Enrico Fermi of Scientific Research and Development, as the Advisory Committee on Uranium was now known, met on 18 December 1941, with the U.S. now engaged in World War II, making its work urgent. Most of the effort sponsored by the Committee had been directed at producing enriched uranium, but Committee member Arthur Compton determined that a feasible alternative was plutonium, which could be mass-produced in nuclear reactors by the end of 1944. He decided to concentrate the plutonium work at the University of Chicago. Fermi reluctantly moved, and his team became part of the new Metallurgical Laboratory there. The possible results
Enrico Fermi him early so that he could see it happen. Getting X-10 operational was another milestone in the plutonium project. It provided data on reactor design, training for DuPont staff in reactor operation, and produced the first small quantities of reactor-bred plutonium. Fermi became an American citizen in July 1944, the earliest date the law allowed. In September 1944, Fermi inserted the first uranium fuel slug into the B Reactor at the Hanford Site, the production reactor designed to breed plutonium in large quantities. Like X-10, it had been designed by Fermi's team at the Metallurgical Laboratory, and built by DuPont,