Document: NUREG-0800
Document ID: e32f0820-4e33-476e-aa36-4ca8c2c64af0
Document Type: srp
Title: Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking:
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0119/ML011940192.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
structure and particular features of the core damage sequences that characterize that plant type. Based on these insights, draft NUREG/CR-6595 presents a screening approach to evaluate the frequencies of dominant containment failure modes and bypass events. The purpose of this approach is to provide estimates of LERF, given certain characteristics of core damage sequences as input. The review approach presented in this SRP section builds upon the underlying insights from draft NUREG/CR-6595. For each major containment type, particular considerations are suggested for attention ii the review process. However, it is not intended to suggest that these considerations exhaust the technical issues that affect the potential for large early release. For example, where plant-specific PRA Level 2 analyses exist, these could provide further insights into LERF considerations for that plant. For each major containrment type, the factors that most strongly affect the potential for large early release (given that a core damage sequence is underway) are as follows: PWR Large Dry: Containment bypass Containment isolation RCS depressurization Emergency core cooling (ECC) restoration before vessel failure PWR Ice Condenser: Containment isolation Containment bypass Hydrogen igniters RCS depressurization ECC restoration before vessel failure BWR Mark I and 11: Containment isolation Containment bypass Ven ring Containment heat removal: decay heat Containment heat removal: ATWS RCS depressurization ECC restoration before vessel failure BWR Mark IIl: All Mark I and Mark I issues lgn ýlers It should be noted that, at some BWRs, many sequences that result in vessel breach have a significant probability ol also failing the containment. Also, the reader should note that a loss of containment heat removal may significantly contribute to CDF. In reviewing the calculation of change in LERF for a given plant type, reviewers should consider the following factors: SRP 19-A22 Containment Bypass: *