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TANKS - ANS 2009

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TANKS - ANS 2009

  1. 1. Analysis of Enriched Uranyl Nitrate in Nested Annular Tank Array John Bess James Cleaver Idaho National Laboratory ANS Annual Meeting, Atlanta, GA June 14-19, 2009
  2. 2. Objective Benchmark analysis of an array of nested annular tanks containing highly enriched uranyl nitrate solution Follow guidelines for inclusion in the International Handbook of Evaluated Criticality Safety Benchmark Experiments 2
  3. 3. Background Rocky Flats Critical Mass Laboratory during the 1980s Tanks of typical sizes found in nuclear production plants Series of experiments: ¤ 1) Co-located set of tanks (Benchmarked) ¤ 2) 1x2 array of nested tanks ¤ 3) 1x3 array of nested tanks 3
  4. 4. Basic Experimental Configuration Six stainless steel tanks Surrounded by concrete slabs, walls, and floor 357.4 g/L uranium in dilute nitric acid Two to six tanks filled until criticality achieved
  5. 5. Annular Tank Experimental Setup
  6. 6. Variations of the Experimental Design Addition of neutron absorbers ¤ Borated concrete plugs One with cadmium lining Placed in center of a pair of annular tanks ¤ Borated plaster plugs ¤ Borated plaster slabs Placed between pairs of tanks
  7. 7. Plugs and Slabs
  8. 8. Critical Solution Case No. Absorbers/Moderators Tanks with Solution Level (cm) 1 None 1-2-2*-3*-3-4 103.24 2 None 1-2-2*-3* 116.08 3 None 2*-3* 174.48 4 None 1-2*-3* 150.04 5 3 Concrete Plugs 1-2-2*-3*-3-4 166.54 6 3 Concrete Plugs 1-2-2*-3* 194.58 7 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3*-3-4 164.575 8 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3* 196.46 2 Concrete Plugs + Small Cd-Lined 9 1-2-2*-3*-3-4 158.89 Concrete Plug Large Concrete Plug + 2 Plaster Plugs 10 1-2-2*-3*-3-4 207.9 and 2 Plaster Slabs Large Concrete Plug + Small Plaster 11 1-2-2*-3*-3-4 121.41 Plug and 2 Plaster Slabs Large Concrete Plug + Small Plaster 12 Plug and 2 Plaster Slabs 2*-3*-3-4 135.12
  9. 9. Additional Non-Benchmark Experiments Placement of nested hemispheres of highly enriched uranium between the tank pairs Placement of bottled highly enriched uranyl nitrate between the tank pairs Subcritical configuration
  10. 10. Benchmark Model Development Both detailed and simple models were developed Simplification include the following: ¤ Omission of rebar and steel reinforcements in concrete ¤ Omission of wood ¤ Leveling the bottom of the tanks ¤ Simplification of room layout ¤ Correction of solution temperature for difference between experimental conditions (25ºC) and measurement of solution density (20ºC) Removal of impurities is essentially negligible
  11. 11. Side
  12. 12. Cases 1-4
  13. 13. Cases 5-6
  14. 14. Cases 7-8
  15. 15. Case 9
  16. 16. Case 10
  17. 17. Cases 11-12
  18. 18. Uncertainties Analysis Perturbation analysis of parameters compared to the detailed benchmark model Monte Carlo N-Particle (MCNP) version 1.5.1.4 ENDF/B-VI.8 cross-section library for evaluation of uncertainties
  19. 19. Uncertainties Analysis Experimental Tanks measurements ¤ Steel properties ¤ Temperature ¤ Thickness ¤ Solution critical ¤ Diameter height ¤ Annular thickness Solution Composition ¤ Eccentricity ¤ Density ¤ Placement ¤ Acid concentration Wood ¤ Uranium ¤ Physical properties ¤ Solution impurities ¤ Thickness and chemistry
  20. 20. Uncertainties Analysis Concrete and Largest plaster contributors to the ¤ Water content total uncertainty ¤ Boron content ¤ Boron-free concrete density ¤ Density ¤ Solution annular ¤ Isotopic abundance region thickness of boron and lithium ¤ Thickness
  21. 21. Results Uncertainties determined to be between 0.79 and 0.90 %∆k/k Expected benchmark eigenvalues approximately 1.0000 Calculated results within ~1σ-2σ of benchmark values ¤ Unique experiments because they use Gerstley borate in concrete and plaster
  22. 22. MCNP5 Case No. Absorbers/Moderators Tanks with Solution ENDF/B-VII.0 keff 1 None 1-2-2*-3*-3-4 0.9984 2 None 1-2-2*-3* 0.9999 3 None 2*-3* 0.9871 4 None 1-2*-3* 0.9907 5 3 Concrete Plugs 1-2-2*-3*-3-4 1.0047 6 3 Concrete Plugs 1-2-2*-3* 1.0089 7 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3*-3-4 0.9933 8 Large Concrete Plug + 2 Plaster Plugs 1-2-2*-3* 1.0011 2 Concrete Plugs + Small Cd-Lined 9 1-2-2*-3*-3-4 1.0000 Concrete Plug Large Concrete Plug + 2 Plaster Plugs 10 1-2-2*-3*-3-4 0.9855 and 2 Plaster Slabs Large Concrete Plug + Small Plaster 11 1-2-2*-3*-3-4 0.9810 Plug and 2 Plaster Slabs Large Concrete Plug + Small Plaster 12 Plug and 2 Plaster Slabs 2*-3*-3-4 0.9747
  23. 23. Conclusions Benchmark analysis of an array of nested annular tanks containing highly enriched uranyl nitrate solution was performed Report to be published in the International Handbook of Evaluated Criticality Safety Benchmark Experiments ¤ HEU-SOL-THERM-026, September 2009 23
  24. 24. Questions? Rocky Flats This work was done by Battelle Energy Alliance, LLC under Contract No. DE-AC07-05ID14517 with the U.S. Department of Energy

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