Review and Prioritization of Technical Issues Related to Burnup Credit for BWR Fuel

This report has been prepared to support technical discussion of and planning for future
research supporting implementation of burnup credit for boiling-water reactor (BWR) spent fuel
storage in spent fuel pools and storage and transport cask applications. The review and
discussion in this report are based on knowledge and experience gained from work performed
in the United States and other countries, including experience with burnup credit for
pressurized-water reactor (PWR) spent fuel. Relevant physics and analysis phenomena are
identified, and an assessment of their importance to burnup credit implementation is given.
Results from sensitivity studies of some of the key phenomena are presented.
The work presented in this report is primarily a sensitivity study designed to identify and rank
phenomena and parameters important to BWR burnup credit methodology. This work is an
extension of the work reported in NUREG/CR-7157, Computational Benchmark for Estimated
Reactivity Margin from Fission Products and Minor Actinides in BWR Burnup Credit, which
defines the baseline BWR spent fuel cask model used in this report and provides estimates for
the reactivity margin associated with fission products and minor actinides. All calculations
supporting this work were performed using the SCALE 6.1 code system with the 238-neutron
energy group ENDF/B-VII-based nuclear data library.
Discussion of and recommendations for future work supporting implementation of BWR burnup
credit beyond the currently used peak reactivity method are provided. A high priority is
recommended for development of guidance for identification and use of axial burnup distribution
data, for treatment of axial moderator density distributions, and for treatment of control blade
usage during depletion calculations. In addition to these higher priority items, several medium
and lower priority items are identified and discussed.