Enrico Fermi to be nuclear fission products. Fermi left Italy in 1938 to escape new Italian racial laws that affected his Jewish wife, Laura Capon. He emigrated to the United States, where he worked on the Manhattan Project during World War II. Fermi led the team that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first human-created, self-sustaining nuclear chain reaction. He was on hand when the X-10 Graphite Reactor at Oak Ridge, Tennessee, went critical in 1943, and when the B Reactor at the Hanford Site did so the next year. At Los Alamos, he
Marshall Holloway as a laboratory instrument to test critical mass calculations and the effect of various tamper materials. The Water Boiler group was headed by Donald W. Kerst from the University of Illinois, and the group designed and built the Water Boiler, which achieved its criticality in May 1944 under the control of Enrico Fermi, after one final addition of uranium enriched to 14% uranium 235. It was world third reactor but the first reactor to use enriched uranium as a fuel, using most of the world's supply at the time, and the first to use liquid nuclear fuel in the form