United States Nuclear Regulatory Commission - Protecting People and the Environment

Validation of keff Calculations for Extended BWR Burnup Credit (NUREG/CR-7252, ORNL/TM-2018/797)

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Publication Information

Manuscript Completed: July 2018
Date Published: December 2018

Prepared by:
W. J. Marshall
J. B. Clarity
S. M. Bowman

Oak Ridge National Laboratory
Managed by UT-Battelle, LLC
Oak Ridge, Tennessee 37831-6170

Mourad Aissa, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

The US Nuclear Regulatory Commission and consensus standards recommend validation of the numerical methods used in criticality safety analyses. This validation requires the comparison of computational results with measurements of physical systems which are neutronically similar to those used in the safety analysis being performed. To this end, this document examines the methods available to generate sensitivity data to help identify systems similar to spent boiling-water reactor (BWR) fuel in a flooded spent nuclear fuel transportation or storage cask. A large number of critical benchmark experiments are surveyed using sensitivity/uncertainty (S/U) techniques to assess their applicability to BWR burnup credit (BUC) beyond the burnup of peak reactivity. Multiple burnups of BWR assemblies are considered herein, as well as the actinide-only (AO) and actinide-and-major-fission-product (AFP) isotope sets. Sample validations are completed for representative application models to demonstrate that appropriate validation is possible and to indicate the bias and bias uncertainty values expected for related applications.

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