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Peak uranium is the point in time that the maximum global uranium production rate is reached. After that peak, according to Hubbert peak theory, the rate of production enters a terminal decline. While uranium is used in nuclear weapons, its primary use is for energy generation via nuclear fission of the uranium-235 isotope in a nuclear power reactor. Each kilogram of uranium-235 fissioned releases the energy equivalent of millions of times its mass in chemical reactants, as much energy as 2700 tons of coal, but uranium-235 is only 0.7% of the mass of natural uranium.〔(【引用サイトリンク】title=Coal Equivalent )〕 Uranium-235 is a finite non-renewable resource.〔 However, the current reserves of uranium have the potential (assuming breeder reactor technology) to provide power for humanity for billions of years, until the death of our sun, so nuclear power can be termed sustainable energy.〔http://www-formal.stanford.edu/jmc/progress/cohen.html〕 Observers contend that idea of "energy independence" is an unrealistic concept in relation with Liquid metal fast breeder reactor.〔For more, see: United States. Congress. Senate. Committee on Appropriations. U.S. Government Printing Office, 1975. Page 7349.〕 M. King Hubbert created his peak theory in 1956 for a variety of finite resources such as coal, oil, and natural gas. He and others since have argued that if the nuclear fuel cycle can be closed, uranium could become equivalent to renewable energy sources as concerns its availability.〔 〕 Breeding and nuclear reprocessing potentially would allow the extraction of the largest amount of energy from natural uranium. However, only a small amount of uranium is currently being bred into plutonium and only a small amount of fissile uranium and plutonium is being recovered from nuclear waste worldwide. Furthermore, the technologies to completely eliminate the waste in the nuclear fuel cycle do not yet exist.〔 〕 Since the nuclear fuel cycle is effectively not closed, Hubbert peak theory applies. The rate of discovery and the rate of production which initially increase must reach a maximum and decline. The rate at which uranium can be bred and the rate at which fuel can be reprocessed cannot indefinitely suffice to meet the growing gap between demand and the rate that uranium can be mined. Pessimistic predictions of future high-grade uranium production operate on the thesis that either the peak has already occurred in the 1980s or that a second peak may occur sometime around 2035. In 2011, the identified uranium resources recoverable at US$130/kg were 5.3 million tons and annual consumption was 65,000 tons, providing sufficient reserves for 81 years ignoring growth. Nuclear reactors provided 375 GWe of electricity capacity. Optimistic predictions are based upon 3 factors: # Light Water Reactors only consume about half of one percent of their uranium fuel while fast breeder reactors will consume closer to 99%, # current reserves of U are about 5.3 million tons. Theoretically 4.5 billion tons of uranium are available from sea water at about 10 times the current price of uranium. Currently no practical methods for high volume extraction exist. # thorium (3-4 times as abundant as uranium) can be used when supplies of uranium are depleted. If these predictions became reality it has the potential to increase the supply of nuclear fuel significantly. However at the current time the current supply of uranium will fuel 375 reactors with 1 GWe capacity for about 81 years. Optimistic predictions claim that the supply is far more than demand and do not predict peak uranium. ''Uranium depletion'' is the result of extracting and consuming uranium, a non-renewable resource. The availability of high-grade uranium ore will deplete over time meaning the fuel will become more environmentally and economically expensive to extract. ==Hubbert's peak and uranium== Uranium-235, the fissile isotope of uranium used in nuclear reactors, makes up about 0.72% of uranium from ore. It is the only naturally-occurring isotope capable of directly generating nuclear power, and is a finite, non-renewable resource. It is believed that its availability follows M. King Hubbert's peak theory, which was developed to describe peak oil. Hubbert saw oil as a resource which would soon run out, but he believed that uranium had much more promise as an energy source,〔 and that breeder reactors and nuclear reprocessing, which were new technologies at the time, would allow uranium to be a power source for a very long time. The technologies Hubbert envisioned would substantially reduce the rate of depletion of uranium-235, but they are still more costly than the "once-through" cycle, and have not been widely deployed to date. If these and other more costly technologies such as seawater extraction are used, the Hubbert peak would be extended into the very distant future. According to the Hubbert Peak Theory, Hubbert's peaks are the points where production of a resource, has reached its maximum, and from then on, the rate of resource production enters a terminal decline. After a Hubbert's peak, the rate of supply of a resource no longer fulfills the previous demand rate. As a result of the law of supply and demand, at this point the market shifts from a buyer's market to a seller's market.〔(【引用サイトリンク】title=Seller's market definition )〕 Many countries are not able to supply their own uranium demands any longer and must import uranium from other countries. Thirteen countries have hit peak and exhausted their uranium resources. 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「peak uranium」の詳細全文を読む スポンサード リンク
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