Kyshtym

The Kyshtym disaster was a radiation contamination accident that occurred on 29 September 1957 at Mayak, a Soviet nuclear fuel reprocessing plant located near Ozyorsk (then called Chelyabinsk-40), in the Chelyabinsk Oblast of Russia (then part of the Soviet Union). It is considered the third-worst nuclear accident in history, behind only the Chernobyl and Fukushima disasters.

The accident was caused by the failure of the cooling system in one of the tanks storing liquid radioactive waste. Without cooling, the tank's contents overheated and exploded, releasing an estimated 50 to 100 tonnes of highly radioactive waste into the surrounding area. The explosion did not involve a nuclear reaction.

The area most affected was along the northeast path of the radioactive plume. This area, later dubbed the East Ural Radioactive Trace (EURT), covered a region approximately 300 kilometers long and 30-50 kilometers wide, encompassing parts of the Chelyabinsk, Sverdlovsk, and Tyumen Oblasts. Hundreds of villages were evacuated, and tens of thousands of people were relocated from the contaminated area.

Due to the Cold War secrecy surrounding the Soviet nuclear program, the Kyshtym disaster was initially concealed both from the Soviet public and the international community. Information about the accident only began to emerge in the late 1970s, largely due to the research of Soviet biologist Leo Tumerman and the later work of Zhores Medvedev, who published a detailed account of the event in 1976.

The severity of the Kyshtym disaster led to the establishment of stricter safety regulations and monitoring procedures at nuclear facilities both in the Soviet Union and internationally. The term "Kyshtym disaster" is often used as a generic term for the accident at Mayak, although Kyshtym is the nearest large town.