page_title: Hanford Site
section_title: Plutonium production
hierarchical_section_title: Hanford Site / Manhattan Project / Plutonium production
caption_attribution_description: English: Front face of the B reactor at the Hanford site. Image #N1D0029049 at http://www5.hanford.gov/ddrs/index.cfm.
context_page_description: The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. The site has been known by many names, including Hanford Project, Hanford Works, Hanford Engineer Works and Hanford Nuclear Reservation.
  Established in 1943 as part of the Manhattan Project in Hanford, south-central Washington, the site was home to the B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first nuclear bomb, tested at the Trinity site, and in Fat Man, the third bomb that was detonated over Nagasaki, Japan.
  During the Cold War, the project expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the more than 60,000 weapons built for the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements.
context_section_description: The B Reactor (105-B) at Hanford was the first large-scale plutonium production reactor in the world. It was designed and built by DuPont based on an experimental design by Enrico Fermi, and originally operated at 250 megawatts (thermal). The reactor was graphite moderated and water cooled. It consisted of a 28-by-36-foot (8.5 by 11.0 m), 1,200-short-ton (1,100 t) graphite cylinder lying on its side, penetrated through its entire length horizontally by 2,004 aluminium tubes. Two hundred short tons (180 t) of uranium slugs, 1.625 inches (4.13 cm) diameter by 8 inches (20 cm) long, sealed in aluminium cans went into the tubes. Cooling water was pumped through the aluminium tubes around the uranium slugs at the rate of 30,000 US gallons (110,000 L) per minute.
  Construction on B Reactor began in August 1943 and was completed on September 13, 1944. The reactor went critical in late September and, after overcoming neutron poisoning, produced its first plutonium on November 6, 1944. Plutonium was produced in the Hanford reactors when a uranium-238 atom in a fuel slug absorbed a neutron to form uranium-239. U-239 rapidly undergoes beta decay to form neptunium-239, which rapidly undergoes a second beta decay to form plutonium-239. The irradiated fuel slugs were transported by rail to three huge remotely operated chemical separation plants called "canyons" that were about 10 miles (16 km) away.
  A series of chemical processing steps separated the small amount of plutonium that was produced from the remaining uranium and the fission waste products. This first batch of plutonium was refined in the 221-T plant from December 26, 1944, to February 2, 1945, and delivered to the Los Alamos laboratory in New Mexico on February 5, 1945.
  The material was used in Trinity, the first nuclear explosion, on July 16, 1945.
  Two identical reactors, D Reactor and F reactor, came online in December 1944 and February 1945, respectively. By April 1945, shipments of plutonium were headed to Los Alamos every five days, and Hanford soon provided enough material for the bombs tested at Trinity and dropped over Nagasaki. Throughout this period, the Manhattan Project maintained a top secret classification. Until news arrived of the bomb dropped on Hiroshima, fewer than one percent of Hanford's workers knew they were working on a nuclear weapons project. General Groves noted in his memoirs that "We made certain that each member of the project thoroughly understood his part in the total effort; that, and nothing more."
  Initially six reactors or "piles" were proposed, when the plutonium was to be used in the gun-type Thin Man bomb. In mid-1944 a simple gun-type bomb was found to be impractical for plutonium, and the more advanced Fat Man bomb, an implosion device, required less plutonium. The number of piles was reduced to four and then three; and the number of chemical separation plants from four to three.
caption: The B Reactor during construction
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