Graphite pile for nuclear reactor. Cutaway view of the graphite pile for the B Reactor, the first large-scale nuclear reactor ever built. It was built at the Hanford Site, near Richland, Washington, USA. This diagram was produced in 1945, with the reactor built from 1943 to 1944. This reactor was part of the Manhattan Project during World War II, used to produce plutonium for the United States nuclear weapons program. The graphite is used around the reactor core to moderate the neutrons produced. The labels also refer to holes for water tubes, helium channels, and thermal shields. This photograph is part of the Historic American Engineering Record.