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:
Information is current. • The analysis is based on comprehensive data, including geological, seismological, and geophysical data, local site topography and historical information. RG 1.247, Page 34 • The analysis reflects the composite distribution of the informed technical community. • The level of analysis depends on the application and site complexity. • The hazard analysis considers uncertainties in characterizing the seismic sources and the ground motion propagation. Uncertainties should— o be properly accounted for, o be fully propagated, o allow estimates of fractile hazard curves and median and mean hazard curves, and o reflect uniform hazard response spectra. • Features of spectral shapes used in the seismic PRA include the following: o They should be based on a site-specific evaluation. o Broad-band, smooth spectral shapes for lower seismicity sites are acceptable if shown to be appropriate for the site. o Uniform hazard response spectra are acceptable if they reflect the site-specific shape. • The analysis should assess whether other seismic hazards should be included in the seismic PRA, such as fault displacement, landslide, soil liquefaction, or soil settlement. The objective of the seismic fragility analysis is to estimate the conditional probability of SSC failures at a given value of a seismic motion parameter, such as peak ground acceleration, peak spectral acceleration, and floor spectral acceleration. Seismic fragilities used in a seismic PRA are realistic and plant-specific based on actual current conditions of the SSCs in the plant for various POSs, as confirmed through a detailed walkdown of the plant. The fragilities of all the systems modeled in the event sequences for each POS are included. It is likely that a specific site would not be identified during the design phase. In addition, the actual current configuration of SSCs in the plant and its confirmation by a detailed physical walkdown of the plant may not be feasible