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Thorium-based nuclear power is nuclear reactor-based electrical power generation fueled primarily by the nuclear fission of the isotope uranium-233 produced from the fertile element thorium. According to proponents, a thorium fuel cycle offers several potential advantages over a uranium fuel cycle—including much greater abundance on Earth, superior physical and nuclear fuel properties, and reduced nuclear waste production. However, development of thorium power has significant start-up costs. Proponents also cite the lack of weaponization potential as an advantage of thorium, while critics say that development of breeder reactors in general (including thorium reactors that are breeders by nature) increase proliferation concerns. Since about 2008, nuclear energy experts have become more interested in thorium to supply nuclear fuel in place of uranium to generate nuclear power. This renewed interest has been highlighted in a number of scientific conferences, the latest of which, ThEC13 〔( The international Thorium Energy Committee, iThEC organises the international Thorium Energy Conference ThEC13, at CERN, in Geneva Switzerland, from October 27 to 31, 2013. ), ThEC13 website〕 was held at CERN by iThEC and attracted over 200 scientists from 32 countries. A nuclear reactor consumes certain specific fissile isotopes to produce energy. The three most practical types of nuclear reactor fuel are: * Uranium-235, purified (i.e. "enriched") by reducing the amount of uranium-238 in natural mined uranium. Most nuclear power has been generated using low-enriched uranium (LEU), whereas high-enriched uranium (HEU) is necessary for weapons. * Plutonium-239, transmuted from uranium-238 obtained from natural mined uranium. Plutonium is also used for weapons. * Uranium-233, transmuted from thorium-232, derived from natural mined thorium. This is the subject of this article. Some believe thorium is key to developing a new generation of cleaner, safer nuclear power. According to an opinion piece by a group of scientists at the Georgia Institute of Technology, considering its overall potential, thorium-based power "can mean a 1000+ year solution or a quality low-carbon bridge to truly sustainable energy sources solving a huge portion of mankind’s negative environmental impact."〔("Should We Consider Using Liquid Fluoride Thorium Reactors for Power Generation?" ), ''Environmental Science & Technology'', July 6, 2011〕 After studying the feasibility of using thorium, nuclear scientists Ralph W. Moir and Edward Teller suggested that thorium nuclear research should be restarted after a three-decade shutdown and that a small prototype plant should be built.〔Moir, Ralph W. and Teller, Edward. “Thorium-fueled Reactor Using Molten Salt Technology”, ''Journal of Nuclear Technology'', Sept. 2005 Vol 151 ((PDF file available )). This article was Teller's last, published after his death in 2003.〕〔Hargraves, Robert and Moir, Ralph. ( “Liquid Fluoride Thorium Reactors: An old idea in nuclear power gets reexamined” ), ''American Scientist'', Vol. 98, p. 304 (2010).〕〔Barton, Charles. ("Edward Teller, Global Warming, and Molten Salt Reactors" ), Nuclear Green Revolution, March 1, 2008〕 Research and development of thorium-based nuclear reactors, primarily the liquid fluoride thorium reactor, (LFTR), MSR design, has been or is now being done in India, China, Norway, United States, Israel and Russia. ==Background and brief history== After World War II, uranium-based nuclear reactors were built to produce electricity. These were similar to the reactor designs that produced material for nuclear weapons. During that period, the government of the United States also built an experimental molten salt reactor using U-233 fuel, the fissile material created by bombarding thorium with neutrons. The reactor, built at Oak Ridge National Laboratory, operated critical for roughly 15000 hours from 1965 to 1969. In 1968, Nobel laureate and discoverer of Plutonium, Glenn Seaborg, publicly announced to the Atomic Energy Commission, of which he was chairman, that the thorium-based reactor had been successfully developed and tested: In 1973, however, the U.S. government shut down all thorium-related nuclear research—which had by then been ongoing for approximately twenty years at Oak Ridge National Laboratory. The reasons were that uranium breeder reactors were more efficient, the research was proven, and byproducts could be used to make nuclear weapons. In Moir and Teller’s opinion, the decision to stop development of thorium reactors, at least as a backup option, “was an excusable mistake.”〔 Science writer Richard Martin states that nuclear physicist Alvin Weinberg, who was director at Oak Ridge and primarily responsible for the new reactor, lost his job as director because he championed development of the safer thorium reactors.〔(Weinberg Foundation ), Main website, London, UK〕〔Pentland, William. ("Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly" ) ''Forbes'', Sept. 11, 2011〕 Weinberg himself recalls this period: Martin explains that Weinberg's unwillingness to sacrifice potentially safe nuclear power for the benefit of military uses forced him to retire: Despite the documented history of thorium nuclear power, many of today’s nuclear experts were nonetheless unaware of it. According to ''Chemical & Engineering News'', "most people—including scientists—have hardly heard of the heavy-metal element and know little about it...," noting a comment by a conference attendee that "it's possible to have a Ph.D. in nuclear reactor technology and not know about thorium energy."〔("Reintroducing Thorium" ), Nov. 16, 2009〕 Nuclear physicist Victor J. Stenger, for one, first learned of it in 2012: Others, including former NASA scientist and thorium expert Kirk Sorensen, agree that "thorium was the alternative path that was not taken … "〔("Energy From Thorium" ), talk at Google Tech Talks, July 23, 2009, video, 1 hr. 22 min.〕〔Martin, Richard. ''Superfuel: Thorium, the Green Energy Source for the Future.'' Palgrave – Macmillan (2012)〕 According to Sorensen, during a documentary interview, he states that if the U.S. had not discontinued its research in 1974 it could have "probably achieved energy independence by around 2000."〔("The Thorium Dream" ), Motherboard TV video documentary, 28 min.〕 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-based nuclear power」の詳細全文を読む スポンサード リンク
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