The Chernobyl disaster (also referred to as the Chernobyl accident or simply Chernobyl) was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the city of Pripyat, then located in theUkrainian Soviet Socialist Republic of the Soviet Union (USSR). An explosion and fire released large quantities of radioactive particles into the atmosphere, which spread over much of the western USSR and Europe.