Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
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:
pplicable significant seismic causes, initiating events, and seismic-induced SSC failures, as well as significant non-seismic failures and human errors. All POSs should be evaluated for differences in the seismic plant response analysis PRA analysis element. It is important that the walkdowns evaluate the differences between the different POSs that impact the plant response analysis. The characteristics and attributes needed to achieve the objectives of a seismic plant response analysis PRA analysis element are as follows: • The seismic PRA model for all POSs includes the following: o seismic-caused initiating events, RG 1.247, Page 36 o seismic-induced SSC failures, o non-seismic-induced unavailabilities, and o other significant failures (including human errors) that can contribute to seismic risk and radiological consequences. • The seismic PRA model is adapted to incorporate seismic analysis aspects that are different from the corresponding internal events PRA model. • The seismic PRA model reflects the as-designed or as-to-be built and as-to-be operated or as-built and as-operated plant being analyzed. • Quantification of risk metrics for each POS integrates the following: o the seismic hazard analysis, o the seismic fragilities analysis, and o the plant response logic analysis. • The uncertainties related to the seismic plant response model are identified and characterized. The seismic PRA model reflects the as-built and as-operated plant or the as-designed or the as-to-be built and as-to-be operated plant, as applicable in each stage. Assumptions used in seismic plant response analysis (e.g., screening out seismic-induced failures, human error event identification and development) should be clearly identified, documented, and tracked to ensure their continued validity across different stages. In meeting the technical characteristics and attributes for the seismic portion of an external hazard PRA, a seismic margins method is outside the scope of this