CP-1 and the Dawn of the #AtomicAge
Chicago Pile-1 (CP-1) was the world's first artificial nuclear reactor. On December 2, 1942, the first human-made self-sustaining nuclear chain reaction occurred.
The development of the reactor was the first major technical achievement of the Manhattan Project. Developed by the Metallurgical Laboratory at the University of Chicago, CP-1 was built in a squash court located under the west stands of Stagg Field, the University of Chicago’s football stadium, without consulting university officials. After a series of attempts, the reactor was assembled in November 1942 by a team of about thirty scientists led by Fermi, working in shifts.
As the reactor used natural uranium, large amounts of material, including graphite for a neutron moderator, would be required to reach criticality. By September, deliveries of materials from various sources began to arrive in covered trucks. The reactor contained 45,000 ultra-pure graphite blocks weighing 360 tons (720,000 pounds) provided by National Carbon and other suppliers. It was fueled by 5.4 tons (10,800 pounds) of uranium metal and 45 tons (90,000 pounds) of uranium oxide, provided by the Mallincrodt Chemical Works in St. Louis. The reactor had no radiation shielding or cooling system, operating at about 0.5 watts.
Successive layers of graphite blocks were arranged on the squash court floor, forming a sphere, the most efficient shape to maximize fission. Holes were drilled to contain the uranium and uranium oxide. The pile was supported by wood framing and surrounded on three sides by a shield of balloon cloth. The fourth side faced the viewing balcony of the squash court.
Forty-nine scientists were present for the successful experiment on December 2, 1942. The pile had run for about 4.5 minutes at about 0.5 watts. Hungarian refugee physicist, Eugene Wigner, opened a bottle of Chianti, which they drank from paper cups.
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Caption: CP-1 drawing
Credit: DOE