The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Chapter 5 Appendix — Waste Management prinCipleS oF WaSte manaGement Radioactive waste, like any other forms of waste, is the residual product from the operation of a facility. Its potential impact on the public and the environment depends on its physical, chemical and radionuclide characteristics. These characteristics determine risk and establish a recommended disposition path for the material. For any hazardous waste, there are only three waste management options: destruction (transformation to a less hazardous substance), dilution to acceptably low concentrations in the environment, or isolation from mankind and the biosphere for a period commensurate with the longevity of the hazard. The primary method for management of radioactive wastes is isolation. The isolation should be long enough such that if and when the radioactive residues eventually re-appear in the biosphere, they will be present at concentrations low enough to satisfy some health-based dose acceptance criteria. This waste management strategy is a consequence of the defining characteristic of radioactive materials—they decay to non-radioactive elements over time. For example, radioactive cobalt-60 has a half-life of ~5 years. With a half-life of 5 years, half the cobalt-60 decays away to stable nickel-60 in 5 years. In another 5 years, half of the remaining cobalt-60 decays away. The process continues until all the cobalt-60 is gone. Most radioactive wastes contain mixtures of different radioactive isotopes where the characteristics of the longerlived radionuclides usually determine the preferred disposal option. Figure 5A.1 shows the SNF radioactivity versus time after discharge from the reactor. For any radioactive waste, the waste isolation technology chosen depends upon the half-life of the radionuclide, geochemical mobility, and radiotoxicity. For radionuclides with halflives of a few days or less, such as some medical wastes, the waste may be stored in a cabinet or closet at the facility until the radionuclides have decayed to very low concentrations. For longer-lived wastes, the disposal (storage) facility must isolate the waste for longer periods of time. WaSte Generation Different fuel cycles generate different waste streams. Table 5A.1 lists wastes from the open and closed fuel cycles. The United States has an open fuel cycle. Several countries (France, Japan, etc.) recycle fissile materials back to reactors. appendix to chapter 5: Waste Management 155
Figure 5a.1 decay of radioactivity in Spent nuclear Fuel with time 100% radioactivity 1% 1 month 1 year 40 years 100 y 1,000 y 10,000 y 1% 0.01% 100 years 1000 y 10,000 y 100,000 y 0.01% 10,000 ears y 100,000 ears y Source: a. hedin, Spent nuclear Fuel—how dangerous Is It?, Svensk Kambranslehantering aB, Tr-97-13, March 1997. The primary waste from today’s once through fuel cycle is LWR SNF. The composition of a typical spent LWR assembly 1 is shown in Figure 5A.2. Other types of fuel assemblies will have different characteristics; however, in general the actinides and fission products are generally a small fraction of the total fuel assembly. The fuel cycle incentives for recycle of SNF are discussed elsewhere. If SNF is recycled, there are three potential waste management benefits. p Reduced uranium mining. Significant wastes are generated in uranium mining and assessments 2 show that the largest fuel cycle impacts are from uranium mining—not the repository. Recycle reduces the impacts from these operations by reducing uranium mining operations. p Option for superior storage and or disposal forms relative to SNF. If SNF is recycled, the waste form chemistry can be selected to maximize repository performance. p Reduction of fissile materials from waste streams. This has three potential benefits. • Reduced heat generation in the wastes that can reduce repository size. Actinides are responsible for the longer term heat generation in the repository—particularly 241 Pu 156 MIT STudy on The FuTure oF nuclear Fuel cycle
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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
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Study Findings and Recommendations
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Recommendation We recommend that a
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p Innovative nuclear energy applica
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p In line with many of our R&D reco
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The “once through” or open fuel
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have been implemented slowly. This
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Recommendation We recommend that th
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oped policies for specific wastes r
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nuClear Fuel CyCleS The united Stat
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- The primary differences were in t
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Recommendation Integrated system st
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Table 1.2 Summary of R&D Recommenda
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18 MIT STudy on The FuTure oF nucle
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the once-through Fuel Cycle for lig
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tricity costs. Waste management cos
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Figure 2.3 partial recycle of lWr S
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history of the nuclear Fuel Cycle B
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• What is the impact of timing of
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nuclear fuel cycles, the wastes (SN
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Because ore demand is closely coupl
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eStimatinG Future CoStS oF uranium
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Figure 3.3 relative uranium Cost vs
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Figure 3.4 100 year price trend for
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Stockpiling If supply interruption
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CitationS and noteS 1. Uranium 2007
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If SNF is to be shipped, typically
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a policy that maintains fuel cycle
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Dry cask storage is used for short
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For decommissioned sites, our econo
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with its attractiveness of jobs and
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2. The United States should create
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Table 5.1 United States Waste Class
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table 5.3 examples of operational G
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Waste Isolation Pilot Plant The uni
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Successful repository programs are
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designed with limited SNF storage c
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CitationS and noteS 1. A Handbook f
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energy spectrum centered at higher
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light Water reactor Fuel technical
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(fertile-free) to CR=1.0 (break-eve
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license. However, fuel reprocessing
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Figure 6.4 densification Factors as
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As expected, the breeder installed
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Figure 6.8 shows the development of
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Table 6.8 Uranium Cost in $/kg, Sta
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Figure 6.11 location of the tru inv
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SenSitivity analySiS: alternative a
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Fast reactor technical Characterist
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cooled fast reactor (SFR) fueled by
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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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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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