The Manhattan Project: Making the Atomic Bomb

X-10 in Operation: Fall 1943

The moment everyone had been waiting for came in late October when DuPont completed construction and tests of the X-10 pile at Clinton Engineer Works. After thousands of slugs were loaded, the pile went critical in the early morning of November 4 and produced plutonium by the end of the month. Criticality was achieved with only half of the channels filled with uranium. During the next several months, Compton gradually raised the power level of the pile and increased its plutonium yield. Chemical separation techniques using the bismuth phosphate process were so successful that Los Alamos received plutonium samples beginning in the spring. Fission studies of these samples at Los Alamos during summer 1944 heavily influenced bomb design.

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