Document: NUREG-0800
Document ID: 838f03f5-e038-48e3-9af7-74af5e319676
Document Type: srp
Title: through 3.5.3.3 for earth retaining walls).
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550054.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.5.3.1
CFR Part: 
CFR Title: 

Content:
of the fuel bundle and the fuel racks. Design and analysis procedures in accordance with this SRP, Subsection II, are acceptable. The effect on gaps, sloshing water, and increase of effective mass and damping resulting from submergence in water should be quantified. If the spent fuel racks are designed to be free standing (i.e., without connections to the pool walls/floor), then their response involves a complex combination of motions that includes sliding, rocking, and twisting and involves impacts between the fuel assemblies and the fuel cell walls, rack-to-rack, and rack-to-wall. In view of this, the seismic analysis of these fuel racks is typically performed using nonlinear dynamic time history analysis methods. NUREG/CR-5912 provides further guidance on the design and analysis of free-standing fuel racks. When pool walls are used to provide lateral restraint at higher elevations, the applicant should provide a determination of the flexibility of the pool walls and the capability of the walls to sustain such loads. If the pool walls are flexible (having a fundamental frequency less than 33 hertz), the floor response spectra corresponding to the lateral restraint point at the higher elevation are likely to be greater than those at the base of the pool. To use the response spectrum approach in such a case, the following two separate analyses should be performed: A. A spectrum analysis of the rack system using response spectra corresponding to the highest support elevation provided that there is not significant peak frequency shift between the response spectra at the lower and higher elevations B. A static analysis of the rack system by subjecting it to the maximum relative support displacement 3.8.4-32 Revision 2 - March 2007 The resulting stresses from the two analyses above should be combined by the absolute sum method. To determine the flexibility of the pool wall, it is acceptable for the applicant to use equivalent mass and stiffness properties obtained from