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The thorium fuel cycle is a nuclear fuel cycle that uses the isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts of fissile material (such as ), which are insufficient to initiate a nuclear chain reaction. Additional fissile material or another neutron source are necessary to initiate the fuel cycle. In a thorium-fueled reactor, absorbs neutrons eventually to produce . This parallels the process in uranium breeder reactors whereby fertile absorbs neutrons to form fissile . Depending on the design of the reactor and fuel cycle, the generated either fissions in situ or is chemically separated from the used nuclear fuel and formed into new nuclear fuel. The thorium fuel cycle claims several potential advantages over a uranium fuel cycle, including thorium's greater abundance, superior physical and nuclear properties, better resistance to nuclear weapons proliferation〔 ()〕〔(Nuclear Materials ) FAQ〕 and reduced plutonium and actinide production.〔 ==History== Concerns about the limits of worldwide uranium resources motivated initial interest in the thorium fuel cycle.〔 It was envisioned that as uranium reserves were depleted, thorium would supplement uranium as a fertile material. However, for most countries uranium was relatively abundant and research in thorium fuel cycles waned. A notable exception was India's three-stage nuclear power programme. In the twenty-first century thorium's potential for improving proliferation resistance and waste characteristics led to renewed interest in the thorium fuel cycle.〔 〕 At Oak Ridge National Laboratory in the 1960s, the Molten-Salt Reactor Experiment used as the fissile fuel as an experiment to demonstrate a part of the Molten Salt Breeder Reactor that was designed to operate on the thorium fuel cycle. Molten Salt Reactor (MSR) experiments assessed thorium's feasibility, using thorium(IV) fluoride dissolved in a molten salt fluid that eliminated the need to fabricate fuel elements. The MSR program was defunded in 1976 after its patron Alvin Weinberg was fired. In 2006, Carlo Rubbia proposed the concept of an energy amplifier or "accelerator driven system" (ADS), which he saw as a novel and safe way to produce nuclear energy that exploited existing accelerator technologies. Rubbia's proposal offered the potential to incinerate high-activity nuclear waste and produce energy from natural thorium and depleted uranium.〔 〕 Kirk Sorensen, former NASA scientist and Chief Nuclear Technologist at Teledyne Brown Engineering, has been a long-time promoter of thorium fuel cycle and particularly liquid fluoride thorium reactors (LFTRs). He first researched thorium reactors while working at NASA, while evaluating power plant designs suitable for lunar colonies. In 2006 Sorensen started "energyfromthorium.com" to promote and make information available about this technology.〔(【引用サイトリンク】title=Flibe Energy )〕 A 2011 MIT study concluded that, although there is little in the way of barriers to a thorium fuel cycle, with current or near term light-water reactor designs there is also little incentive for any significant market penetration to occur. As such they conclude there is little chance of thorium cycles replacing conventional uranium cycles in the current nuclear power market, despite the potential benefits. 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「thorium fuel cycle」の詳細全文を読む スポンサード リンク
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