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:
the stresses resulting from the use of damping-compatible structural response will still be less than the applicable code stress limits, as defined in Section 3.8 of NUREG-0800 [Ref. 15]. However, for in-structure response spectra generation, it is necessary to use the damping-compatible structural response. Consequently, the following additional guidance is provided for analyses used to determine in-structure response spectra: (1) Use the OBE damping values specified in Table 2, which are acceptable to the staff without further review. (2) Submit a plant-specific technical basis for use of damping values higher than the OBE damping values specified in Table 2, but not greater than the SSE damping values specified in Table 1 (e.g., see NUREG/CR-6919, Section 3.2.3), subject to staff review on a case-by-case basis. In general, for certified standard plant designs where the design-basis in-structure response spectra represent the envelope of the in-structure responses obtained from multiple analyses conducted to consider a range of expected site soil conditions, it is not necessary for combined license applicants to address this issue. However, if plant-specific seismic analyses are conducted for Category I structures and/or structures not included as part of the standard plant design, then the applicant is expected to address this issue accordingly. Rev. 1 of RG 1.61, Page 6 2. Piping Damping Table 3 presents the constant damping values specified for SSE and OBE (where required) analyses of piping systems. These values are applicable to time-history, response spectra, and equivalent static analysis procedures for structural qualification. Table 3. Damping Values for Piping Systems Category Damping Value SSE OBE > SSE/3 Piping Systems 4% 3% As an alternative for response spectrum analyses using an envelope of the SSE or OBE response spectra at all support points (uniform support motion), frequency-dependent damping values shown in Figure 1 may be used, subject to the