Description: The Chernobyl (Tchernobyl) accident occurred on April 26, 1986, at the Chernobyl nuclear power plant in Ukraine (then part of the Soviet Union). It is regarded as the worst nuclear accident in the history of nuclear power, producing a plume of radioactive debris that drifted over parts of the western Soviet Union, Eastern Europe, Scandinavia, UK, and eastern USA. Large areas of Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of roughly 200,000 people. About 60% of radioactive fallout landed in Belarus. More information.