Document: NRC Regulatory Guide
Document ID: c576d7be-9b19-4dd6-b001-ce0856ea4dc5
Document Type: regulatory_guide
Title: Design Response Spectra for Seismic Design of Nuclear Power Plants + HISTORY - HISTORY 01/2025 – Periodic Review of Revision 2 – Revise 10/2010 – Periodic Review of Revision 1 – No issues identified (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2504/ML25042A133.pdf
Revision Date: 2025-03
Chapter: 
Section ID: RG-1.60
CFR Part: 
CFR Title: 

Content:
Regulatory Guide Number: 1.60, Revision 2 Title: Design Response Spectra for Seismic Design of Nuclear Power Plants Office/division/branch: RES/DE/SGSEB Technical Lead: Scott Stovall Staff Action Decided: Revise 1. What are the known technical or regulatory issues with the current version of the Regulatory Guide (RG)? Regulatory Guide 1.60, Revision 2, “Design Response Spectra for Seismic Design of Nuclear Power Plants”, issued July 2014, describes an approach that the staff of the U.S. Nuclear Regulatory Commission (NRC) considers acceptable for defining response spectra for the seismic design of nuclear power plants. The current version of the regulatory guide (RG) provides a spectral shape for both horizontal and vertical design anchored to a ground acceleration of 1.0 gravity (g). NRC staff have identified the following in the RG that need to be assessed. • The horizontal spectral shapes defined in the current RG were developed using a select group of recorded earthquakes in the western United States (WUS) that occurred on or before 1971. Current studies for ground motion models in the central and eastern United States (CEUS) such as the EPRI (2004, 2006) Ground-Motion Model (GMM) Review Project (EPRI 2013) and Next Generation Attenuation for Central and Eastern North America (NGA-East, PEER 2018/08) show significant differences in the spectral shapes for the CEUS compared to the WUS. More specifically, spectral shapes in the CEUS display significantly higher ground motions for frequencies above 10 Hz. • The vertical ground motions, also developed using the same set of WUS earthquake ground motions, defined in RG 1.60 may be overly conservative leading to excessive design ground motions in the vertical direction resulting in adverse effects on soil structure interaction analyses. 2. What is the impact on internal and external stakeholders of not updating the RG for the known issues, in terms of anticipated numbers of licensing and inspection activities