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:
nt, soil liquefaction, soil settlement, and earthquake-induced external flood. For all the various hazards, the objective is to estimate the probability or frequency of the hazard as a function of its intensity. The complexity of the hazard analysis depends on the complexity of the seismic situation at the site, as well as the ultimate intended use of the seismic PRA. When no prior study exists, the site-specific probabilistic seismic hazard should be generated. However, in many cases, an existing study can be used to develop the site-specific probabilistic seismic hazard. In a probabilistic seismic hazard analysis, an essential part of the methodology is the consideration of uncertainties associated with the randomness of events and the state of knowledge (i.e., aleatory and epistemic uncertainties). This typically results in the generation of a set of hazard curves, defined at specified fractile (confidence) levels and a mean hazard curve. It is likely that a specific site would not be identified during the design phase. In such a case, a representative or bounding site can be identified with justification that the site is either representative of or bounding for the anticipated sites for the reactor, and the seismic hazard analysis PRA analysis element discussed above should be applied to that representative or bounding site. Various plant POSs are expected to be evaluated using the same seismic hazard analysis. The characteristics and attributes needed to achieve the objectives of a seismic hazard analysis element are as follows: • The frequency of ground motion levels at a site is established. • A specific site is identified, or a representative or bounding site is identified with justification. • All credible sources of damaging earthquakes are examined. • 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