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:
stems, and strut-type cantilever and braced cantilever support systems) is permissible, subject to obtaining NRC review for acceptance on a case-by-case basis. The analysis methodology should consider the flexibility of supports in determining the system response to seismic excitation. Rev. 1 of RG 1.61, Page 8 Table 4. Damping Values for Electrical Distribution Systems Category Damping Value SSE OBE > SSE/3 Cable Tray System4 Maximum Cable Loading1 Empty2 Sprayed-on Fire Retardant or other cable-restraining mechanism3 10% 7% 7% 7% 5% 5% Conduit Systems4 Maximum Cable fill1 Empty2 7% 5% 5% 3% Notes: 1. Maximum cable loadings, in accordance with the plant design specification, are to be utilized in conjunction with these damping values. 2. Spare cable tray and conduit, initially empty, may be analyzed with zero cable load and these damping values. (Note: Re-analysis is expected when put into service.) 3. Restraint of the free relative movement of the cables inside a tray reduces the system damping. 4. When cable loadings of less-than maximum are specified for design calculations, the applicant or licensee is expected to justify the selected damping values and obtain NRC review for acceptance on a case-by-case basis. 4. Heating, Ventilation, and Air Conditioning Duct Damping Table 5 presents the constant damping values specified for SSE and OBE (when required) analyses of HVAC duct systems. These values are applicable to response spectra and equivalent static analysis procedures for structural qualification. The analysis methodology must consider the flexibility of supports in determining system response to seismic excitation. Table 5. Damping Values for HVAC Duct Systems Type of Duct Construction Damping Value SSE OBE > SSE/3 Pocket Lock 10% 7% Companion Angle 7% 5% Welded 4% 3% Rev. 1 of RG 1.61, Page 9 5. Mechanical and Electrical Component Damping Table 6 presents the damping values for mechanical and electrical components, which are applicable to passive