HTTR - PHYSOR2010
- 1. Benchmark Evaluation of the Start-Up Core Reactor Physics Measurements of the High Temperature Engineering Test Reactor John Darrell Bess R&D Staff Engineer Reactor Physics Analysis and Design www.inl.gov PHYSOR 2010 May 12, 2010 This paper was prepared at Idaho National Laboratory for the U.S. Department of Energy under Contract Number (DE-AC07-05ID14517)
- 2. Objective • Perform a detailed benchmark analysis of the start-up physics tests at the High Temperature Engineering Test Reactor – High priority benchmark for the Next Generation Nuclear Plant (NGNP) Project and Very High Temperature Reactor (VHTR) Program – Submit completed work for inclusion in the IRPhEP Handbook 2
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- 4. Evaluation Process: ICSBEP & IRPhEP 4
- 5. High Temperature Test Reactor (HTTR) • 30 MWt • Graphite Moderated/Reflected • Core Diameter = 2.3 m • Core Height = 2.9 m • Helium Coolant • 150 Fuel Assemblies • 30 Fuel Columns 5
- 6. HTTR Core • Prismatic Pin-in-Block Fuel • UO2 Fuel – Enriched 3 to 10 wt.% – ~6 wt.% average • Reflector Thickness ~1 m • 16 Pairs of B4C Control Rods • Burnable Poison Pellets – 2.0 and 2.5 wt.% Bnat 6
- 7. Summary of Start-Up and Zero-Power Tests • Six cold critical • Three axial reaction rate configurations measurements – One full core – Instrumentation columns – Five annular cores • Full core • Excess reactivity • 24-column core (2) measurements • Isothermal temperature – Fuel loading coefficients • Shutdown margins – 340 to 740 K – All rods at once • Two warm criticals – Two-step by region – 400 and 420 K • Full core subcritical • Differential rod worth (C) – Insufficient data 7
- 8. Challenges • Limitation in available public information • Some data is unknown • Availability of some information only in Japanese • Conflicting reported values for some information • Large biases in eigenvalue calculations 8
- 9. TRISO in Prismatic Fuel Blocks 09-GA50001-158-4 9
- 10. 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. 10
- 12. Control Rods 12
- 13. Annular Core Loadings 19 21 24 27 13
- 14. MCNP5 : ENDF/B-VII.0 Criticality T = 300 K MCNP5 : JENDL-3.3 results ~0.5% lower Uncertainties in Graphite Impurities and Cross Section Data 14
- 15. Excess Reactivity Measurements • Obtained by measuring and adding all fuel loading increments 15
- 16. Shutdown Margin 1. Full insertion of reflector region rods from critical 2. Full insertion of fuel region rods from previous insertion 3. Full insertion of all control rods from critical Shadowing Effects in the Core 16
- 17. Isothermal Temperature Coefficients • Two different 0.000 reports -0.005 13σ • IAEA-TECDOC- Temperature Reactivty Coefficient (%∆k/k/K) Good 3σ - 4σ 1382 data invalid -0.010 • CR positions -0.015 known exactly for first two points -0.020 • CR positions -0.025 Bad estimated with Measurement? adjusted rod worth -0.030 data for others Experimental -0.035 Calculated • Significant shadowing effect -0.040 300 350 400 450 500 550 600 650 700 750 800 Isothermal Temperature (K) 17
- 18. Instrumentation holes Axial Reaction Rates 10 108 360 D123 • Instrumentation columns in 24- and 30-fuel column cores • Uncertainties Evaluated – Measurement 4160 – Repeatability Total height 5220 mm (522 segments) – Graphite Composition – Graphite Dimensions – Control Rod Positions – Digitization – Renormalization 1060 Dimensions in mm 09-GA50001-103 18
- 19. Axial Neutron Reaction-Rate in the Instrumentation Axial Neutron Reaction-Rate in the Instrumentation Columns of the Fully-Loaded HTTR Core Columns of the Annular 24(F23)-Fuel-Column HTTR Core 500 500 400 400 Axial Distance (cm) from the Bottom of the Lowest Fuel Block Axial Distance (cm) from the Bottom of the Lowest Fuel Block Core Top Core Top 300 300 Fuel Top Fuel Top 200 200 100 100 0 0 Fuel Bottom Fuel Bottom -100 -100 Core Bottom Core Bottom -200 -200 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 Normalized Neutron Flux Normalized Neutron Flux 19 Instrumentation Columns Benchmark Values Core Boundaries Instrumentation Columns Benchmark Values Core Boundaries
- 20. Additional Eigenvalue Measurements • Full shutdown subcritical of fully loaded core • Two warm criticals in support of temperature coefficients • Warm critical in IAEA-TECDOC-1382 invalid • Similar results to cold critical analyses MCNP5 : ENDF/B-VII.0 20
- 21. Benchmark Status • Evaluation of the start-up physics tests has been completed – Two approved benchmarks included in the 2010 edition (in press) of the IRPhEP Handbook • Evaluation of the zero-power, elevated- temperature measurements has been performed – Benchmark to be prepared and submitted for inclusion in the 2011 edition of the IRPhEP Handbook 21
- 22. Conclusions • Eigenvalue calculations ~2% higher than benchmark values – Comparable to results from Japanese evaluations – Graphite composition and cross section uncertainties • Generally good agreement for excess reactivity, shutdown margin, axial reaction rate, and isothermal temperature coefficient measurements • All completed benchmark analysis to be publicly available in the IRPhEP Handbook 22
- 23. Acknowledgments • Nozomu Fujimoto – JAEA • Luka Snoj – Jožef Stefan Institute • Atsushi Zukeran – Consultant • Blair Briggs, Barbara Dolphin, Hikaru Hiruta, Dave Nigg, Jim Sterbentz, and Chris White – INL 23
- 24. Questions