The single largest problem during the early Soviet project was the procurement of uranium ore, as the USSR had limited domestic sources at the beginning of the project. The era of domestic uranium mining can be dated exactly, to November 27, 1942, the date of a directive issued by the all-powerful wartime State Defense Committee. The first Soviet uranium mine was established in Taboshar, present-day Tajikistan, and was producing at an annual rate of a few tons of uranium concentrate by May 1943.[43] Taboshar was the first of many officially secret Soviet closed cities related to uranium mining and production.[44]

Demand from the experimental bomb project was far higher. The Americans, with the help of Belgian businessman Edgar Sengier in 1940, had already blocked access to known sources in Congo, South Africa, and Canada. In December 1944 Stalin took the uranium project away from Vyacheslav Molotov and gave to it to Lavrentiy Beria. The first Soviet uranium processing plant was established as the Leninabad Mining and Chemical Combine in Chkalovsk (present-day Buston, Ghafurov District), Tajikistan, and new production sites identified in relative proximity. This posed a need for labor, a need that Beria would fill with forced labor: tens of thousands of Gulag prisoners were brought to work in the mines, the processing plants, and related construction.

Domestic production was still insufficient when the Soviet F-1 reactor, which began operation in December 1946, was fueled using uranium confiscated from the remains of the German atomic bomb project. This uranium had been mined in the Belgian Congo, and the ore in Belgium fell into the hands of the Germans after their invasion and occupation of Belgium in 1940.

Further sources of uranium in the early years of the program were mines in East Germany (via the deceptively-named SAG Wismut), Czechoslovakia, Bulgaria, Romania (near Stei) and Poland. Boris Pregel sold 0.23 tonnes of uranium oxide to the Soviet Union during the war, with the authorisation of the U.S. Government.[45][46][47]

Eventually, large domestic sources were discovered in the Soviet Union (including those now in Kazakhstan).

The uranium for the Soviet nuclear weapons program came from mine production in the following countries,[48]