The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Chapter 6 — Analysis of Fuel Cycle Options introduCtion The evolution of the nuclear energy system will depend on future demand for nuclear energy, and the reactor and fuel cycle technologies deployed to meet this demand. As discussed in Chapter 2, there are several options for the nuclear fuel cycle. The simplest cycle, which is applied today in the U.S., relies only on mined uranium as fuel, while advanced cycles rely at least partially on fissile material extracted from the discharged fuel of other reactors. Therefore, the fuel cycle options imply different levels of demand for the uranium resource and for industrial infrastructure for fuel recycling, and result in different amounts of spent fuel and of materials to be disposed of as waste. This chapter presents implications of some of the fuel cycle options for a range of demand scenarios, and the sensitivity of the results to key assumptions and constraints involved in the analysis. The base case assumes that the nuclear energy capacity grows to 120 MWe in 2020, due in part to power uprates of existing reactors, followed by an annual nuclear energy growth rate of 2.5% from 2020 until the end of this century. Such a growth rate will be higher than the growth rate of nuclear energy production in the last two decades, and will result in an increase in the portion of electricity supplied by nuclear plants given the expected annual growth in electricity of 1 to 1.5%. If annual electricity growth between now and 2050 is at 1.5%, the nuclear share will be about 28% in that year. Thus it reflects an assumption that nuclear energy will be relied upon for part of the carbon emission reduction while meeting future demand for energy. A case of lower growth rate of 1% per year and a case of higher growth rate of 4% after 2020 are also examined. The fuel cycle options considered include the Once-Through Cycle (OTC) using Light Water Reactors, practiced today in the U.S.. Three advanced fuel cycle schemes are also explored in this study (1) Pu recycling in the form of Mixed Oxides in LWRs(“MOX scheme”), (2) Transuranic (TRU) multi-recycling in fast reactors (FR) designated as Advanced Burner Reactors (ABR) of various fissile conversion ratios from 0 to 1, and (3) TRU recycling in a fast reactor designated as breeder (FBR), of which the fissile conversion ratio is 1.23. The schemes involving recycling of TRU in fast reactors have also assumed uranium recycling. On the other hand, we have restrained the study of the MOX scheme to a “twice-through cycle”, which means that the plutonium extracted from uranium fueled LWRs is recycled only once as MOX in LWRs. In principle, the plutonium can be recycled more than once, although this has not been adopted in practice anywhere. All power reactors in the United States today are LWRs, which operate as thermal reactors. In a thermal reactor, a large fraction of neutrons exist at thermal neutron energies (below 1eV), and most of the fissions occur due to these neutrons. Fast reactors have a neutron chapter 6: analysis of Fuel cycle options 71
energy spectrum centered at higher energies than the thermal reactors, and most of their fissions are due to neutrons with energy greater that 1000 eV. Reprocessing and fabrication facilities associated with thermal or fast reactors may be called thermal or fast facilities. Prototype fast reactors have been built in the U.S. and several other countries, but only two large scale semi-commercial reactors were built: the BN-600 in Russia and the Superpheonix in France. A fast-spectrum reactor can be designed to fission transuranics efficiently, and these are referred to as burner reactors. Alternatively a fast reactor can be designed to convert abundant fertile materials (uranium-238 or thorium-232) into fissile fuels (principally plutonium-239 or uranium-233) faster than the fissile fuels are consumed. Such a reactor is called a breeder reactor because it produces more fissile fuel than it consumes. The analysis is conducted via the MIT developed fuel cycle system simulation code CAFCA [Busquim et.al., 2008]. The code tracks the infrastructure involved in the nuclear energy supply, the basic material flows in and out of facilities, the inventories in storage and awaiting waste disposal and the economics of the entire enterprise. It applies several simplifying assumptions, but has been found sufficiently accurate for the level of detail required for a system study [Guerin et. al., 2009]. All the advanced fuel cycles considered here are for a one-step switch from the once through cycle to an advanced fuel cycle. However, two-tier scenarios, which include a two-step switch using first the MOX option then the FR option, are also possible and have been explored by Guerin and Kazimi [2009]. Key CharaCterIstICs of the fuel CyCles Once-Through Fuel Cycle Scheme The once-through scheme (denoted OTC) is the fuel cycle currently practiced in the U.S. and is considered as the reference case. In this scheme, UO 2 assemblies are loaded in the thermal spectrum light water cooled reactors, irradiated for a period of a few years, discharged and left in “cooling storage” (typically in reactor pools) for a few years (“minimum cooling time”). Finally, the spent fuel is sent either to interim storage or to a repository. Figure 6.1 once-through Fuel Cycle Scheme Mining Milling conversion enrichment uo 2 fuel fabrication lWr (irradiation + cooling storage Interim Storage Waste disposal 72 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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Page 45 and 46: • What is the impact of timing of
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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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Page 91 and 92: light Water reactor Fuel technical
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Page 97 and 98: Figure 6.4 densification Factors as
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Page 113 and 114: Summary oF ConCluSionS Among the in
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Page 117 and 118: This chapter reports the cost of th
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Page 131 and 132: Figure 8.1 Weapons-usability Charac
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Reprocessing choices Commercial rep
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Table 8.2 Safeguard Technical Objec
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126 MIT STudy on The FuTure oF nucl
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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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