Manhattan Project: The Plutonium Path to the Bomb, 1942-1944

Time Periods

1890s-1939:
Atomic Discoveries

1939-1942:
Early
Government Support

1942:
Difficult
Choices

1942-1944:
The Uranium
Path to
the Bomb

1942-1944:
The Plutonium
Path to
the Bomb

1942-1945:
Bringing It All Together

1945:
Dawn of the
Atomic Era

1945-present:
Postscript --
The Nuclear Age

THE PLUTONIUM PATH TO THE BOMB
(1942-1944)
Events > The Plutonium Path to the Bomb, 1942-1944

Plutonium, produced in a uranium-fueled reactor (pile), was the second path taken toward achieving an atomic bomb. Design work on a full-scale plutonium production reactor began at the Met Lab in June 1942. Scientists at the Met Lab had the technical expertise to design a production pile, but construction and management on an industrial scale required an outside contractor. General Groves convinced the DuPont Corporation to become the primary contractor for plutonium production. With input from the Met Lab and DuPont, Groves selected a site at Hanford, Washington, on the Columbia River, to build the full-scale production reactors.

On December 2, 1942, on a racket court under the west grandstand at the University of Chicago's Stagg Field, researchers headed by Enrico Fermi achieved the first self-sustaining chain reaction in a graphite and uranium pile known as CP-1. Using theoretical information garnered from the operation of CP-1, DuPont constructed an air-cooled experimental production reactor, known as X-10, and a pilot chemical separation facility at Oak Ridge. The separation facility, using methods developed by Glenn T. Seaborg and a team of researchers at the Met Lab, removed plutonium from uranium irradiated in the X-10 reactor. Information from CP-1 was also useful to Met Lab scientists designing the water-cooled plutonium production reactors for Hanford. Construction at the site began in mid-1943. Three production reactors and corresponding chemical separation plants were built, with the first pile, the B Reactor, becoming operational in late September 1944. Los Alamos received its first plutonium from Hanford in early February 1945.

To learn more about any of these events associated with the plutonium path to the bomb, choose a web page from the menu below. To continue with a quick overview of the Manhattan Project, jump ahead to the description of the final process of "Bringing It All Together, 1942-1945."

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Sources and notes for this page.

The text for this page is original to the Department of Energy's Office of History and Heritage Resources. The terms "atomic pile" and "nuclear reactor" refer to the same thing. The term "pile" was more common during early atomic research, and it was gradually replaced by "reactor" in the later years of the Manhattan Project and afterwards. In this web site, the phrase "pile (reactor)" is used to refer to early, experimental piles, and "reactor (pile)" is used to refer to later production reactors, which had more elaborate controls and in general more-closely resembled post-war reactors. Much as the term "pile" gradually gave way to "reactor," "atomic" was gradually replaced by "nuclear." The painting of CP-1 going critical is courtesy the National Archives. Click here for more information on the aerial photograph of Hanford.