The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the environment and deposited radioactive materials in many parts of Europe.

For survivors of ARS, the recovery process may last from several weeks up to 2 years.

Prior to a routine shutdown, the reactor crew at Chernobyl 4 began preparing for a test to determine how long turbines would spin and supply power to the main circulating pumps following a loss of the main electrical power supply. By the time that the operator moved to shut down the reactor, the reactor was in an extremely unstable condition.