The
Chernobyl disaster began on 26 April 1986 with the explosion of the No. 4 reactor of the Chernobyl Nuclear Power Plant near the city of Pripyat in northern Ukraine, near the Belarus border in the Soviet Union. It is one of only two nuclear energy accidents rated at the maximum severity on the International Nuclear Event Scale, the other being the 2011 Fukushima nuclear accident. The response involved more than 500,000 personnel and cost an estimated 18
billion roubles—around US$68
billion in 2019. It remains the worst nuclear disaster in history, and the costliest disaster in human history, with an estimated cost of US$700 billion.