Chernobyl

On April 26, 1986, an accident occurred at Unit 4 of the Chernobyl nuclear power plant in the former Ukrainian Republic of the Union of Soviet Socialist Republics, near the present borders of Belarus, the Russian Federation, and Ukraine. The accident destroyed the reactor, contaminated large areas surrounding the reactor, and led to an increase in radiation levels over practically the whole of the northern hemisphere.

The Chernobyl power station consisted of four Soviet-designed light water–cooled graphite-moderated (RBMK) reactors of 950 MW each. These units used graphite to moderate the nuclear reaction and used water flowing through channels holding the fuel elements to cool it. There was no containment structure. The immediate causes of the accident were a flawed reactor design coupled with serious mistakes made ...