United States Nuclear Regulatory Commission - Protecting People and the Environment

Review and Prioritization of Technical Issues Related to Burnup Credit for BWR Fuel (NUREG/CR-7158, ORNL/TM-2012/261)

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Publication Information

Manuscript Completed: November 2012
Date Published: February 2013

Prepared by:
D. E. Mueller, S. M. Bowman, W. J. Marshall,
and J. M. Scaglione

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

M. Aissa, NRC Project Manager

NRC Job Code V6061

Prepared for:
Division of Systems Analysis
Office of Nuclear Regulatory Research
U. S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

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.

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