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SOURCES :

https://padlet-uploads.storage.googleapis.com/76131477/7baa29c2f5eaa1cfa0afcc3147f55dcc2bc386c6/d8adc80f42426ef812c8b7b74b14569a.pdf

https://www.youtube.com/watch?v=zdkWGsnzTXk

http://www.world-nuclear.org/info/Non-Power-Nuclear-Applications/Transport/Nuclear-Reactors-for-Space

http://science.nationalgeographic.com/science/space/universe/nuclear-comeback.html

http://www.universetoday.com/118431/exploring-the-universe-with-nuclear-power/

http://www.islandone.org/Propulsion/ProjectOrion.html

https://www.youtube.com/wa tch?v=WoiVej1rccs

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Project NERVA was an acronym for Nuclear Engine for Rocket Vehicle Application, a joint program of the U.S. Atomic Energy Commission and NASA managed by the Space Nuclear Propulsion Office (SNPO) at the Nuclear Rocket Development Station in Jackass Flats, Nevada U.S.A.

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Spacecraft Development & Testing of Orion

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Levitation , Teleportation & Lightspeed Travel Prt

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Spacecraft Technology - Light Speed Travel of the Future? (1080p)

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This space video documentary explains current theories on speed of light spacecraft and focusing on propulsion technology which may get us to other planets, solar systems, and galaxies. FOLLOW ON: https://www.facebook.com/documentarytube.net https://twitter.com/DocArchive

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Did you refer to any other sources ?

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Who is the author of this article you have mentioned?

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Did you refer to any other sources?

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How did you get the source of your information

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We think that the production of nuclear energy is the most feasible process since the recent development of technology ensures a growth in it's production and utilization.

It would be a huge leap made by mankind if nuclear energy can be produced in significantly large quantities which in turn can be used not only for domestic purposes but also for space exploration and other areas of science.

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What are the advantages ?

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what is the source of your information?

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What did you chose Krishna?

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I have chosen nuclear enegy.

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Can you describe it?

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What are disadvantages?

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Can you give a brief explanation?

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Please describe it!

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I have chosen nuclear weaponery

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Some of the applications of nuclear power are:

·It can be used to generate a cleaner source of energy.

·It can be used in space research.

·Nuclear technology is useful in many branches of

science.

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The main applications of nuclear science in space exploration

1)Project Orion (http://www.islandone.org/Propulsion/ProjectOrion.html)

2)Project Prometheus

(http://www.space.com/929-nasas-prometheus-fire-smoke-mirrors.html)

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Applications of nuclear weapon technology :

1) Nuclear generators which provide 1000 times more electricity than traditional one does.

2) Does not emit carbondioxide  and is the only solution for global warming.

3)Nuclear weapons are powerful defence to against terrorist activities.

4)  Nobody thinks of waging wars or getting into political or cultural chaos with these nations and nation security can be assured.

5) these can be used in civil engineering to destroy big hills etc.

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These are some of the new words I came across in my article:

Liberalization-The removal or loosening of restrictions on something, typically an economic or political  system

Empowerment

- Authority or power given to someone to do something

Derail-Obstruct(a process) by diverting it from its intended course

Barrage-An over whelming number of

questions,criticisms, or complaints delivered simultaneously or in rapid succession

ABCC-Atomic Bombing Casualty Commission

RERF-Radiation Effects Research Foundation

millisieverts (mSv)-It is the international unit to measure radiation

Abstinence-The practice ofrestrainingoneself fromindulgingin something

Endorse-Declare one’s public approval or support of

Mitigate-Lessen the gravity of (an offence or mistake)

Escapism-an activity, a form of entertainment, etc. that

helps you avoid or forget unpleasant or boring things

IAEA-International Atomic Energy Agency

Vitrification-Convert(something) into glass or aglass-likesubstance

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These are few new abbreviations and words I came across in my article.

Abbreviations

COPUOS - Committee on the Peaceful Uses of Outer Space

UNOOSA - United Nations Office for Outer Space Affairs

RTG- Radioisotope Thermoelectric Generator

GRHS RTG-General Purpose Heat Source Radioisotope Thermoelectric Generator

MM RTG - Multi-Mission Radioisotope Thermoelectric Generator

SRG - Stirling Radioisotope Generator

Ti M E - Titan Mare Explorer

RHU - Radioactive Heater Units

RORSATs - Radar Ocean Reconnaissance Satellites

NNSA -National Nuclear Security Administration

VASIMR - Variable Specific Impulse Magnetoplasma Rocket

SAFE - Safe Affordable Fission Engine

HOMER - Heatpipe-Operated Mars Exploration Reactor

Meanings

Eutectic - of greatest fusibility

Brayton cycle - A thermodynamic cycle that describes the workings of a constant pressure heat engine.

Epithermal Neutrons -  neutrons of kinetic energy greater than that of thermal motion

Plasma - An ionized gas consisting of positive ions and free electrons in proportions

Envisage - Contemplate or conceive of as a possibility or a desirable future event.

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Few new words i came across in my article

Escalation - a rapid increase

Pervasiveness - having the quality or tendency to pervade or permeate

Pyrrhic - won at too great a cost to have been worthwhile for the victor

Doctrine - a belief or set of beliefs held and taught by a church, political party, or other group

Deterrence -  the inhibition of criminal behavior by fear especially of punishment

Denial - a statement that sometimes is not true

Vulnerable - exposed to the possibility of being attacked or harmed

Subtleties - the quality or state of being subtle

Recuperation - the recovery or regaining of something

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Audience- Scientists

1: Can nuclear weapons be used in civil engineering?

2: Is there a chance to use nuclear weapons for energy production?

3: What measures are be taken to minimise radioactivity emitted during an explosion?

4: What makes nuclear weapons more powerful than chemical explosives?

5.Can we achieve 99% of  light speed by continuous nuclear propulsion?

6. Is it possible for a spacecraft to withstand such high speed?(If it is possible to attain that speed)

7. Can we use ion thrusters (electric propulsion ) and nuclear propulsion together?

8. Why is nuclear power still not being used in spacecrafts ?

9.Can Nuclear waste be disposed off safely without any harmful effects by using the improving  technology?

10.What safety measures should be taken in order to minimise power plant disasters?

11.Are there any alternative energy sources which have more advantages than nuclear energy and have a scope of development in the future?

12.Out of Thorium and Uranium ,which will act as a better fossil fuel?

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Exploring the latest in scientific discoveries from prehistoric life to missions to Mars.

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Project Orion: Its Life, Death, and Possible Rebirth

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The race to the moon, in the forms of Project Apollo and the still-shadowy Soviet lunarprogram, dominated manned space flight during the decade of the 1960's. In the United States, the project sequence Mercury-Gemini-Apollo succeeded in putting roughly sixty people into space, twelve of them on the moon.

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Effects of Nuclear Weapons | Science | atomicarchive.com

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Examine the thermal radiation, blast and human effects of nuclear weapons. Nuclear explosions produce both immediate and delayed destructive effects. Blast, thermal radiation, and prompt ionizing radiation are produced and cause significant destruction within seconds or minutes of a nuclear detonation.

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Follow me on Twitch! https://www.twitch.tv/enigmahood Like me on Facebook, https://www.facebook.com/Enigmahood Follow me on Twitter, https://twitter.com/EnigmaHood This is an overview of the 4th generation of nuclear weapons outlined in the report, Fourth Generation Nuclear Weapons: Military effectiveness and collateral effects, condensed into an easy to digest video.

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10 Horrifying Facts About Nuclear Weapons

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Brahmasthra a Nuclear Weapon From History Channel

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The brahmastra is similar to the modern nuclear weapon manipulated by atomic energy SB 1.7.27 The Son of Drona Punished TEXT 27 TEXT sri-bhagavan uvaca vetthedam drona-putrasya brahmam astram pradarsitam naivasau veda samharam prana-badha upasthite SYNONYMS sri-bhagavan--the Supreme Personality of Godhead; uvaca--said; vettha--just know from Me; idam--this; drona-putrasya--of the son of Drona; brahmam astram--hymns of the brahma (nuclear) weapon; pradarsitam--exhibited; na--not; eva--even; asau--he; veda--know it; samharam--retraction; prana-badhe--extinction of life; upasthite--being imminent.

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These are a few

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Over 2,000 atomic bombs have been detonated worldwide since 1945. This is a brief timeline showing every blast on a world map up until 1998.

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An article written by Bruno Comby

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"America is addicted to oil," George W Bush told us in 2006. W was worried particularly about America, but the problem is really a global one. Of course you might not want to believe the ex-president, because he also said (in the same speech): "Americans should not fear our economic future, because we intend to shape it" - two years before the most massive financial recession seen since the 1930s.

But Bush was right about the oil part. Regardless of where you stand on climate change, the world at some point and maybe sooner than we think, is going to run out of oil. According to the Hirsch report, commissioned by the US department of energy, peak oil has already occurred or is about to occur. "Peak oil" is simply when the world is at the peak of extracting oil from the ground, after which we will go into steep decline. If you are optimistic, peak oil isn't coming anytime soon. If like W and the Hirsch report, you are not so optimistic, peak oil has happened or is just about to and we have on the outside about 20 years until we feel the effects.

Running out of oil has much bigger consequences than just not being able to drive your car to work or not being able to watch TV. Most of the world's hydrogen comes from cracking of oil into useful stuff like octane for engines, or hydrogen for hydrogen-storage, hydrogen for fertilisers that keep the world's population fed. Hydrogen can also be produced by splitting water but this also requires energy - which often ultimately comes from a fossil-fuel base. If we are not prepared when the world runs out of oil, bad things are going to happen.

So what are the alternatives? There are many. Wind - but it has to be windy; solar - but it has to be sunny; hydroelectric - but you have to have water. While many of these energy technologies are good short-to-medium-term solutions and often the perfect local solution, what about the longer term? What about the global energy problem? What about nuclear? Until we develop new technologies, nuclear power is currently the best alternative to oil.

Europe in general, and Germany in particular, have fallen out of love with nuclear power. Angela Merkel announced a plan in 2010 to phase out nuclear by 2021 - marking a complete reversal in Germany's current energy policy. The US, on the other hand, seems to be re-enamored with the nuclear idea. Barack Obama recently announced that The US department of energy, in conjunction with none other than philanthrocapitalist Bill Gates, have an aim to increase the number of nuclear reactors in the US by the year 2022.

Nuclear power often gets a raw deal, partially for some very good reasons. The waste, for starters. It is difficult to know what to do with nuclear waste. It takes for ever to lose its radioactivity - so long that at the moment the only viable solution is to immobilise and store it. This is not ideal for obvious reasons.

Nuclear accidents also get some rather scary press - Chernobyl, Fukushima and Three Mile Island. Not that these weren't nuclear or industrial accidents, they definitely were, but it is good to be a bit careful about throwing out the baby with the cooling bath water. Nuclear accidents are sort of like plane crashes in our cultural mentality. Planes are by and large one of the safest ways to travel, yet plane crashes can hit the news for days at a time. I am not saying plane crashes aren't tragic, they are; but so is dying in a car crash - an event that happens much more often.

In all of these "disasters" some relatively dumb mistakes and painful oversights were made. Such as waiting almost 18 hours to flood Fukushima Daiichi with sea water to cool the reactor. The potential environmental consequences seem fairly large with Chernobyl, though it is hotly debated whether this is solely the result of radiation. In the Three Mile Island meltdown, no one =even got hurt, which isn't bad going for an industrial accident. If anything, the Three Mile Island meltdown should make us all feel better about reactor safety in general. Big meltdown, no one died. There is an excellent book that compares the relative environmental and health risks of nuclear reactors with other industries - Terrestrial Energy by William Tucker, who argues that more deaths are caused by our traditional power plants than by nuclear power.

Despite the downsides, the benefits of nuclear power should not be overlooked. It is not oil. Nuclear fuel does not produce CO ₂. Nuclear plants are relatively accident-free. There is plenty of radioactive material around currently. Nuclear fuel itself is non-renewable but breeder reactors produce more fuel than they use. The few cons there are, like storage and safety issues, are actually why governments need to fund nuclear energy research. Research monies for making safer reactors and better containment would be nice for a start, but government money needs to be found for "blue skies" nuclear research too. Blue-skies funding is what led scientists to find a way to split the atom in the first place. Now it is time to figure out how to safely get rid of radioactive waste. Now is the time to put some serious funding into nuclear energy research, because in 10 years we may not be able to turn the lights on.

Sylvia McLain runs a research lab in Oxford. She is GirlInterruptin on Twitter.
Topics

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"America is addicted to oil," George W Bush told us in 2006. W was worried particularly about America, but the problem is really a global one. Of course you might not want to believe the ex-president, because he also said (in the same speech): "Americans should not fear our economic future, because we intend to shape it" - two years before the most massive financial recession seen since the 1930s.

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Energy cannot be created nor be destroyed but it can be converted from one form to another. Nearly all the mass of the atom is concentrated in a tiny nucleus in the center. The nucleus is composed principally of two sorts of particles: the proton which carries the positive charge and the neutron which is electrically neutral and has a mass slightly bigger than that of proton. Nuclear energy is the energy released from the nucleus of an atom. When nuclear reaction occurs weather fission or fusion, it produces large amount of energy.

Lately, debates have raged over nuclear energy, which begs the question: Is nuclear energy the perfect formula that will finally satisfy the needs of the world's electricity or will it end up to be the evil power that devastates the world? Read on to find the answers to this question.

Although the subject of nuclear power has evoked bitter memories such as the destruction of Hiroshima and Nagasaki, the Three Mile Island disaster, the Chernobyl accident and the nuclear catastrophe in Japan, it has one very attractive feature; it's not fossil fuel. This means it does not need pumping out of the ground and does not contribute to dangerous emissions.

Nuclear energy is produced using two main processes; fission and fusion. Nuclear fission is able to generate well over 10 million times the energy which is produced by the combustion of fossil fuels. That's the good part. On the flip side, nuclear fusion (which involves joining nuclei) is able to produce vast amounts of nuclear energy, but safe control mechanisms have not been developed yet. Fusion occurs naturally up in the sun and the stars as well as in nuclear reactors built by humans.

Various Advantages of Nuclear Energy

While using fossil fuels to generate electricity may carry no threat of a large disaster, they are not good for the environment since they emit unlimited amounts of greenhouse gasses. Nuclear energy is completely safe for the environment if managed properly. Here is a rundown on the main advantages of nuclear energy:

Nuclear reactors offer impressive based-load electricity and operate and produce power over 90% of the time. The periods between refueling have been substantially extended, plus downtime for refueling has been significantly minimized. In the United States, for example, these enhancements through the years have been equated to building one reactor each year to the existing ones. Most nuclear reactors are designed to operate for more than 40 years. Most of the reactors are nearing that age in perfect condition and projections are that they could still operate for another 20 years.

Nuclear reactor operations emit zero greenhouse gasses. Although the process of mining, enrichment, construction and waste management of uranium involves emission of greenhouse gasses, the total emissions are way lower compared to emissions from fossil fuels.

The cost of nuclear power is very much stable and competitive. On the other hand, the cost of power derived from fossil fuels pretty much depends on the market. When the market is good, oil prices become stable. When the market is volatile, oil prices may shoot up or plummet.

A nuclear power station is compact, which means it quintessentially covers an area the size of a football stadium and the surroundings. Wind turbines, solar cells, and growing biomass all need huge area of land.

The modern day nuclear power plants are safe

Developers of the current nuclear power plants have drawn from the weaknesses of the past disasters like the Three Mile Island, Chernobyl, and Japan. The current nuclear power plants do not depend on external electricity supplies or external water supplies for purposes of cooling. Instead, they utilize water fed by gravity, gas pressurized water tanks, and natural convection heat exchangers. These systems are referred to as ''passive safety systems." Another advantage is the reactors can be installed underground offering added insulation against unauthorized access and external hazards

Costs of operation are substantially low

Although the costs of setting up a nuclear power plant are extremely high, the electricity produced afterward is very cheap. To start with, the cost of uranium, the raw material for the production of nuclear energy, is not expensive. When the plant is up and running, the maintenance cost will hardly be felt. Even if market shifts occur and the cost of uranium shoots up, the effect on the cost of power will hardly be felt.

The other main advantage of using nuclear energy is that it is very powerful and efficient than other alternative energy sources. Advancement in technologies has made it more viable option than others. This is one the reason that many countries are putting huge investments in nuclear power. At present, a small portion of world's electricity comes through it.

Is Nuclear Energy Renewable?

The definition of renewable energy involves unlimited availability of the resource, the capability to replenish itself and the characteristic to cause minimum impact on the environment. The question of whether nuclear energy is renewable still elicits debates to this day despite the fact that it is a low-carbon power generation source. The 5 substantiated renewable sources of energy used on a daily basis include solar, wind, hydro, geothermal and biomass.

However, the largest point of view stipulates that nuclear energy is not really renewable. This hinges on a wide range of facts such as:

The chief raw material for the production of nuclear energy (uranium) is not a renewable resource. Uranium resources are quite limited, and the mining and refining process mightily impacts the environment. Also, transportation of uranium is risky. Safe transportation involves significant capital outlay and a lot of energy consumption.

After processing uranium, significant amounts of radioactive waste are generated. The resultant elements have extensive storage requirements and are known to stay radioactive and hazardous for thousands of years. Most countries have tried to recycle it, but the whole process is ineffective and relatively expensive, not to mention it's a daunting task to store it safely. To add insults to the injury, nuclear storage sites can become prime targets for terrorists who are hellbent on killing more people simultaneously.

Some facts show that nuclear energy could become renewable

It's a well-known fact that uranium resources are limited. However, their conversion to plutonium can relatively elongate their availability. Light water reactors make use of use uranium-235, which attributes to 0.7% of all natural uranium. On the other hand, IFRs or fast breeder reactors utilize uranium-238, which attributes to 99.3% of all natural uranium. Fast-breeder kinds of nuclear reactors are able to generate huge quantities of fissionable plutonium capable of sustaining nuclear reactions way longer than traditional fuels. This process of plutonium production could give nuclear energy the renewable status. Another advantage to plutonium production is that the waste left behind is a lot less hazardous. The waste will stop being radioactive after a few hundred years.

The good thing about nuclear waste from nuclear power plants is that it can be transferred into reprocessing units such that 95% of the spent fuel is able to be recycled and transported back for use in the nuclear plant. This process enormously minimizes the amount and toxicity of radioactive waste, making room for separate handling (storage or destruction) of the waste. Reprocessing of radioactive waste has since turned political with anti-technology lobby groups striving to end the proliferation of anything related to nuclear by dwelling on the extraordinary costs of reprocessing and the threat of terrorism.
Verdict
Despite the raging debates and contradictions, nuclear energy doesn't qualify yet as a renewable energy considering the present state of production and waste disposal. Uranium, the chief raw material for nuclear energy production, is still a limited fuel resource (in fact, it occurs only in specific countries) and the reactors have the possibility of one day becoming unstable and dangerous. Also, reprocessing of nuclear waste is not happening as it should.

Nevertheless, if adjustments to the reactors under development and safe processing of radioactive waste would happen, nuclear energy could well be on its way to becoming a renewable energy.

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Advantages of Nuclear Energy - Conserve Energy Future

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Energy cannot be created nor be destroyed but it can be converted from one form to another. Nearly all the mass of the atom is concentrated in a tiny nucleus in the center. The nucleus is composed principally of two sorts of particles: the proton which carries the positive charge and the neutron which is electrically neutral and has a mass slightly bigger than that of proton.

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"If it begins to overheat, a little plug melts and the salts drain into a pan. There is no need for computers, or the sort of electrical pumps that were crippled by the tsunami. The reactor saves itself," he said.

"They operate at atmospheric pressure so you don't have the sort of hydrogen explosions we've seen in Japan. One of these reactors would have come through the tsunami just fine. There would have been no radiation release."

Thorium is a silvery metal named after the Norse god of thunder. The metal has its own "issues" but no thorium reactor could easily spin out of control in the manner of Three Mile Island, Chernobyl, or now Fukushima.

Professor Robert Cywinksi from Huddersfield University said thorium must be bombarded with neutrons to drive the fission process. "There is no chain reaction. Fission dies the moment you switch off the photon beam. There are not enough neutrons for it continue of its own accord," he said.

Dr Cywinski, who anchors a UK-wide thorium team, said the residual heat left behind in a crisis would be "orders of magnitude less" than in a uranium reactor.

The earth's crust holds 80 years of uranium at expected usage rates, he said. Thorium is as common as lead. America has buried tons as a by-product of rare earth metals mining. Norway has so much that Oslo is planning a post-oil era where thorium might drive the country's next great phase of wealth. Even Britain has seams in Wales and in the granite cliffs of Cornwall. Almost all the mineral is usable as fuel, compared to 0.7pc of uranium. There is enough to power civilization for thousands of years.

I write before knowing the outcome of the Fukushima drama, but as yet none of 15,000 deaths are linked to nuclear failure. Indeed, there has never been a verified death from nuclear power in the West in half a century. Perspective is in order.

We cannot avoid the fact that two to three billion extra people now expect - and will obtain - a western lifestyle. China alone plans to produce 100m cars and buses every year by 2020.

The International Atomic Energy Agency said the world currently has 442 nuclear reactors. They generate 372 gigawatts of power, providing 14pc of global electricity. Nuclear output must double over twenty years just to keep pace with the rise of the China and India.

If a string of countries cancel or cut back future reactors, let alone follow Germany's Angela Merkel in shutting some down, they shift the strain onto gas, oil, and coal. Since the West is also cutting solar subsidies, they can hardly expect the solar industry to plug the gap.

BP's disaster at Macondo should teach us not to expect too much from oil reserves deep below the oceans, beneath layers of blinding salt. Meanwhile, we rely uneasily on Wahabi repression to crush dissent in the Gulf and keep Arabian crude flowing our way. So where can we turn, unless we revert to coal and give up on the ice caps altogether? That would be courting fate.

US physicists in the late 1940s explored thorium fuel for power. It has a higher neutron yield than uranium, a better fission rating, longer fuel cycles, and does not require the extra cost of isotope separation.

The plans were shelved because thorium does not produce plutonium for bombs. As a happy bonus, it can burn up plutonium and toxic waste from old reactors, reducing radio-toxicity and acting as an eco-cleaner.

Dr Cywinski is developing an accelerator driven sub-critical reactor for thorium, a cutting-edge project worldwide. It needs to £300m of public money for the next phase, and £1.5bn of commercial investment to produce the first working plant. Thereafter, economies of scale kick in fast. The idea is to make pint-size 600MW reactors.

Yet any hope of state support seems to have died with the Coalition budget cuts, and with it hopes that Britain could take a lead in the energy revolution. It is understandable, of course. Funds are scarce. The UK has already put its efforts into the next generation of uranium reactors. Yet critics say vested interests with sunk costs in uranium technology succeeded in chilling enthusiasm.

The same happened a decade ago to a parallel project by Nobel laureate Carlo Rubbia at CERN (European Organization for Nuclear Research). France's nuclear industry killed proposals for funding from Brussels, though a French group is now working on thorium in Grenoble.

Norway's Aker Solution has bought Professor Rubbia's patent. It had hoped to build the first sub-critical reactor in the UK, but seems to be giving up on Britain and locking up a deal to build it in China instead, where minds and wallets are more open.

So the Chinese will soon lead on this thorium technology as well as molten-salts. Good luck to them. They are doing Mankind a favour. We may get through the century without tearing each other apart over scarce energy and wrecking the planet.

This is my last column for a while. I am withdrawing to the Mayan uplands.

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Safe nuclear does exist, and China is leading the way with thorium

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A few weeks before the tsunami struck Fukushima’s uranium reactors and shattered public faith in nuclear power, China revealed that it was launching a rival technology to build a safer, cleaner, and ultimately cheaper network of reactors based on thorium.

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Nuclear Power in India | Indian Nuclear Energy - World Nuclear Association

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India has a vision of becoming a world leader in nuclear power technology due to its expertise in fast reactors and thorium nuclear fuel cycle.

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Lord Julian Hunt on the risks of nuclear power and advantages of renewable energy sources 2

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Yes some of them are

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Lord Julian Hunt on advantages of nuclear power 3

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an article in wwww.universetoday.com

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In the past four decades, NASA and other space agencies from around the world have accomplished some amazing feats. Together, they have sent manned missions to the Moon, explored Mars, mapped Venus and Mercury, conducted surveys and captured breathtaking images of the Outer Solar System. However, looking ahead to the next generation of exploration and the more-distant frontiers that remain to be explored, it is clear that new ideas need to be put forward of how to quickly and efficiently reach those destinations.

Basically, this means finding ways to power rockets that are more fuel and cost-effective while still providing the necessary power to get crews, rovers and orbiters to their far-flung destinations. In this respect, NASA has been taking a good look at nuclear fission as a possible means of propulsion.

In fact, according to presentation made by Doctor Michael G. Houts of the NASA Marshall Space Flight Center back in October of 2014, nuclear power and propulsion have the potential to be "game changing technologies for space exploration."

As the Marshall Space Flight Center's manager of nuclear thermal research, Dr. Houts is well versed in the benefits it has to offer space exploration. According to the presentation he and fellow staffers made, a fission reactor can be used in a rocket design to create Nuclear Thermal Propulsion (NTP). In an NTP rocket, uranium or deuterium reactions are used to heat liquid hydrogen inside a reactor, turning it into ionized hydrogen gas (plasma), which is then channeled through a rocket nozzle to generate thrust.

A second possible method, known as Nuclear Electric Propulsion (NEC), involves the same basic reactor converted its heat and energy into electrical energy which then powers an electrical engine. In both cases, the rocket relies on nuclear fission to generates propulsion rather than chemical propellants, which has been the mainstay of NASA and all other space agencies to date.

Compared to this traditional form of propulsion, both NTP and NEC offers a number of advantages. The first and most obvious is the virtually unlimited energy density it offers compared to rocket fuel. At a steady state, a fission reactor produces an average of 2.5 neutrons per reaction. However, it would only take a single neutron to cause a subsequent fission and produce a chain reaction and provide constant power.

In fact, according to the report, an NTP rocket could generate 200 kWt of power using a single kilogram of uranium for a period of 13 years - which works out of to a fuel efficiency rating of about 45 grams per 1000 MW-hr.

In addition, a nuclear-powered engine could also provide superior thrust relative to the amount of propellant used. This is what is known as specific impulse, which is measured either in terms of kilo-newtons per second per kilogram (kN·s/kg) or in the amount of seconds the rocket can continually fire. This would cut the total amount of propellent needed, thus cutting launch weight and the cost of individual missions. And a more powerful nuclear engine would mean reduced trip times, another cost-cutting measure.

Although no nuclear-thermal engines have ever flown, several design concepts have been built and tested over the past few decades, and numerous concepts have been proposed. These have ranged from the traditional solid-core design to more advanced and efficient concepts that rely on either a liquid or a gas core.

In the case of a solid-core design, the only type that has ever been built, a reactor made from materials with a very high melting point houses a collection of solid uranium rods which undergo controlled fission. The hydrogen fuel is contained in a separate tank and then passes through tubes around the reactor, gaining heat and converted into plasma before being channeled through the nozzles to achieve thrust.

Using hydrogen propellant, a solid-core design typically delivers specific impulses on the order of 850 to 1000 seconds, which is about twice that of liquid hydrogen-oxygen designs - i.e. the Space Shuttle's main engine.

However, a significant drawback arises from the fact that nuclear reactions in a solid-core model can create much higher temperatures than the conventional materials can withstand. The cracking of fuel coatings can also result from large temperature variations along the length of the rods, which taken together, sacrifices much of the engine's potential for performance.

Many of these problems were addressed with the liquid core design, where nuclear fuel is mixed into the liquid hydrogen and allowing the fission reaction to take place in the liquid mixture itself. This design can operate at temperatures above the melting point of the nuclear fuel thanks to the fact that the container wall is actively cooled by the liquid hydrogen. It is also expected to deliver a specific impulse performance of 1300 to 1500 (1.3 to 1.5 kN·s/kg) seconds.

However, compared to the solid-core design, engines of this type are much more complicated, and therefore more expensive and difficult to build. Part of the problem has to do with the time it takes to achieve a fission reaction, which is significantly longer than the time it takes to heat the hydrogen fuel. Therefore, engines of this kind require methods to both trap the fuel inside the engine while simultaneously allowing heated plasma the ability to exit through the nozzle.

The final classification is the gas-core engine, a modification of the liquid-core design that uses rapid circulation to create a ring-shaped pocket of gaseous uranium fuel in the middle of the reactor that is surrounded by liquid hydrogen. In this case, the hydrogen fuel does not touch the reactor wall, so temperatures can be kept below the melting point of the materials used.

An engine of this kind could allow for specific impulses of 3000 to 5000 seconds (30 to 50 kN·s/kg). But in an "open-cycle" design of this kind, the losses of nuclear fuel would be difficult to control. An attempt to remedy this was drafted with the "closed cycle design" - aka. the "nuclear lightbulb" engine - where the gaseous nuclear fuel is contained in a series of super-high-temperature quarts containers.

Although this design is less efficient than the open-cycle design, and has a more in common with the solid-core concept, the limiting factor here is the critical temperature of quartz and not that of the fuel stack. What's more, the closed-cycle design is expected to still deliver a respectable specific impulse of about 1500-2000 seconds (15-20 kN·s/kg).

However, as Houts indicated, one of the greatest assets nuclear fission has going for it is the long history of service it has enjoyed here on Earth. In addition to commercial reactors providing electricity all over the world, naval vessels (such as aircraft carriers and submarines) have made good use of slow-fission reactors for decades.

Also, NASA has been relying on nuclear reactors to power unmanned craft and rover for over four decades, mainly in the form of Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units (RHU). In the case of the former, heat is generated by the slow decay of plutonium-238 (Pu-238), which is then converted into electricity. In the case of the latter, the heat itself is used to keep components and ship's systems warm and running.

These types of generators have been used to power and maintain everything from the Apollo rockets to the Curiosity Rover, as well as countless satellites, orbiters and robots in between. Since its inception,a total of 44 missions have been launched by NASA that have used either RTGs or RHUs, while the former-Soviet space program launched a comparatively solid 33.

Nuclear engines were also considered for a time as a replacement for the J-2, a liquid-fuel cryogenic rocket engine used on the S-II and S-IVB stages on the Saturn V and Saturn I rockets. But despite their being numerous versions of a solid-core reactors produced and tested in the past, none were ever put into service for an actual space flight.

Between 1959 and 1972, the United States tested twenty different sizes and designs during Project Rover and NASA's Nuclear Engine for Rocket Vehicle Application (NERVA) program. The most powerful engine ever tested was the Phoebus 2a, which during a high-power test operated for a total of 32 minutes - 12 minutes of which were at power levels of more than 4.0 million kilowatts.

But looking to the future, Houts' and the Marshall Space Flight Center see great potential and many possible applications. Examples cited in the report include long-range satellites that could explore the Outer Solar System and Kuiper Belt, fast, efficient transportation for manned missions throughout the Solar System, and even the provisions of power for settlements on the Moon and Mars someday.

One possibility is to equip NASA's latest flagship - the Space Launch System (SLS) - with chemically-powered lower-stage engines and a nuclear-thermal engine on its upper stage. The nuclear engine would remain "cold" until the rocket had achieved orbit, at which point the upper stage would be deployed and reactor would be activated to generate thrust.

This concept for a "bimodal" rocket - one which relies on chemical propellants to achieve orbit and a nuclear-thermal engine for propulsion in space - could become the mainstay of NASA and other space agencies in the coming years. According to Houts and others at Marshall, the dramatic increase in efficiency offered by such rockets could also facilitate NASA's plans to explore Mars by allowing for the reliable delivery of high-mass automated payloads in advance of manned missions.

These same rockets could then be retooled for speed (instead of mass) and used to transport the astronauts themselves to Mars in roughly half the time it would take for a conventional rocket to make the trip. This would not only save on time and cut mission costs, it would also ensure that the astronauts were exposed to less harmful solar radiation during the course of their flight.

To see this vision become reality, Dr. Houts and other researchers from the Marshall Space Center's Propulsion Research and Development Laboratory are currently conducting NTP-related tests at the Nuclear Thermal Rocket Element Environmental Simulator (or "NTREES") in Huntsville, Alabama.

Here, they have spent the past few years analyzing the properties of various nuclear fuels in a simulated thermal environment, hoping to learn more about how they might effect engine performance and longevity when it comes to a nuclear-thermal rocket engine.

These tests are slated to run until June of 2015, and are expected to lay the groundwork for large-scale ground tests and eventual full-scale testing in flight. The ultimate goal of all of this is to ensure that a manned mission to Mars takes place by the 2030s, and to provide NASA flight engineers and mission planners with all the information they need to see it through.

But of course, it is also likely to have its share of applications when it comes to future Lunar missions, sending crews to study Near-Earth Objects (NEOs), and sending craft to the Jovian moons and other locations in the outer Solar System. As the report shows, NTP craft can be easily modified using modular components to perform everything from Lunar cargo landings to crewed missions, to surveying Near-Earth Asteroids (NEAs).

The universe is a big place, and space exploration is still very much in its infancy. But if we intend to keep exploring it and reaping the rewards that such endeavors have to offer, our methods will have to mature. NTP is merely one proposed possibility. But unlike Nuclear Pulse Propulsion, the Daedalus concept, anti-matter engines, or the Alcubierre Warp Drive, a rocket that runs on nuclear fission is feasible, practical, and possible within the near-future.

Nuclear thermal research at the Marshall Center is part of NASA's Advanced Exploration Systems (AES) Division, managed by the Human Exploration and Operations Mission Directorate and including participation by the U.S. Department of Energy.

Alcubierre Warp Drive, anti-matter, bimodal, Daedalus star ship, gas-core nuclear engine, hydrogen fuel, liquid-core nuclear engine, manned mission to Mars, NASA, nuclear electric propulsion (NEC), nuclear engine for rocket vehicle application (NERVA), nuclear fission, nuclear lightbulb engine, nuclear pulse, nuclear reactor, nuclear spacecraft, nuclear thermal propulsion (NTP), Radioisotope Heater Unit (RHU), Radioisotope Thermoelectric Generator (RTG), solid-core nuclear engine, Space Launch System (SLS), Space Shuttle, specific impulse, uranium

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Exploring the Universe with Nuclear Power - Universe Today

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In the past four decades, NASA and other space agencies from around the world have accomplished some amazing feats. Together, they have sent manned missions to the Moon, explored Mars, mapped Venus and Mercury, conducted surveys and captured breathtaking images of the Outer Solar System.

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Only nuclear power is not necessarily used in spacecrafts. A combination of nuclear power and other propellants can also be used. For example, chemical propellants can be used for travelling from a planet to its orbit and nuclear power can be used for travelling between the planets.

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These disadvantages can be resolved by specific methods mentioned in the articles below.

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1)Less availability of nuclear substances.

2)Creating very high temperatures and velocity withstandingmetals.

3)Hard to design and build

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Advantages of nuclear powered spacecraft

1)High specific impulse.

2)Less time for traveling.

3)Achieving very high speed.

4)Virtual unlimited energy(Ex:1 kg of uranium can be used up to 13 years)

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While I was searching through the web for a good article relevant to my topic,I stumbled upon the one I have uploaded above

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The authors are:

LARRY GILMAN

K. LEE LERNER

DEAN ALLEN HAYCOCK

HERMAN KAHN.

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International encyclopedia and encyclopedia ofEspionage

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Nuclear Weapons. The possibility of creating nuclear weapons of almost unimaginable destructive power was first realized in the 1930s as physicists developed a fundamental understanding of the nucleus of the atom. A nuclear explosion is created when heavy nuclei are split-or fissioned -into several of their component parts that are smaller and more stable.

Nuclear fission is a fundamentally different process from chemical explosions that occur in conventional high‐explosive or incendiary bombs. In chemical explosions, larger molecular structures are broken apart and rearranged into smaller parts, but the individual atomic nuclei remain untouched. A chemical explosion produces a sudden release of energy that generates an explosive blast, whose resulting high air pressures and strong winds can crush and knock down nearby structures and people. In the case of early nuclear weapons based on the fission process, the energy release, which occurs in microseconds, is enormously larger because the nuclear bonds that hold nuclei together and are broken during fission are so much stronger than the chemical bonds that bind atoms into molecules. Since the nuclear forces are typically 100,000 to 1 million times stronger than the electrical ones responsible for molecular structures, the resultant energy releases are correspondingly larger.

The nuclear blast is so powerful that it can crush objects many miles away with high winds in excess of 150 mph generated at distances greater than a mile. The release of the enormous energy in a nuclear explosion leads to extremely high temperatures, comparable to those that occur at the center of the Sun, causing massive and deadly fires. As a measure of comparison, the temperatures generated by nuclear weapons are hundreds to thousands of times higher than the temperatures on the surface of the Sun, which heats the surface of the Earth from a distance of more than 90 million miles. Dangerous radioactive fallout is also spread over large distances by the resulting nuclear radiation emerging with the nuclear debris.

The ability to release such enormous energy from single weapons, on a scale unparalleled in human history, profoundly alters the very nature of war, as well as its consequences. An appreciation of the consequences of a nuclear explosion can be learned from the experience of the only nuclear weapons used in war, the atomic bombs dropped by U.S. air forces on Hiroshima and Nagasaki in 1945. These two weapons devastated two entire cities. They had yields of 15-20 kilotons. That measure simply means that the energy release was the same as that from detonating 15,000-20,000 tons of TNT (TNT is an acronym for the chemical formula of dynamite). By way of comparison, the largest conventional bombs used in World War II-the so‐called blockbusters used by the Royal Air Force (RAF)-detonated 10 tons (20,000 pounds) of TNT.

Those fission bombs of 1945 are no more than primitive versions of the first stage, or triggers, of modern nuclear weapons, whose yields range into the megatons, or millions of tons of TNT equivalent, and whose deadly devastating impact ranges over many miles. (One kiloton is equivalent to 2 million pounds of TNT; 1 megaton is equivalent to 2 billion pounds of TNT.) In modern nuclear weapons, such fission triggers are known as the primaries. They ignite a secondary stage by creating very high temperatures in order to generate still larger quantities of energy by driving together, or fusing, light nuclei into more stable ones. This is known as fusion. Such modern weapons are commonly referred to as thermonuclear weapons-or, more simply, H‐bombs.

The effect of a 1‐megaton thermonuclear weapon has an energy release 100,000 times greater than the largest 10‐ton blockbusters of World War II; the area destroyed by blast would be several thousand times larger than that leveled by such blockbusters. Collateral destruction and casualties due to fires and radioactive fallout would extend even further than the area destroyed by blast.

Soon after World War II, it was realized that the existence of nuclear weapons posed a new and fearsome threat to modern civilization and that it was vital to treat them differently from "conventional"-nonnuclear-weapons. Serious initiatives during the decade immediately following WWII tried to bring these terrifying new weapons under international control. These efforts failed as the confrontation between the Western powers and the Soviet Union and its allies grew into a cold war. Fueled by this dangerous competition during the 1960s, the individual nuclear arsenals of the United States and the Soviet Union accumulated to tens of thousands of warheads. In addition, France, England, and China acquired their own, albeit much smaller, nuclear arsenals. Furthermore, the newly developed delivery systems of intercontinental‐range, and in particular, land‐based intercontinental ballistic missiles (ICBMs)-and long‐range ballistic missiles on submarines (SLBMs) moving about invisibly under the surface of the oceans-brought the threat of nuclear annihilation very close to home, less than thirty minutes away from a nation's borders.

It also became clear before long that there was no known or prospective technology that could provide a defense against a determined nuclear attack. In contrast to previous wars, essentially nothing would be left of a large urban "target"-its population and industry-if just one, or at most a few, nuclear warheads exploded over it. Witness the bombings of Hiroshima and Nagasaki.

A defense would have to be essentially perfect to provide protection against nuclear weapons, and that is neither a realistic standard of performance today nor a prospective one for future military systems. In World War II, during the Battle of Britain, the RAF defense system managed to destroy no more than one in ten of the attacking planes. At such a rate, the German Air Force was reduced faster than it could replace its losses. At the same time, cities like London could put out the fires and rebuild after the damage. Human defenselessness is a basic fact of the nuclear age. It is also troubling since it denies one of the most basic instincts of the human race: to defend ourselves, our families, our friends, our vital interests. Recognition of the ineffectiveness of defenses against the almost unimaginable destructive potential of a massive attack by nuclear bombs led the United States and the former Soviet Union to acknowledge that their very survival was based on mutual deterrence -ensuring that nuclear weapons were not used.

The first step in detonating a thermonuclear weapon is to ignite the high explosive that causes a shock wave to travel inward and compress the nuclear material the explosive surrounds, known as the pit. At the same time, a strong source of neutrons is activated to flood the compressed pit.

If the material in the compressed pit reaches a condition known as criticality, the neutrons initiate a strong fission chain reaction. This is the fission, or primary, stage of a thermonuclear explosion. In a chain reaction, an incoming neutron splits the nucleus of fissile material (either an isotope of uranium, U ²³⁵, that occurs in nature, or of plutonium, Pu ²³⁹, that is man‐made), releasing at least two neutrons, which then run into other fissile material, producing more neutrons, which then run into other fissile material, and so on. Thus, in successive steps, or "generations," of fission, the neutrons will multiply: 2, 2 × 2, 2 × 2 × 2, ... After very roughly 100 generations, if the fissile material can be held together long enough, (i.e., for microseconds), enough nuclei will have fissioned and enough energy will have been created to generate an explosive equivalent to 10 kilotons or so of TNT.

Several years after the development of such first‐generation fission bombs, weapons designers concentrated on improving their performance by using the material more efficiently. U.S. and Soviet weapons technology advanced rapidly after the first Soviet nuclear detonation, "Joe 1," in 1949. The biggest advance occurred when the process of fusion was introduced into the explosive process. Fusion, in contrast to fission, involves combining, or fusing together, several nuclei of the lightest elements, such as hydrogen isotopes, to form more stable heavy ones. High temperatures are required to ignite the fusion process effectively. This is because at high temperatures, individual nuclei acquire high speeds, and move sufficiently rapidly to push their way though their mutual electric repulsion and get near enough to each other to collide and "fuse" together. The new nucleus thus formed is generally more stable, leading to the release of a large energy, plus more neutrons. Fusion is the process fueling the Sun's burning.

Modern weapons with both fission and fusion stages are called thermonuclear or hydrogen bombs. In a thermonuclear weapon, the primary, or fission, stage creates the necessary high temperatures to ignite the fusion stage, which provides additional neutrons to initiate still more fission, thereby releasing much more energy. A thermonuclear weapon can be built with virtually no limit on the amount of fusion materials it contains. Such weapons generate explosions as large as tens of megatons of TNT, or the equivalent of billions of pounds of TNT. In thinking about the totality of destruction in a nuclear war waged with modern thermonuclear weapons of such enormous yield, it is well to keep in mind that many of the destructive effects of nuclear weapons were not anticipated, and were discovered with surprise by atomic scientists when they were used or tested. This calls for great humility when it comes to predicting the consequences of nuclear warfare.

Since 1945, the total number of known nuclear tests, worldwide, adds up to some 2,000. A major purpose of testing has been to validate and confirm appropriate performance specifications for new weapons types designed in response to military needs formulated during the Cold War. Starting in the mid‐1950s, U.S. weapons were designed and built "ready to go." They conserved special nuclear materials (SNM)-the fissile materials Pu ²³⁹ and U ²³⁵-and were essentially maintenance‐free, ready to go at any time. "Ready" means that no physical changes or steps such as inserting the SNM had to be made in order to detonate a bomb. One merely had to launch and detonate the warhead by signal.

In response to growing worldwide concerns about radioactive fallout from continued nuclear testing, the United States, the Soviet Union, and the United Kingdom joined in 1963 in a Limited Test Ban Treaty that forbade testing aboveground, in the atmosphere, underwater, and in outer space. Only underground testing was allowed. A further restriction on testing was negotiated in 1974, limiting the yields of underground tests to a maximum of 150 kilotons, roughly ten times the yield of the Hiroshima bomb. This so‐called Threshold Test Ban Treaty was generally obeyed henceforth, though it was not ratified until 1990.

In 1992, progress in negotiated reductions in the nuclear arsenals, and further progress in reducing reliance on nuclear weapons after the end of the Cold War, led President George Bush to rule out nuclear weapons tests for new warheads and to declare a nine‐month moratorium on all nuclear testing. This moratorium was continued by his successor and has also been honored by Russia and the United Kingdom. On 11 August 1995, President Bill Clinton announced U.S. support for negotiating a comprehensive test ban treaty in 1996. The treaty would be of unending duration, and would include, as do all such tests, a "supreme national interest" clause should unanticipated circumstances present compelling arguments for renewed tests. Such arguments might arise if there were serious reversals from the present progress toward reducing nuclear danger in the world, or if unforeseen technical problems arose over time in the enduring nuclear stockpile.

By the best current technical judgment, U.S. weapons appear to be safe, reliable, age‐stable, and fully adequate for deterrence; but it will be a new challenge to maintain that confidence without being able to conduct tests that produce any nuclear yield. Under its recently formulated program for stockpile stewardship and management, the United States has accepted this challenge, following a comprehensive scientific review of prospects and needs for its nuclear arsenal. So have the United Kingdom, Russia, France, and China.

On September 1996 President Clinton was the first world leader to sign the Comprehensive Test Ban Treaty at the United Nations in New York. Soon thereafter the other declared nuclear powers-England, France, China, and Russia-also signed, and as of November 1998 150 nations have signed the Treaty and twenty‐one have ratified it. For it to go into effect it must be ratified by all forty‐four nuclear capable nations, i.e., nations with nuclear reactors for research or for civilian energy production, in addition to those with nuclear weapons. A Comprehensive Test Ban after more than 2,000 tests over a 50‐year period would be a tremendous achievement. Efforts to accomplish that goal are currently in progress, together with continuing efforts to reduce the size of the nuclear arsenals at the Strategic Arms Reduction Talks (START) underway between the U.S. and Russia.
[See also Arms Control and Disarmament: Nuclear; Cold War: External Course; Cold War: Domestic Course; War Plans; Weaponry; World War II: Military and Diplomatic Course.]

Bibliography

Margaret Gowing , Britain and The Atomic Energy, 1939-1945, 1964.
Samuel Glasstone and Philip J. Dolan, eds., The Effects of Nuclear Weapons, 3rd ed. 1977.
Richard Rhodes , The Making of the Atomic Bomb, 1986.
Robert Serber ,
David Holloway , Los Alamos Primer: The First Lectures on How to Build an Atomic Bomb, 1992.Stalin and the Bomb, 1994.
Richard Rhodes , Dark Sun: The Making of the Hydrogen Bomb, 1995.

Sidney Drell

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nuclear weapons facts, information, pictures | Encyclopedia.com articles about nuclear weapons

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Nuclear Weapons. The possibility of creating nuclear weapons of almost unimaginable destructive power was first realized in the 1930s as physicists developed a fundamental understanding of the nucleus of the atom. A nuclear explosion is created when heavy nuclei are split-or fissioned -into several of their component parts that are smaller and more stable.

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Advantages:

It can be used in civil engineering,as power source.

Disadvantages:

it can be used as bombs in wars. It was used in world war 2 also.

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There are two authors

A.P.J ABDUL KALAM

SRIJAN PAL SINGH

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An article in The Hindu website

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what is the source of your study?

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An article in a world nuclear organisation website

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Radioisotope power sources have been an important source of energy in space since 1961.

Nuclear fission reactors for space have been used mainly by Russia, but new and more powerful designs are under development in both the USA and Russia.

Plutonium-238 is a vital power source for deep space missions.

Nuclear power reactors use controlled nuclear fission in a chain reaction. With the use of neutron absorbers, the rate of reaction is controlled, so the power depending on the demand.

Radioisotope Thermoelectric Generators (RTGs) are an alternative source of power where a chain reaction does not take place. The power depends on the initial amount of the radioisotope used as fuel and the power is provided by converting the heat generated by radioactive decay of the radioisotope into electricity using thermocouples. Most RTGs use plutonium-238. With the use of RTGs, the power generated cannot be varied or shut down so supplementary batteries need to be taken into account for the peak times. RTGs are used when spacecraft require less than 100 kW. Above that, fission systems are much more cost effective than RTGs.

The United Nations has an Office for Outer Space Affairs (UNOOSA)* which implements decisions of the Committee on the Peaceful Uses of Outer Space (COPUOS) set up in 1959 and now with 71 member states. UNOOSA recognises "that for some missions in outer space nuclear power sources are particularly suited or even essential owing to their compactness, long life and other attributes" and "that the use of nuclear power sources in outer space should focus on those applications which take advantage of the particular properties of nuclear power sources." It has adopted a set of principles applicable "to nuclear power sources in outer space devoted to the generation of electric power on board space objects for non-propulsive purposes," including both radioisotope systems and fission reactors.

* UNOOSA has the dual objective of supporting the intergovernmental discussions in the Committee and its Scientific and Technical Subcommittee (S&T) and Legal Subcommittee, and of assisting developing countries in using space technology for development. In addition, it follows legal, scientific and technical developments relating to space activities, technology and applications in order to provide technical information and advice to Member States, international organizations and other United Nations offices.

Radioisotope systems - RTGs

Radioisotope Thermoelectric Generators (RTGs) have been the main power source for US space work since 1961. The high decay heat of Plutonium-238 (0.56 W/g) enables its use as an electricity source in the RTGs of spacecraft, satellites and navigation beacons. Its intense alpha decay process with negligible gamma radiation calls for minimal shielding. Americium-241, with 0.15 W/g, is another source of energy, favoured by the European Space Agency, though it has high levels of relatively low-energy gamma radiation. Heat from the oxide fuel is converted to electricity through static thermoelectric elements (solid-state thermocouples), with no moving parts. RTGs are safe, reliable and maintenance-free and can provide heat or electricity for decades under very harsh conditions, particularly where solar power is not feasible.

The importance of such power sources was illustrated by the European Space Agency's Rosetta mission, which successfully landed the Philae probe on comet 67P/Churymov-Gerasimenko in 2014. Equipped with batteries and solar panels, the position in which Philae came to rest on the comet's surface - shielded from the Sun's rays by cliffs - meant that the lander was unable to make use of solar energy and was only able to send 64 hours' worth of data before its battery power ran out.

So far over 45 RTGs have powered in excess of 25 US space vehicles including Apollo, Pioneer, Viking, Voyager, Galileo, Ulysses and New Horizons space missions as well as many civil and military satellites. The Cassini spacecraft carried three RTGs providing 870 watts of power from 33 kg plutonium-238 oxide as it explored Saturn. It was launched in 1997, entered Saturn's orbit in 2004, and functioned very well until it was terminated in September 2017. Voyager spacecraft which have sent back pictures of distant planets have already operated for over 35 years since 1977 launch and are expected to send back signals powered by their RTGs through to 2025. Galileo, launched in 1989, carried a 570-watt RTG. The Viking and Rover landers on Mars in 1975 depended on RTG power sources, as does the Mars Science Laboratory rover launched in 2011. Three RTGs (each with 2.7 grams of plutonium-238 dioxide) were used as heat sources on the Pathfinder Mars robot lander launched in 1996, producing 35 watts. Each produced about one watt of heat. (The 10.5 kg Pathfinder rovers in 1997 and the two Mars rovers operating 2004-09 used solar panels and batteries, with limited power and life.)

The latest plutonium-powered RTG is a 290-watt system known as the GPHS RTG. The thermal power for this system is from 18 general purpose heat source (GPHS) units. Each GPHS contains four iridium-clad ceramic Pu-238 fuel pellets, stands 5 cm tall, 10 cm square and weighs 1.44 kg. The multi-mission RTG ( MMRTG) (see below image) uses eight GPHS units with a total of 4.8 kg of plutonium oxide producing 2 kW thermal which can be used to generate some 110 watts of electric power, 2.7 kWh/day.
Multi-Mission Radioisotope Thermoelectric Generator (MMRT). Source: NASA
MMRTG technology is being used in the NASA Mars Science Laborator y mission's rover Curiosity (see below image), which at 890 kg is about five times the mass of previous Mars rovers. Another rover project, Mars 2020, will utilise the MMRTG, and is planned for launch in 2020.
NASA's Curiosity Mars rover. Source: NASA/JPL-Caltech/MSSS
Russia's Institute of Space Research (IKI) of the Russian Academy of Sciences and the Bauman Moscow State Technical University are developing three types of lunar rovers, one of them a heavy, 'nuclear-powered' lunar rover. This will weigh 550-750 kg and is designed to study polar regions of the Moon. In addition to solar panels and batteries, a nuclear power source is to be installed on the rover to enable it to operate for up to 400 kilometres, including in the shade. It will carry up to 70 kg of scientific equipment, including special drills to extract soil samples from a depth of 1.5 metres. The rover will also be equipped with 16 small stations to study the regolith and seismic activity of the Moon.

ExoMars is a joint project between the Russian space agency Roscosmos and European Space Agency (ESA) to research evidence of life on Mars, and will utilise RTGs. The mission will ultimately deliver a European rover and a Russian surface platform to Mars. The first part of the mission was launched in 2016, the primary purpose of which is to test for evidence of methane and other trace atmospheric gases. The second part of the mission is planned to launch in 2020.

The New Horizons spacecraft which flew by Pluto in July 2015 has a 250 watt, 30 volt GPHS RTG which would have decayed to about 200 watts by the time of the Pluto flyby (it was launched in 2006). It uses 10.9 kg of Pu-238 oxide and is less powerful than originally designed, due to production delays. There are 16 Aerojet thrusters controlling trajectory and attitude of the 478 kg craft. Four of the thrusters generate 4.4 N, while 12 generate 0.9 N thrust. The fuel for these is 65 kg of hydrazine

The Stirling Radioisotope Generator (SRG) is based on a 55-watt electric converter powered by one GPHS unit. The hot end of the Stirling converter reaches 650°C and heated helium drives a free piston reciprocating in a linear alternator, heat being rejected at the cold end of the engine. The AC is then converted to 55 watts DC. This Stirling engine produces about four times as much electric power from the plutonium fuel than an RTG. Thus each SRG will utilise two Stirling converter units with about 500 watts of thermal power supplied by two GPHS units and will deliver 130-140 watts of electric power from about 1 kg Pu-238. The SRG and Advanced SRG (ASRG) have been extensively tested but have not yet flown. NASA planned to use two ASRGs for its probe to Saturn's moon Titan (Titan Mare Explorer, TiME) or that to the comet Wirtanen, though these missions have been postponed in favour of the Mars InSight mission originally scheduled for March 2016, now likely mid-2018. In November 2013, after spending $270 million on it, NASA halted development of the ASRG due to budget constraints, claiming that it had enough Pu-238 for MMRTGs.

NASA also said that production of Pu-238 was being ramped up to 1.5 kg/yr by the mid-2020s, and by the end of 2015 over $200 million had been spent on this (see information paper on Plutonium). Since the 1990s the USA has relied on Russian supplies of Pu-238 produced at Mayak, and has bought 16.5 kg of it. However, Russia no longer produces or sells it.

Russia has developed RTGs using Po-210, two are still in orbit on 1965 Cosmos navigation satellites. But it concentrated on fission reactors for space power systems. China's Chang'e 3 lunar lander apparently uses RTGs with Pu-238.

Americium-241 can be used for RTGs. It has about one-quarter of the energy of Pu-238, but is cheaper and readily available from clean-up of aged civil plutonium stocks such as in the UK. It also has a longer half-life - 432 years instead of 88 years. However it has much higher gamma activity (8.48 mSv/hr/MBq at one metre is quoted) and has been disregarded for that reason. However the European Space Agency is setting out to use it and is paying for Am-241 recovered from the UK's civil plutonium by the National Nuclear Laboratory to be used for its RTGs.

As well as RTGs, radioactive heater units ( RHUs) are used on satellites and spacecraft to keep instruments warm enough to function efficiently. Their output is only about one watt and they mostly use Pu-238 - typically about 2.7g of it. Dimensions are about 3 cm long and 2.5 cm diameter, weighing 40 grams. Some 240 have been used so far by the USA and two are in shutdown Russian lunar rovers on the moon, these using polonium-210. Eight were installed on each of the US Mars Rovers Spirit and Opportunity, which landed in 2004, to keep the batteries functional. China's Chang'e 3 lunar rover Yutu apparently uses several RHUs.

The Idaho National Laboratory's (INL) Centre for Space Nuclear Research (CSNR) in collaboration with NASA is developing an RTG-powered hopper vehicle for Mars exploration. When stationary the vehicle would study the area around it while slowly sucking up carbon dioxide from the atmosphere and freezing it, after compression by a Stirling engine. Meanwhile a beryllium core would store heat energy required for the explosive vaporisation needed for the next hop. When ready for the next hop, nuclear heat would rapidly vaporise the carbon dioxide, creating a powerful jet to propel the craft up to 1000 metres into the 'air'. A small hopper could cover 15 km at a time, repeating this every few days over a ten-year period. Hoppers could carry payloads of up to 200 kg and explore areas inaccessible to the Rovers. INL suggests that a few dozen hoppers could map the Martian surface in a few years, and possibly convey rock samples from all over the Martian surface to a craft that would bring them to Earth.

Both RTGs and RHUs are designed to survive major launch and re-entry accidents intact.

A Stirling engine uses any external heat source through a gaseous working fluid to drive a reciprocating piston which turns a crankshaft to do mechanical work. The working fluid is permanently contained, and through a regenerator with heat exchanger can recycle continuously. The working gas is expanded in the hot portion and compressed in the cold portion of the engine, thus converting heat to work. The larger the temperature difference between the hot and cold sections of a Stirling engine, the greater its efficiency. In single-cylinder designs a displacer piston moves the working gas back and forth between the hot and cold heat exchangers.

Fission systems - heat and propulsion

For higher power requirements, fission power systems (FPS) have a distinct cost advantage over RTGs. As currently conceived, FPS would be launched cold, with essentially no radioactive hazards. Reactor start-up is after the device is in orbit. Then the reactor automatically responds to thermal load changes and maintains safe operating temperatures based on negative temperature reactivity feedback, giving it load-following capability. Low reactor power would reduce thermal stresses and provide tolerance to potential damaging transients. The low fuel burn-up minimises fission products that would cause adverse radiation effects on reactor materials and spacecraft components.

After a gap of several years, there is a revival of interest in the use of nuclear fission power for space missions. While Russia has used over 30 fission reactors in space, the USA has flown only one - the SNAP-10A (System for Nuclear Auxiliary Power) in 1965.

Early US program: 1960s to 1980s

Early on, from 1959-73 there was a US nuclear rocket programme - Nuclear Engine for Rocket Vehicle Applications (NERVA) - which was focused on nuclear power replacing chemical rockets for the latter stages of launches. NERVA used graphite-core reactors heating hydrogen and expelling it through a nozzle. Some 20 engines were tested in Nevada and yielded thrust up to more than half that of the space shuttle launchers. Since then, 'nuclear rockets' have been about space propulsion, not launches. The successor to NERVA is today's nuclear thermal rocket (NTR).

Another early idea was the US Project Orion, which would launch a substantial spacecraft - about 1000 tonnes - from the earth using a series of small nuclear explosions to propel it. The project was commenced in 1958 by General Atomics and was aborted in 1963 by the Atmospheric Test Ban Treaty. The Orion project gave ideas for other projects for example ICAN-II and AIMStar as other means of generating the propulsive pulses are considered.

The US SNAP-10A launched in 1965 was a 45 kWt thermal nuclear fission reactor to produce 650 watts with ZrH moderator (or UZrH fuel) and eutectic NaK coolant feeding thermoelectric converter panels. It operated for 43 days at 590 watts, but was shut down due to a voltage regulator (not reactor) malfunction. It remains in orbit.

The last US space reactor initiative in this period was a joint NASA-DOE-Department of Defense program developing the SP-100 reactor - a 2 MWt fast reactor unit and thermoelectric system delivering up to 100 kWe - as a multi-use power supply for orbiting missions or as a lunar/Martian surface power station. This was terminated in the early 1990s after absorbing nearly $1 billion. The reactor used uranium nitride fuel and was lithium-cooled.

There was also a Timberwind pebble bed reactor concept under the Deparment of Defense Multi-Megawatt (MMW) space power program during the late 1980s, in collaboration with the DOE. This had power well beyond any civil space program requirements. But see MegaPower below.

For spacecraft propulsion, once launched, some experience has been gained with nuclear thermal rocket (NTP or NTR) propulsion systems, which are said to be well-developed and proven. Nuclear fission heats a hydrogen propellant which is stored as liquid in cooled tanks. The hot gas (about 2500°C) is expelled through a nozzle to give thrust (which may be augmented by injection of liquid oxygen into the supersonic hydrogen exhaust). This is more efficient than chemical reactions. Bimodal versions will run electrical systems on board a spacecraft, including powerful radars, as well as providing propulsion. Compared with nuclear electric plasma systems, these have much more thrust for shorter periods and can be used for launches and landings.

Later US programs: 1990s on

In the late 1980s attention turned to nuclear electric propulsion (NEP) systems, where nuclear reactors are a heat source for electric ion drives expelling plasma out of a nozzle to propel spacecraft already in space. Superconducting magnetic cells ionise xenon (or hydrogen), heat it to extremely high temperatures (millions °C), and use very high voltage to accelerate it and expel it at very high velocity ( e.g. 30 km/s) to provide thrust. While the thrust is miniscule relative to a rocket, its application in space over a long period ( e.g. years) can lead to high velocity of the spacecraft. NASA's Dawn spacecraft operating between Mars and Jupiter since 2007 uses an ion thruster, as do over 100 geosynchronous Earth orbit communication satellites. They both extend the operating lifetimes of satellites and reduce launch and operation costs. Xenon is used because it is easily ionised and has relatively high atomic mass, as well as being inert and having high storage density.

The first NASA space mission with an ion thruster was from 1998 to 2001. The NASA Solar Technology Application Readiness ( NSTAR) ion propulsion system enabled the Deep Space 1 mission, the first spacecraft propelled primarily by ion propulsion, to travel over 260 million kilometres and make flybys of the asteroid Braille and the comet Borelly. The NASA Evolutionary Xenon Thruster (NEXT) and the Annular Engine are developments of this. NEXT is a high-power ion propulsion system designed to reduce mission cost and trip time, operating at three times the power level of NSTAR. NASA's patented Annular Engine has the potential to exceed the performance capabilities of NEXT and other electric propulsion thruster designs, with a total (annular) beam area that is twice as great.

Research for one version, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) draws on that for magnetically-confined fusion power (tokamak) for electricity generation, but here the plasma is deliberately leaked to give thrust. The system works most efficiently at low thrust (which can be sustained), with small plasma flow, but shorter high thrust operation is possible. It is very efficient, with 99% conversion of electric to kinetic energy, though only 70% is claimed for the short thrust firings. The VX200, a 200kW version, was being tested in 2015 with a view to deployment on space missions for nuclear electric propulsion. It could also be used for removal of space debris, pushing into low orbit for burn-up. NASA has contracted Ad Astra Rocket Co to develop a new version, VX-200SS ("SS" stands for "steady state"), featuring a new core design and thermal controls, operating at temperatures of 1,000,000 ºC while almost entirely eliminating the need for vast quantities of rocket fuel.

Heatpipe Power System (HPS) reactors are compact fast reactors producing up to 100 kWe for about ten years to power a spacecraft or planetary surface vehicle. They have been developed since 1994 at the Los Alamos National Laboratory as a robust and low technical risk system with an emphasis on high reliability and safety. They employ heatpipes* to transfer energy from the reactor core to make electricity using Stirling or Brayton cycle converters.
* A heatpipe is a heat transfer device combining thermal conductivity with phase change. At the hot end a liquid vapourises under low pressure and at the other end it condenses, releasing its latent heat of vapourisation. The liquid then returns to the hot end, either by gravity or capillary action, to repeat the cycle. (If using gravity, they are sometimes called two-phase thermosiphons, but capillary 'pumping' using surface tension is the main mechanism used.)
In the 1990s design, energy from fission is conducted from the fuel pins to the heatpipes filled with sodium vapour which carry it to the heat exchangers and then in hot gas to the Stirling or Brayton power conversion systems to make electricity. The gas is 72% helium and 28% xenon. The reactor itself contains a number of heatpipe modules with the fuel. Each module has its central heatpipe with rhenium-clad fuel sleeves arranged around it. They are the same diameter and contain 97% enriched uranium nitride fuel, all within the cladding of the module. The modules form a compact hexagonal core. Control is by six stainless steel clad beryllium drums each 11 or 13 cm diameter with boron carbide forming a 120 degree arc on each. The drums fit within the six sections of the beryllium radial neutron reflector surrounding the core, and rotate to effect control, moving the boron carbide in or out.

Shielding is dependent on the mission or application, but lithium hydride in stainless steel cans is the main neutron shielding.

The SAFE-400 space fission reactor (Safe Affordable Fission Engine) is a 400 kWt HPS of 100 kWe to power a space vehicle using two Brayton power systems - gas turbines driven directly by the hot gas from the reactor. Heat exchanger outlet temperature is 880°C. The reactor has 127 identical heatpipe modules made of molybdenum, or niobium with 1% zirconium. Each has three fuel pins 1 cm diameter, nesting together into a compact hexagonal core 25 cm across. The fuel pins are 70 cm long (fuelled length 56 cm), the total heatpipe length is 145 cm, extending 75 cm above the core, where they are coupled with the heat exchangers. The core with reflector has a 51 cm diameter. The mass of the core is about 512 kg and each heat exchanger is 72 kg. SAFE has also been tested with an electric ion drive.

A smaller version of this kind of reactor is the HOMER-15 - the Heatpipe-Operated Mars Exploration Reactor. It is a 15 kW thermal unit similar to the larger SAFE model, and stands 2.4 metres tall including its heat exchanger and 3 kWe Stirling engine (see above). It operates at only 600°C and is therefore able to use stainless steel for fuel pins and heatpipes, which are 1.6 cm diameter. It has 19 sodium heatpipe modules with 102 fuel pins bonded to them, 4 or 6 per pipe, and holding a total of 72 kg of fuel. The heatpipes are 106 cm long and fuel height 36 cm. The core is hexagonal (18 cm across) with six BeO pins in the corners. The total mass of reactor system is 214 kg, and diameter is 41 cm.

Another small fission surface power system for the moon and Mars was announced by NASA in 2008. The 40 kWe system could utilise one of two design concepts for power conversion. The first, by Sunpower of Athens, Ohio, uses two opposed piston engines coupled to alternators that produce 6 kilowatts each, or a total of 12 kilowatts of power. The second, by Barber Nichols of Arvada, Colorado, is for development of a closed Brayton cycle engine which uses a high-speed turbine and compressor coupled to a rotary alternator that also generates 12 kilowatts of power. NASA itself will develop the heat rejection system and provide the space simulation facility. In mid-2012 NASA reported successful tests of power conversion and radiator components of this 40 kWe system, which is based on a small fission reactor heating up and circulating a liquid metal coolant mixture of sodium and potassium. The heat differential between this and the outside temperature would drive two complementary Stirling engines to turn a 40 kWe generator. Some 100 square metres of radiators would remove process heat to space.

US Project Prometheus: 2003-2007

In 2002 NASA announced its Nuclear Systems Initiative for space projects, and in 2003 this was renamed Project Prometheus and given increased funding. Its purpose was to enable a major step change in the capability of space missions. Nuclear-powered space travel will be much faster than is now possible, and will enable manned missions to Mars. (See section below.)

One part of Prometheus, which was a NASA project with substantial involvement by the DOE in the nuclear area, was to develop the Multi-Mission Thermoelectric Generator and the Stirling Radioisotope Generator described in the RTG section above.

A more radical objective of Prometheus was to produce a space fission power system (FPS) such as those described above for both power and propulsion that would be safe to launch and which would operate for many years with much greater power than RTGs. Power of 100 kW is envisaged for a nuclear electric propulsion system driven by plasma.

The FY 2004 budget proposal was for $279 million, with $3 billion to be spent over five years. This consisted of $186 million ($1 billion over five years) building on FY 2003 allocation plus $93 million ($2 billion over five years) towards a first flight mission to Jupiter - the Jupiter Icy Moon Orbiter (JIMO), was expected to launch in 2017 and explore for a decade. However, Project Prometheus received only $430 million in the 2005 budget and this shrank to $100 million in 2006, most of which was to compensate for cancelled contracts, so it is effectively stalled. A similar project has been initiated and planned to launch in 2022 named the JUpiter ICy moons Explorer (JUICE), as an interplanetary spacecraft in development by the European Space Agency (ESA) with Airbus Defence and Space as the main contractor.

In 2003 Project Prometheus successfully tested a High Power Electric Propulsion (HiPEP) ion engine. This operates by ionizing xenon with microwaves. At the rear of the engine is a pair of rectangular metal grids that are charged with 6,000 volts of electric potential. The force of this electric field exerts a strong electrostatic pull on the xenon ions, accelerating them and producing the thrust that propels the spacecraft. The test was at up to 12 kW, though twice that is envisaged. The thruster is designed for a 7 to 10-year lifetime with high fuel efficiency, and to be powered by a small nuclear reactor.

Current US program

Space reactors in the kilowatt class are designated KiloPower by NASA, and may include a variety of designs of comparable power and mass to RTGs. They use liquid metal heatpipes to transfer fission heat to either thermoelectric or Stirling power conversion. Los Alamos National Laboratory and NASA Glenn Research Center completed a proof-of-concept test at the Nevada National Security Site in 2012 using the Flattop reactor and two small Stirling convertors to produce 24 watts.

In December 2014 NASA's Glenn Centre announced progress with its 4 kWt/1 kWe KiloPower project, using high-enriched uranium powering a heatpipe system and Stirling engine to generate electricity - Kilopower Reactor Using Stirling Technology (KRUSTY). This is a fast reactor relying entirely on negative thermal feedback for control, the objective being to design self-regulation as a major feature and demonstrate that it is reliable. The design is scalable up to 10 kWe. Los Alamos Nuclear Laboratory (LANL) with NASA in April 2018 announced completion of full-power testing of a prototype KRUSTY unit. The testing ran from November 2017 to March 2018, during which time the unit successfully handled multiple simulated failures, including power reduction, failed engines and failed heat pipes. This was the first US nuclear-powered ground test on an in-space nuclear reactor for several decades.

Prior to testing, NASA had appealed to the US National Nuclear Security Administration (NNSA) to let it proceed. The testing is being carried out under the Department of Energy's Criticality Safety Program working with NASA. The optimum fuel for the fast reactor was proposed as an HEU (93% enriched) alloy with 7% molybdenum as a solid casting, 129 mm in diameter and 300 mm long*. A 250 mm diameter beryllium oxide reflector would surround this, with 18 sodium heatpipes between the fuel and the reflector. Criticality is achieved by raising the BeO reflector to generate fission in the reactor core. Once fission has begun, the BeO reflector would be slowly raised to increase the temperature in the system to 800°C. There is a single central boron carbide control rod. The heatpipes will deliver 13 kWt heat from the core to eight free-piston Stirling engines and allow each to produce about 125 watts of electric power. The Stirling engine would have a cylindrical radiator of nearly 10 m ². The system mass is about 750 kg, and the length about 5 m. The science payload is assumed to be about 10 m from the core, and shielded by 45 kg of depleted uranium and 40 kg of lithium hydride.
* The 1 kWe test reactor in November 2017 is reported to use an alloy of 92% uranium, 8% molybdenum, with enrichment to 95%, and diameter 11 cm with 4 cm central hole and eight heat pipes recessed. There are two axial neutron reflectors and one radial one, total 70.5 kg beryllium.
NASA estimates that about 40 kWe would be needed for power on Mars, using ten 4 kWe KiloPower units.

Experience of the KiloPower project will be fed to a MegaPower project, with 2 MWe units. Features would include reactor self-regulation, low reactor core power density and the use of heatpipes for reactor core heat removal. The reactor would be attached to an open air Brayton cycle power conversion system using air as the working fluid and as the means of ultimate heat removal. The reactor would weigh about 40 tonnes including 3 t of LEU fuel (16-19% enriched), and be 4 m long, 2 m diameter. It would be scalable to 10 MWe, and could also be used in military bases, with 72-hour installation.

Russian fission systems

Between 1967 and 1988 the former Soviet Union launched 31 low-powered fission reactors in Radar Ocean Reconnaissance Satellites (RORSATs) on Cosmos missions. They utilised thermoelectric converters to produce electricity, as with the RTGs. Romashka reactors were their initial nuclear power source, a fast spectrum graphite reactor with 90%-enriched uranium carbide fuel operating at high temperature. Then the Bouk fast reactor produced 3 kW for up to four months. Later reactors, such as on Cosmos-954 which re-entered over Canada in 1978, had U-Mo fuel rods and a layout similar to the US heatpipe reactors described above.

These were followed by the multi-cell Topaz-1 reactors with thermionic conversion systems, generating about 5 kWe of power over 3-5 years for on-board uses from 12 kg of fuel. Reactor mass was about 320 kg. This was a US idea developed during the 1960s at the Kurchatov Institute in Russia and first tested in 1971. Topaz-1 was flown in 1987 on Cosmos 1818 & 1867 for ocean surveillance. One reactor ran for six months, the other for a year, and the Topaz-1 program was then halted.

In the single-cell ENISY or Topaz-2 reactor, each fuel pin (96% enriched UO ₂) sheathed in an emitter is surrounded by a collector and these form the 37 fuel elements which penetrate the cylindrical ZrH moderator. This in turn is surrounded by a beryllium neutron reflector with 12 rotating control drums in it. NaK coolant surrounds each fuel element. It operated at about 10 kWe and the mass of the reactor was about 1060 kg. Later Topaz-2 units were aiming for 40 kWe via an international project undertaken largely in the USA from 1990, which tested six reactors. Two Topaz-2 reactors (without fuel) were sold to the USA in 1992. Budget restrictions in 1993 forced the cancellation of a Nuclear Electric Propulsion Spaceflight Test Program associated with this.

In 2010 the Russian Presidential Commission on Modernization and Technology Development of Russia's Economy allocated federal funds to design a nuclear power propulsion unit (NPPU) in the megawatt power range, capable of powering a craft on long-haul interplanetary missions. In particular, SC Rosatom was to get RUR 430 million and Roskosmos (Russian Federal Space Agency) RUR 70 million to develop a Transport and Energy Module based on the NPPU, though it was reported that Roskosmos did not include the project in its space programme budget for 2016-2025. N.A. Dollezhal NIKIET (Research & Development Institute for Power Engineering) in Moscow was appointed the sole contractor for the NPPU, based on previous developments including those of nuclear rocket engines. In November 2015 NIKIET reported that the engineering design of the reactor was complete, and tests had "confirmed the integrity of the reactor vessel" and checked for leaks and deformation. The tests had also validated the "reliability of design calculations" to determine the ability of the vessel to withstand stress. The prototype propulsion reactor for space applications is expected to be tested in 2018. The total cost of the project of the propulsion and power module based on the propulsion reactor is estimated at RUR 20 billion (US$ 274 million) with the reactor part of it RUR 7 billion.

Russia's S.P.Korolyov Rocket and Space Corporation Energia space corporation started work in 2011 on standardized space modules with nuclear-powered propulsion systems, initially involving 150 to 500 kilowatt systems. A conceptual design in 2011 led to the basic design documentation and engineering design. The idea now being pursued by Russia's Keldysh Research Centre is to use a small gas-cooled fission reactor aboard the rocket to turn a turbine and generator set and thereby produce electricity for a plasma thruster. The reactor unit should be developed about 2015, then life-service tests are planned for 2018. The first launches, are envisaged for about 2020.

The Director of Roskosmos says that development of megawatt-class nuclear space power systems for manned spacecraft is crucial if Russia wants to maintain a competitive edge in the space race, including the exploration of the moon and Mars. The NPPU appears to meet this requirement. Energia earlier said that it is ready to design a space-based nuclear power station with a service life of 10-15 years, to be initially placed on the moon or Mars. It is also working on a concept of a nuclear-powered space tug, which could be used for launching satellites.
Space Reactor Power Systems * In the 1980s the French ERATO program considered three 20 kWe turboelectric power systems for space. All used a Brayton cycle converter with a helium-xenon mix as working fluid. The first system was a sodium-cooled UO₂-fuelled fast reactor operating at 670°C, the second a high-temperature gas-cooled reactor (thermal or epithermal neutron spectrum) working at 840°C, the third a lithium-cooled UN-fuelled fast reactor working at 1150°C.
Radiation in space

The 2011-12 space mission bearing the Mars Science Laboratory - the rover Curiosity - measured radiation en route. The spacecraft was exposed to an average of 1.8 mSv/day on its 36-week journey to Mars. This means that astronauts would be exposed to about 660 mSv on a round trip. Two forms of radiation pose potential health risks to astronauts in deep space. One is galactic cosmic rays (GCRs), particles caused by supernova explosions and other high-energy events outside the solar system. The other, of less concern, is solar energetic particles (SEPs) associated with solar flares and coronal mass ejections from the sun. One way to reduce the crew exposure would be to use nuclear propulsion, reducing the transit time considerably.

The radiation dose on the International Space Station orbiting Earth is about 100 mSv over six months.

Notes & references

General sources

Poston, D.I. 2002, Nuclear design of SAFE-400 space fission reactor, Nuclear News, Dec 2001.
Poston, D.I. 2002, Nuclear design of HOMER-15 Mars surface fission reactor, Nuclear News, Dec 2001.
Vrillon et al, 1990, ERATO article, Nuclear Europe Worldscan 11-12, 1990.
US DOE website - space applications.
space.com 21/5/00, 16/6/00, 22/7/00, 17/1/03, 7/2/03.
Delovy Mir 8/12/95.
G. Kulcinski, University of Wisconsin material on web.
Kleiner K. 2003, Fission Control, New Scientist 12/4/03.
OECD 1990, Emergency Preparedness for Nuclear-Powered Satellites.
NASA website
J.A. Angelo & D. Buden, Space Nuclear Power, Orbit Book Co., 1985
KiloPower Space Reactor Concept - Reactor Materials Study, May 2014, DOE Los Alamos National Laboratory
Dasari V. Rao and Patrick McClure, Los Alamos National Laboratory, Nuclear Reactors to Power Space Exploration, article on KiloPower published in R&D magazine (14 February 2017)
Marc A. Gibson et al, Development of NASA's Small Fission Power System for Science and Human Exploration, prepared for the 50th Joint Propulsion Conference cosponsored by AIAA, ASME, SAE, and ASEE, Cleveland, Ohio, 28-30 July 2014
NASA Glenn Research Centre Ion Propulsion website
Patrick McClure, Design and Testing of Small Nuclear Reactors for Defense and Space Applications, Invited Talk to ANS Trinity Section, 20 September 2013, Santa Fe, New Mexico, Los Alamos National Laboratory, LA-UR-13-27054
Lee Mason et al, Kilowatt-Class Fission Power Systems for Science and Human Precursor Missions (NETS-2013-6814), NASA Glenn Research Center, presented at the Nuclear and Emerging Technologies for Space (NETS-2013) meeting held in Albuquerque, New Mexico on 25-28 February 2013
Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration, US National Academy of Sciences (2009)
KRUSTY: First of a New Breed of Reactors, Kilopower Part II, Beyond NERVA (19 November 2017)

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Nuclear Reactors for Space - World Nuclear Association

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Radioisotope power sources have been an important source of energy in space since 1961. Nuclear fission reactors for space have been used mainly by Russia, but new and more powerful designs are under development in both the USA and Russia. Plutonium-238 is a vital power source for deep space missions.

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A book published by IAEA (INTERNATIONAL ATOMIC ENERGY AGENCY) Vienna, printed bye IAEA Austria , published in the year 2005

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What are the advantages and disadvantages of nuclear weaponary?

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What is the source of your information?

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I have chosen "space exploration" using nuclear energy.

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                                                         Krishna

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                                                         Krishna

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what did you choose?

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Summary:

Nuclear weapons are an explosive device that derives its destructive force from nuclear reactions (fission or fusion).Both these reactions release vast amount of energy from small amounts. Nuclear weapons are first invented by USA. They tested the first nuclear weapon in 1945.Fission bombs are reffered as atom bombs. Fusion bombs are reffered as hydrogen bombs.

There are other types of bombs called as neutron bomb, salted bomb. The first nuclear bomb was droped on a city in japan during world war 2.

In 1974, India conducted its first nuclear test: a subterranean explosion of a nuclear device (not weapon). India declared it to be a "peaceful" test, but it announced to the world that India had the scientific know-how to build a bomb. On May 11, 1998, India shocked the world by exploding three nuclear devices amounting to about six times the destructive power of the American bomb dropped on Hiroshima in 1945. The next day, it tested two more
nuclear explosions. The world was stunned when Pakistan responded with six
nuclear arsenal tests of its own.

example of fission reaction :

neutron + uranium-235 → fission products + energy + more neutrons

The effects of nuclear weapons lasts for very long period as they are radioactive and are harmful for humans and other living beings.

Many treats had been placed to disbarment of nuclear weapons.

The world has serious trouble with these weapons.

But they can be used in an advantages way to humans like using in civil engineering, energy production etc. They should be used vicely and in a useful way.

-Akshith Reddy T

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NUCLEAR ENERGY :GATEWAY FOR A PROSPEROUS FUTURE

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NUCLEAR ENERGY :GATEWAY FOR A PROSPEROUS FUTURE

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SUMMARY:

Nuclear Energy is created by using the control chain reactions of Type01 fuels.The process mainly consists of utilizing the heat produced in the reaction to convert water into steam,which in turn is used to rotate turbines to generate electricity. Though it has many advantages like less pollution,less fuel consumption,more power generation,etc,in India it is being used in a very minor quantity due to it's disadvantages like possible explosions,no proper procedure for the disposal of nuclear waste,etc.As the technology is advancing,we can reduce the danger level.Since the fossil fuels are becoming scarce and also the atmospheric pollution is increasing rapidly,there is an imminent need to establish more nuclear power plants in India.

Thorium is the nuclear fuel of the future .It has many advantages when compared to uranium like less amount of fuel,it cannot be used as a weapon ,more power,etc.India has one of the largest deposits of thorium ,but as it follows the conventional fossil fuel burning to generate electricity it has to import tons of coal from other countries.Hence,utilizing nuclear power not only allows us to create a greener environment but also increases the state of Indian economy.There is a saying that "every scientific invention is both a boon and bane,it depends on us how we utilize it",hence if we make use of nuclear energy in a proper way it would be a great advancement in the development of India.

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Every single atom in the universe carries an unimaginably powerful battery within its heart, called the nucleus. This form of energy, often called Type-1 fuel, is hundreds of thousands, if not millions, of times more powerful than the conventional Type-0 fuels, which are basically dead plants and animals existing in the form of coal, petroleum, natural gas and other forms of fossil fuel. To put things in perspective, imagine a kilometre-long train, with about 50 freight bogies, all fully laden with the most typical fossil fuel - about 10,000 tonnes of coal. The same amount of energy can be generated by 500 kg i of Type-1 fuel, naturally occurring Uranium, enough to barely fill the boot of a small car. When the technology is fully realised, one can do even better with naturally occurring Thorium, in which case the material required would be much less, about 62.5 kg, or even less according to some estimates ii, and thus enough to fit in a small bag iii. (Note: 500 kg of naturally occurring Uranium would contain about 3.5 kg of Uranium-235 fuel.)

Energy and economy

Energy is the most fundamental requirement of every society or nation as it progresses through the ladder of development. Of course, once it reaches a relative degree of development, the energy demand becomes more stable. There is a distinct and categorical correlation between the energy consumption and income of a nation - each reinforcing the other. Look around you: every step into progress comes with an addition of demand for energy - cars, ships and aircraft to move, hospitals to give quality healthcare, education, as it follows the model of e-connectivity, production of more and better goods, irrigation for better farming. In fact, every element of our lives is increasingly going to become energy-intensive - that is a necessary prerequisite for development. This is clearly reflected in the average energy consumption per person across nations - for instance, an average American consumes more than 15 times the energy consumed by an average Indian (see >Figure 1) iv

Today, India finds itself going through a phase of rapid ascent in economic empowerment. Industries are evolving at a significantly higher rate since liberalisation. Our focus for this decade will be on the development of key infrastructure and the uplifting of the 600,000 villages where 750 million people live, as vibrant engines of the economy. In 2008, we crossed the trillion-dollar mark, and it took more than six decades for us to reach that milestone. However, it is predicted that the Indian economy will double again, to reach the $2-trillion mark by 2016, and then again redouble, to reach the $4 trillion milestone by 2025 v. All this economic growth will need massive energy. It is predicted that the total electricity demand will grow from the current 150,000 MW to at least over 950,000 MW by the year 2030 vi - which will still be less than one-fourth of the current U.S. per capita energy need. In fact, by 2050, in all likelihood the demand could go even higher, and the per capita energy demand would be equal to the current French or Russian figure of about 6000 W per capita.

Analysing the international scenario on nuclear energy

So, will we allow an accident in Japan, in a 40-year-old reactor at Fukushima, arising out of extreme natural stresses, to derail our dreams to be an economically developed nation? When a few European countries, particularly Germany, decide to phase out nuclear power, that should not become a blanket argument to take a view against our nuclear programme.

A few things need to be put in context here. The decision of Germany suits its current scenario which goes beyond mere concerns of risk posed by nuclear power. Germany is a developed nation, a power-surplus nation - so it can afford to lose a few plants. More important, Germany has completely exhausted its nuclear resources. Against a total demand of 3,332 tonnes (2006-08) vii it was able to produce only 68 tonnes (Note: This was the production in 2006) of Uranium, and for the deficit it was relying on imports viii. Thus, nuclear energy never fits into its goal of energy independence. India, on the other hand, is the leader of the new resource of nuclear fuel called Thorium, which is considered to be the nuclear fuel of the future.

The Indian population is misled when it is said that some Western nations have ended their nuclear programme, or that Japan is reconsidering nuclear power plant expansion. Study the >accompanying Table, which shows what share of energy these advanced nations are generating by means of nuclear power.

The study indicates that most of the prosperous nations are extracting about 30-40 per cent of power from nuclear power and it constitutes a significant part of their clean energy portfolio, reducing the burden of combating climate change and the health hazards associated with pollution. Meanwhile in India, we are not generating even 5000 MW of nuclear power from the total of about 150 GW of electricity generation, most of it coming from coal.

We should be careful not to be carried away by the barrage of anti-nuclear news often being generated by many of the same nations that are enjoying the maximum benefits from it. The economically developed world has a well-trained habit of presenting their success in a distorted context to misguide emerging nations like India, which are a potential challenge to their neo-age proxy-imperial economic subjugation. What is needed for our India, we Indians have to decide.

Hence, we and we alone will decide what is the best needed action for our economic prosperity, based on our context and resource profile. India is blessed with the rare, and very important, nuclear fuel of the future - Thorium. We cannot afford to lose the opportunity to emerge as the energy capital of the world, which coupled with the largest youth power, will be our answer to emerge as the leading economy of the world. India has the potential to be the first nation to realise the dream of a fossil fuel-free nation, which will also relieve the nation of about $100 billion annually which we spend in importing petroleum and coal. Besides the billions spent on importing coal or oil, we are also importing millions of tonnes of CO ₂ and other greenhouse gases, which are a hazard to the environment and human health. It is noteworthy that in 2010-11, India imported about 82 billion tonnes of coal xii, a large fraction of which was for the thermal power plants. Experts believe that this number will continue to rise exponentially in the times ahead, as shown in >Figure 3 xiii.

The greenest sources of power are definitely solar and wind. With abundant sunshine and places of high wind velocity, the nation definitely has potential for these forms of energy. But solar and wind power, despite all their advantages, are not stable and are dependent excessively on weather and sunshine conditions. Nuclear power, on the other hand, provides a relatively clean, high-density source of reliable energy with an international presence. Today, there are 29 countries operating 441 nuclear power plants, with a total capacity of about 375 GW(e). The industry now has more than 14,000 reactor-years of experience. Sixty more units, with a total target capacity of 58.6 GW, were under construction. (Note: This is according to data from 2010.)

Much of the destructive power of nuclear accidents is compared against the benchmarks of the atomic bombing of Japan by the U.S. forces during the Second World War. Pictures of mushroom clouds looming over cities, charred buildings, and massive death scenes are awakened to form our opinion of nuclear dangers and disasters. But that is far from the reality. It is poor judgment and a deliberate act of spreading fear to compare a nuclear bomb with a nuclear plant. The bomb is designed to deliver a large amount of energy over a very short period of time, leading to explosions, firestorms and massive heat energy generated to obliterate every object in its path. That is what a bomb is supposed to do!

Civilian nuclear applications in the form of a power plant, on the other hand, are designed to deliver small amounts of energy in a sustainable manner over a far larger time frame. It is designed with systems to control and cool the nuclear reaction. There are safety procedures and back-ups, and even in the event of failures, as in the 2011 disaster, the destructive might will never be even a fraction of what happens in the case of a nuclear bomb.

Nuclear risks

We need to put the Fukushima-Daiichi events in the historic frame of nuclear accidents and analyse them. While there was huge loss to property and disruption of normal life, there was no direct loss of life due to the accident or during the operation in its aftermath to contain it. As a silver lining, the way the accident was handled - compared to the Chernobyl disaster of 1986 - showed how much progress we have achieved in nuclear emergency management over a period of two and half decades. The Fukushima-Daiichi plant was almost five times as big in terms of power generation and, more significantly, contained about nine times the nuclear fuel at the time of the accident. Yet, with better emergency management learnt over the years, the maximum radiation was less than 0.4 per cent of that released during the Chernobyl disaster. So, while the Fukushima-Daiichi accident was unfortunate and needs review, one must also acknowledge the advancement of national and international capabilities to manage nuclear emergencies now.

Another argument which surrounds the nuclear debate is that nuclear accidents and the radiation fallout as the aftermath would not only harm the exposed generation but also continue to impact generations to come. If available facts and scientific inquiry was given more weightage than mere conjectures and comic-bookish imagination, this argument will in all probability be proved a myth. The strongest case of human exposure and destruction due to radiation is, without argument, the Hiroshima and Nagasaki nuclear bombings of 1945. These are the only two occasions when nuclear force was intentionally developed and deployed to kill human life. Post the bombing, the U.S. government established the Atomic Bombing Casualty Commission (ABCC) in 1946 to assess the late-effects of radiation among the atomic bomb survivors of Hiroshima and Nagasaki. It operated for 30 years until, in 1974, it was reconstituted as a joint venture between the U.S. and Japan under the name of Radiation Effects Research Foundation (RERF). It is operational even today. The ABCC and the RERF have extensively studied the long-term impact of radiation and nuclear disaster across generations for over six decades now, and the findings throw light on the possible effects of radiation. Its report says that chronic (sustained) exposure of about 100 millisieverts (mSv, which is the international unit to measure radiation), increases cancer risk by 0.5 per cent to 0.7 per cent. Notably, the areas in close proximity of Fukushima had a peak exposure of 800 mSv xiv.

Of course, there is some correlation between radiation exposure and cancer risk, which must be acknowledged. But the notable aspect is that, contrary to popular belief, the findings clearly state that the effect of such exposure is limited only to the exposed generation. To quote the report, "Our studies have not found thus far any inherited genetic effects from parental radiation exposure among the children of A-bomb survivors." xv (Note: A-bomb stands for the atom bomb. Two atomic bombs were dropped by the U.S. on the Japanese cities of Hiroshima and Nagasaki on August 6 and 9, 1945, as part of the Second World War.) Thus, while radiation due to a nuclear disaster is dangerous, it would amount to wrong propaganda to state that nuclear disasters will affect generations to come. Of course, the technology has been advancing over the decades and the human capability to contain nuclear disasters has definitely advanced.

There is no doubt that nuclear power is superior along three dimensions, namely, energy density, effect on improved quality of living, and the economic benefits. Now let us look at the key challenges which pertain to the sector, especially in the wake of the recent natural disaster impacting the Daiichi plant in Fukushima. Two concerns are prominent here. The first is that of safety against the plant's disaster, and the second relates to the environmental impact and the nuclear waste which the plant generates.

Let us consider the second issue first.

Opportunity cost of nuclear energy

a) Abstinence from nuclear power is an incomplete response without the logical alternative. If we look at the complete picture of alternative measures, we will have to endorse the fact that our current and future energy demands have to be met. In economics, there is a concept called "opportunity cost," which refers to the cost incurred when one chooses the next alternative. So what happens if we pronounce a total ban on nuclear energy generation? Some part of the future need, although only a small fraction, would come from solar and wind sources, with great unpredictability as pointed out earlier. A part would be offset by hydro-power too. But in all probability we will continue to increase our reliance on fossil-based fuel power generation methods, at least in the near and mid-term future. And that is where the problem lies.

Every year, human activities are adding about 30 billion tonnes of CO ₂ xvi into the atmosphere. The IPCC estimates that 26 per cent of this emission (about 7.6 billion tonnes) is a direct consequence of electricity generation requirements. This is not really air pollution but it adds to the risk of climate change, which is exhibited in changing rainfall patterns, sea levels and temperatures, leading to food shortages, malnutrition, and disease alterations. The WHO estimates that about 1.3 million people xvii lose their lives as a result of urban outdoor air pollution alone, and about 140,000 are causalities to adaptation challenges of climate change xviii. (Note: Additionally, about two million lives are lost due to indoor pollution, the primary victims being women, and children under the age of five.) Thus, the pollution caused by power generation activities, and the climate change associated with them, are directly or indirectly responsible for about 481,000 deaths every year. Comparatively, in the case of the worst civilian nuclear disaster ever at Chernobyl, the United Nations Scientific Committee on the Effects of Atomic radiation (UNSCEAR) predicted up to 4,000 cancer xix cases (often curable) due to the accident, besides 57 direct causalities. Unclean fossil energy is definitely not sustainable in the future. Moreover, fossil-based fuels are fast depleting, and their scarcity is inspiring geopolitical instabilities around the world.

Furthermore, it is believed that the changing climate patterns will carry a costly adaptation price tag in the future - an enormous $300 billion every year, which will be a huge drain on the global GDP xx. All these issues can be addressed only when we graduate from Type-0 fuels to the next-generation fuels - the most prominent amongst them being nuclear fuels, which will also power our deep space missions of the future. A standard approximate comparison between a 1000-MW coal plant and a similar nuclear plant is given in >Table 6.

Safety issues of nuclear power

b) Now, let us delve more into the other issue - that of plant safety. Throughout the history of nuclear power generation there have been four major incidents of plant failure - the Kyshtym accident in fuel reprocessing in 1957, the relatively smaller Three Mile Island meltdown (United States), the much bigger Chernobyl accident (USSR, 1986) and the recent Japanese incident at Fukushima. The first accident was purely due to underdeveloped technology, and much of the blame for the next two disasters is attributed to human error. Even in the case of the Fukushima disaster of 2011, there were extraordinary natural forces in action - the rare occurrence of the tremendous stress load of an earthquake coupled with the unprecedented shear load of a tsunami. Of course, there is a need for better technology and more stable plant design across the world, but the occurrence of four failures in six decades cannot be made out as a case for completely disbanding the technology - which is one of our foremost keys to graduating beyond the fossil fuel-based low-end energy. The best of technological progress, while being the biggest ally of mankind, does come at an incremental risk. The key is to learn and evolve to mitigate the risk, rather than use the first incident as an excuse to disband science.

Let us take a few examples. In 1903, the Wright brothers translated into reality the remarkable dream of controlled human flight. Not more than half a decade later, in 1908, the first flight disaster occurred, which severely injured Orville Wright and killed his co-passenger. Many accidents followed, and even today air accidents kill more than 1,500 people every year. Imagine whether we would be flying between distant cities, across oceans and continents, if the incident of 1908, or the ones later, were used as a reason to disband human flight? When the mighty ship Titanic set sail in 1912, it was heralded as the pioneering mission in the field of large and comfortable ocean liners. But on its first voyage it struck an iceberg and sank, killing more than 1,500 people, more than two-thirds of those on board. But that never stopped our quest for bigger and faster means of ocean travel. The very first attempt to send man to the moon, Apollo-1, met with an accident and killed three prominent astronauts. It took another 10 missions, with mixed results, before Apollo-11 finally made it to the moon in 1969, with Neil Armstrong setting foot on the lunar surface and declaring to the world those never-to-be-forgotten words: "One small step for man, one giant leap for mankind." Indeed, that small step was preceded by many a stumble.

The Indian space programme, which is now ranked among the best in the world, started with a failure in 1979 when our first rocket, instead of putting the satellite into a near-earth orbit, went into the Bay of Bengal. I was the Mission Director of the launch, and we were accused of putting a few crores of rupees into the sea. We did not wind up our dreams with that one accident and the criticism. The mission continued and the next year we were successful. Today, that programme, which started with a failure, is the first and only one to discover the presence of water on the moon with its Chandrayan mission, and is now a pride of the nation. The argument is, of course, that all failures and accidents propel us to think and develop better and safer technologies towards better service. And in the case of nuclear power, we do acknowledge that the effects of radiation can reach a wider impact zone. But then, improvement, and not escapism, should be our step forward.

Nuclear fuel of the future: Thorium

Let us introduce a lesser-known member among radioactive materials - Thorium. It is perhaps the best solution possible in the future and would be technologically and commercially the best option in another two decades. Thorium, the 90th element in the Periodic Table, is slightly lighter than Uranium. Thorium is far more abundant, by about four times xxvi, than the traditional nuclear fuel, Uranium, and occurs in a far purer form, too. It is believed that the amount of energy contained in the Thorium reserves on earth is more than the combined total energy that is left in petroleum, coal, other fossil fuels and Uranium, all put together. And information revealed in an IAEA Report (2005) on Thorium fuels indicates that India might have the largest reserves of Thorium in the world, with over 650,000 tonnes. (Note: The IAEA, the International Atomic Energy Agency, is the world's centre of cooperation in the nuclear field. It was set up in 1957 as the world's 'Atoms for Peace' organisation within the U.N. family.) This is more than one-fourth of the total deposits of Thorium; in comparison, we have barely 1 per cent of the world's Uranium deposits, which is currently being put to effective use, our having opted for the closed fuel cycle technology. Thorium has many other advantages. It is estimated that Thorium may be able to generate (through Uranium-233 that could be produced from it) eight times the amount of energy per unit mass compared to (natural) Uranium xxvii. In the much debated issue of waste generation also, Thorium has a relative advantage. It produces waste that is relatively less toxic due to the absence of minor actinides (that are associated with Uranium).

At the same time, it is acknowledged that the long-lived high-level waste from Uranium, especially in light of the Indian strategy of adopting the closed fuel cycle involving reprocessing for the recovery of Plutonium and Uranium, can be effectively managed using technologies available today. Indian nuclear experts tell us that the relatively small volumes of such waste (long-term storage space of less than a quarter of the size of a football field is adequate for the estimated waste from a 1000 MWe plant) can be safely stored after vitrification for hundreds of years without causing any risk to the environment or the people.

One question that crops up is, why then has Uranium rather than Thorium become the popular choice for nuclear energy programmes across the world? There are two reasons: one is technological and the other is historical.

The technological reason stems from the simple fact that at first one needs to produce Uranium-233 from Thorium, and for this, reactors based on the naturally available nuclear fuel material, Uranium-235, are required. In addition, the recovery of Uranium-233 by large-scale reprocessing of irradiated thorium, as well as the likely presence of hard gamma emitting Uranium-232, pose certain practical hurdles. But according to experts, all these can be overcome technologically.

The second and the historical reason why Thorium has lagged behind in the ladder of development, comes from its advantage of being able to provide Thorium-based fuel, as seen from the context of the relatively unstable geopolitical conditions - which is that Thorium cannot be weaponised. Unlike Uranium, which is always on a tight-rope walk between being a power source and finding destructive applications, Thorium bombs just cannot be made. Here history steps in. It must be remembered that much of the current civil nuclear applications are direct offshoots of the military nuclear technologies of the Cold War period. So, the first significant outcome of nuclear technology was the Manhattan Project during the Second World War, which ultimately culminated in the Hiroshima and Nagasaki bombing of 1945 by the U.S.

A nuclear weapon is different from a nuclear plant, as in the former there is no need to control or slow down the reactions that lead to a catastrophic energy release in a short time interval - which is the essence of a bomb. However, a nuclear plant needs moderation of the reaction to sustain a steady but controlled release of energy. It was only by the end of 1951 that some noteworthy work was done in controlled nuclear power generation at the EBR-1 experiment in Idaho to produce 100 KW of nuclear power. This "weapon first" approach to nuclear technology led to the fact that there was little focus on developing methods to energise from Thorium, which is non-weaponisable, and a larger focus on Uranium, which can be weaponised.

But now, being the largest owner of Thorium, and also being amongst the nations which will see the highest surge in power demand with its growth, the opportunity is for India to pursue its existing nuclear programme with a special focus on research and development on the Thorium route as the long term sustainable option, which we are already undertaking. For this purpose, it is imperative to continue to implement the current Indian plan of making use of the uranium and plutonium-based fuel cycle technologies as well as irradiate larger amounts of Thorium in fast reactors to breed Uranium-233 fuel as it graduates to the Thorium-based plants. It is noteworthy that the Indian plan for an advanced heavy water reactor (AHWR) is an important step to launch early commencement of Thorium utilisation in India, while considerable further efforts to use Thorium in both thermal and fast reactors would be essential to harness sustainable energy from Thorium-generated Uranium-233.

Various technologies for Thorium-based plants are already being developed and deployed on a test basis across the world including in India, which have a promising future. These include first breeding it to fissile Uranium-233 isotope in the conventional reactors or through the revived interest in technologies like the Molten Salt Reactors (MSR) which use salts to trap the fissile material and do not react with air or burn in air or water. In this technology, the operational pressure is near the ordinary atmospheric pressure, and hence the cost of construction is low and there is no risk of a pressure explosion xxviii.

A significantly large quantity of highly active nuclear material exists, and will continue to exist in the form of nuclear armaments - which was the mother programme of the nuclear energy programme. In 2010, there were about 22,000 nuclear warheads spanning at least nine countries of the world, and 8,000 xxix of them are in active state, carrying a risk far greater than controlled nuclear power reactors. If the argument of risk is to be used to eliminate the peaceful energy generation programme, then the nuclear opposition factions must first direct their efforts at Washington and Moscow, the owners of 90 per cent of the world's nuclear warheads, to disband their nuclear arsenal - which is, by design, intended to be hostile. Would that happen? Unlikely, at least in the foreseeable future. Our aim should be to minimise the risks associated with nuclear power.

The power of the nucleus is mighty and the future of humanity lies in harnessing it in a safe and efficient manner. In the years to come, it will fuel not only our earth-based needs but also our space missions and perhaps even our civilisation's reach to other planets for habitation. Our current nuclear projects will expand into better and safer materials, like Thorium, and later on, into better reactions like fusion, which once completely developed, will be able to generate hundreds of times more of power than current fission methods. Affordable, clean and abundant energy provided by nuclear sources is our gateway to a future that is healthy, learned and connected - a future that will span deep into space and crosses the boundaries of current human imagination.

Coalfields and burning earth

The Jharia coalfields in Jharkhand constitute the richest coal-bearing area in the country: they contain large quantities of high-grade coking coal. But the presence of this natural resource has been a curse for the local tribal villagers. The Jharia area also has a large number of ongoing mine fires, which have a history of more than a century and have been causing great loss to life and property.

I am reminded of an incident that happened when I was President of India. I was travelling from Sindri to Dhanbad. Hundreds of villagers rushed to my car. We immediately stopped and listened to them. They narrated the heating and spot-fire which regularly take place near their houses. A major challenge to the mining community is that of tackling fires, which have engulfed large and densely populated coal-bearing areas. I and my team visited their houses, where we discovered intense, unbearable heat, emanating not from the skies but the ground below. Occasionally, jets of flames would spurt out from the ground, scorching the earth.

The entire area has been destroyed by the mining activity and rendered uninhabitable for humans or any other life form. Sadly, it can never be restored, at least not for the next million years. Much of the coal mined today is used for electricity generation across the world, and there are many more Jharias being created across the rural and forest lands of earth. These will continue to swell in numbers and size - unless we find sustainable alternative fuel sources to replace fossil fuels.

Pollution, outdoor and indoor

Urban Outdoor Pollution (UOP): It refers to the air pollution experienced by people living in and around urban areas, generally in open space, for example, roads.

Indoor Air Pollution (IAP) refers to pollutants found indoors, generally due to inefficient fuel consumption, chemical pollution to building material, and so on. UOP contributes to IAP. Nearly two million lives are lost due to Indoor Air Pollution, the most common victims being women, and children under the age 5.

Endnotes

i >http://www.world-nuclear.org/education/whyu.htm

ii Thorium as a Secure Nuclear Fuel Alternative, A Canon Bryan, 23-April-2009, Journal of Energy Security (available at >http://www.ensec.org/index.php?option=com_content&view=article&id= 187:thorium-as-a-secure-nuclear-fuel-alternative&catid= 94:0409content&Itemid=342)

iii Steve Kirsch, The Most Important Investment that We Aren't Making to Mitigate the Climate Crisis, 26.12.2009 Huff Post Green, (>http://www.huffingtonpost.com/steve-kirsch/the-most-important-invest_b_402685.html)

iv Data from World Resources Institute (for 2003)

v India and China, Raghav Behal

vi India envisages about 950,000 MW power requirement by 2030, >http://bit.ly/vTv5Qx

vii "World Nuclear Power Reactors 2006-08 and Uranium Requirements." World Nuclear Association. 2008-01-14.

viii "World Uranium Production U3O8/ million lbs." Ux Consulting Company, LLC

ix World Nuclear Power Reactors & Uranium Requirements, World Nuclear Association (21 October 2011) (available at >http://www.world-nuclear.org/info/reactors.html) Data is for 2010

x Nuclear Power Plant Information, IAEA PRIS (2010), available at >http://www.iaea.org/cgi-bin/db.page.pl/pris.nucshare.htm

xi International Monetary Fund, 2010

xii India 2011/12 coal import needs may jump to 114 mln T, Reuters, September 27, 2011

xiii Rise of the Coal Bill, RN Bhaskar, Forbes India Magazine (April 2010)

xiv Matters elucidated thus far by RERF studies, >http://www.rerf.or.jp/rerfrad_e.pdf

xv Matters elucidated thus far by RERF studies, >http://www.rerf.or.jp/rerfrad_e.pdf

xvi IPCC Reports on climate change

xvii Air quality and health, Fact Sheet, WHO (>http://www.who.int/mediacentre/factsheets/fs313/en /index.html)

xviii Climate Change and Health, WHO 2010, >http://www.who.int/mediacentre/factsheets/fs266/en/

xix "UNSCEAR assessment of the Chernobyl accident." >Unscear.org.

xx Climate change fight to cost $300 billion a year, Alister Doyle (12-August-2009), OneWorld (available at >http://southasia.oneworld.net/globalheadlines/climate-change-fight-to-cost-300-billion-a-year)

xxi How Coal Works, Union of Concerned Scientists (available at >http://www.ucsusa.org/clean_energy/coalvswind/brief_coal.html)

xxii Each kg of coal generates about 2.93 kg of CO2

xxiii Considering the following calculations. About 30,000 million tons of CO2 is responsible for the casualties of about 1.3 million lives per year. (1 billion ton = 1000 million ton). Thus, 1 MT corresponds to about 43.33 causalities per year. And 8.37 million tons would be responsible (by interpolation) for about 362 lives being lost.

xxiv Similar to the above derivation

xxv Based on the eight fold mass to energy advantage we have earlier cited from the article: Thorium as a Secure Nuclear Fuel Alternative, A Canon Bryan, 23-April-2009, Journal of Energy Security

xxvi IAEA, 2005

xxvii Extracted from >http://www.world-nuclear.org/info/inf62.html

xxviii Liquid Fluoride Thorium Reactors >http://www.americanscientist.org/issues/feature/2010/4/liquid-fluoride-thorium-reactors Thorium Fuel for Nuclear Energy, >http://www.americanscientist.org/issues/feature/thorium-fuel-for-nuclear-energy/3

xxix "Federation of American Scientists: Status of World Nuclear Forces." >Fas.org.

A.P.J. Abdul Kalam was the 11th President of India, from 2002 to 2007, and pioneered the Vision for an Economically Developed India by 2020. He is at apj@abdulkalam.com

Srijan Pal Singh is an expert in the area of sustainable development and is an Electrical Engineer with an MBA from the IIMA. He is at 7srijanpal@iimahd.ernet.in

© Copyright: Authors

For pdf of Part 1 of the essay, click >here>

For pdf of Part 2 of the essay, click >here

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Nuclear power is our gateway to a prosperous future

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Every single atom in the universe carries an unimaginably powerful battery within its heart, called the nucleus. This form of energy, often called Type-1 fuel, is hundreds of thousands, if not millions, of times more powerful than the conventional Type-0 fuels, which are basically dead plants and animals existing in the form of coal, petroleum, natural gas and other forms of fossil fuel.

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SUMMARY:

Nuclear power can be used to explore all universes. Even though it is not used till now (for exploration), it will be used in future. Project Orion (http://www.islandone.org/Propulsion/ProjectOrion.html) is an example. Orion is a spacecraft that travels using nuclear energy. Usage of nuclear power in spacecrafts is better than using other energy suppliers (chemical propellants) because more energy can be obtained by using less amount of fuel: which results in decreasing weight of the rocket / spacecraft. A nuclear powered engine can provide very high thrust relative to the amount of propellant used in the rocket/spacecraft. This is known as specific impulse. Nuclear energy in a spacecraft is mainly used for propulsion. Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP) are main 2 types of propulsion systems. Both of them depend on nuclear fission reactions leading to create high temperatures that are sufficient to create hydrogen ion plasma (which is used to get very high thrust).This thrust can be used for traveling (exploring).