Validating Actinides and Fission Products for Burnup Credit Criticality Safety Analyses - Nuclide Compositions Prediction with Extended Validation Basis (NUREG/CR-7303)

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Publication Information

Manuscript Completed: May 2023
Published: September 2023

Prepared by:
Germina Ilas
Rabab Elzohery

Oak Ridge National Laboratory
Oak Ridge, TN 37831-6170

Lucas Kyriazidis, NRC Project Manager

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

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Abstract

Criticality safety evaluations accounting for burnup credit require validation of the computational tools and associated nuclear data used to perform the fuel depletion and criticality calculations. The NUREG/CR-7108 report published in 2012 documents an approach for establishing the bias and bias uncertainty in the calculated neutron multiplication factor (k_eff) that is associated to calculated spent nuclear fuel nuclide compositions, using as validation basis radiochemical assay (RCA) measurement data for nuclide concentrations.

Studies documented in the current report build upon the NUREG/CR-7108 approach. The bias and bias uncertainty in calculated k_eff for a representative analysis model that includes pressurized water reactor (PWR) spent fuel is determined by applying a stochastic sampling method. The validation basis presented herein is improved compared to that in NUREG/CR-7108 to fill data gaps at high burnups, with practical impact on burnup credit for modern discharged fuel. This extended validation basis includes recent RCA measurements performed at Oak Ridge National Laboratory under an experimental program jointly funded by the Nuclear Regulatory Commission and the Department of Energy. The improvement in the validation basis led to an overall decrease in the k_eff bias uncertainty for the considered analysis model compared to the corresponding values in ISG-8 Rev.3.