Document: NUREG-0800
Document ID: 215ec1da-bdbb-48d3-b871-6010c1f4bc55
Document Type: srp
Title: SEISMIC SUBSYSTEM ANALYSIS REVIEW RESPONSIBILITIES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1319/ML13198A239.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.3
CFR Part: 
CFR Title: 

Content:
.4. These references also contain acceptable calculation techniques for the implementation of these criteria. The use of other approaches meeting the intent of these criteria can also be considered if adequate justification is provided. A. A minimum acceptable analysis should incorporate at least two horizontal modes of combined fluid-tank vibration and at least one vertical mode of fluid vibration. The horizontal response analysis should include at least one impulsive mode in which the response of the tank shell and roof are coupled together with the portion of the fluid contents that moves in unison with the shell. In addition, the fundamental sloshing (convective) mode of the fluid should be included in the horizontal analysis. B. The fundamental natural horizontal impulsive mode of vibration of the fluid-tank system should be estimated giving due consideration to the flexibility of the supporting medium and to any uplifting tendencies for the tank. It is unacceptable to assume a rigid tank unless the assumption can be justified. The horizontal impulsive-mode spectral acceleration, Sa1, is then determined using this frequency and the appropriate damping for the fluid-tank system. Alternatively, the maximum spectral acceleration corresponding to the relevant damping may be used. C. Damping values used to determine the spectral acceleration in the impulsive mode should be based upon the system damping associated with the tank shell material as well as with the SSI, as specified in NUREG/CR-1161 and Veletsos and Tang (1989). D. In determining the spectral acceleration in the horizontal convective mode, Sa2, the fluid damping ratio should be 0.5% of critical damping unless a higher value can be substantiated by experimental results. E. The maximum overturning moment, Mo, at the base of the tank should be obtained by the modal and spatial combination methods discussed in Subsection II of SRP Section 3.7.2. The uplift tension resulting from Mo should be resisted either