新托福阅读训练：IsSpentNuclearFuelaWasteoraResource?

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核能源的合理利用正成为许多掌握了核技术国家重点发展的项目，而如何安全的使用和回收核原料和废料则关系着许多人的生命健康和幸福。  
# H# y( c( R' Q6 J. V# @! @　　On September 15, the U.S. Nuclear Regulatory Commission affirmed its expert opinion that spent nuclear fuel could be safely stored on nuclear power plant grounds—whether in pools or dry casks—for "at least 60 years beyond the licensed life of any reactor." That is good news, because there is nowhere else for such waste to go.
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　　As President Obama's Blue Ribbon Commission on America's Nuclear Future continues to ponder what role nuclear power might play in the U.S. electricity supply, a group of scientists, engineers and other experts assembled by the Massachusetts Institute of Technology (M.I.T.) released a report on the nuclear fuel cycle paid for by the nuclear industry. In short, the report finds that uranium resources are not likely to run out in the next century, even if the U.S. alone builds as many as 1,000 nuclear reactors. Therefore, either reprocessing or recycling spent nuclear fuel, as the French and Japanese do, is likely to be a waste of money better spent on improving the light-water reactors presently in use. The funds could also be used to create a $670-million-per-year research and development program for nuclear power as well as to determine the best fuel cycle over the course of the next several decades. Finally, the global expansion of nuclear power plants should be enabled by some form of leasing program for the uranium fuel rods—one up for renewal every decade or so.

　　"For the next several decades in the U.S. the once-through fuel cycle using light-water reactors is the preferred option," said M.I.T. physicist and report co-chair Ernest Moniz at its release on September 16 in Washington, D.C. "Light-water reactors are the workhorse, and there's a lot we can do to improve [them]." The U.S. employs 104 light-water reactors to generate 20 percent of its electricity today; the reactors moderate uranium fission and the heat it produces with water, which is also boiled into steam to turn an electricity-generating turbine.

　　M.I.T. nuclear engineer Charles Forsberg, another co-chair of the report, noted that a typical light-water reactor in the U.S. needs 200 metric tons of mined uranium resulting in 20 metric tons of uranium fuel per year. All this uranium represents as little as 2 percent of the final cost of the electricity from that nuclear power plant. Therefore, even if uranium prices doubled or more, the impact on electricity prices would be minimal.

9 }0 O9 E3 @7 c3 c2 _4 A　　The M.I.T. report predicts that even if the world's fleet of more than 400 nuclear power plants grew to be 4,000 such plants that then operated for a century, the cost of the electricity from those facilities would rise by a mere 1 percent as a result of the increased demand for uranium. "There's no shortage of uranium that might constrain future commitments to build new nuclear plants for much of the century," Forsberg said. This also argues against alternate fissile fuels such as thorium. "What do you get by complicating the fuel cycle by looking at thorium when we have plenty of uranium?" asked M.I.T. nuclear engineer and report co-chair Mujid Kazimi.
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  b( `" r. b/ L  S# e　　The question then becomes what to do with that abundant uranium once it's been fissioned in a nuclear reactor. After all, the spent nuclear fuel still contains fissionable uranium 235 and plutonium 239. "Today, we don't know whether spent nuclear fuel from light-water reactors is waste or a resource," Moniz noted. Forsberg added that the spent nuclear fuel currently awaiting a home in the U.S. could be compared with "a super-strategic petroleum reserve. We should be cautious before we throw it away."
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+ D. Z; k7 h& s, y　　But a place to throw such radioactive waste remains necessary. Even though the spent nuclear fuel from the entire U.S. fleet of reactors—roughly 2,000 metric tons per year—requires just two hectares of land to be stored in dry casks, some form of geologic isolation—such as the proposed repository at Yucca Mountain in Nevada—will be needed ultimately. But rather than choosing a site for political reasons, as in the case of Yucca, the M.I.T. report authors argue for selecting a site based on the type of waste to be placed there, the geology that then best shields that type of waste, and even the initial reactor design as a result (to make sure the right kind of waste is made). For example, an entire nuclear cycle involving light-water reactors, reprocessing of the spent fuel, and disposal of small "packages" of highly radioactive nuclear waste in deep boreholes could prove an attractive option, Moniz noted.

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　　Such reprocessing—or even fast-neutron reactors that don't use water to moderate fission and can potentially create more fuel than they consume—remain a distant prospect. Since the 1950s roughly $100 billion has been spent on the research and development of such reactors around the world, yet there is currently only one producing electricity—the BN-600 reactor in Russia, operational since 1980. And even with such fast-neutron reactors, the amount of potentially worrisome material for making nuclear weapons does not change. "Transuranics are not magically changed in terms of their inventory by these things," Moniz said. In fact, the M.I.T. report argues that creating reactors that produce more fuel than they consume may never be necessary. "Light-water reactors are with us for the entire century," Kazimi noted. "They are the backbone of the system."

. ~4 h4 f& ~6 }5 q　　So that leaves the question of proliferation, particularly as many countries in Asia begin to build new nuclear power plants, ranging from the United Arab Emirates to Vietnam. The M.I.T. report argues that a leasing program, in which countries with the capability to enrich uranium fuel supply it to other countries and then take back the spent fuel for disposal in one form or another at the end of its useful life. "One might combine climate and proliferation concerns with a way of attaching carbon credits to new nuclear construction in countries that took certain kinds of agreements around enrichment and reprocessing," Moniz said.
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　　Regardless, the U.S., at least, appears to be in no hurry to build nuclear reactors; only one is currently under construction at Watts Bar in Tennessee, with another potentially in the works at Vogtle in Georgia as a result of a loan guarantee from the Obama administration. The problem, as always, with nuclear is construction costs—the M.I.T. report assumes a nuclear reactor costs $4,000 per kilowatt of electricity produced to build—or $4 billion for a typical one-gigawatt nuclear power plant. Actual industry estimates for reactors being built today are at least $6 billion for such power plants and as much as $10 billion. "If you build a nuclear power plant and operate it well, it's going to produce a steady stream of income," Moniz noted. But "the disadvantage of nuclear is the enormous capital commitment that is made up front."

　　Or as the report notes: "The track record for the construction costs of nuclear plants completed in the U.S. during the 1980s and early 1990s was poor. Actual costs were far higher than had been projected…. The first few U.S. plants will be a critical test for all parties involved."