Outline of the Chernobyl disaster

The following outline provides an overview of and topical guide to the Chernobyl disaster, a nuclear accident that occurred on 26 April 1986, when the no. 4 reactor of the Chernobyl Nuclear Power Plant, located near Pripyat, Ukrainian SSR, Soviet Union (now Ukraine), exploded during a test. The explosion and reactor core fire spread radioactive contaminants across the Soviet Union and Europe. An exclusion zone was formed around the plant, evacuating over 100,000 people primarily from the cities of Pripyat and Chernobyl. With dozens of direct casualties, it is one of only two nuclear energy accidents rated at the maximum severity on the International Nuclear Event Scale. The response involved more than 500,000 personnel and cost an estimated 18 billion rubles (about $84.5 billion USD in 2025). It remains the worst nuclear disaster and the most expensive disaster in history, with an estimated cost of US$700 billion.