HTTR - ANSWM 2009
- 1. Criticality Benchmark Analysis of the HTTR Annular Startup Core Configurations John Darrell Bess R&D Engineer – Reactor Physics ANS Winter Meeting November 19, 2009
- 2. Objective • The benchmark assessment of Japan’s High Temperature Engineering Test Reactor (HTTR) is one of the high priority activities for the Next Generation Nuclear Plant (NGNP) Project and Very High Temperature Reactor (VHTR) Program. • Current efforts at the Idaho National Laboratory (INL) involve development of reactor physics benchmark models in conjunction with the International Reactor Physics Experiment Evaluation Project (IRPhEP) for use with verification and validation (V&V) methods. 2
- 3. IRPhEP Process (for the HTTR) 3
- 4. HTTR Primary Design Specifications - I Thermal Power 30 MW Outlet Coolant Temperature 850/950 ºC Inlet Coolant Temperature 395 ºC Primary Coolant Pressure 4 MPa Core Structure Graphite Equivalent Core Diameter 2.3 m Effective Core Height 2.9 m Air cooler 3 Crane Average Power Density 2.5 W/cm Refueling machine Fuel UO2 Enrichment 3 to 10 wt. % Spent fuel 6 wt. % (average) storage pool Fuel Type Pin-in-Block Type Coated Fuel Particles Burn-Up Period (EFPD) 660 days Reactor pressure Fuel Block Graphite Block vessel Coolant Material Helium Gas Intermediate Flow of Direction in Core Downward heat exchanger Reflector Thickness Pressurized water cooler Top 1.16 m Side 0.99 m Bottom 1.16 m Number of Fuel Assemblies 150 Reactor containment vessel Number of Fuel Columns 30 Number of Pairs of Control Rods In Core 7 In Reflector Plant Lifetime 9 20 years JAEA’s HTTR Facility at the Oarai Research and Development Center 4
- 5. HTTR Primary Design Specifications - II 5
- 6. Fuel Specifications of the HTTR - II 6
- 7. Fuel and Burnable Poison Loading The top The bottom number of number each block represents the represents boron content the uranium in the burnable enrichment. poison pellets. 7
- 9. Dummy Fuel Columns IG-11 graphite blocks with higher impurity content than the IG-110 fuel blocks were initially placed in the core 9
- 10. HTTR Fuel Loading 10
- 11. Thin Annular 19-Fuel-Column Core Central Pattern 11
- 12. Thin Annular 21-Fuel-Column Core Flat-Standard Pattern 12
- 13. Thick Annular 24-Fuel-Column Core Flat-Standard Pattern 13
- 14. Thick Annular 24-Fuel-Column Core Radial Reflectors Pattern 14
- 15. Thick Annular 27-Fuel-Column Core Flat-Standard Pattern 15
- 16. Uncertainty Analysis - I • The uncertainty • All random analysis consisted of uncertainties are the perturbation of the treated as 25% benchmark model systematic parameters and a – The large number of comparison of the components in the computed eigenvalues reactor tend to reduce to determine the random uncertainties effective uncertainty in to negligible quantities the model. – This preserves some of the uncertainty in the HTTR model 16
- 17. Uncertainty Analysis - II • Experimental measurements • Computational analyses – Isothermal temperature – Room return effects – Control rod positions – Stochastic modeling of TRISO particles • Geometric properties – Instrumentation bias – Diameter – Height – Thickness – Pitch • Compositional variations – Fuel enrichment – Material density – Impurity content – Boron absorber content – Isotopic abundance of boron – Clad composition – Fuel Mass 17
- 18. Uncertainty Results • The most significant contributions to the overall uncertainty include the following: – Impurities in the IG-110 graphite blocks, – Impurities in the PGX graphite reflector blocks, and – Impurities in the IG-11 graphite dummy blocks. • Other ICSBEP/IRPhEP benchmarks demonstrate similar sensitivities to graphite impurities. • The influence of random uncertainty is negligible: <0.0005 Δkeff – Dominant uncertainties are systematic in nature. – Better characterization of these parameters will reduce the overall uncertainty. • A calculation bias of +2-3% still exists 18
- 19. Eigenvalue Results Benchmark Calculated Fuel (B) (K) Core CRs (K-B)/B% Columns keff ± σ keff 1 19 C 1.0048 ± 0.0103 1.0283 2.33 2 21 FS 1.0040 ± 0.0099 1.0304 2.63 3 24 FS 1.0035 ± 0.0085 1.0260 2.24 4 24 RR 1.0032 ± 0.0081 1.0296 2.63 5 27 FS 1.0029 ± 0.0078 1.0225 1.96 6 30 FS 1.0025 ± 0.0073 1.0248 2.13 MCNP5 + ENDF/B-VII.0 19
- 20. Annular Core Benchmarking Effort 1.0350 Benchmark Calculated 1.0300 1.0250 1.0200 keff (± 1σ) 1.0150 1.0100 1.0050 1.0000 0.9950 0.9900 19 21 24 24 27 30 Number of Loaded Fuel Columns 20
- 21. Points of Interest • Calculated eigenvalues are within 1% of the expected benchmark experiment values but the uncertainties are on the order of 0.75 to 1% (1σ). – This model is based on available public HTTR data; much of the HTTR data is proprietary and unpublished because the reactor is currently in operation. – The inclusion of more detailed HTTR data should reduce the uncertainty in the benchmark. • Equivalent boron content in graphite • Measured uncertainties vs. manufacturing tolerances 21
- 22. Current and Future Benchmark Analyses • Reactivity measurements from the initial start-up core physics tests – Isothermal temperature coefficient – Axial reaction rate distribution – Kinetics measurements – Shutdown margin – Control rod worth – Excess reactivity • Hot zero-power critical • Rise-to-power tests • Irradiation tests • Radiation shielding • Safety demonstration tests 22
- 23. Acknowledgments • Funding for the HTTR benchmark was provided by the INL VHTR Program. • Work was performed at the INL for th US DOE under contract number DE-AC07-05ID14517. • The author would like to acknowledge the time and expertise provided by N. Fujimoto from the Japan Atomic Energy Agency; Luka Snoj from the Jožef Stefan Institute; Atsushi Zukeran, acting as Senior Reactor Physics Consultant; and Blair Briggs, Barbara Dolphin, Dave Nigg, Jim Sterbentz, and Chris White from the INL, for review, preparation, and presentation of the HTTR benchmarks. • Complete benchmarks available in the March 2010 Edition of the IRPhEP Handbook: – HTTR-GCR-RESR-001 and -002. 23
- 24. Questions? 24
- 25. 25
- 26. Extra Slides 26
- 27. Primary References • N. Fujimoto, K. Yamashita, N. Nojiri, M. Takeuchi, and S. Fujisaki, “Annular Core Experiments in HTTR’s Start-Up Core Physics Tests,” Nucl. Sci. Eng., 150, 310-321 (2005). • “Evaluation of high temperature gas cooled reactor performance: Benchmark analysis related to initial testing of the HTTR and HTR-10,” IAEA-TECDOC-1382, International Atomic Energy Agency, Vienna, November 2003. • S. Shiozawa, S. Fujikawa, T. Iyoku, K. Kunitomi, and Y. Tachibana, “Overview of HTTR Design Features,” Nucl. Eng. Des., 233:11-21 (2004). • N. Nojiri, S. Shimakawa, N. Fujimoto, and M. Goto, “Characteristic Test of Initial HTTR Core,” Nucl. Eng. Des., 233: 283-290 (2004). 27
- 28. IRPhEP Handbook – 2009 Edition • 15 Contributing Countries • Data from 36 Experimental Series – 21 Reactor Facilities • Data from 7 reactor types – Up to 8 types of measurements • Data from 33 out of the 36 series are published as approved benchmarks • Data from 3 out of the 36 series are published in draft form • http://nuclear.inl.gov/irphep/ 28
- 29. Fully-Loaded Control Rod Positions 29
- 30. HTTR Instrumentation 30
- 31. Fuel Specifications of the HTTR - I Fuel Kernel Fuel Rod Material UO2 Outer Diameter (cm) 3.4 Diameter (µm) 600 Sleeve Thickness (mm) 3.75 Density (g/cm3) 10.41 Length (cm) 54.6 Coated Fuel Particle Number of Fuel Compacts 14 Type / Material TRISO Number of Rods in a Block 31 / 33 Diameter (µm) 920 Graphite Sleeve Impurity (ppm) <3 (Boron Equivalent) Type Cylinder Material IG-110 Graphite Fuel Compact Impurity (ppm) <1 (Boron Equivalent) Type Hollow Cylinder Length (cm) 58 Material CFPs, Binder, and Graphite Gap Width between Compact and Sleeve (mm) 0.25 Outer / Inner Diameter (m) 2.6 / 1.0 Length (cm) 3.9 Graphite Block Packing Fraction of CFPs (vol. %) 30 Type / Configuration Pin-in-Block / Hexagonal Density of Graphite Matrix (g/cm3) 1.7 Material IG-110 graphite Impurity in Graphite Matrix (ppm) <1.2 (Boron Equivalent) Width across Flats (cm) 36 Height (cm) 58 Fuel Hole Diameter (cm) 4.1 3 Density (g/cm ) 1.75 Impurity (ppm) <1 (Boron Equivalent) 31
- 32. TRISO Particle 32
- 33. Fuel Element 33
- 34. Burnable Poisons 34
- 35. Fuel Blocks 35
- 36. Dummy Blocks 36
- 37. Control Rods 37
- 38. Control Rod Column 38
- 39. Instrumentation Column 39
- 40. Replaceable Reflectors 40
- 41. MCNP View 41
- 42. Possible Fix: HTTR Fuel Loading • The benchmark model was adjusted to conserve UO2 fuel mass. – Initially thought to be U metal mass. It is U metal mass. • TRISO fuel parameter over specified: – Kernel diameter, density, packing fraction, etc. • The number of TRISO particles was reduced from ~13,000 to ~11,500 per compact (14 per fuel rod) – Reduced the nominal packing fraction. • (~30 26.4%) – Preserved all other specified parameters. – Conserved nominal fuel mass per rod. • 188.58 g • Reduced a computational bias of ~ +2% ∆keff 42