Manhattan Project feed materials program

The Manhattan Project feed materials program located and procured uranium ores, and refined and processed them into feed materials for use in the Manhattan Project's isotope enrichment plants at the Clinton Engineer Works in Oak Ridge, Tennessee, and its nuclear reactors at the Hanford Engineer Works in Washington state.

The original goal of the feed materials program in 1942 was to acquire approximately 1,500 tonnes (1,700 short tons) of triuranium octoxide (U₃O₈) (black oxide). By the time of the dissolution of the Manhattan District on 1 January 1947, it had acquired about 9,100 tonnes (10,000 short tons), 68.3% of which came from the Belgian Congo, 13.2% from the Colorado Plateau, and 11.1% from Canada. An additional 7.3% came from "miscellaneous sources", which included quantities recovered from Europe by the Manhattan Project's Alsos Mission.

Ores from the Belgian Congo contained the most uranium per mass of rock by far. Much of the mined ore from the Shinkolobwe mine had a black oxide content as high as 65% to 75%, which was many times higher than any other global sources. In comparison, the Canadian ores could be as rich as 30% uranium oxides, while American ores, mostly byproducts of the mining of other minerals (especially vanadium), typically contained less than 1% uranium. In 1941, both the Shinkolobwe mine and the Eldorado Mine in Canada were closed and became flooded; the Manhattan Project had them reopened and returned to service.

Beyond their immediate wartime needs, the American and British governments attempted to control as much of the world's uranium deposits as possible. They created the Combined Development Trust in June 1944, with the director of the Manhattan Project, Major General Leslie R. Groves Jr. as its chairman. The Combined Development Trust procured uranium and thorium ores on international markets. A special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and his resignation from the Trust in 1947, Groves deposited a total of $37.5 million (equivalent to $669.83 million in 2024). In 1944, the Combined Development Trust purchased 3,440,000 pounds (1,560,000 kg) of uranium oxide ore from the Belgian Congo.

The raw ore was dissolved in nitric acid to produce uranyl nitrate, which was reduced to highly pure uranium dioxide. By July 1942, Mallinckrodt was producing a ton of oxide a day, but turning this into uranium metal initially proved more difficult. A branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding to investigate alternatives. This became known as the Ames Project, and the Ames process it developed to produce uranium metal became available in 1943. Uranium metal was used to fuel the nuclear reactors. Uranium tetrachloride was produced as feed for the calutrons used in the Y-12 electromagnetic isotope separation process, and uranium hexafluoride for the K-25 gaseous diffusion process.