Technical Challenges for Conversion of U.S. High-Performance Research Reactors (USHPRR) John G. Stevens, Ph.D. Argonne National Laboratory Technical Lead of Reactor Conversion GTRI USHPRR Conversion Program
USHPRR Reactor Conversion Outline Overview of the 5 USHPRR Common Current barriers to conversion of the USHPRR Overview of likely extent of performance penalties Applications precluded by performance penalties Principle of Fuel Acceptability for Conversion 3 Pillars of the USHPRR Conversion Program to Address Fuel Acceptability Specific Discussion of Mitigation Strategies for conversion of the USHPRR For Each of the 5 USHPRR, Pre Mitigated and Post Mitigated Likely extent of performance penalty Key Challenges of the Conversion and Mitigation Strategy Working Group Approach to USHPRR Conversions 2
U.S. High Performance Research Reactors Base Fuel Reactors, each regulated by Nuclear Regulatory Commission (NRC): MITR Massachusetts Institute of Technology MURR University of Missouri Columbia NBSR National Institute of Science and Technology (US Dept. of Commerce) Complex Fuel Reactors, each regulated by Department of Energy: ATR, Idaho National Laboratory (DOE Office of Nuclear Energy) ATRC Critical assembly for ATR 3 HFIR Oak Ridge National Laboratory (DOE Office of Science)
U.S. High Performance Research Reactors Reactor HEU Core Power Primary Uses Regulator MITR 5 MW (6 MW planned) Mixed MURR 10 MW Isotope Production, Activation NRC Regulated NBSR 20 MW Beam Science ATR (ATRC) HFIR 100-250 MW (ATRC 600 W) 85 MW Fuel & Material Irradiation Beam Science & Isotope Production DOE Regulated 4
Common Current Barriers to Conversion of the USHPRR All are High Flux Reactors that cannot be converted with existing qualified, commercially available fuels Require very high density fuels able to withstand High to very high heat flux (fission rate) High burnup (fission density) High to very high coolant flows (potential for hydrodynamic challenges) Two very high density fuel systems have been under development by GTRI Conversion program : U Mo Dispersion (U density limit around ~8.5 g/cc) U Mo Monolithic fuel (U density up to ~17 g/cc.) 5 U Mo Monolithic fuel selected by USHPRR Conversion Program as most probable fuel to meet the needs of all 5 USHPRR
USHPRR cannot be converted with existing qualified, commercially available fuels Reactor HEU Assemblies Per Year (Plates Per Year) LEU Assemblies Per Year (Plates Per Year) LEU Needed MITR 9 (135 plates) 8 (144 plates) MURR 23 (552 plates) 19 (456 plates) Base Monolithic Fuel NBSR 30 (1020 plates) 30 (1020 plates) ATR (ATRC) HFIR 110 (2090 plates) 7 Cores (3780 plates) 100 (preliminary) (1900 plates) Complex 7 Cores (3780 plates) Monolithic Fuel 6
USHPRR Overview of likely extent of performance penalty Reactor Pre-Mitigated Performance Penalty Key Mitigation Post-Mitigated Penalty MITR 5-10% MURR 15% NBSR 10% ATR (ATRC) 5-10% Preliminary HFIR 10-15% Power Increase (6 MW 7 MW) Power Increase (10 MW 12 MW) Cold Source Upgrade Mitigation Not Yet Identified Power Increase (85 MW 100 MW) None None Potential Slight Gains None Thermal Small Losses Cold Small Gains Mitigation Not Yet Identified None Potential Small Gains 7
USHPRR Applications precluded by performance penalty? Short Common Answer: No applications precluded by un mitigated performance penalty Throughput is key issue for all of the USHPRR Subscription Rates for Devices already limiting scientific output Isotope Production already limited in the US (and volume is a key) 8 Significant Mitigations being pursued to avoid throughput penalties Hence the difference from prior conversions where ex core mitigations were unnecessary (due to less utilization) or were compensated by changes to core layout
Addressing the Common Barrier to Conversion Principle of Fuel Acceptability for Conversion QUALIFIED Fuel Assembly Fuel assembly that has been successfully irradiation tested and is licensable from the point of view of fuel irradiation behavior COMMERCIALLY AVAILABLE Fuel Assembly Fuel assembly that is available from a commercial manufacturer SUITABLE Fuel Assembly Safety criteria are satisfied Fuel assembly that satisfies criteria for LEU conversion of a specific reactor Fuel Service Lifetime comparable to current HEU fuel (e.g., Number of FA used per year is the same as or less than with HEU fuel) Performance of experiments is not significantly lower than with HEU fuel To be ACCEPTABLE for LEU conversion of a specific reactor, a fuel assembly must be qualified, commercially available, and suitable for use in that reactor, then reactor operator & regulator must agree to ACCEPT fuel assembly for conversion 9
Addressing the Common Barrier to Conversion 3 Pillars of the USHPRR Conversion Program QUALIFIED Fuel Assembly Fuel Development Pillar COMMERCIALLY AVAILABLE Fuel Assembly Fuel Fabrication Capability Pillar SUITABLE Fuel Assembly Reactor Conversion Pillar To be ACCEPTABLE for LEU conversion of a specific reactor, a fuel assembly must be qualified, commercially available, and suitable for use in that reactor, then reactor operator & regulator must agree to ACCEPT fuel assembly for conversion 10 Parallel Collaboration of Facilities, DOE Lab Complex, Regulators
Specific Discussion of Mitigation Strategies for Conversion of the USHPRR For Each of the 5 USHPRR Pre Mitigated and Post Mitigated Likely extent of performance penalty Key Challenges of the Conversion and Mitigation Strategy 11
MITR MITR fuel assembly Rhomboid Finned Clad on each fuel plate surface to increase heat transfer Flexible Number Fuel Elements and Dummy/Experiment Assemblies Number of plates increased from 15 HEU to 18 LEU to preserve cycle length & improve thermal margin Power Increase 6 MW HEU to 7 MW LEU to preserve operational flexibility Mitigations will not require significant system modification 12 Pre-Mitigated Penalty 5-10% No Post-Mitigated Penalty
MURR 13 Very Compact Core Design Core Volume 33 liters Fuel Meat 4.3 liters MURR fuel assembly 24 curved plates 45 degree arc No grid flexibility Weekly refueling for > 90% capacity factor for > 20 years Weekly cycle and initial control blade position key to efficient isotope production LEU Plate thicknesses reduced Variable fuel meat thickness for power peaking control Thinner clad for better moderation (fuel utilization) Power Increase 10 MW HEU to 12 MW LEU to preserve Production Rates
MURR Pre Mitigated Penalty 5 15% No Post Mitigated Penalty, potential for small improvements Mitigations will not require significant system modification Key Challenges Reduced Plate Thickness HEU 50 mil plates LEU interior plates 38 mil Hydrodynamic stability must be demonstrated Power Increase faces regulatory hurdle Power > 10 MW defines a test reactor, with additional regulatory requirements 14
NBSR NBSR fuel assembly Unfueled region at core axial centerline provides flux peak for experiments 34 slightly curved plates per assembly No grid flexibility, Compact LEU core design would not preserve sufficient range and flexibility of experiments Pre Mitigated Penalty ~10% No Post Mitigated Penalty Thermal loss to be overcome by improved instruments Cold losses completely overcome by upgrade of cold source potential for small gains in cold neutron performance 15 Key Challenge will be timing i.e., planning and execution have little margin for problems or adjustments
ATR ATR fuel assembly 19 curved plates 45 degree arc No grid flexibility Integral burnable absorber required to control power peaking within inner and outer plates 48 Inch plate length (others <24 ) 5 Lobes of reactor operated at distinct powers, so operational flexibility a key Detailed performance penalties still being determined, but preliminary estimates are 5 10% Detailed mitigation strategy also being developed 16 Burnable Absorber is key challenge
HFIR 17 HFIR fuel assembly Involute plates maintain constant water gap between concentric cylinders Graded fuel meat within plates to control power peaking at radial edges of fuel Burnable Absorber in inner element filler to further control radial peaking Single Use Core Original Power Rating 100 MW was reduced to 85 MW due to vessel pressure concern coupled with 60s safety basis Plan to return to 100 MW with LEU via modern safety basis Pre Mitigated Penalty 15% BOC No Post Mitigated Penalty
HFIR Key Challenges Onset of Nucleate Boiling (ONB) at Core Exit is the active thermal constraint Definitive Complex Fuel Radial grading of fuel must be maintained for LEU Burnable absorber apparently still necessary in inner element Axial grading of last several cm at exit apparently necessary to avoid ONB 18 Power Increase from 85 MW HEU to 100 MW LEU presents additional challenges Computational Fluid Dynamics (CFD) Safety Basis will be required to show that sufficient thermal margin exists at current system pressures Cold Source must be managed/modified to allow power increase
USHPRR Working Group Approach to Conversions Communication for Collaborative Success USHPRR Working Group Key Stakeholders all involved USHPRR Faciltiy Operators DOE Complex for 3 Pillars of Program (Fuel Development, Fuel Fabrication Capability, and Reactor Conversion ) Regulators as observers 2 3 Meetings per Year since 2006 to have each of the five reactors and three program pillars exchange information on progress and challenges Experts Meetings for more focused topics: Thermal Hydraulics, Fuel Procurement 19 USHPRR Project Web Site We post presentations on the project web site shortly after the meeting s Key reports from the USHPRR Conversion Program pillars and the facilities archived for common access
USHPRR Specific Collaboration Structures All Unique MITR Joint analyses at MITR & Argonne PM Lead by Woolstenhulme of INL, at request of MITR (and with active participation) MURR Joint analyses at MURR & Argonne PM Lead by MURR with active GTRI participation NBSR Joint analyses at NIST & Brookhaven PM Lead by NBSR staff at NIST ATR Analysis at INL (independent review to be established) PM Lead by INL 20 HFIR Analysis at ORNL but Argonne will perform independent review in 2011 PM Lead by HFIR
Conclusions Common Current barriers to conversion of USHPRR Fuel must be Qualified, Commercially Available, and Suitable Likely extent of performance penalty 5 15% Pre Mitigated No Post Mitigated Performance Penalty Expected Economic impact will only be determined once LEU fuel production commercial Applications precluded by performance penalty: None Significant Mitigations being pursued to avoid throughput penalties Mitigations a one time expense rather than an ongoing expense Each facility able to continue to pursue mission without significant impact Collaborations through USHPRR Working Group Key to Success 21
Supporting Material 22
Fuel Development Organization 23 From July 2010 USHPWG Mtg FD_Pillar_and_Tech_Status_Wachs_USHPRRWG_MURR_100720.ppt
FFC Organization 24 From July 2010 USHPWG Mtg FFC_Pillar_Jollay_USHPRRWG_MURR_100720.pptx
USHPRR Reactor Conversion What does it take to succeed at individual facility? Make it so. GTRI USHPRR Reactor Conversion Technical Lead John Stevens (ANL) Conversion Analysis Technical Lead & PM John Stevens (INL) ANL Conversion Projects Section and Matrixed Resources of Nuclear Engineering Division Reactor Specific Test Specification (ANL interface with Facilities) Flow Testing Irradiation Demonstrations DOE Work Packages for Facilities: BNL (NBSR), INL, (ATR) ORNL (HFIR) Subcontracts to Facilities: MURR, MITR Conversion Implementation Tech Lead & PM Eric Woolstenhulme (INL) Implementation Support: INL Fuel Procurement Support: INL, ORNL Reactor Specific Test Implementation (INL interface with Fuel Development) Flow Testing Irradiation Demonstrations DOE Work Packages for Facilities: BNL (NBSR), INL, (ATR) ORNL (HFIR) Subcontracts to Facilities: MURR, MITR 25
RERTR Experiments Adapted from July 2010 USHPWG Mtg FD_Pillar_and_Tech_Status_Wachs_USHPRRWG_MURR_100720.ppt 2010 2011 2012 2013 2014 2015 AFIP 6 03/13 RERTR 12 AFIP 0313 7 FE NRC Qualification Report Base Fuel Demonstration BASE FUEL 0313 Generic Fuel Form OSU Flow Loop MITR DDE 0313 MURR DDE NBSR DDE 0313 0313 MITR OSU Flow Loop MURR OSU Flow Loop 0313 NBSR OSU Flow Loop NRC Conversion Reports AFIP 6 03/13 ATR LTA COMPLEX FUEL RERTR 13 RERTR 14 AFIP 8 AFIP 8A HFIR LTC AFIP 9 AFIP 9A 26 RERTR ALT 26
Key Parameters of the Five USHPRR Reactors: HEU* Key Parameters ATR HFIR NBSR MURR MITR-II Core Power (MW) 250 85 20 10 5 Avg. Power Density (kw / l) (kw / m) 900 270 Average Heat Flux (W/cm 2 ) 200 210 60 60 15 Peak Flux, (W/cm 2 ) Without Hot Channel Factors With Hot Channel Factors 454? Coolant H 2 O H 2 O D 2 O H 2 O H 2 O Flow Direction downward downward upward downward downward Nominal Channel Thickness (mils) Range, w/specified tolerances 77 / 78 (68-86) 1640 305 342? 50 (40-60) 37 72 107 163 116 (107 to?) 303 85 113 ~230 80 (72-88) 70 24 29? 78 (71-85) up to105 @ fin base Range w/ End Channels & tolerances (mils) 40-60 62-138 37-102 Mean Core Velocity, m/s 14.6 15.4 3.0 7.0 2.5 Pressure, bar (absolute) 25.5 32.3 1.15 4.7 1.35 Saturation Temperature, C 225 238 105 150 108 Bergles & Rohsenow ΔT SAT, C 8 6 11 12 9 Fuel Meat Length, inches 46.5 20.0 11 x 2** 24.0 22.38 Normal Inlet Temperature, C 51.7 49 37.8 49 40 Normal Core Temp. Rise, C 23 23 8 9 9 *Draft data pending confirmation by USHPRR reactor; compiled from 2006-2010 USHPRR web archive. **Two 11-inch sections separated by a 7-inch gap. 27
Key Parameters of the Five USHPRR Reactors: LEU* Key Parameters ATR (Cd) HFIR NBSR MURR MITR-II Core Power (MW) 250 100 20 12 7 Peak Fission Rate Density (10 14 /cm 3 /s) 10 19 2.5 5 1.4 Avg. Power Density (kw / l) (kw / m) 900 270 1930 360 37 72 364 103 100 34 Average Heat Flux (W/cm 2 ) 190 245 60 12 Peak Flux, (W/cm 2 ) Without Hot Channel Factors With Hot Channel Factors 436? 428? ave x 2.05 ave x 2.96 145 ~249 Coolant H 2 O H 2 O D 2 O H 2 O H 2 O Flow Direction downward downward upward downward downward Nominal Channel Thickness (mils) Range, w/specified tolerances 77 / 78 (68-86) 50 (40-60) 116 (107 to?) 92 (84-100) 21? 72 (65-79) <105@fin base Range w/ End Channels, all-points (mils) 40-60 67-123 31-96 Mean Core Velocity (m/s) 2.08 Pressure (bar, absolute) 25.5 1.15 4.7 1.35 Saturation Temperature (C) 225 150 108 Bergles & Rohsenow ΔT SAT (C) 8 11 12 9 Fuel Meat Length (inches) 46.5 11.0 x 2 24.0 22.38 Normal Inlet Temperature (C) 51.7 37.8 49 40 Normal Core Temp. Rise (C) 8 *Draft data pending confirmation by USHPRR reactor; compiled from 2006-2010 USHPRR web archive. 28