Nuclear Fuel Cycle: Environmental Impact
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clear Fuel Cycle: Environmental Impact Rodney C. Ewing (University of Michigan, USA)
Nuclear Fuel Cycles Every energy source has environmental impacts—positive and negative. Nuclear power is a carbon-free source of energy that can reduce CO2 emissions by displacing the use of fossil fuels. The present level of carbon displacement is approximately 0.5 gigatonnes of carbon per year (GtC/year), compared to the nearly 8 GtC/year emitted by the use of fossil fuels. However, there are three major negative environmental impacts of nuclear power: catastrophic accidents, nuclear weapons, and nuclear waste.1 The last two, weapons and waste, are directly tied to the type of nuclear fuel cycle (Figure 4 in the main nuclear article by Raj et al. in this issue). The different fuel cycles reflect different strategies for the utilization of fissile nuclides, mainly 235U and 239Pu, and these different strategies have important implications for nuclear waste management and nuclear weapons proliferation. The “once-through” open cycle treats the spent fuel as a “waste” without any attempt to reclaim the remaining fissile nuclides, 235U and newly created 239Pu, and the spent nuclear fuel (SNF) is directly disposed in a geological repository. This is the present strategy in the United States, and its success rests on the opening of the proposed geologic repository at Yucca Mountain in Nevada. A closed fuel cycle utilizes chemical reprocessing of the used fuel and retrieves approximately 99% of the fissile nuclides. However, the recovered fissile nuclides are only a supplement to the nuclear fuel that is mainly derived from newly mined uranium ore. The highly radioactive waste from reprocessing and the unprocessed SNF are disposed in a geological repository. Other fuel cycles are possible, such as the breeder reactor cycle, which creates more fissile material in the SNF than in the original fuel. The breeder reactor cycle envisions multiple cycles of reprocessing in order to extend the uranium resource. One can also develop fuel cycles based on 232Th from which fissile 233U is bred, as has been done in India. In 1977, President Carter decided to indefinitely defer reprocessing of spent nuclear fuel in the United States in order to have a more proliferation-resistant fuel cycle. In 1981, President Reagan lifted the ban on reprocessing, but he placed the financial responsibility for reprocessing on the private sector. By the mid-1980s, the commercial reprocessing of SNF had little attraction from a technical, economic, regulatory, or policy perspective.2 Thus, most of the spent fuel created at nuclear power plants has remained temporarily stored on site until a geologic repository is available. To the extent that the choice between fuel cycles is driven by economic considerations, an open fuel cycle prevails as long as the price of uranium is lower than the cost of reprocessing.3 Thus, there are no simple criteria that can serve as a basis for the selection of a fuel cycle, as environmental, proliferation, and economic issues are closely ti
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