THE CASE FOR FUSION-FISSION HYBRIDS ENABLING SUSTAINABLE NUCLEAR POWER WESTON M STACEY GEORGIA TECH JANUARY 22, 2010

Transcription

1 THE CASE FOR FUSION-FISSION HYBRIDS ENABLING SUSTAINABLE NUCLEAR POWER WESTON M STACEY GEORGIA TECH JANUARY 22, 2010

2 SUSTAINABLE NUCLEAR POWER Sustainable nuclear power requires closing the nuclear fuel cycle by i) utilizing the fissionable transuranics in spent fuel discharged from LWRs as fuel to produce energy, rather than storing them in geological repositories for hundreds of thousands of years (a new Yucca Mntn would be required every years). and ii) using more than the <1% of the potential uranium energy content recovered in present LWR once-through fuel cycles (uranium would be depleted this century with OTC) Closing the nuclear fuel cycle requires augmenting with fast reactors the present and expanding fleet of LWRs i) Fast Burner Reactors which fission the transuranics (Pu, Am, Np..) in spent nuclear fuel discharged from LWRs ii) Fast Breeder Reactors which transmute the non-fissionable U-238 (>99% U) into fissionable plutonium and perhaps ultimately replacing the LWR fleet with a fleet of sustainable fast reactors that performs both of these functions.

3 The Fusion-Fission Hybrid A Fusion-Fission Hybrid (FFH) is a subcritical nuclear reactor with a fusion neutron source. The motivation for the FFH is to enlarge the design and operational space of nuclear (fast burner and fast breeder) reactors to include subcritical operation in order to enable closing the nuclear fuel cycle to achieve sustainable nuclear power.

4 PROs OF FFH---ADDITIONAL FLEXIBILITY IN REACTOR DESIGN AND OPERATION A FFH has additional flexibility, relative to a comparable critical reactor, for minimizing the number of complex fuel reprocessing and refabrication steps needed to safely achieve deep fuel burnup. A variable-strength fusion neutron source can be increased to compensate fuel burnup and fission product buildup and maintain the neutron balance. This allows fuel to be left in the reactor longer to the radiation damage limit to achieve deeper burnup.

5 Sub-critical operation increases fuel residence time in Burner Reactor before reprocessing is necessary ()(),,11,fusfisfisremfusremfisfisfisfisfisfisfusfusPSkNSkkEE As k decreases due to fuel burnup, Pfus can be increased to compensate and maintain Pfis constant. Thus, sub-critical operation enables fuel burnup to the radiation damage limit before it must be removed from the reactor for reprocessing.

6 PROs OF FFH---ADDITIONAL FLEXIBILITY IN REACTOR DESIGN AND OPERATION A FFH can support a larger number of LWRs than can a comparable critical reactor because it can safely accommodate a larger percentage (up to 100%) of transuranics in the fuel. The reactivity margin of safety to prompt critical is 1-2 orders of magnitude larger for a subcritical reactor than for a critical reactor, in which it is the delayed neutron fraction, _. _ is 2-3 times smaller for transuranics (Pu, Am, Np..) than for uranium fuel, which limits the transuranic fuel fraction in a critical reactor.

7 CONs OF FFH A FFH will cost more than a comparable critical reactor, but the relative costs of the overall systems (reactors+repositories+reprocessing) is the issue, and the FFH will lead to fewer burner reactors, fewer repositories and fewer reprocessing steps. A FFH will be more complex, hence more difficult to refuel and maintain than a comparable critical reactor. A FFH will introduce additional safety issues relative to a critical reactor, but subcritical operation offers other safety advantages. The FFH environment may introduce technology integration issues (e.g. magnetic field effects on liquid metal coolants).

8 MOTIVATION FOR THE GEORGIA TECH STUDIES OF A FFH BURNER REACTOR BASED ON A SODIUM-COOLED FAST REACTOR AND A TOKAMAK FUSION NEUTR0N SOURCE The growing stockpile of discharged LWR spent nuclear fuel (SNF) is a more immediate impediment to the expansion of carbon-free nuclear power than is the shortage of uranium fuel. Burner reactors could dramatically reduce the required number of high-level waste repositories by fissioning the transuranics in LWR SNF. The sodium-cooled fast reactor is the most developed burner reactor technology, and most of the world-wide fast reactor R&D is being devoted to it. (deploy 20-25yr) The tokamak is the most developed fusion neutron source technology, and most of the world-wide fusion R&D is being devoted to it. (deploy yr)

9 SUB-CRITICAL ADVANCED BURNER REACTOR (SABR) ANNULAR FAST REACTOR (3000 MWth) Fuel TRU from spent nuclear fuel. TRU-Zr metal being developed by ANL. Sodium cooled, loop-type fast reactor. Based on fast reactor designs being developed by ANL in DoE Nuclear Program. TOKAMAK D-T FUSION NEUTRON SOURCE ( MWth) Based on ITER plasma physics and fusion technology. Tritium self-sufficient (Li 4 SiO 4 ). Sodium cooled.

10 R-Z cross section SABR calculation model

11 Fuel R=2 mm LiNbO 3 t=0.3 mm ODS Clad t=0.5 mm FUEL Na Gap t=0.83 mm Axial View of Fuel Pin Composition 40Zr-10Am-10Np-40Pu (w/o) (Under development at ANL) Design Parameters of Fuel Pin and Assembly Length rods (m) 3.2 Total pins in core Length of fuel material (m) 2 Diameter_Flats (cm) 15.5 Length of plenum (m) 1 Diameter_Points (cm) 17.9 Length of reflector (m) 0.2 Length of Side (cm) 8.95 Radius of fuel material (mm) 2 Pitch (mm) 9.41 Thickness of clad (mm) 0.5 Pitch-to-Diameter ratio 1.3 Thickness of Na gap (mm) 0.83 Total Assemblies Thickness of LiNbO 3 (mm) 0.3 Pins per Assembly Radius Rod w/clad (mm) 3.63 Flow Tube Thickness (mm) 2 Mass of fuel material per rod (g) 241 Wire Wrap Diameter (mm) 2.24 Volume Plenum / Volume fm 1 Coolant Flow Area/ assy (cm 2 ) 75 Cross-Sectional View Fuel Assembly

12 SABR Fuel Cycle LWR SNF HLW Repository Fresh TRU FP Reprocessing Facility Burned TRU Fuel Fabrication Facility Plasma # burn cycles fuel has been in reactor at BOC Fuel Assembly row numbers

13 4-BATCH FUEL CYCLE Fuel cycle constrained by 200 dpa clad radiation damage lifetime. 4 (700 fpd) burn cycles per residence OUT-to-IN fuel shuffling BOL k eff = 0.972, P fus = 75MW, 32 MT TRU BOC k eff = 0.894, P fus = 240MW, 29 MT TRU EOC k eff = 0.868, P fus = 370MW, 27 MT TRU 24% TRU burnup per 4-batch residence, >90% with repeated recycling 1.05 MT TRU/FPY fissioned 3000 MWth SABR supports MWe LWRs (0.25 MT TRU/yr) at 76% availability during operation (2 mo refueling). ANNULAR CORE CONFIGURATION SABR TRU FUEL COMPOSITION (w/o) Isotope Np-237 Pu-238 Pu-239 Pu-240 Pu-241 Pu-242 Am-241 Am-242 Am-243 Cm-242 Cm-243 Cm-244 Cm-245 Fresh Fuel To Re- Process Core Av EOC/BO C 9.1/ / / / / / / / / / / / /0.49

14 Decay Heat to the Repository Long term integral decay heat limits repository loading 1% TRU assumed going to repository on each reprocess Higher dpa limit _ fewer reprocess_ less TRU in HLW repository Watts per Megawatt Day Decay Heat to the Repository DPA DPA DPA Once Through 0.1 LWR SNF Time (Years)

15 Neutron Source Design Parameters Parameter Nominal SABR Extended SABR ITER Pure Fusion Electric ARIES-AT Current, I (MA) SABR TOKAMAK NEUTRON SOURCE PARAMETERS P fus (MW) Major radius, R (m) Magnetic field, B (T) Confinement H IPB98 (y,2) (?) Normalized beta, β N Plasma Mult., Q p >30 Htg&CD Power, MW Neutron Γ n (MW/m 2 ) CD _cd/fbs.61/.31.58/.26?/??/.91 Availability (%) (4) >90

16 ADAPTED ITER NEUTRON SOURCE TECHNOLOGY Six 20 MW ITER LHR launchers. Adapted ITER FW and divertor for Na and He coolant. Replaced SS with ODS steel. Confirmed heat removal with FLUENT code. FW lifetime 6.5 FPY at 200 dpa. Replace every 3 rd refueling shutdown. Scaled down ITER SC CS and TF magnet designs, maintaining ITER design standards. Multilayer shield. MCNP and EVENT predict > 30 FPY (40 75% avail) radiation damage lifetime for SC magnets.

17 Li 4 SiO 4 Tritium Breeding Blanket 15 cm Thick Blanket Around Plasma (Natural LI) and Reactor Core (90% Enriched Li) Achieves TBR = NA-Cooled to Operate in the Temperature Window C. Online Tritium Removal by He Purge Gas System. Dynamic ERANOS Tritium Inventory Calculations for 700 d Burn Cycle, 60 d Refueling Indicated More Than Adequate Tritium Production.

18 Dynamic Safety Analysis Coupled fission core power level with the thermal hydraulics of the thermal heat removal system using RELAP5-3D. Fusion neutron source calculated from plasma particle and power balance, coupled to the point neutron kinetics equation through source term. ATHENA version of RELAP5-3D allows for liquid metal coolants.

19 Accident Simulations Source Neutrons I H X Fission Core I H X Accidents simulated: Loss of Power Accident (LOPA), Loss of Flow Accident (LOFA), Loss of Heat Sink Accident (LOHSA), and P Accidental Increase in Fusion Neutron Source Strength. Coolant Boiling Temperature: 1,156 K, Fuel Melting Temperature: 1,473 K Small < 0 Doppler and >0 sodium coefs. Large < 0 fuel expansion reactivity coefficient not included in calculations. P

20 LOPA SABR can tolerate (no fuel melting or coolant boiling) a Loss of Power Accident resulting in zero power to SABR s auxiliary systems. All sodium coolant pumps shut off, Heating power to the plasma is lost

21 LOFA SABR can tolerate (no fuel melting or coolant boiling) a Loss of Flow Accident resulting from two of the four primary coolant loop pumps failing. (neutron source remains on) <0 fuel expansion reactivity coef not included in calculation

22 LOHSA SABR can tolerate (no fuel melting or coolant boiling) the Loss of Heat Sink Accident resulting from the loss of up to 50% of the secondary system heat removal capability. (Neutron source stays on). <0 fuel expansion reactivity coef not included in calc.

23 CONCLUSIONS SABR FFH BURNER REACTOR The physics and technology performance parameters of ITER (many of which have been achieved already) will be more than adequate for a fusion neutron source for a FFH burner reactor. ITER would be the prototype. Additional R&D will be needed to obtain greater component and plasma reliability than demanded of ITER, tritium breeding technology, a more radiation resistant structural material, remote maintenance and refueling, and integration of fusion and nuclear technologies. The physics performance parameters and FW neutron and heat loads for a FFH are significantly less than are required for pure fusion electric power. The feasibility of deployment of a tokamak fusion neutron source, based on ITER physics and technology, in a FFH burner reactor by about 2040 is compatible with several nuclear power scenarios for deploying burner reactors over roughly

24 SABR CONCLUSIONS (cont.) A nuclear fleet of 75% LWRs and 25% SABR burner reactors (% nuclear power) would reduce geological repository requirements by a factor of 10 relative to a nuclear fleet of 100% LWRs. Initial dynamic simulations indicate favorable safety characteristics for a SABR burner reactor. Thus, FFH burner reactors would seem to be the first opportunity for fusion to contribute to the nation s energy needs by enabling sustainable nuclear power starting in the first half of the present century.

25 R&D FOR A TOKAMAK FFH NEUTRON SOURCE IS ON THE PATH TO PURE FUSION ELECTRIC POWER FUSION R&D FOR A TOKAMAK F-F HYBRID 1. Ongoing worldwide tokamak physics R&D program, including ITER-specific issues (e.g. ELM suppression, startup scenarios). 2. ITER construction and operation experience-- prototype. 3. Physics R&D on reliable steady-state, disruption-free operation, burn control, etc. 4. Plasma Support Technology (magnets, heating systems, etc.). R&D for component reliability. 5. Remote Maintenance R&D. 6. Fusion Nuclear Technology (tritium breeding, etc.) R&D. 7. Advanced Structural Materials (200 dpa) R&D. 8. Integration of fusion and nuclear technologies. FURTHER FUSION R&D FOR TOKAMAK ELECTRIC POWER 9. Advanced confinement and pressure limits physics R&D. 10.Advanced DEMO.

26 RECOMMENDATIONS Undertake an in-depth conceptual design of the burner reactor-neutron source-reprocessing-repository system to determine if it is technically feasible to deploy a FFH Burner Reactor within 30 years and to identify needed R&D. Undertake a comparative systems study to determine if FFH Burner and Breeder Reactors are needed to enable sustainable nuclear power. Evaluate the reduction in geological repository requirements that can be achieved by various combinations of Critical and FFH burner reactors, under various scenarios for the expansion of nuclear power. Perform similar Critical and FFH breeder reactor studies.

27 References Georgia Tech FFH Burner Reactor Studies Neutron Source for Transmutation (Burner) Reactor W. M. Stacey, Capabilities of a D-T Fusion Neutron Source for Driving a Spent Nuclear Fuel Transmutation Reactor, Nucl. Fusion 41, 135 (2001). J-P. Floyd, et al., Tokamak Fusion Neutron Source for a Fast Transmutation Reactor, Fusion Sci. Technol, 52, 727 (2007). W. M. Stacey, Tokamak Neutron Source Requirements for Nuclear Applications, Nucl. Fusion 47, 217 (2007). Transmutation (Burner) Reactor Design Studies W. M. Stacey, J. Mandrekas, E. A. Hoffman and NRE Design Class, A Fusion Transmutation of Waste Reactor, Fusion Sci. Technol. 41, 116 (2001). A. N. Mauer, J. Mandrekas and W. M. Stacey, A Superconducting Tokamak Fusion Transmutation of Waste Reactor, Fusion Sci. Technol, 45, 55 (2004). W. M. Stacey, D. Tedder, J. Lackey, J. Mandrekas and NRE Design Class, A Sub-Critical, Gas-Cooled Fast Transmutation Reactor (GCFTR) with a Fusion Neutron Source, Nucl. Technol., 150, 162 (2005). W. M. Stacey, J. Mandrekas and E. A. Hoffman, Sub-Critical Transmutation Reactors with Tokamak Fusion Neutron Sources, Fusion Sci. Technol. 47, 1210 (2005). W. M. Stacey, D. Tedder, J. Lackey, and NRE Design Class, A Sub-Critical, He-Cooled Fast Reactor for the Transmutation of Spent Nuclear Fuel, Nucl. Technol, 156, 9 (2006). W. M. Stacey, Sub-Critical Transmutation Reactors with Tokamak Neutron Sources Based on ITER Physics and Technology, Fusion Sci. Technol. 52, 719 (2007). W. M. Stacey, D. W. Tedder, R. W. Johnson, Z. W. Friis, H. K. Park and NRE Design Class., Advances in the Subcritical, Gas-Cooled Fast Transmutation Reactor Concept, Nucl. Technol. 159, 72 (2007). W. M. Stacey, W. Van Rooijen and NRE Design Class, A TRU-Zr Metal Fuel, Sodium Cooled, Fast, Subcritical Advanced Burner Reactor, Nucl. Technol. 162, 53 (2008). W. M. Stacey, Georgia Tech Studies of Sub-Critical Advanced Burner Reactors with a D-T Fusion Tokamak Neutron Source for the Transmutation of Spent Nuclear Fuel, J. Fusion Energy 38, 328 (2009). Transmutation Fuel Cycle Analyses E. A. Hoffman and W. M. Stacey, Comparative Fuel Cycle Analysis of Critical and Subcritical Fast Reactor Transmutation Systems, Nuclear Technol. 144, 83 (2003). J. W. Maddox and W. M. Stacey, Fuel Cycle Analysis of a Sub-Critical, Fast, He-Cooled Transmutation Reactor with a Fusion Neutron Source, Nuclear Technol, 158, 94 (2007). C. M. Sommer, W. M. Stacey and B. Petrovic, Fuel Cycle Analysis of the SABR Subcritical Transmutation Reactor Concept, Nuclear Technol., submitted (2009). Dynamic Safety Analyses T. S. Sumner, W. M. Stacey and S. M. Ghiaasiaan, Dynamic Safety Analysis of the SABR Subcritical Transmutation Reactor Concept, Nuclear Technol., submitted (2009).

28 Backup

29 The Issues for the FFH Burner Reactor System Is a FFH Burner Reactor Technically Feasible and on what timescale? A detailed conceptual design study of an FFH Burner Reactor and the fuel reprocessing/ refabrication system should be performed to identify: a) the readiness and technical feasibility issues of the separate fusion, nuclear and fuel reprocessing/refabricating technologies; and b) the technical feasibility and safety issues of integrating fusion and nuclear technologies in a FFH burner reactor. This study should involve experts in all physics and engineering aspects of a FFH system: a) fusion; b) fast reactors; c) materials; d) fuel reprocessing/refabrication; e) high-level radioactive waste (HLW) repository; etc. The study should focus first on the most advanced technologies in each area; e.g. the tokamak fusion system, the sodium-cooled fast reactor system. Is a FFH Burner Reactor needed for dealing with the accumulating inventory of spent nuclear fuel (SNF)discharged from LWRs? A comparative systems study of several scenarios for permanent disposal of the accumulating SNF inventory should be performed, under different assumptions regarding the future expansion of nuclear power. The scenarios should include: a) burying SNF in geological HLW repositories without further reprocessing; b) burying SNF in geological HLW repositories after separating out the uranium; c) reprocessing SNF to remove the transuranics for recyling in a mixture of critical and FFH burner reactors (0-100% FFH) and burying only the fission products and trace transuranics remaining after reprocessing; d) scenario c but with the plutonium set aside to fuel future fast breeder reactors (FFH or critical) and only the minor actinides recycled; e) scenarios (c) and (d) but with pre-recycle in LWRs; etc. Figures of merit would be: a) cost of overall systems; b) long-time radioactive hazard potential; c) long-time proliferation resistance; etc. What additional R&D is needed for a FFH Burner Reactor in addition to the R&D needed to develop the fast reactor and the fusion neutron source technologies? This information should be developed in the conceptual design study identified above.

30 Sub-critical operation provides a larger margin of safety against accidental reactivity insertions that could cause prompt critical power excursions. ρ+ ()()10611,,,expexp10,0.110fisdnknCneutronkineticsdtkdCnCdelayedneutronpre = ;