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Uranium-233 is a fissile isotope of uranium that is bred from thorium-232 as part of the thorium fuel cycle. Uranium-233 was investigated for use in nuclear weapons and as a reactor fuel.〔 It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years. Uranium-233 is produced by the neutron irradiation of thorium-232. When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of only 22 minutes. Thorium-233 decays into protactinium-233 through beta decay. Protactinium-233 has a half-life of 27 days and beta decays into uranium-233; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur. 233U usually fissions on neutron absorption but sometimes retains the neutron, becoming uranium-234. The capture-to-fission ratio is smaller than the other two major fissile fuels uranium-235 and plutonium-239. ==Fissile material== In 1946 the public first became informed of U-233 bred from thorium as "a third available source of nuclear energy and atom bombs" (in addition to U-235 and Pu-239), following a United Nations report and a speech by Glenn T. Seaborg. The United States produced, over the course of the Cold War, approximately 2 metric tons of uranium-233, in varying levels of chemical and isotopic purity. These were produced at the Hanford Site and Savannah River Site in reactors that were designed for the production of plutonium-239. Historical production costs, estimated from the costs of plutonium production, were 2–4 million USD/kg. There are few reactors remaining in the world with significant capabilities to produce more uranium-233. 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「Uranium-233」の詳細全文を読む スポンサード リンク
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