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.

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 "Forty".

Rather than cease production of plutonium until new underground waste storage tanks could be built, between 1949 and 1951, Soviet managers dumped 76 million cubic metres (2.7 billion cubic feet) of toxic chemicals, including 3.2 million curies of high-level radioactive waste into the Techa River, a slow-moving hydraulic system that bogs down in swamps and lakes.

[4] In the 45 years afterwards, about half a million people in the region have been irradiated in one or more of the incidents,[3][5] exposing them to up to 20 times the radiation suffered by the Chernobyl disaster victims outside of the plant itself.

[8] 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 750 km2 (290 sq mi) (a nine-mile radius) in the eastern Urals, causing sickness and death from radiation poisoning.

[citation needed] In recent years, proposals that the plant reprocess waste from foreign nuclear reactors have given rise to controversy.

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.

[note 1] 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 Lavrentiy Beria, it was the utmost priority to produce enough weapons-grade material to match the U.S. nuclear superiority following the atomic bombings of Hiroshima and Nagasaki.

Little to no consideration was paid to worker safety or responsible disposal of waste materials, and the reactors were all optimised for plutonium production, producing many tons of contaminated materials and utilising primitive open-cycle cooling systems which directly contaminated the thousands of gallons of cooling water the reactors used every day.

The closer Lake Karachay, too small to provide sufficient cooling water, was used as a dumping ground for large quantities of high-level radioactive waste too "hot" to store in the facility's underground storage vats.

This led to greater caution among the administration, fearing international attention, and caused the dumping grounds to be spread out over a variety of areas (including several lakes and the Techa River, along which many villages lay).

Residents of Chelyabinsk district in the Southern Urals reported observing "polar-lights" in the sky near the plant, and American aerial spy photos had documented the destruction caused by the disaster by 1960.

When Zhores Medvedev exposed the disaster in a 1976 article in New Scientist, some exaggerated claims circulated in the absence of any verifiable information from the Soviet Union.

"[21] Professor Leo Tumerman, former head of the Biophysics Laboratory at the Institute of Molecular Biology in Moscow, disclosed what he knew of the accident around the same time.

The shift supervisor then entered the room of the incident, caused another, larger nuclear reaction and irradiated himself with a deadly dose of radiation.

In January 2018, the French Institute of Radioprotection and Nuclear Security (IRSN) reported that the source of the contamination is located in the Volga – Southern Ural region between 25 and 28 September for a duration of less than 24 hours.