Oak Ridge National Laboratory was completed, later renamed to "Oak Ridge National Laboratory". The site was chosen for the X-10 Graphite Reactor, used to show that plutonium can be created from enriched uranium. Enrico Fermi and his colleagues developed the world's second self-sustaining nuclear reactor after Fermi's previous experiment, the Chicago Pile-1. The X-10 was the first reactor designed for continuous operation. After the end of World War II the demand for weapons-grade plutonium fell and the reactor and the laboratory's 1000 employees were no longer involved in nuclear weapons. Instead, it was used for scientific research. In 1946 the first medical isotopes were
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