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This Week in Illinois History: World’s first man-made nuclear reaction (December 2, 1942)

CP-1
An artist’s rendering of the moment Enrico Fermi’s experiment achieved the world’s first controlled, self-sustaining nuclear reaction.

As Nazi forces marched across Europe during World War II, many of the world’s greatest scientists fled to the United States. Several came to the University of Chicago, where they participated in one of the earliest stages of the Manhattan Project.

The Manhattan Project was a desperate race to create the atomic bomb before Germany. The Chicago team, led by Italian scientist Enrico Fermi, was tasked with building the world’s first self-sustaining nuclear reaction, the first step toward an atomic weapon.

Fermi needed a large space to build and test his reactor. His team chose the squash courts underneath a grandstand at the University of Chicago’s Stagg Field. City and university officials knew nothing of the experiment, and some of the scientists involved were leery of experimenting with atomic energy in the middle of the population-dense city. Fermi assured everyone the experiments would be small and controlled.

The University of Chicago's Stagg Field in 1942, when Enrico Fermi's group was using round-the-clock shifts to construct Chicago Pile-1 under the grandstand.
U.S. Department of Energy
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Stagg Field, University of Chicago, in 1942 when Enrico Fermi's group was using round-the-clock shifts to construct Chicago Pile-1 under the grandstand.

On Nov 16, 1942, Fermi's group begins began constructing Chicago Pile-1 (or CP-1) using round-the-clock shifts. The pile consisted of uranium slugs deposited into graphite blocks.

The blocks were then stacked to form a cylinder, with the uranium lumps concentrated in the middle. The pile used 400 tons of graphite and 50 tons of uranium. The work was finished in only 15 days.

On December 2, 1942, Fermi brought his experiment to life. At 3:25pm, the pile went critical, reaching the world’s first controlled, self-sustained nuclear reaction.

After the test. Silence. Then a somber celebration with a bottle of chianti poured into paper cups. Everyone knew they had succeeded. They also knew they were one step closer to building the world’s most destructive bomb.

After the test, CP-1 was dismantled and reassembled at a new facility in the Argonne Forrest outside Chicago. Much of the nuclear research for the Manhattan Project shifted to the research facility at Los Alamos.

Today, the original Stagg Field no longer exists, but the site of the world’s first sustained nuclear reaction is marked by the Henry Moore sculpture Nuclear Energy.

Clint Cargile is the host of This Week in Illinois History and the creator and host of the podcast Drinkin’ with Lincoln.