The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Recommendation We recommend (1) the integration of waste management with the design of fuel cycles, and (2) a supporting R&D program in waste management to enable full coupling of fuel cycle and waste management decisions. Future nuClear Fuel CyCleS The choice of nuclear fuel cycle (open, closed, or partially closed [limited SNF recycle]) depends upon (1) the features of proven technology options and (2) societal weighting of goals (economics, safety, waste management, and nonproliferation). That fuel cycle choice will lead to fundamentally different futures for nuclear power. We do not today have sufficient knowledge about future options and goals to make informed choices . To understand the implications of alternative fuel cycles for the United States, we created a dynamic model of the nuclear energy system through the year 2100. Dynamic modeling is a method to follow in time the consequences of deployment of alternative fuel cycles for different sets of assumptions. Such comprehensive mathematical models of fuel cycles have only been developed in the last few years. Several alternative futures were examined. p Nuclear growth scenarios. Three nuclear growth scenarios were considered: 1% per year (low), 2.5% per year (medium), and 4% per year (high). Fuel cycle choices partly depend upon nuclear growth rates. At low growth rates continuation of today’s open fuel cycle is the preferred choice. At high growth rates there are incentives for improved utilization of the energy potential of mined uranium and for reduction of the long-term burden of SNF, but technical constraints exist and incentives may change depending upon the available technology and economics. p Fuel cycles. Three fuel cycles were modeled in detail: today’s once-through fuel cycle with LWRs, a partly-closed LWR fuel cycle with recycle of plutonium from LWR SNF back into LWRs and direct disposal of the recycle SNF, and a closed fuel cycle with LWRs and fast reactors. In the closed fuel cycle, LWR SNF is reprocessed and the transuranic elements including plutonium are used to start up fast reactors. The SNF uranium and transuranics from discharged fuel of fast reactors are recycled back to the fast reactors. p Fast reactors. Our analysis of closed fuel cycles included three classes of fast reactors with different goals. In the first scenario the goal was to destroy actinides; thus, the fast reactors had a conversion ratio of 0.75. In the second scenario the goal was a self-sustaining fuel cycle; thus, the fast reactors had a conversion ratio of 1.0. In the third scenario the goal was to rapidly expand the availability of fissile fuel for fast reactors; thus the fast reactors had a conversion ratio of 1.23 with the excess transuranics used to start added fast reactors. a reactor with a conversion ratio near unity may be the best option for a closed fuel cycle. it could be started with uranium rather than plutonium. Results from the models under the stated assumptions indicate that: p The transition from a system dominated by one fuel cycle to another requires 50 to 100 years. p For medium and high growth scenarios, there were relatively small differences in the total transuranic (plutonium, americium, etc.) inventories between different fuel cycles in this century. Chapter 1 — The Future of the Nuclear Fuel Cycle — Overview, Conclusions, and Recommendations 9
nuClear Fuel CyCleS The united States uses the once-through open fuel cycle to fuel light water reactors (lWrs). This fuel cycle is the simplest and the most economic fuel cycle today. There are six major steps (Top line of Fig. 1). • 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 and thus 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 and enrichment. The uranium is chemically purified. uranium contains two major isotopes: uranium-235 and uranium-238. uranium-235 is the initial fissile fuel for nuclear reactors. natural uranium contains 0.7% uranium-235. In the uranium enrichment process, natural uranium is separated into an enriched uranium product containing 3 to 5% uranium-235 and ≥95% uranium-238 that becomes lWr fuel and depleted uranium that contains ~0.3% uranium-235 and ~99.7% uranium-238. There will be 10 to 20 times as much depleted uranium as product. • Fuel fabrication. The enriched uranium is converted into uranium dioxide and fabricated into nuclear fuel. an lWr requires ~20 tons of fuel per year. • Light-water reactor. all power reactors in the united States are lWrs. The initial fuel is uranium-235 that is fissioned to produce heat. The fuel also contains uranium-238, a fertile non-fuel material. In the nuclear reactor some of it is converted to plutonium-239—a fissile fuel that is also fissioned to produce heat. The heat is converted into electricity. With a fresh fuel assembly, all the energy is from fissioning of uranium-235. When 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. • Storage of 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 uranium-238. The SnF is stored for several decades to reduce radioactivity and radioactive decay heat before disposal. • Waste disposal. after interim storage, the SnF is disposed of as a waste in a repository. nuclear fuel cycles are different from fossil fuel cycles because nuclear reactors burn only a fraction of the fuel before the fuel is discharged as SnF. Full burnup of the fuel before discharge is not possible. • The reactor produces heat by fissioning uranium-235 or plutonium-239. The resultant fission product “ash” in high concentrations will shut down the reactor • The materials of fuel element construction have a limited endurance in the reactor and limit fuel burnup. Because reactors can not fully utilize the fissile and fertile materials in a fuel assembly, there are many possible fuel cycles. • LWR partly closed fuel cycle (Top two lines of Fig. 1). The fissile material in lWr SnF can be recycled back into lWrs. The lWr SnF is reprocessed, the plutonium and uranium recovered, and the plutonium and some uranium are fabricated into fresh fuel, and the resultant transuranic fuel is sent to the lWr. Because of the low fissile content of the lWr SnF, recycle of the plutonium reduces uranium fuel demand by only 15% and recycle of the uranium reduces uranium fuel demand by only 10%. The high-level waste (hlW) from reprocessing is stored for several decades to reduce radioactivity and radioactive decay heat before disposal. lWr SnF recycle changes the plutonium isotopes such that the SnF can only be recycled one or two times. The recycle SnF must either wait to go to a repository or could fuel fast reactors. Several countries recycle lWr SnF. continued next page 10 MIT STudy on The FuTure oF nuclear Fuel cycle
Page 3 and 4: Other Reports in This Series The Fu
Page 5 and 6: MIT Nuclear Fuel Cycle Study Adviso
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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
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Page 37 and 38: the once-through Fuel Cycle for lig
Page 39 and 40: tricity costs. Waste management cos
Page 41 and 42: Figure 2.3 partial recycle of lWr S
Page 43 and 44: history of the nuclear Fuel Cycle B
Page 45 and 46: • What is the impact of timing of
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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
Page 61 and 62: If SNF is to be shipped, typically
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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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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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