complained of various illnesses and symptoms—chronic fatigue, sleep and fertility problems, weight loss, and increased hypertension. The frequency of congenital disabilities and complications at birth was three times greater than normal. In 1953, doctors examined 587 of 28,000 exposed people and found that 200 had clear cases of radiation poisoning. In 1957 Mayak was the site of the Kyshtym disaster, which at the time was the worst nuclear accident in history. During this catastrophe, a poorly maintained storage tank exploded, releasing 20 million curies (740 PBq) in the form of 50–100 tons of high-level radioactive waste. The resulting radioactive cloud contaminated an expansive territory of more than (a nine-mile radius) in the eastern Urals, causing sickness and death from radiation poisoning. The Soviet government kept this accident secret for about 30 years. It is rated at 6 on the seven-level INES scale. It is third in severity, surpassed only by Chernobyl in Ukraine and Fukushima in Japan. Mayak is still active , and it serves as a reprocessing site for spent nuclear fuel. Today the plant makes tritium and radioisotopes, not plutonium. In recent years, proposals that the plant reprocess waste from foreign nuclear reactors have given rise to controversy. An incompletely reported accident appears to have occurred in September 2017; see Airborne radioactivity increase in Europe in autumn 2017. Location The nuclear complex is 150 km south of Ekaterinburg, between the towns of Kasli and Tatysh, and 100 km northwest of Chelyabinsk. The closest city, Ozyorsk, is the central administrative territorial district. As part of the Russian (formerly Soviet) nuclear weapons program, Mayak was formerly known as Chelyabinsk-40 and later as Chelyabinsk-65, referring to the postal codes of the site. Design and structure Mayak's nuclear facility plant covers about . The site borders Ozyorsk, in which a majority of the staff of Mayak live. Mayak itself was not shown on Soviet public maps. The location of the site together with the plant city was chosen to minimise the effects that harmful emissions could potentially have on populated areas. Mayak is surrounded by a ~ exclusion zone. Nearby is the site of the South Urals nuclear power plant. Notes History Built in total secrecy between 1945 and 1948, the Mayak plant was the first reactor used to create plutonium for the Soviet atomic bomb project. In accordance with Stalinist procedure and supervised by NKVD Chief Lavrenti Beria, it was the