the most damaging nuclear power plant accident occured at
List of nuclear power accidents by country The world's worst nuclear accident has been the 1986 Chernobyl disaster in the Soviet Union, one of two accidents that has been rated as a level 7 (the highest) event on the International Nuclear Event Scale.[9] Note that the Chernobyl disaster may have scored an 8 or 9, if the scale continued. The accident occurred at the Chernobyl Nuclear Power Plant after an unsafe systems test led to a rupture of the reactor vessel and a series of steam explosions that destroyed reactor number four. The radioactivity plume spread to the surrounding city of Pripyat and covered extensive portions of Europe with traces of radioactivity, leaving reindeer in Northern Europe and sheep in portions of England unfit for human consumption. A 30 kilometres (19Â mi) "Zone of alienation" has been formed around the reactor.[10]