Gas-Cooled Reactors – International Reactor Physics Experimental Benchmark Analysis J. M. Kendall

1. IAEA-ICTP Workshop onNuclear Reaction Data forAdvanced Reactor TechnologiesICTP – Trieste, Italy, 18-30 May 2008 Gas-Cooled Reactors – International Reactor Physics Experimental Benchmark Analysis J. M. Kendall Global Virtual LLC -1-

2. Benchmark Activities • IAEA-TECDOC-1249 • PROTEUS (Pebble Bed) Critical Facility • VHTRC (Prismatic Block) Critical Facility • IAEA-TECDOC-1382 • HTR-10 (Pebble Bed) Core Physics • HTTR (Prismatic Block) Core Physics • http://www.iaea.org/inisnkm/nkm/aws/htgr/abstracts/index.html -2-

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5. PROTEUS Benchmarks • Critical Balances • Reaction rate ratios and distributions • Control rod worths • Water ingress effects • Reactivity of small samples • Kinetic parameter (β/Λ) -5- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

6. PROTEUS Benchmarks -6- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

7. PROTEUS Benchmarks -7- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

8. PROTEUS Benchmarks -8- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

9. PROTEUS Benchmarks Methods - Critical Balances Including Streaming -9- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

10. PROTEUS Benchmarks Experimental and Calculated Critical Balances Cores 1A, 2, 3 and 4.3 -10- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

11. PROTEUS Benchmarks Experimental and Calculated Critical Balances Cores 5, 7, 9 and 10 -11- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

12. PROTEUS Benchmarks Reactivity vs. Percentage of Polyethylene Rods in Core 10 -12- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

13. VHTRC Benchmark -13- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

14. VHTRC Benchmark -14- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

15. VHTRC Benchmark -15- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

16. VHTRC Benchmark -16- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

17. VHTRC Benchmark OKBM* - Macroscopic cross sections by WIMS-D4/UKNDL -17- IAEA-TECDOC-1249, Critical experiments and reactor physics calculations for low enriched high temperature gas cooled reactors, October 2001.

18. HTR-10 Benchmarks -18- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

19. HTR-10 Benchmarks Core physics calculation Geometric model -19- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

20. HTR-10 Benchmarks • Post-Test Adjustment to Benchmark Problem Assumptions/Conditions • Density of dummy balls: 1.73 → 1.84 g/cm3 • Boron equivalent of impurities in dummy balls: 1.3 → 0.125 ppm • Core atmosphere: Helium → Air • Temperature: 20˚C → 15˚C -20- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

21. HTR-10 Benchmarks Example Results – Initial Criticality (B1) -21- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

22. HTR-10 Benchmarks • Reasons for Differences in Results • Some control rod cross section cell calculations more appropriate for rod array than single rod worth evaluations • Uncertainty in the modeling of neutron streaming • Choice of selected cross section library (JEFF, ENDF, JENDL, etc.) • Water content of graphite pores • Library dependent cross-sections for temperature coefficients • Effective fuel homogenization methods • Modeling of fuel with Monte Carlo Calculations • Explicit geometry (particle distribution in pebble, pebble distribution in core) • Modeling of fuel/dummy ball ratio IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003. -22-

23. HTTR Benchmarks -23- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

24. HTTR Benchmarks Core Cross Section with Fuel Block Loading Order -24- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

25. HTTR Benchmarks Core Region Block Configurations -25- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

26. HTTR Benchmarks Fuel Rod Fuel Compacts & Burnable Poison Pellets -26- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

27. HTTR Benchmarks Analysis Methods – Diffusion Calculations -27- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

28. HTTR Benchmarks Analysis Methods – Monte Carlo Calculations -28- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

29. HTTR Benchmarks -29- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

30. HTTR Benchmarks FC - Initial Criticality Diffusion Calculations Monte Carlo Calculations -30- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.

31. HTTR Benchmarks • Reasons for Differences in Results • Uncertainties in levels of impurities in dummy blocks, and in water and air or nitrogen in graphite pores • Monte Carlo model geometry representation • Choice of selected cross section data library and version (JEF, ENDF, JENDL, etc.) • Uncertainties in modeling neutron streaming with diffusion methods • Difficulties in modeling harmonics in thin annular cores with diffusion methods -31- IAEA-TECDOC-1382, Evaluation of HTGR performance: Benchmark analysis related to initial testing of the HTTR and HTR-10, November 2003.