Core Damage Frequency Estimation Using Accident Sequence Precursor Data: 1990-1993

摘要

The Nuclear Regulatory Commission's (NRC's) ongoing Accident Sequence Precursor (ASP) program uses probabilistic risk assessment (PRA) techniques to assess the potential for severe core damage (henceforth referred to simply as core damage) based on operating events. The types of operating events considered include accident sequence intiators, safety equipment failures, and degradation of plant conditions that could increase the probabilitythat various postulated accident sequences occur. Such operating events potentially reduce the margin of safety available for prevention of core damage and thus can be considered as precursors to core damage. The current process for identifying, analyzing, and documenting ASP events is described in detail in Vanden Heuval et al[1]. The significance of a Licensee Event Report (LER) event (or events) is measured by means of the conditional probability that the event leads to core damage, the so-called conditional core damage probability or, simply, CCDP.