Document: NRC Regulatory Guide
Document ID: cfc61809-5745-460f-8a26-13c168659924
Document Type: regulatory_guide
Title: Identification and Characterization of Seismic Sources and Determination of Safe Shutdown Earthquake Ground Motion
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740084.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.165
CFR Part: 
CFR Title: 

Content:
s determining whether the new information is consistent with the fol lowing LLNL and EPRI parameters: (1) the range of seismogenic sources as interpreted by the seismicity experts or teams involved in the study, (2) the range of seismicity rates for the region around the site as inter preted by the seismicity experts or teams involved in the studies, and (3) the range of maximum magnitudes determined by the seismicity experts or teams. The new information is considered not significant and no further evaluation is needed if it is consistent with the assump tions used in the PSHA, no additional alternative seis mic sources or seismic parameters are needed, or it sup ports maintaining or decreasing the site median seismic hazard. An example is an additional nuclear unit sited near an existing nuclear power plant site that was recently investigated by state-of-the-art geosciences techniques and evaluated by current hazard methodologies. De tailed geological, seismological, and geophysical site specific investigations would be required to update ex isting information regarding the new site, but it is very unlikely that significant new information would be found that would invalidate the previous PSHA. On the other hand, after evaluating the results of the site-specific investigations, if there is still uncertainty about whether the new information will affect the esti mated hazard, it will be necessary to evaluate the 1.165-39 I I potential impact of the new data and interpretations on the median of the range of the input parameters. Such new information may indicate the addition of a new seismic source, a change in the rate of activity, a change in the spatial patterns of seismicity, an increase in the rate of deformation, or the observation of a relationship between tectonic structures and current seismicity. The new findings should be assessed by comparing them with the specific input of each expert or team that par ticipated in the PSHA. Regarding a new source, for