Document: NUREG-0800
Document ID: edf4dd70-2629-4e4a-a196-eb7b18beaf08
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1319/ML13198A223.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
ations, including the treatment of the stored water in internal water pools inside the structures. Other SRP 3.8.5 subsections provide guidance on seismic stability evaluations, foundation design, and maximum toe bearing pressures. However, the SRP does not provide specific guidance on permissible levels of foundation uplift to be considered in the SSI analysis and the foundation design. The staff performed the literature search and identified that only the Japanese codes specifically address foundation uplifting effect in design of nuclear facilities. The proposed SRP revision is based on Japanese design criteria, which presented a comprehensive set of criteria for assessing foundation uplift effect. The Japanese codes utilize the ground contact ratio concept. The ground contact ratio is defined as the ratio of the minimum area of the foundation in contact with the soil to the total area of the foundation. The seismic response computed over the entire duration of the seismic ground motion should be considered to determine the minimum value of this ratio. The proposed SRP revision sets a limit of 80 percent to the ground contact ratio to accept the results from the linear SSI analysis. The corresponding limit in the Japanese criteria is 75 percent (Section 3.5.5.4 in the Japanese design code JAEC 4601-2008). The proposed revision of SRP Section 3.7.2 addresses the validity of linear SSI analysis if some foundation uplift occurs. If the limit of 80 percent is not met then the nonlinearity due to the foundation uplift should be assessed, and if found important, then it should be accounted for in the seismic design, which is then reviewed on a case-by-case basis.