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The B Reactor at the Hanford Site, near Richland, Washington, USA, 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.〔(【引用サイトリンク】url=http://manhattanprojectbreactor.hanford.gov/ )〕 ==Reactor design and construction== 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 (about and is (approximately five stories) tall, occupying a volume of . The reactor core itself consisted of a graphite box measuring occupying a volume of and weighing . 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 thick weighing . 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 concrete pad topped by cast-iron blocks. The graphite composition was selected to moderate the nuclear reaction fueled by of uranium slugs approximately diameter 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 per minute. The water was discharged into settling basins, then returned to the river after allowing time for the decay of radioactive materials and the settling out of particulate matter.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「B Reactor」の詳細全文を読む スポンサード リンク
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