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:
us meetings and reviews of licensing issues. Nuclear industry groups and licensees have suggested that the NRC ought to accept more realistic damping values for seismic design and analysis of SSCs, in place of the damping values provided in the original Regulatory Guide 1.61. Structural Damping In 1993, the NRC completed an investigation of the adequacy of original Regulatory Guide 1.61 structure damping values and other recommendations, and reported the results in NUREG/CR-6011 [Ref. 3]. Data were analyzed to identify the parameters that significantly influenced structure damping. Based on that study, the NRC determined that the original Regulatory Guide 1.61 damping values for structure design were adequate but required one significant revision. Specifically, Regulatory Guide 1.61 should distinguish between “friction-bolted” and “bearing-bolted” connections for steel structures. Friction-bolted connections are also referred to as “slip-critical” connections. In these connections, the bolt preload is high enough to ensure that friction is not overcome, and the bolt does not experience shear loading. Regulatory Position 1 in Section C of this revised guide provides the updated structural damping values. Rev. 1 of RG 1.61, Page 3 Piping Damping In 1986, the American Society of Mechanical Engineers (ASME) established Code Case N-411, “Alternative Damping Values for Response Spectra Analysis of Class 1, 2, and 3 Piping,” in Section III, Division 1, of the ASME Boiler and Pressure Vessel Code [Ref. 4]. The NRC staff used Code Case N-411, with certain limitations specified in Regulatory Guide 1.84 [Ref. 5], to review operating reactor issues until Code Case N-411 expired in 2000. The staff also approved the use of alternate damping values for the General Electric Advanced Boiling Water Reactor Design in 1994 [Ref. 6], Combustion Engineering System 80+ Design in 1992 [Ref. 7], and Westinghouse AP600 Design in 1998 [Ref. 8]. Regulatory Position 2 in Section