is expected to cost $2.3 billion to decommission and dismantle over about 12-15 years, by CDI after ownership passed to Holtec in April 2021. Unit 1 of 277 MWe, in Safstor since 1974, would cost $598 million, unit 2 $702 million and unit 3 $1 billion. Decommissioning trust funds for the three reactors amounted to $2.1 billion in 2019 so were expected to cover the work by the time unit 3 shut down in 2021. Only an ISFSI would remain onsite after 2032.

Duke's Crystal River 3 (860 MWe) was expected to cost $1.18 billion (2013 dollars) to decommission via Safstor over 60 years, during which time the funds reserved for the purpose would accrue interest, thereby fully covering the cost, despite the fact that is was closed after only 35 years of operation. Immediate decommissioning (Decon) was then expected to cost $994 million, but the decommissioning fund would have had less time to grow sufficiently to cover it, and a $195 million impact on Florida ratepayers would have resulted.

Construction of an onsite dry cask storage facility commenced in 2016, and fuel transfer started in summer 2017 and completed in January 2018. The spent fuel is planned to remain at the onsite storage facility until 2036, when it would be moved to a federal facility. Safstor was expected to end with removal of the unit's remaining components about 2070 and site restoration in 2074. In August 2020 the Florida Public Service commission approved Accelerated Decommissioning Partners completing demolition by 2027 and managing the ISFSI to 2038 for a fixed price of $540 million, fully covered by the existing trust funds of over $700 million (with balance plus any money recovered from suing the DOE returned to ratepayers). Duke will remain the owner to 2038, but Accelerated Decommissioning Partners became the licensed operator of the plant and ISFSI in October 2020.

However, in May 2019 Duke announced that it had contracted with Accelerated Decommissioning Partners (NorthStar and Orano joint venture) for decommissioning Crystal River by 2027, and that this would be covered by the decommissioning fund, which was worth $717 million in the first quarter of 2019. The contract structure transfers the risk of potential cost overruns and latent liabilities to the joint venture. Duke would remain the NRC-licensed owner of the plant, as well as the owner of the land and the trust fund. However, Accelerated Decommissioning Partners would become the plant operator and would take ownership of the associated dry cask storage facility as well as spent nuclear fuel onsite.

Omaha Public Power District's Fort Calhoun plant (482 MWe) closed in 2016 after 43 years operation, since 2012 by Exelon. It is being decommissioned by EnergySolutions from 2019. Safstor was originally intended at a cost of $1.3 billion, but following an OPPD board decision in October 2018 and a contract with EnergySolutions it will now be cleaned up by mid-2020s with an expected saving of $200 million.

In summary, US plants with Decon completed are: Big Rock Point, Elk River, Fort St Vrain, Haddam Neck/Connecticut Yankee, La Crosse, Maine Yankee, Pathfinder, Rancho Seco, San Onofre 1, Saxton, Shippingport, Shoreham, Trojan, Zion 1&2 and Yankee Rowe. (Also Santa Susana Field Laboratory's Sodium Reactor Experiment, which is not included in power reactor tables.) Decon is in progress at Humboldt Bay 3, and will now be adopted at Fort Calhoun and Indian Point.
Yankee Rowe after decommissioning (Yankee Rowe)
US plants in Safstor, either in part or in full, include Crystal River 3, Dresden 1, Fermi 1, Indian Point 1, Kewaunee, Millstone 1, and Peach Bottom 1, as well as NS Savannah. Three Mile Island 2 is in post-defuelling monitored storage. San Onofre 2&3 will also enter Safstor when defuelled.

The only US plants subject to the Entomb option are small experimental ones: Bonus BWR in Puerto Rico, Piqua organic-moderated reactor in Ohio, Hallam graphite-moderated sodium-cooled reactor in Nebraska, and in 2015, EBR-II. No NRC-licensed plant has used this option.

In addition to the above is the first floating nuclear power plant, installed in a former liberty ship, and utilised at Panama 1967-76. The Sturgis had a 45 MWt/10 MWe (net) PWR which provided power to the Canal Zone. After it was defuelled in 1977, some 89 m ³ of solid radioactive waste and 363 m ³ of liquid waste was removed and the vessel placed in safstor at Fort Belvoir, Virginia. In 2014 CB&I was awarded a contract from the US Army to decommission and dismantle the MH-1A PWR. In 2015 the vessel was towed to Texas for dismantling, which was completed in 2019. About 700 tonnes of radioactive waste was removed and 270 tonnes of lead was recycled.

The US Army's SM-1A reactor at Fort Greely in Alaska was shut down in 1972 after ten years' operation. Most of the radioactive waste was then removed and primary components were sealed inside the containment with concrete to Safstor status. Further work is planned to 2022. It operated at 1.8 MWe and 10 MW thermal. The Army's SM-1 at Fort Belvoir, Virginia, was similar and shut down in 1973. It is in Safstor and further work is planned from 2020.

Further information on decommissioning in USA is available from the Nuclear Energy Institute, and from the NRC.

Russian reactors

Rostechnadzor oversees a major program of decommissioning old fuel cycle facilities, financed under the Federal target program on Nuclear and Radiation Safety. Six civil reactors are being decommissioned: three early LWGRs, the Melekess VK-50 prototype BWR, and two larger prototype VVER-440 units at Novovoronezh. Most were shut down 1981-90, the fuel removed, and they now await dismantling, which is staring to progress at Novovronezh.

Russia's Rosenergoatom has concluded that moving from the 'deferred' to 'immediate' dismantling approach to its nuclear reactors being decommissioned would bring a 20% cost saving. Immediate dismantling enables the maximum use of the residual life of the equipment and structures of the shutdown units, reduces maintenance costs, makes use of existing radioactive waste management facilities, and employs the skills of personnel.

Graphite

A number of first-generation reactors had graphite blocks as moderator. This is high-quality reactor-grade material produced at about 3000°C which accumulates some radionuclide contamination while in service, particularly carbon-14 at levels which often means that it must be classified as intermediate-level waste. While it oxidizes slightly under neutron bombardment and also at high temperatures (to CO), it does not burn, but sublimes at 3652°C. There is no risk of oxidation under Safstor conditions.

A 2006 report commissioned by EPRI states: "The graphite moderators of retired gas-cooled nuclear reactors present a difficult challenge during demolition activities. As a result, utilities have not dismantled any moderators of CO2 cooled power reactors to date." However, it concludes that adequate information exists to enable the safe dismantling and processing of graphite moderators, and that the three main options for disposal of this graphite are oxidation to the gas phase and release as carbon dioxide (difficult), direct burial, or recycling into new products for the nuclear industry. In each case, opportunities exist for pre-processing to concentrate or remove radionuclides to enhance the safety of the chosen option. The radionuclide inventory of irradiated graphite is unusual in comparison with other nuclear wastes. Cobalt-60 and tritium are the principal isotopes of short-term importance, carbon-14 and chlorine-36 are dominant in the longer term.

Fast neutron reactors

Several sodium-cooled fast reactors have been decommissioned, but only a few have been dismantled. Germany's KNK-2 at Karlsruhe was shut down in 1991 after 14 years' operation, with fuel removal and initial dismantling in 1993. High levels of activation products meant that much work was remote, and residual sodium meant that some cutting was done in a nitrogen atmosphere. Total cost is estimated as €364 million, with completion expected in 2020.

Other facilities

The French Atomic Energy Commission is decommissioning the UP1 reprocessing plant at Marcoule. This plant started up in 1958 and treated 18,600 tonnes of metal fuels from gas-cooled reactors (both defence and civil) to 1997. Progressive decontamination and dismantling of the plant and waste treatment will span 40 years and cost some EUR 5.6 billion, nearly half of this for treatment of the wastes stored on the site.

Areva is decommissioning the Eurodif enrichment plant at Marcoule since 2012. This involved over 2012-15 the decontamination with ClF ₃ gas to remove the residual uranium left inside, and extract it as UF ₆, then recovery of all produced chloride and fluoride gas before the opening of equipments and circuits. Then over 2016-25 the plant is being dismantled.

Areva completed the dismantling and clean-up of the MOX fuel fabrication plant and plutonium technology workshops (ATPu) at CEA's Cadarache site in 2017. The small fuel fabrication plant had produced fuel for French fast reactors and was closed down in 2003; the ATPu was closed in 2008. Areva described the project as "one of the largest dismantling projects in the world."

The US Department of Energy in August 2010 awarded a $2.1 billion contract to a joint venture between Fluor Corp and Babcock and Wilcox (B&W, now BWXT) for decontamination and decommissioning of the huge (1500 ha) Portsmouth Gaseous Diffusion Plant (GDP) uranium enrichment site in Ohio, from March 2011. In March 2016 the contract was extended by 30 months.

The US Department of Energy in May 2017 awarded a $1.5 billion contract to Four Rivers Nuclear Partnership LLC for the continued deactivation and remediation (D&R) of facilities at the Paducah gaseous diffusion uranium enrichment plant in Kentucky and clean-up of the 1400 ha site. Four Rivers is a CH2M-led company with partners Fluor and BWX Technologies. The Paducah plant was commissioned in 1952 for defence purposes and was leased to USEC from 1993 to 2013. The D&R contract is valued at $750 million for five years, followed by three-year and two-year option periods together worth about $750 million. Fluor had a three-year $420 million DOE contract to clean up the Paducah site from 2014-17.

The US Department of Energy contractors in 2016 finished demolishing the Oak Ridge diffusion enrichment plant in Tennessee, which operated from the early 1940s to 1985, making 120 ha available for other uses.

Many nuclear submarines have been decommissioned over the last decade. In USA, after defuelling, the reactor compartments are cut out of the vessels and are transported inland to Hanford, where they are buried as low-level waste. Russia has decommissioned three nuclear powered icebreakers: Lenin, Sibir and Arktika.

Cost and finance

In most countries the operator or owner is responsible for the decommissioning costs.

The total cost of decommissioning is dependent on the sequence and timing of the various stages of the program. Deferment of a stage tends to reduce its cost, due to decreasing radioactivity, but this may be offset by increased storage and surveillance costs.

Even allowing for uncertainties in cost estimates and applicable discount rates, decommissioning contributes a small fraction of total electricity generation costs. In USA many utilities have revised their cost projections downwards in the light of experience.

Financing methods vary from country to country. Among the most common are:
Prepayment, where money is deposited in a separate account to cover decommissioning costs even before the plant begins operation. This may be done in a number of ways but the funds cannot be withdrawn other than for decommissioning purposes.
External sinking fund (Nuclear Power Levy): This is built up over the years from a percentage of the electricity rates charged to consumers. Proceeds are placed in a trust fund outside the utility's control. This is the main US system, where sufficient funds are set aside during the reactor's operatinig lifetime to cover the cost of decommissioning.
Surety fund, letter of credit, or insurance purchased by the utility to guarantee that decommissioning costs will be covered even if the utility defaults.

In the USA, utilities are collecting 0.1 to 0.2 cents/kWh to fund decommissioning. They must then report regularly to the NRC on the status of their decommissioning funds. About two-thirds of the total estimated cost of decommissioning all US nuclear power reactors has already been collected, leaving a liability of about $9 billion to be covered over the remaining operating lives of about 100 reactors (on the basis of an average of $320 million per unit). NRC data for the end of 2018 indicated that there was a combined total of $64.7 billion held in the decommissioning trust funds covering the 119 operational and retired US nuclear power reactors.

An OECD Nuclear Energy Agency survey published in 2016 reported US dollar (2013) costs in response to a wide survey. For US reactors the expected total decommissioning costs range from $544 to $821 million; for units over 1100 MWe the costs ranged from $0.46 to $0.73 million per MWe, for units half that size, costs ranged from $1.07 to $1.22 million per MWe. For Finland's Loviisa (2 x 502 MWe) the estimate was €326 million. For a Swiss 1000 MWe PWR the detailed estimate amounts to CHF 663 million (€617 million). In Slovakia, a detailed case study showed a total cost of €1.14 billion to decommission Bohunice V1 (2 x 440 MWe) and dismantle it by 2025.

Recycling and reuse of materials from decommissioning

Significant volumes of concrete and steel arise from demolishing decommissioned nuclear facilities. Much of this can be recycled or reused in some way where allowed by national regulation, and unlike 'wastes', transferred to other countries. Clearance levels differ internationally, leaving scope for greater harmonisation, and some levels are unjustifiably conservative, e.g. 100 Bq/kg applying for many radionuclides. Public acceptance of recycling and reuse is often low.

There are several options for recycle and reuse:

Material which is essentially uncontaminated and unconditionally released.

Material that can be melted in a regulated environment followed by metal recycle for consumer products (conditional clearance).

Material with short half-life products that is melted and fabricated in a regulated environment and released for specific industrial applications (e.g. steel bridge).

Material that cannot be released from regulatory control but which may be recycled in the nuclear industry.

Recycling materials from decommissioned nuclear facilities is constrained by the level of radioactivity in them. This is also true for materials from elsewhere, such as gas plants, but the levels specified can be very different. For example, scrap steel from gas plants may be recycled if it has less than 500,000 Bq/kg (0.5 MBq/kg) radioactivity (the exemption level). This level however is one thousand times higher than the clearance level for recycled material (both steel and concrete) from the nuclear industry, where generally anything above 500 Bq/kg may not be cleared from regulatory control for recycling.*
* EC proposed clearance levels for specific nuclides in 1996 were 10 MBq/kg for Fe-55 and Ni-63. Those for the IAEA were 0.3 and 3 MBq/kg respectively. For mixtures of artificial radionuclides, the weighted sum of the nuclide specific activities or concentrations in the same matrix divided by the corresponding release limit must be applied.
There is increasing concern about double standards developing in Europe which allow 30 times the dose rate from non-nuclear recycled materials than from those out of the nuclear industry. Norway and Holland are the only countries with consistent standards. Elsewhere, 0.3 to 1.0 mSv/yr individual dose constraint is applied to oil and gas recyclables, and 0.01 mSv/yr for release of materials with the same kind of radiation from the nuclear industry. The double standard means that the same radionuclide, at the same concentration, can either be sent to deep disposal or released for use in building materials, depending on where it comes from. The 0.3 mSv/yr dose limit is still only one-tenth of most natural background levels, and two orders of magnitude lower than those experienced naturally by many people, who suffer no apparent ill effects.

The main radionuclide in scrap from the oil and gas industry is radium-226, with a half-life of 1600 years as it decays to radon. Those in nuclear industry scrap are cobalt-60 and caesium-137, with much shorter half-lives. Application of a 0.3 mSv/yr dose limit results in a clearance level for Ra-226 of 500 Bq/kg, compared with 10 Bq/kg for nuclear material.

In 2011, 16 decommissioned steam generators from Bruce Power in Canada were to be shipped to Sweden for recycling. Although the Canadian Nuclear Safety Commission (CNSC) approved Bruce Power's plans in 2011 and confirmed steam generator processing is an excellent example of responsible and safe nuclear waste management practices, this caused public controversy at the time, and following the Fukushima nuclear accident plans for this shipment were shelved. These steam generators were each 12m long and 2.5m diameter, with mass 100 t, and contained some 4g of radionuclides with about 340 GBq of activity. Exposure was 0.08 mSv/hr at one metre. They were classified as low-level waste (LLW). Studsvik in Sweden would recycle much of the metal and return about 10% of the overall volume as LLW for disposal in Ontario. The balance would be under 100 Bq/kg, which appeared to be the clearance level.

In 2012 five steam generators from UK plants were shipped to Studsvik in Sweden for recycling. Studsvik has also set up a plant in the UK, at Lillyhall in Cumbria, to recycle materials from nuclear facilities, and this became fully operational in 2013 after processing 2000 t of metal from numerous sites and recycling 96% of it. The balance went to a LLW repository.

To 2015, Studsvik had processed by melting 32,000 tonnes of carbon steel, 5200 t stainless steel, 2033 t aluminium, 1153 t lead, and 3896 t copper cables. All this could be released. EnergySolutions in the USA has recycled over 62,000 tonnes of metal, mostly ferrous.

Under the NEA CPD program ( see below) a 2017 report on Recycling and Reuse of Materials Arising from the Decommissioning of Nuclear Facilities has been published.

International cooperation

The IAEA, the OECD's Nuclear Energy Agency and the Commission of the European Communities are among a number of organisations through which experience and knowledge about decommissioning is shared among technical communities in various countries.

In 1985, the OECD Nuclear Energy Agency launched the International Co-operative Program for the Exchange of Scientific and Technical Information Concerning Nuclear Installation Decommissioning Projects, now known as the Co-operative Program on Decommissioning (CPD). This international collaboration has produced a great deal of technical and financial information. Initially consisting of 10 decommissioning projects in eight countries, the programme has since grown to 70 projects (40 reactors and 30 fuel cycle facilities) in 14 NEA member countries, one non-member economy, and the European Commission. The current agreement runs to 2018.

In 2013, following the Fukushima accident, an International Research Institute for Nuclear Decommissioning (IRID) was established, based in Japan. As well as bringing together knowledge and experience from wrecked reactors, IRID will build up the knowledge base for routine decommissioning.

In January 2015 the IAEA launched an International Project on Decommissioning and Remediation of Damaged Nuclear Facilities, the DAROD project, to help increase nuclear safety under the agency's Nuclear Safety Action Plan that was unanimously adopted by IAEA member states following the 2011 Fukushima accident. The project will run for three years, and involves 35 international experts from 19 IAEA member states.

The important areas where experience is being gained and shared are the assessment of the radioactive inventories, decontamination methods, cutting techniques, remote operation, radioactive waste management and health and safety. The aims are to minimise the radiological hazards to workers and to optimise the dismantling sequence and timing to reduce the total decommissioning cost.

Reasons for shutdown

Most decommissioned reactors were shut down because there was no longer any economic justification for running them. Practically all are relatively early-model designs, and about 45 are experimental or prototype power reactors. Three categories are listed here:

1. Experimental, early commercial types and commercial units whose continued operation was no longer justified, usually for economic reasons. Most of these started up before 1980 and their short operating lifetime is not surprising for the first couple of decades of a major new technology. Many of these (marked with an asterisk in the Table) ran relatively full-term, for design lifetimes of 25-35 years or so (design lifetimes today are 40-60 years).

2. Units which closed following an accident or serious incident (not necessarily to the reactor itself) which meant that repair was not economically justified.

3. Units which were closed prematurely by political decision or due to regulatory impediment without clear or significant economic or technical justification.

In fact the distinctions are not always sharp, e.g. Chernobyl 2 was closed in 1991 after a turbine fire when it would have been politically impossible to repair and restart it, Rheinsberg was closed in 1990 though it was nearly at the end of its design lifetime - both these are in the 'political decision' category.
Reactors closed following damage in an accident or serious incident (12) Reactors closed prematurely by political decision or consideration (46) Reactors closed having fulfilled their purpose or being no longer economic to run (139)
prot= prototype, exp= experimental, (total prototype + experimental = 44), * = ran approx full-term

Notes & references

IMechE Conference Transactions, International Conference on Nuclear Decommissioning, ISBN 978-0852989555 (1995-7)
OECD Nuclear Energy Agency, Recycling and Reuse of Scrap Metals, A Report by a Task Group of the Co-operative Programme on Decommissioning (1996)
OECD Nuclear Energy Agency, Decommissioning Nuclear Power Plants: Policies, Strategies and Costs (2003)
OECD Nuclear Energy Agency, Decommissioning Funding: Ethics, Implementation, Uncertainties, A Status Report, NEA No. 5996 (2006)
OECD Nuclear Energy Agency, Costs of Decommissioning Nuclear Power Plants, NEA No. 7201 (2016)
OECD Nuclear Energy Agency, Recycling and Reuse of Materials Arising from the Decommissioning of Nuclear Facilities, NEA No. 7310 (2017)
Dennis Reisenweaver and Michele Laraia, Preparing for the End of the Line: Radioactive Residues from Nuclear Decommissioning, IAEA Bulletin, 42/3/2000 (September 2000)
Nuclear Energy Institute, Decommissioning of Nuclear Power Plants factsheet (August 2016)
Edward C. Doubleday, A Decommissioning Wrapup: Commercial Reactor Decommissioning Status in 2006, Radwaste Solutions, Volume 14, Number 2 (March/April 2007)
International Atomic Energy Agency, Power Reactor Information System (PRIS)
International Atomic Energy Agency, Policies and Strategies for the Decommissioning of Nuclear and Radiological Facilities, Nuclear Energy Series No. NW-G-2.1, STI/PUB/1525 (December 2011)
Graphite Decommissioning: Options for Graphite Treatment, Recycling, or Disposal, including a discussion of Safety-Related Issues, EPRI, 1013091 (March 2006)
Decommissioning in Germany, Nuclear Engineering International (27 March 2013)

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Nuclear Decommissioning: Decommission nuclear facilities - World Nuclear Association

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Decommissioning costs for nuclear power plants, including disposal of associated wastes, contribute only a small fraction of the total cost of electricity generation. Proven techniques and equipment are available to dismantle nuclear facilities.

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Myth- Nuclear energy is less efficient than renewable energy

"Nuclear is far more reliable than renewables like wind and solar. Nuclear can operate even when the sun is not shining and the wind is not blowing." - Change Oracle

"Nuclear energy is a low-carbon energy; 4x less CO2 and 2x less hydroelectricity than solar power." - Orano Group

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While renewable energy is widely touted as the future of energy, nuclear power is increasingly being discussed as a necessary part of the mix

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Myth- write out your statement.

Evidence- two lines of evidence from two different sources.

Post the link to one of your sources.

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Historic Rule Making

The published final rule making allows utilities to reference NuScale's SMR design when applying for a combined license to build and operate a reactor.

The design is an advanced light-water SMR with each power module capable of generating 50 megawatts of emissions-free electricity.

NuScale's VOYGR™ SMR power plant can house up to 12 factory-built power modules that are about a third of the size of a large-scale reactor. Each power module leverages natural processes, such as convection and gravity, to passively cool the reactor without additional water, power, or even operator action.

The NRC accepted NuScale's SMR design certification application back in March 2018 and issued its final technical review in August 2020. The NRC Commission later voted to certify the design on July 29, 2022-making it the first SMR approved by the NRC for use in the United States.

"We are thrilled to announce the historic rulemaking from the Nuclear Regulatory Commission for NuScale's small modular reactor design, and we thank the Department of Energy (DOE) for their support throughout this process," said NuScale Power President and Chief Executive Officer John Hopkins. "The DOE has been an invaluable partner with a shared common goal - to establish an innovative and reliable carbon-free source of energy here in the U.S. We look forward to continuing our partnership and working with the DOE to bring the UAMPS Carbon Free Power Project to completion."

"SMRs are no longer an abstract concept," said Assistant Secretary for Nuclear Energy Dr. Kathryn Huff. "They are real and they are ready for deployment thanks to the hard work of NuScale, the university community, our national labs, industry partners, and the NRC. This is innovation at its finest and we are just getting started here in the U.S.!"

NuScale is currently seeking an uprate to enable each module to generate up to 77 megawatts. The NRC is expected to review their application this year.

Supporting SMR Development

The U.S. Department Energy provided more than $600 million since 2014 to support the design, licensing, and siting of NuScale's VOYGR SMR power plant and other domestic SMR concepts.

DOE is currently working with Utah Associated Municipal Power Systems (UAMPS) through the Carbon Free Power Project to demonstrate a six-module NuScale VOYGR plant at Idaho National Laboratory.

The first module is expected to be operational by 2029 with full plant operation the following year.

UAMPS finished subsurface field investigation activities at the proposed INL site and expects to submit a combined license application to the NRC in the first quarter of 2024.

NuScale Power has 19 signed and active domestic and international agreements to deploy SMR plants in 12 different countries, including Poland, Romania, the Czech Republic, and Jordan in addition to the Carbon Free Power Project.

Learn more about NuScale Power design certification process with the NRC.

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NRC Certifies First U.S. Small Modular Reactor Design

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NuScale power module becomes the first SMR design certified by the NRC.