Chicago Pile-1

Chicago Pile-1 (CP-1) was the first artificial nuclear reactor, built under the west stands of Stagg Field at the University of Chicago, where the first human-made self-sustaining nuclear chain reaction was initiated on 2 December 1942. A team of about 30 led by Enrico Fermi assembled it from natural uranium and ultra-pure graphite blocks, which served as the neutron moderator. It ran at about half a watt, without shielding or cooling, and was the first major technical achievement of the Manhattan Project. In 1943 it was rebuilt near Chicago as Chicago Pile-2.