The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Chapter 2 – Framing Fuel Cycle Questions The potential growth in nuclear power has resulted in a renewed interest in alternative nuclear fuel cycles. This leads to three questions. What are the criteria for selection of a fuel cycle? What are the choices? What are the constraints? Fuel CyCle ConSiderationS Central to the choice of fuel cycle is the question of what considerations or criteria should be used as a basis to make long-term fuel cycle decisions. We developed a list of criteria (Table 2.1) that were used to aid our thinking about fuel cycles. These include technical and institutional components. The criteria of importance from a business perspective (economics, safety, environment) are different from the criteria of importance from a national or governmental perspective (waste management, long-term resource utilization and energy independence, and nonproliferation). Many of the difficulties and controversies associated with choosing a fuel cycle follow from the relative importance of different criteria to different groups. Table 2.1 Criteria to Compare Fuel Cycles Criteria teChniCal (examples) inStitutional (examples) economics overnight capital costs Financing, regulation Safety risk assessment regulatory structure Waste Management Waste form, time of storage regulation, Societal views of intergenerational risk environment Water consumption, land consumption Water regulation, Greenhouse gas regulation resource utilization uranium resources and costs Security of supply (uranium resource distribution by nation) nonproliferation Separated plutonium, safeguards Institutional arrangements for fuel materials. The criteria were chosen based on the characteristics of nuclear fuel cycles. To understand the criteria some understanding is required of fuel cycles. The sidebar describes the oncethrough (open) fuel cycle—the fuel cycle that is most economic today and used in the United States for all power reactors. If nuclear power growth is limited, there are limited incentives to change from the oncethrough fuel cycle. It would take decades to transition to another fuel cycle and require major investments. However if there is major growth, then alternative fuel cycles may become attractive and decisions must be made about the choice of fuel cycle and the criteria used chapter 2 — Framing Fuel cycle Questions 19
the once-through Fuel Cycle for light-Water reactors Most of the world’s reactors are light water reactors that use a once-through open fuel cycle. This fuel cycle consists of seven steps. • Uranium mining and milling. uranium is the starting fuel for all fuel cycles. uranium mining and milling is similar to the mining and milling of copper, zinc, and other metals. uranium is often found with copper, phosphates, and other minerals; thus, it is often a co-product of other mining operations. about 200 tons of natural uranium is mined to fuel a 1000-MW(e) light-water reactor for one year. • Uranium conversion. The uranium is chemically purified and converted into the chemical form of uranium hexafluoride (uF 6 ) • Uranium enrichment. uranium contains two major isotopes: uranium-235 and uranium-238. uranium-235 is the initial fissile fuel for nuclear reactors. natural uranium contains only 0.7% uranium-235. In the uranium enrichment process, natural uranium is converted into an enriched uranium product stream containing 3 to 5% uranium-235 and depleted uranium that contains ~0.3% uranium-235. • Fuel fabrication. The enriched uranium is converted into the chemical form of uranium dioxide and fabricated into nuclear fuel. a typical lWr requires ~20 tons of enriched uranium fuel per year. • Light-water reactor. When fresh fuel with uranium-235 is loaded into a reactor, the fissioning of uranium-235 produces heat. The fuel also contains uranium-238, which upon absorption of neutrons produces plutonium-239, a readily fissionable material like uranium-235 that also fissions to produce heat. Just before the fuel is discharged from the reactor as SnF, about half the energy being generated is from the fissioning of plutonium-239 that was created in the reactor. The heat is converted into electricity. • Interim storage of spent nuclear fuel (SNF). a typical lWr fuel assembly remains in the reactor for three to four years. upon discharge of the SnF, it contains ~0.8% uranium-235, ~1% plutonium, ~5% fission products, and the rest is mostly uranium-238. The SnF is stored for several decades to reduce radioactivity and radioactive decay heat before disposal. • Waste disposal. If no advanced fuel cycle is deployed that can use plutonium and uranium-238, then the SnF would be considered a waste that ultimately must be sent to a geological repository for disposal. Figure 2.1 once-through Fuel Cycle Mining & Milling Conversion Enrichment Fuel Fabrication Light Water Thermal Reactor Interim Storage Waste Disposal 20 MIT STudy on The FuTure oF nuclear Fuel cycle
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70 MIT STudy on The FuTure oF nucle
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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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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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