Document: NRC Regulatory Guide
Document ID: b6726dc6-2968-4ca9-a925-c831eaaecc69
Document Type: regulatory_guide
Title: 03/2007
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0702/ML070260029.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.61
CFR Part: 
CFR Title: 

Content:
ff used in the seismic response analysis of Seismic Category I nuclear power plant structures, systems, 1 and components (SSCs) in accordance with Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50), “Domestic Licensing of Production and Utilization Facilities” [Ref. 1]. Specifically, General Design Criterion 2, “Design Bases for Protection Against Natural Phenomena,” of Appendix A, “General Design Criteria for Nuclear Power Plants,” to 10 CFR Part 50 requires that SSCs important to safety be designed to withstand the effects of natural phenomena such as earthquakes without losing the ability to perform their safety functions. Such SSCs must also be designed to accommodate the effects of and be compatible with the environmental conditions associated with normal operation and postulated accidents. Appendix S, “Earthquake Engineering Criteria for Nuclear Power Plants,” to 10 CFR Part 50 specifies the requirements for the implementation of General Design Criterion 2 with respect to earthquakes.2 Rev. 1 of RG 1.61, Page 2 This regulatory guide specifies the damping values that the NRC staff considers acceptable for complying with the agency’s regulations and guidance for seismic analysis. The specified damping values are intended for elastic modal dynamic seismic analysis where energy dissipation is accounted for by viscous damping (i.e., the damping force is proportional to the velocity). This regulatory guide contains information collections that are covered by the requirements of 10 CFR Part 50, which the Office of Management and Budget (OMB) approved under OMB control number 3150-0011. The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number. B. DISCUSSION Background Damping is a measure of the energy dissipation of a material or structural system as it responds to dynamic