The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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If SNF is to be disposed of in a repository, it will be stored for 40 to 60 years (Chapter 5: Waste management). Peak temperatures in a geological repository are limited to assure long-term repository performance. If the temperatures are too high, the performance of the waste form, waste package, and geology may be impaired. Peak repository temperatures are controlled by limiting the allowable decay heat per waste package. If the SNF is stored for several decades, the decay heat per ton of SNF decreases, more SNF can be placed in each waste package, the waste packages can be spaced closer to each other underground, the size (footprint) of the repository is reduced, and the cost of the repository is reduced. Like the SNF, the HLW will be cooled for 40 to 60 years before ultimate disposal to reduce the decay heat. SNF sent to a reprocessing plant may be stored for long periods of time before reprocessing. • Product specifications (Appendix E: Status of Fuel Cycle Technology). In closed fuel cycles, SNF is converted into fresh fuel assemblies and wastes for disposal. One complication is that each SNF assembly has different plutonium isotopics. To fabricate fresh fuel assemblies with the proper plutonium isotopic content, selected SNF assemblies are chosen so when reprocessed together as a batch, the plutonium isotopic specifications for the plutonium fuel are met (Appendix E). This is conceptually similar to the recycle of steel where different grades of scrap metal are mixed together to produce a recycle steel that meets product specifications. In both cases, large inventories of recycle materials help provide the right selection of feed materials to produce the desired products. • Reduced reprocessing costs. As SNF ages and its radioactivity and decay heat decrease, it becomes easier and less expensive to reprocess. The requirement for SNF storage to allow decreases in decay heat resulted in several countries building centralized facilities for SNF or HLW storage in the 1980s to age the wastes before disposal. The U.S. passed laws requiring disposal of SNF on a specific schedule without considering storage; however, those legal requirements did not change the need for storage. The technical solution at the proposed Yucca Mountain repository was to place the SNF in waste packages, put the waste packages in the repository, and cool the repository with air flow through the disposal drifts for 50 years after the repository was filled. The strategy of SNF storage (at the reactor, a centralized storage facility, or a ventilated repository), wherever it is done, significantly reduces the size and cost of the repository. In effect, the proposed Yucca Mountain repository would have been functionally a SNF storage facility that would be functionally converted into a geological repository after the 50-year cooling of the SNF. reCommendation For SnF StoraGe For up to a Century Technical and economic factors define nominal SNF storage times—60 to 70 years in the proposed Yucca Mountain system. These storage times may be increased or decreased by policy considerations. Technical and policy considerations have led to our recommendation that: Planning for long term managed storage of spent nuclear fuel—for about a century—should be an integral part of nuclear fuel cycle design. SNF is a significant potential source of energy; however, we do not know today if LWR SNF is a waste or a valuable national resource. Because of this uncertainty, we recommend chapter 4: Interim Storage of Spent nuclear Fuel 45
a policy that maintains fuel cycle options—long-term storage of SNF. There are several factors that lead to this conclusion • There is no incentive today to recycle SNF. Economic uranium resources will be available for most of this century (Chapter 3). Current waste management technologies can safely dispose of SNF (Chapter 5). The cost to recycle LWR SNF is greater than making new fuel from mined uranium (Chapter 7). • The energy content of SNF is significant and thus the incentive to maintain the option of future use of SNF. The historical vision of the future of the nuclear fuel cycle was that LWR SNF is a valuable resource. Plutonium from LWR SNF was to be recovered and fabricated into fuel for the startup of fast reactors. Such a system could increase the available energy from uranium by more than an order of magnitude. • New fast-reactor technologies may not require plutonium from LWR SNF. Advances in technology indicate that fast reactors may be started up on low-enriched (
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Other Reports in This Series The Fu
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MIT Nuclear Fuel Cycle Study Adviso
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vi MIT STudy on The FuTure oF nucle
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viii MIT STudy on The FuTure oF nuc
Page 11 and 12: Study Findings and Recommendations
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Page 31 and 32: Recommendation Integrated system st
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Page 37 and 38: the once-through Fuel Cycle for lig
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Page 49 and 50: Because ore demand is closely coupl
Page 51 and 52: eStimatinG Future CoStS oF uranium
Page 53 and 54: Figure 3.3 relative uranium Cost vs
Page 55 and 56: Figure 3.4 100 year price trend for
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Page 59 and 60: CitationS and noteS 1. Uranium 2007
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Page 79 and 80: Waste Isolation Pilot Plant The uni
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Page 85 and 86: CitationS and noteS 1. A Handbook f
Page 89 and 90: energy spectrum centered at higher
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Summary oF ConCluSionS Among the in
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[hoffman et al., 2006] e.a. hoffman
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This chapter reports the cost of th
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Table 7.1 Input Parameter Assumptio
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Twice-Through Cycle Table 7.3 shows
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Table 7.4 The LCOE for the Fast Rea
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higher cost of disposal of the spen
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110 MIT STudy on The FuTure oF nucl
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power program might be used, as is
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Figure 8.1 Weapons-usability Charac
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inStitutional approaCheS to Fuel Cy
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the iaea additional protocol an Iae
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in technology innovation are likely
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Reprocessing choices Commercial rep
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Table 8.2 Safeguard Technical Objec
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port for nuclear power over the per
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Those Americans who have an opinion
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who are very concerned with global
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p Waste management must be integrat
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options because we do not know toda
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Nuclear Security. Nonproliferation
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There have been major changes in ou
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There are large financial and polic
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Figure 3A.2 shows the results. As c
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Figure A.3 plots Eq (2), where adva
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Again, assuming that q = 0.29, the
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Note that Eq. [7] suggests employin
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Figure 3b.1 Cumulative probability
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Figure 5a.1 decay of radioactivity
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and 241 Am. For the short term, hea
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Repository Engineering All reposito
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epreSentative repoSitory deSiGnS: u
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orehole diSpoSal There are three me
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table 7a.1 list of variables , 1 lc
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The Twice-Through Cycle The LCOE fo
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A proper representation of the chai
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In the Twice-Through Cycle, the pai
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table 7a.2 once-through Fuel Cycle
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above ground storage. However, the
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CitationS and noteS 1. The methodol
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Historically, the interest in thori
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p Analogous to plutonium. Plutonium
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In case self-protection of U-232 da
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Figure a.3 Schematic view of Sbu an
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eaCtor teChnoloGieS Nuclear power e
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via 239 Pu and 240 Pu, and then the
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urnups, but the gap between the nec
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(~700°C) with higher thermal-to-el
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There are several unique consequenc
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performance goals can be achieved.
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is that it will be many decades bef
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system [1]. The nuclear power plant
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The HTRs can be used to provide hig
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[http://nextgenerationnuclearplant.
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CitationS and noteS Brinkmann, H. U
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The analysis is based on the assump
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considerations discussed above. We
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In our analysis we make the explici
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Figure d.4 transmutation Consequenc
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Figure d.5 breeder Consequences LWR
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facilities. These concerns are the
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Technological applicability Geologi
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It must be noted, that net risks an
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p Once-through fast reactor fuel. T
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Table E.1 Recycling Plant Functions
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Table E.3 Conventional Fuel Fabrica
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eactor. A summary of inputs from in
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