Weapons-grade plutonium in the context of Isotope separation

A nuclear reactor is a device used to sustain a controlled fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production and research. Fissile nuclei (primarily uranium-235 or plutonium-239) absorb single neutrons and split, releasing energy and multiple neutrons, which can induce further fission. Reactors stabilize this, regulating neutron absorbers and moderators in the core. Fuel efficiency is exceptionally high; low-enriched uranium is 120,000 times more energy-dense than coal.

Heat from nuclear fission is passed to a working fluid coolant. In commercial reactors, this drives turbines and electrical generator shafts. Some reactors are used for district heating, and isotope production for medical and industrial use.

The Mayak Production Association (Russian: Производственное объединение «Маяк», Proizvodstvennoye ob′yedineniye "Mayak", from Маяк 'lighthouse') is one of the largest nuclear facilities in the Russian Federation, housing production reactors (non electricity) and a reprocessing plant. The closest settlements are Ozyorsk to the northwest and Novogornyi to the south.

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.