The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Figure 2.2 Closed Fuel Cycle Mining & Milling Conversion Enrichment Fuel Fabrication Light Water Thermal Reactor Interim Storage A fast (fast neutron spectrum) reactor such as the SFR can extract about 50 times more energy per kilogram of uranium than an LWR based on the reactor physics of fast reactors. LWRs produce energy primarily by fissioning uranium-235. Some of the uranium-238 in the reactor is converted to plutonium-239 that is then fissioned to produce energy. In a fast spectrum reactor, the reactor can convert fertile non-fuel uranium-238 into fissile plutonium-239 faster than it consumes the fissile fuels uranium-235 and plutonium-239; thus, it can effectively lead to burning all the uranium. Waste Disposal Fuel Fabrication Fast Neutron Reactor The conversion ratio (CR) defines the rate of fissile fuel production versus consumption in a reactor. A CR greater than one implies the reactor produces fissile material faster than it is consumed by converting fertile uranium-238 to plutonium-239. If a fast reactor has a conversion ratio of 1.2, one ton of fast reactor SNF has sufficient fissile material to produce 1.2 tons of fresh fast-reactor fuel. The SNF can be chemically processed to recover uranium and plutonium with the fission products becoming wastes. The plutonium and makeup uranium-238 would be combined to produce new fuel assemblies. The only makeup material is uranium-238. All of the depleted uranium from the uranium enrichment plants or the uranium in the LWR SNF could be used as make up for the uranium converted to plutonium. TRU Spent Fuel Reprocessing With a CR of one or greater, a fast reactor is a sustainable large-scale energy source, in principle for tens of thousands of years. About 200 tons per year of uranium must be mined to operate a 1000 MW(e) LWR for a year whereas only 4 tons of uranium would be required for a fast reactor. In the 1960s and 1970s this vision led worldwide to large programs for development and commercialization of (1) reprocessing to recover uranium and plutonium from SNF and (2) sustainable fast reactors. The SFR was selected as the preferred fast reactor because it had the highest conversion ratio (1.3) of the feasible reactor options based on the technology of that time. Sodium fast reactors with closed fuel cycles were not commercialized because experience with demonstration plants indicated that (1) SFR capital costs would be ~ 20% greater than LWRs, (2) the plants had higher maintenance costs than LWRs, and (3) uranium was found to be more abundant than initially thought. Over 70% of the cost of nuclear electricity is associated with the initial cost of the power plant while the cost of uranium for an LWR is only a few percent of the total cost of electricity. chapter 2 — Framing Fuel cycle Questions 23
Figure 2.3 partial recycle of lWr SnF LWR SNF Recycle Mining & Milling Conversion Enrichment Fuel Fabrication Light Water Thermal Reactor Interim Storage MOX SNF Storage Fuel Fabrication The development of the SFR required the development of reprocessing technology to recover plutonium and uranium from both LWR and SFR SNF. With the delayed introduction of SFRs, several countries (France, Great Britain, Japan) chose to use the reprocessing technology to recover plutonium from LWR SNF and recycle that plutonium back to LWRs as mixed oxide (MOX) fresh fuel that contained uranium and recycled plutonium (Fig. 2.3). Because of the current limitations of LWR technology, it is difficult to recycle MOX SNF; thus, the plans are to store the MOX SNF and ultimately process the MOX SNF and recycle the fissile and fertile materials into future fast reactors. The partial recycle of LWR SNF back into LWRs increases the energy output per ton of mined natural uranium by about 25%, but is uneconomic and adds several percent to the overall cost of nuclear electricity. Fuel cycle options are much broader than these choices. Spent Fuel Reprocessing Waste Disposal • Missions. Fast reactors can operate with variable conversion ratios depending upon goals. If the CR < 1, plutonium and other actinides are destroyed. A CR = 1 implies fissile material is produced from fertile at the same rate it is consumed. All uranium and thorium can be converted to fissile fuel. A CR > 1 implies that fissile fuel is produced faster than it is consumed and thus enables the startup of added fast reactors over time. • Conversion ratio. Historically it has been believed that a CR significantly greater than unity is desirable for advanced reactors because it results in the most rapid conversion of fertile materials to fissile materials. That belief led to the choice of the SFR—the only reactor that could be practically built with a conversion ratio greater than 1.2. Improved understanding of fuel cycles, as described in this report, indicate that CRs significantly greater than one places major constraints on fuel cycle choices but may not offer significant advantages over a reactor with a CR near unity. Lowering the CR to near unity creates a wider set of fuel cycle options with desirable features; however, today we do not know the preferred options among this set of options. • Reactor choices. Advances in technology have created multiple reactors (hard spectrum LWRs, some types of high-temperature reactors, etc.) that can have CRs of unity but can’t be built with high CRs. Relaxing the requirements for the CR opens up the choice of reactor with potential economic and other advantages. Pu 24 MIT STudy on The FuTure oF nuclear Fuel cycle
Page 3 and 4: Other Reports in This Series The Fu
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Page 11 and 12: Study Findings and Recommendations
Page 13 and 14: Recommendation We recommend that a
Page 15 and 16: p Innovative nuclear energy applica
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Page 19 and 20: The “once through” or open fuel
Page 21 and 22: have been implemented slowly. This
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Page 31 and 32: Recommendation Integrated system st
Page 33 and 34: Table 1.2 Summary of R&D Recommenda
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Page 37 and 38: the once-through Fuel Cycle for lig
Page 39: tricity costs. Waste management cos
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Page 45 and 46: • What is the impact of timing of
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Page 51 and 52: eStimatinG Future CoStS oF uranium
Page 53 and 54: Figure 3.3 relative uranium Cost vs
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Page 59 and 60: CitationS and noteS 1. Uranium 2007
Page 61 and 62: If SNF is to be shipped, typically
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Page 85 and 86: CitationS and noteS 1. A Handbook f
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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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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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