The Chernobyl isaster, reactor accident at the Chernobyl nuclear power plant, or simply Chernobyl, was the worst nuclear power plant accident in history and the only instance so far of level 7 on the International Nuclear Event Scale, resulting in a severe release of radioactivity into the environment following a massive power excursion which destroyed the reactor. Thirty people died in the explosion, but most deaths from the accident were attributed to fallout.