The Chernobyl nuclear disaster

The Chernobyl nuclear power plant had four working reactors. The incident happened on April 26, 1986, when operators of the power plant ran a test on an electric control system at the reactor number four. There was a sudden power output surge which prompted an attempt of emergency shutdown. A reactor vessel ruptured and a series of explosions followed. The disastrous sequence of events destroyed the Chernobyl 4 reactor, killing 30 operators and firemen within three months and several further deaths later. The resulting fire sent a plume of highly radioactive smoke into the atmosphere spreading over large parts of the western Soviet Union and Europe. It is considered as one of two worst nuclear crisis in history, classified as a level 7 event on the International Nuclear Event Scale.