United States Nuclear Regulatory Commission - Protecting People and the Environment

Regulatory Effectiveness of Unresolved Safety Issue (USI) A-45, "Shutdown Decay Heat Removal Requirements" (NUREG/CR-6832)

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Publication Information

Manuscript Completed: July 2003
Date Published: August 2003

Prepared by:
S.A. Faridi, R.W. Youngblood, B.B. Mrowca, F. Zikria, J.F. Meyer
Information Systems Laboratories, Inc.
11140 Rockville Pike, Suite 500
Rockville, Maryland 20852

J.V. Kauffman, NRC Technical Monitor

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

NRC Job Code Y6406

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Abstract

As part of the U.S. Nuclear Regulatory Commission's program to assess regulatory effectiveness, the Office of Nuclear Regulatory Research has examined regulations such as the station blackout rule, and anticipated transient without scram rule. As part of this program, the Office of Nuclear Regulatory Research is also reviewing the effectiveness of generic safety issue resolution. One such issue currently being reviewed is Unresolved Safety Issue (USI) A-45 to determine if the requirements are achieving the desired outcomes. It is anticipated that the results of these reviews can be used to improve the effectiveness of NRC requirements and guidance, staff inspection guidance, and oversight decision processes for NRC licensee performance. This report evaluates the effectiveness of the USI A-45 resolution by comparing USI A-45 expectations to outcomes. A set of baseline expectations was established from NUREG-1289, "Regulatory and Backfit Analysis: Unresolved Safety Issue A-45, Shutdown Decay Heat Removal Requirements," November 1988, and NUREG/CR-5230, "Shutdown Decay Heat Removal Analysis: Plant Case Studies and Special Issues," April 1989, and the actual outcomes were obtained from the individual plant examinations and individual plant examination of external events in the areas of total core damage frequency, decay heat removal risk categories and decay heat removal vulnerability. The report concludes that the USI A-45 program expectation regarding decay heat removal-related contribution to core damage frequency was generally met without the imposition of generic hardware fixes expressly for USI A-45. In addition, it is likely that licensees' awareness of the significance of decay heat removal strategies was fostered through the conduct of the individual plant examinations and individual plant examination of external events. Therefore, the USI A-45 resolution approach appears effective in achieving its goals.

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