Regulatory Effectiveness of Unresolved Safety Issue (USI) A-45, 'Shutdown Decay Heat Removal Requirements'

摘要

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.