page_title: B Reactor
section_title: Reactor design and construction
hierarchical_section_title: B Reactor / Reactor design and construction
context_page_description: The B Reactor at the Hanford Site, near Richland, Washington, was the first large-scale nuclear reactor ever built. The project was commissioned to produce plutonium-239 by neutron activation as part of the Manhattan Project, the United States nuclear weapons development program during World War II. The B reactor was fueled with metallic natural uranium, graphite moderated, and water-cooled. It has been designated a U.S. National Historic Landmark since August 19, 2008 and in July 2011 the National Park Service recommended that the B Reactor be included in the Manhattan Project National Historical Park commemorating the Manhattan Project. Visitors can take a tour of the reactor by advance reservation.
context_section_description: The reactor was designed and built by E. I. du Pont de Nemours and Company based on experimental designs tested by Enrico Fermi at the University of Chicago, and tests from the X-10 Graphite Reactor at Oak Ridge National Laboratory. It was designed to operate at 250 megawatts (thermal).
  The reactor occupies a footprint of 46 by 38 ft (14 by 12 m) (about 1,750 sq ft (163 m²) and is 41 ft (12 m)  tall, occupying a volume of 71,500 cu ft (2,020 m³).  The reactor core itself consisted of a 36-foot-tall (11 m) graphite box measuring 28 by 36 ft (8.5 by 11.0 m) occupying a volume of 36,288 cu ft (1,027.6 m³) and weighing 1,200 short tons (1,100 t). It was penetrated horizontally through its entire length by 2,004 aluminum tubes and vertically by channels for the vertical safety rods.
  The core is surrounded by a thermal shield of cast iron 8 to 10 inches (20 to 25 cm) thick weighing 1,000 short tons (910 t). Masonite and steel plates enclose the thermal shield on its top and sides, forming a biological shield for radiation protection. The bottom of the thermal shield is supported by a 23-foot-thick (7.0 m) concrete pad topped by cast-iron blocks.  The graphite composition was selected to moderate the nuclear reaction fueled by 200 short tons (180 t) of uranium slugs approximately 25 mm (1 in) diameter 70 mm (3 in) long (the approximate size of a roll of quarters), sealed in aluminum cans, and loaded into the aluminum tubes.
  The reactor was water-cooled, with cooling water pumped from the Hanford Reach of the Columbia River through the aluminum tubes around the uranium slugs at the rate of 75,000 US gal (280,000 L) per minute. The water was discharged into settling basins, then returned to the river after allowing time for the decay of radioactive materials, the settling out of particulate matter and for the water to cool so it could be returned to the Columbia River. Water returning to the river was prohibited from raising the temperature of the river by more than 11 °F.
caption: Map of the Hanford site with the B/C reactor site shown at the upper left.
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