1. Fuel Cycle Subcommittee: Overview and Status Fusion-Fission Hybrid Workshop Gaithersburg, MD October 1, 2009 Temitope A. Taiwo for Robert N. Hill Department Head – Nuclear Systems Analysis Nuclear Engineering Division Argonne National Laboratory Work sponsored by U.S. Department of Energy Office of Nuclear Energy, Science & Technology

2. Fusion Hybrid Workshop, September 30, 2009 2 3.1 Fission Fuel Cycles Nuclear energy is a significant contributor to U.S. and international electricity production –16% world, 20% U.S., 78% France Given the concern over carbon emissions, there may be significant growth worldwide In the U.S., a once-through fuel cycle has been employed to-date –Large quantities of spent fuel stored at reactor sites –Final waste disposal is not secured With nuclear expansion, this is not a sustainable approach; thus, advanced fuel cycles being explored – two key goals –Waste Management –Resource Utilization

3. Fusion Hybrid Workshop, September 30, 2009 3 AFCI is considering a variety of fuel cycle options: Closed fuel cycle with actinide management Spent nuclear fuel will be separated into re- useable and waste materials Residual waste will go to a geological repository Uranium recycled for resource extension Fuel fabricated from recycled actinides used in recycle reactor Fuel cycle closure with repeated use in recycle reactor Energy Production Reactor Recycle Reactor Recycle Fuel Fabrication Recycle Used Uranium Extend Uranium Resources

4. Fusion Hybrid Workshop, September 30, 2009 4 Advanced Nuclear Fuel Cycle – Potential Benefits Cs/Sr (and decay products), Cm, and Pu dominate “early” decay heat Am dominates “later” decay heat Removal of decay heat producers would allow for increased utilization of repository space

5. Fusion Hybrid Workshop, September 30, 2009 5 Transmutation for Improved Waste Management Long-term heat, radiotoxicity, and peak dose are all dominated by the Pu- 241 to Am-241 to Np-237 decay chain Thus, destruction of the transuranics (neptunium, plutonium, americium, and curium) is targeted to eliminate all problematic isotopes Some form of reprocessing is necessary to extract transuranic elements for consumption elsewhere The transuranic (TRU) inventory is reduced by fission –Commonly referred to as ‘actinide burning’ –Transmutation by neutron irradiation –Additional fission products are produced This requires the development of transmutation fuel forms –Robust fast reactor fuel form – high reliability –Partial destruction each recycle – high burnup goal In the interim, the TRU inventory is contained in the transmutation fuel cycle

6. Fusion Hybrid Workshop, September 30, 2009 6 Fast and Thermal Reactor Energy Spectra In LWR, most fissions occur in the 0.1 eV thermal “ peak ” In SFR, moderation is avoided – no thermal neutrons

7. Fusion Hybrid Workshop, September 30, 2009 7 Impact of Energy Spectrum on Fuel Cycle (Transmutation) Performance Fissile isotopes are likely to fission in both thermal/fast spectrum –Fission fraction is higher in fast spectrum Significant (up to 50%) fission of fertile isotopes in fast spectrum Net result is more excess neutrons and less higher actinide generation in FR

8. Fusion Hybrid Workshop, September 30, 2009 8 Equilibrium Composition in Fast and Thermal Spectra Equilibrium higher actinide content much lower in fast spectrum system Generation of Pu-241 (key waste decay chain) is suppressed However, if starting from once-through LWR composition (e.g., burner reactor) the higher actinide content will be higher than the U-238 equilibrium

9. Fusion Hybrid Workshop, September 30, 2009 9 Pu-content Fissile in Pu Uranium Enrichment UO2 CORAIL-Pu CORAIL-TRU Mass Evolution with Recycling (CORAIL-Pu) Normalized Cancer Dose LWR Transmutation Studies Assessment of complete recycle in LWR –Impact on reactor and safety performance –Fuel handling (practicality) implications –Different elemental separation schemes considered –Homogeneous and heterogeneous assembly designs evaluated Detailed evaluation of Pu-Np MOX for current LWRs –Double-tier baseline –Focus on quick utilization in existing reactors –Recycle of Am also needed to derive significant benefits

10. Fusion Hybrid Workshop, September 30, 2009 10 LWR Transmutation Studies (Cont’d) Inert Matrix Fuel (IMF) fuel cycle analyses –Significant TRU destruction in first tier –Alternate fuel forms (non-uranium) –Potential safety impacts – blending and partial loading options In all cases, repository benefit of first-tier limited recycle is less than or about a factor of 2 and subsequent fast reactor transmutation required for significant benefits Repository benefits for limited recycle in LWRs

11. Fusion Hybrid Workshop, September 30, 2009 11 Conclusions of Multi-recycle in LWRs Significant research on multi-recycle in conventional LWRs conducted recently both in AFCI and internationally (e.g., CEA) Consensus is that continuous recycle can be achieved within two important constraints: An external fissile “ support ” feed is required –Neutron balance of TRU not sufficient to sustain criticality –Standard 5% LEU pins or fuel mix can provide support A technique to manage higher actinide buildup is required –Initial recycles may be possible, but neutron source from very high actinides (e.g., Cf-252) becomes fuel handling problem –Long cooling time approach can mitigate –Separation/storage of curium prevents higher actinide generation Safety impact of TRU containing fuels must also be considered –May limit fraction of core loading, particularly for current LWRs Thermal recycle will be limited by practical constraints related to fuel handling that get progressively worse each recycle

12. Fusion Hybrid Workshop, September 30, 2009 12 Repository Benefit for Fast Reactor Limited Recycling Fast reactor recycle yields ~1.5 benefit in first recycle –Sustained for subsequent recycles – isotopic denaturing not severe –Small impact for extended cooling time – less sensitive to TRU isotopics Remote processing allows quicker turnaround time for each recycle

13. Fusion Hybrid Workshop, September 30, 2009 13 Low Conversion Ratio Fast Reactor Analyses Fast reactors with closed fuel cycle can effectively manage TRU Can be configured as modest breeders (CR≥1) to moderate burners (CR≥0.5) with conventional technology Low conversion ratio designs (CR<0.5) have been investigated for transmutation applications in AFCI –High enrichment fuels are required (~50% TRU/HM for CR=0.25) –Non-uranium fuel would be needed to achieve CR=0 Conversion RatioTRU/HM Enrichment Equilibrium Fraction of FR Delayed Neutron Fraction 1.111%100%0.0034 0.7520%51%0.0033 0.530%34%0.0031 0.2550%26%0.0028 0.0100%21%0.0020

14. Fusion Hybrid Workshop, September 30, 2009 14 Fuel Cycle Implications The physics distinctions facilitate different fuel cycle strategies Thermal reactors are typically configured for once-through (open) fuel cycle –They can operate on low enriched uranium (LEU) –They require an external fissile feed (neutron balance) –Higher actinides must be managed to allow recycle Separation of higher elements – still a disposal issue Extended cooling time for curium decay Fast reactors are typically intended for closed fuel cycle with uranium conversion and resource extension –Higher actinide generation is suppressed –Neutron balance is favorable for recycled TRU No external fissile material is required Can enhance U-238 conversion for traditional breeding Can limit U-238 conversion for burning

15. Fusion Hybrid Workshop, September 30, 2009 15 Overview of Reactor, Fuel, and Separations Options Objective Reactor OptionsFuel OptionsSeparations Options LWRGasFR LWRGas FR LWRGas FR MOXIMFU-TA-TMOXIMFU-TA-T O1-ProliferationXXXX+XXX???X O2-Waste MgmtXX+X??XX???X O3-SustainableXXX Time to DeployX?XX?X?XX???X EconomicsXX?---------- + = favorable performance- bright greenU-T = Uranium TRISO X = meets objective- dark greenA-T = Actinide TRISO ? = unclear, or requires R&D- yellow blank = does not meet objective- red

16. Fusion Hybrid Workshop, September 30, 2009 16 Conclusions on Advanced Fuel Cycle Transition To achieve large repository benefits, eventual goal must be introduction of a continuous recycle technology –Implies large-scale processing and utilization of advanced fuels In short-term (decades), LWRs will be the dominant reactor type –Separations technology can be developed and implemented –Transmutation fuels (either MOX or IMF) can be developed –Recycle can be initiated with some benefit Continuous recycle in thermal reactors has known limits –Reliance on enriched uranium support –Buildup of higher actinides (Cm separation, handling issues) –Safety issues for high plutonium loadings (burner concepts) Therefore, Generation-IV fast reactors remain an attractive solution –Inhibit production of higher actinides, can burn all transuranics together –Future utilization of all uranium resources without enrichment Combined fuel cycles exist allowing gradual transition from thermal to fast systems with sustained waste management benefits

17. Fusion Hybrid Workshop, September 30, 2009 17 Backup Slides

18. Fusion Hybrid Workshop, September 30, 2009 18 Reduction in the volume of HLW that must be disposed in a deep geologic disposal facility as compared to the direct disposal of spent nuclear fuel –Factor of 2-5 reduction in volume as compared to spent nuclear fuel –Intermediate-level (GTCC) and low-level volumes could be large and disposal pathways would have to be developed Reduction in the amount of long-lived radioactive material (e.g., minor actinides) that must be isolated in a geologic disposal facility (reduction of source term) –Potential for re-design of engineered barriers –Advanced waste forms could result in improved performance and reduced uncertainty over the very long time periods Reduction in decay heat allowing for increased thermal management flexibility, potentially increasing emplacement density –Increased loading density - better utilization of valuable repository space Advanced Nuclear Fuel Cycle – Potential Benefits

19. Fusion Hybrid Workshop, September 30, 2009 19 Radiotoxicity reflects the hazard of the source materials –transuranics dominate after about a 100 years. The fission products contribution to the radiotoxicity is small after 100 years Radiotoxicity alone does not provide any indication of how a geologic repository may perform –Engineered and natural barriers serve to isolate the wastes or control the release of radionuclides Waste Hazard and Risk Measures

20. Fusion Hybrid Workshop, September 30, 2009 20 Reactor Types for Transmutation System: Minimization of Waste Conventional LWRs using LEU fuels produce TRU –At current 50 GWd/MT burnup, 1.3% TRU content at discharge –This corresponds to ~250 kg/year for each GWe power For any fission energy system, 1 gram of actinides destroyed produces roughly 1 MWt-day of energy –This implies 1.3%/5% = 25% of the original LWR energy production is created in the destruction of the TRU content (significant capacity) –Thus, efficient use of this energy is a key to both system economics and resource utilization However for uranium-based fuel, TRUs are also being produced –This behavior is quantified by the conversion ratio (CR) –Dictated primarily by the recycle fuel composition (U content) –Fast system can be designed with CR ranging from >1 (breeders) to <<1 (burners); for thermal reactors CR < 0.7 is achievable with MOX

21. Fusion Hybrid Workshop, September 30, 2009 21 Reactor Types for Transmutation System: Minimization of Waste (cont.) To assure no TRUs remain in waste, the LWR production rate must be balanced by destruction in the actinide burners (AB) –For pure burner (CR=0), 1 burner for every four LWRs –For CR=0.25, 1 burner for every three LWRs –For CR=1, all recycle reactors If only the minor actinides are to be consumed in the burner reactor, the initial production rate by LWRs is only 10% of the TRU content –However, the plutonium must be consumed elsewhere –Additional minor actinides are produced as the plutonium is consumed, particularly if a thermal spectrum is utilized

22. Fusion Hybrid Workshop, September 30, 2009 22 Reactor Types for Transmutation System: Maximization of Energy The opposite trend is observed when the goal is to maximize the energy production for a fixed amount of resource materials –For a given quantity of recovered TRU, the energy can be extended by recycling the material in a high CR system Thus, net resource utilization is vastly improved at high CR –For once-through cycle, 7MT of uranium ore required to produce 1 MT of fuel to 5% burnup --.05/7 = 0.7% of the energy content –With TRU recovery and recycle, burnup extended to.05 +.013/(1-CR) Roughly 1% of energy content at low conversion ratio Limit of 100% utilization at CR=1 where a make-up feed (e.g., depleted uranium or thorium) that contains fertile material is required

23. Fusion Hybrid Workshop, September 30, 2009 23 3.2 Fusion Fuel Cycles Tritium needs to be produced to sustain the fusion cycle –14 MeV neutrons can be used to breed –Typically employ Li-6 capture in fusion blanket For hybrid, fusion blanket must also be utilized –Wide variety of technology options –Homogeneous or heterogeneous with fission blanket –Neutron balance is enhanced through subcritical multiplication in the fission blanket

24. Fusion Hybrid Workshop, September 30, 2009 24 3.x.4 Proliferation Issues The proliferation risks associated with spent fuel reprocessing and recycle continue to be hotly debated –At least partial separation is required Fission products are waste, actinides recycled This reduces the radiation barrier –Safeguards employed for material accounting –Physical protection provides additional barriers –Technology misuse is another concern –Enrichment technology may be an easier pathway Any neutron source can produce fissile material –Fertile targets installed to capture neutrons –This became an issue for ADS concepts

25. Fusion Hybrid Workshop, September 30, 2009 25 3.3 Hybrid Fuel Cycles Waste management role –Lack of criticality constraint allows operation on very low reactivity fuels and potentially very high burnup –However, practical operation (e.g., large power swings) and material (e.g., radiation damage) challenges exist Some proposals: –Burn the entire TRU inventory –Target a smaller fleet of minor actinide burners –Sustain “support” of LWR power production or nuclear close-out scenarios (like ADS) Resource extension role proposals: –Breed fuel for use in fission fuel cycle –Perform an extended in-situ breed and burn –Similar challenges to the burner mode noted above

26. Fusion Hybrid Workshop, September 30, 2009 26 Aqueous Processing Potential Waste Streams and Waste Forms Chopping Cladding: Zircaloy Hardware: SS Volox Dissolu- tion Gases: I, HTO, Kr, Xe, CO 2 UREX UDS: Pd, Ru, Rh, Mo, Tc, Zr, O Ion Exchange Tc U TRUEX TALSPEAK FPEX Cs/Sr: Cs, Sr, Ba, Rb TMFP: Fe, S, Ru, Pd, Rh, Mo, Zr LNFP: Ce, Ln, Pr, Nd, Y TRU: Pu, Am, Cm, Np Metal Waste Form Specialized Waste Forms Metal Waste Form Decay Storage Waste Form (glass or ceramic) Glass Waste Form Losses

27. Fusion Hybrid Workshop, September 30, 2009 27 Advanced Nuclear Fuel Cycle – Waste Form Development Glass Bonded Sodalite Metallic Waste Form from Electro- Chemical Processing Cs/Sr Glass Lanthanide Borosilicate Glass

28. Fusion Hybrid Workshop, September 30, 2009 28 Waste management is an important factor in developing and implementing an advanced closed nuclear fuel cycle –The waste management system is broader than disposal (processing, storage, transportation, disposal) –Deep geologic disposal will still be required –Disposal of low level and intermediate level (GTCC) wastes will be required Volumes potentially larger than once-through An advanced closed nuclear fuel cycle would allow for a re-optimization of the back-end of the current once-through fuel cycle, taking advantage of: –Minor actinide separation/transmutation –Heat producing fission product (Cs/Sr) management (i.e., decay storage) Decisions must consider this entire system –Regulatory, economic, risk/safety, environmental, other considerations Advanced Nuclear Fuel Cycle - Waste Management

29. Fusion Hybrid Workshop, September 30, 2009 29 AFCI Integrated Waste Management Strategy establishes the framework for analyzing and optimizing the waste management system –Emphasizes recycle and reuse, but based on economic recovery evaluation factoring in value of material and cost avoidance of disposal –Considers need for industry to have a reliable system to routinely transport nuclear materials and dispose wastes –Considers disposal options based on the risk of the waste streams and waste forms Rather than requiring all waste be disposed as HLW in a geologic repository Requires change to existing waste classification system embodied in current regulatory framework –A key aspect is the inclusion of managed storage facilities where isotopic concentrations, and heat, are allowed to decay prior to storage Evaluation of alternatives and options are being performed under the context of the IWMS Waste Management System for Advanced Fuel Cycle

30. Fusion Hybrid Workshop, September 30, 2009 30 Integrated Waste Management Strategy – Logic Diagram

31. Fusion Hybrid Workshop, September 30, 2009 31 Comparison of VHTR and Typical PWRs Discharge burnup of VHTR is much higher than for PWRs VHTR has much higher moderator/fuel ratio –Higher epithermal spectral component due to graphite moderator –Power density of 6.6 MW/m 3 compared to 100 MW/m 3 in PWR –Much higher specific power: 100 W/g versus 36 W/g –Enrichment is about 3 times higher: 14 % versus 3~4% High temperature of VHTR results in high thermal efficiency ParameterVHTR PWR (Burnup Type) MediumStandard Burnup, GWd/t1003350 Specific Power, W/g10036 Enrichment, %143.24.2 Thermal Efficiency (%)47.733

32. Fusion Hybrid Workshop, September 30, 2009 32 Conclusions: Once-Through VHTR vs PWRs VHTR produces more transuranics, decay heat, and radiotoxicity (cancer dose) per initial heavy metal mass, compared to PWRs –At higher burnup, more plutonium and higher actinides are created –At similar burnup, NGNP TRU content is similar to LWR Plutonium saturation leads to reduced energy normalized production Improved thermal efficiency leads to 25% lower TRU production –45% reduction compared to standard burnup (50 GWd/MT) PWR Higher discharge burnup and thermal efficiency of the VHTR give advantages in terms of lower heavy-metal waste mass, lower decay heat and radiotoxicity of the spent fuel per energy produced –45% repository loading increase may be possible Uranium utilization slightly worse compared to PWRs because of high initial uranium enrichment for VHTR design –Spent nuclear fuel uranium (>5 w /o U-235) could be recovered and re-used

33. Fusion Hybrid Workshop, September 30, 2009 33 Alternate Burner Designs Reference DesignsTRU Burner Designs Neutron Spectrum Fuel Cycle Size Potential Applications AvailableAttributes SFRFastClosedMed to Large Electricity, Actinide Mgmt. (AM) YesDesigns from high to very low conversion ratios (CRs) Safety and relative cost evaluations LFRFastClosedSmall to Large Electricity, Hydrogen Production YesDesigns from high to very low CRs GFRFastClosedMedElectricity, Hydrogen, AM YesDesigns from high to very low CRs VHTRThermalOpenMedElectricity, Hydrogen, Process Heat YesDeep-burn concept (one-, two-, or multiple-pass) SCWRThermal, Fast OpenLargeElectricityYesDesign of a mixed spectrum core (fast and thermal zones) Significant TRU burning in thermal systems can be accomplished using fissile support or IMF Reference fast reactor designs can be readily configured for TRU burning For the fast reactors (FRs), the most important penalty for the improved TRU destruction rate is a significant increase in the burnup reactivity loss rate Coolant used in the FR design is a cost differentiating factor – GFR and LFR core sizes tend to be much larger (~2-4) than for SFR of same power

34. Fusion Hybrid Workshop, September 30, 2009 34 Comparison of Fast Burner Performance (CR=0.25) System SFR GFR LFR Net TRU Destruction, g/MWt-day0.740.760.75 System Power, MWt840600840 Outlet Temperature, o C510850560 Thermal Efficiency, %384543 Power Density, W/cc30010377 TRU Inventory, kg225034204078 Fuel Volume Fraction, %221012 TRU Enrichment, % TRU/HM44 - 565746 - 59 Fuel Burnup, GWd/t177221180 Because the transmutation physics behavior is similar for the fast burner concepts, a similar design approach was employed to achieve low conversion ratio –By reducing the fuel volume fraction, fertile material was removed For a given conversion ratio, the TRU destruction rate and compositions are very similar Variations in other fuel cycle performance parameters due to design differences (power density) –Compact SFR approach has some economic benefits; although higher thermal efficiency and design simplifications (e.g., removal of secondary loop) are being pursued for GFR and LFR –Lower power density results in a higher TRU inventory (~ a factor of 2 per MWt for SFR vs. LFR)

35. Fusion Hybrid Workshop, September 30, 2009 35 Repository Benefits for Processing 5 Year Old Fuel Limited LWR recycling of plutonium and americium would allow a drift loading increase of about a factor of 2