


During a planned decrease of reactor power in preparation for the test, the operators accidentally dropped power output to near-zero, due partially to xenon poisoning. The accident occurred during a safety test meant to measure the ability of the steam turbine to power the emergency feedwater pumps of an RBMK-type nuclear reactor in the event of a simultaneous loss of external power and major coolant leak. The initial emergency response, together with later decontamination of the environment, involved more than 500,000 personnel and cost an estimated 18 billion roubles-roughly US $68 billion in 2019, adjusted for inflation. Called the world's worst-ever civil nuclear incident, it is one of only two nuclear energy accidents rated at seven-the maximum severity-on the International Nuclear Event Scale, the other being the 2011 Fukushima nuclear disaster in Japan. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the No. Varying estimates of increased mortality over subsequent decades (see Deaths due to the disaster) INES Level 7 (major accident) see Chernobyl disaster effectsįewer than 100 deaths directly attributed to the accident. Reactor 3 can be seen behind the ventilation stackĬhernobyl Nuclear Power Plant, Pripyat, Chernobyl Raion, Kiev Oblast, Ukrainian SSR, Soviet Union Reactor 4 several months after the disaster.
