Mayak

The Mayak Production Association (, , from 'lighthouse') is a nuclear facility near Ozyorsk, Chelyabinsk Oblast, Russia, with production reactors and a reprocessing plant. Its reprocessing capacity, at 400 tonnes of heavy metal per year, is the second-largest in the world, following the La Hague site in France. It is currently used for military and civilian radioisotope production, and was historically central to the Soviet nuclear weapons program.

Lavrentiy Beria led the Soviet atomic bomb project. He directed the construction of the Mayak plutonium plant in the Southern Urals between 1945 and 1948, in a great hurry and secrecy as part of the Soviet Union's atomic bomb project. The plant had a similar purpose to the Hanford Site of the Manhattan Project. Over 40,000 gulag prisoners and POWs built the factory and the closed nuclear city of Ozyorsk, called at the time by its classified postal code "Chelyabinsk-40". The first reactor, A-1, operated from 1948 and fuelled the first nuclear test RDS-1 in 1949. During the Cold War, 10 nuclear reactors were constructed, with a combined power of 7,333 MWth. Of these, four were used for plutonium production, yielding 31 tons of weapons-grade plutonium, out of the Soviet Union's all-time production of 145 tons. The other six reactors primarily produced tritium for thermonuclear weapons. In 1990, weapons-grade plutonium production was ceased.