While Chicago Pile-1 demonstrated the feasibility of nuclear reactors, the Manhattan Project's goal of producing enough plutonium for atomic bombs required reactors a thousand times as powerful, along with facilities to chemically separate the plutonium bred in the reactors from uranium and fission products. An intermediate step was considered prudent. The next step for the plutonium project, codenamed X-10, was the construction of a semiworks where techniques and procedures could be developed and training conducted. The centerpiece of this was the X-10 Graphite Reactor. It was air-cooled, used nuclear graphite as a neutron moderator, and pure natural uranium in metal form for fuel.
DuPont commenced construction of the plutonium semiworks at the Clinton Engineer Works in Oak Ridge on February 2, 1943. The reactor went critical on November 4, 1943, and produced its first plutonium in early 1944. It supplied the Los Alamos Laboratory with its first significant amounts of plutonium, and its first reactor-bred product. Studies of these samples heavily influenced bomb design. The reactor and chemical separation plant provided invaluable experience for engineers, technicians, reactor operators, and safety officials who then moved on to the Hanford site. X-10 operated as a plutonium production plant until January 1945, when it was turned over to research activities, and the production of radioactive isotopes for scientific, medical, industrial and agricultural uses. It was shut down in 1963 and was designated a National Historic Landmark in 1965.
This operation conducted at the Nevada Test Site consisted of 11 atmospheric tests. There were three airdrops, seven tower tests, and one airburst. This operation involved the testing of new theories, using both fission and fusion devices
Dorothy McKibbin (December 12, 1897 – December 17, 1985) worked on the Manhattan Project during World War II. She ran the project's office at 109 East Palace in Santa Fe, through which staff moving to the Los Alamos Laboratory passed. She was known as the "first lady of Los Alamos", and was often the first point of contact for new arrivals. She retired when the Santa Fe office closed in 1963.