Document: NRC Regulatory Guide
Document ID: cde52d5a-adf9-49be-9d1f-59449dfca895
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
ally for the hazard group under consideration. The risk integration PRA element is an aspect of PRA acceptability that addresses the integration of all risk contributors from all radiological sources, hazards, POSs, and levels of PRA analysis. The staff did not develop a staff position in RG 1.200 on the risk integration PRA element as it relates to LWR PRA acceptability; however, the staff is promulgating a position in this RG on risk integration as it relates to NLWR PRA acceptability given the scope of the ASME/ANS NLWR PRA standard and to address the needs of regulatory submittals. C.1.3.1 Plant Operating States Analysis Probabilistic Risk Assessment Element This section identifies the objectives and the characteristics and attributes of the POS analysis for an NLWR PRA that addresses all radiological sources, all hazards, and all levels of PRA analysis. The objectives of the POS analysis PRA element are to identify operating evolutions (e.g., full-power, LPSD types of conditions) important to risk and parse them into distinct operating states in which the plant conditions are assumed to be relatively constant. Since the POS analysis PRA element defines the structure of the NLWR PRA, all POSs and the key attributes of the plant conditions in the POSs should be clearly documented in a format (e.g., table or chart) to facilitate understanding of the NLWR PRA results by an independent reviewer. As a plant transitions from design to operation, POS definitions and assumptions used in the PRA for licensing should be reevaluated and modified with as-operated details. The characteristics and attributes needed to achieve the objectives of a POS analysis PRA element are as follows: • For each plant evolution addressed in the PRA, a set of POSs that represent distinct and relatively constant plant conditions is identified and characterized. • LPSD plant evolutions are divided into POSs based on differences in plant response to initiating events in a given POS to