Document: NUREG-0800
Document ID: 228b9b6e-c81e-4d76-9b8e-12f6c3bd7fa1
Document Type: srp
Title: and Regulatory Guide 1.92,(Reference 10) "Combining Modal Responses
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070336.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
thods For all Category I systems, components, equipment and their supports (including supports for conduit and cable trays, and ventilation ducts), the applicable methods of seismic analysis (response spectra, time history, equivalent static load) are reviewed to ascertain that the techniques employed are in accordance with the acceptance criteria as given in subsection II.2.a of this SRP section. Common industry practice is to assume rigid and fixed attachments between the seismic subsystems (i.e., equipment and piping) and the supporting seismic systems (i.e., structures). This assumption allows the influence of the anchorage system stiffness on the dynamic response to be neglected. In some cases, particularly for heavy equipment, this assumption can potentially result in under- estimation of seismic loadings. For new applications, the reviewer should verify that appropriate assumptions have been made with regard to the stiffness of the seismic subsystem anchorage in the seismic analyses.57 b. Determination of Number of Earthquake Cycles Criteria or procedures used to establish the number of earthquake cycles are reviewed to determine that they are in accordance with the acceptance criteria as given in subsection II.2.b of this SRP section. Justification for deviating from the acceptance criteria is requested from the applicant, as necessary.The number of earthquake cycles during one seismic event, the maximum number of cycles for which applicable systems and components are designed, and the criteria and procedures used by the applicant to establish these parameters are reviewed by the staff in accordance with the guidance in SRP Section 3.7.3.58 c. Basis for Selection of Frequencies As applicable, criteria or procedures used to separate fundamental frequencies of components and equipment from the forcing frequencies of the support structure are reviewed to determine compliance with the acceptance criteria of subsection II.2.c of this SRP section. d. Three