Benchmarks for Quantifying Fuel Reactivity Depletion Uncertainty

Benchmarks for Quantifying Fuel Reactivity Depletion Uncertainty

Product ID: 1022909 Sector Name: Nuclear Date Published: 8/8/2011 Document Type: Technical Report File size: 2.35 MB File Type: Adobe PDF (.pdf) Implementation Category:  Reference Foundational building blocks for product research and development, often including scientific findings and field experience that feed into Category 1 or Category 2 recommendations. View all implementation categories and types descriptions Implementation Type:  Benchmarking Plant operating experience and/or benchmarking studies View all implementation categories and types descriptions

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	Abstract
	Analytical methods, described in this report, are used to systematically determine experimental fuel sub-batch reactivities as a function of burnup. Fuel sub-batch reactivities are inferred using more than 600 in-core pressurized water reactor (PWR) flux maps taken during 44 cycles of operation at the Catawba and McGuire nuclear power plants. The analytical methods systematically search for fuel sub-batch reactivities that minimize differences between measured and computed reaction rates, using Studsvik Scandpower's CASMO and SIMULATE-3 reactor analysis tools. More than eight million SIMULATE-3 core calculations are used to reduce one million measured reaction rate signals to a set of 2500 experimental fuel sub-batch reactivities over the range of 0 to 55 gigawatt-days per metric ton (GWd/T) burnup. Experimental biases derived for the CASMO lattice physics code were used to develop a series of experimental benchmarks that can be used to quantify reactivity decrement biases and uncertainties of other code systems used in spent-fuel pool (SFP) and cask criticality analyses. Specification of 11 experimental lattice benchmarks, covering a range of enrichments, burnable absorber loading, boron concentration, and lattice types are documented in this report. Numerous tests are used to demonstrate that experimental reactivity burnup decrements are insensitive to the specific lattice physics codes and neutron cross-section libraries used to analyze the flux map data. Experimental results also demonstrate that CASMO hot full power (HFP) reactivity burnup decrement biases are less than 250 pcm over the burnup range from 0 to 55 GWd/T, and corresponding 2σ uncertainties are less than 250 pcm. The TSUNAMI tools of Oak Ridge National Laboratory's SCALE 6 package were used to extend HFP results to cold conditions, and cold reactivity burnup decrement uncertainties increased to approximately 600 pcm. This report provides a basis for quantification of combined nuclide inventory and cross-section uncertainties in computed reactivity burnup decrements. Results support the Kopp Memo 5% reactivity decrement uncertainty assumption, often applied in SFP criticality analysis, which is shown to be both valid and conservative for CASMO-based fuel depletion analyses.