Ozersk, Chelyabinsk Oblast, Ural Federal district, Russia

🇷🇺 Ozyorsk or Ozersk is a closed city in Chelyabinsk Oblast, Russia. The town was founded on the shores of Lake Irtyash in 1947. Until 1994, it was known as Chelyabinsk-65, and even earlier, as Chelyabinsk-40 (the digits are the last digits of the postal code, and the name is that of the nearest big city, which was a common practice of giving names to closed towns).

Codenamed City 40, Ozersk was the birthplace of the Soviet nuclear weapons program after the Second World War. In 1994, it was granted town status and renamed Ozyorsk. Within the framework of administrative divisions, it is, together with six rural localities, incorporated as the Town of Ozyorsk—an administrative unit with the status equal to that of the districts. As a municipal division, the Town of Ozyorsk is incorporated as Ozyorsky Urban Okrug.

Economy Ozyorsk was and remains a closed town because of its proximity to the Mayak plant, one of the sources of Soviet plutonium during the Cold War, and now a Russian facility for processing nuclear waste and recycling nuclear material from decommissioned nuclear weapons.

The plant itself covers an area of approximately 90 km² and employs about 15,000 people. The Mayak is primarily engaged in reprocessing of spent nuclear fuel from the nuclear submarines and icebreakers and from nuclear power plants. Commercially, it produces cobalt-60, iridium-192, and carbon-14.

The town's coat of arms depicts a flame-colored salamander.

Southern-Urals Construction Department (ЗАО "Южноуральское управление строительства") is another major enterprise. Its activities include construction for atomic industry needs, production of concrete constructions and construction materials. Main products of Plant of Wiring Products #2 (ЗАО "Завод электромонтажных изделий №2") are low-voltage devices for military-industrial establishments.