Document: NUREG-0800
Document ID: e7548e72-8c59-4c82-98dd-ff425e1de29a
Document Type: srp
Title: SEISMIC DESIGN PARAMETERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12352A305.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.1
CFR Part: 
CFR Title: 

Content:
s between the design features, analytical techniques, and procedural measures proposed for its facility and the SRP acceptance criteria and evaluate how the proposed alternatives to the SRP acceptance criteria provide acceptable methods of compliance with the NRC regulations. 1. Design Ground Motion A. Design Response Spectra. The site-specific GMRS reviewed under SRP Section 2.5.2 are determined in the free-field on the ground surface. For sites with soil layers near the surface that will be completely excavated to expose competent material, the GMRS is specified on an outcrop or a hypothetical outcrop that will exist after excavation. Motions at this hypothetical outcrop should be developed as a free surface motion, not as an in-column motion. Although the definition of competent material is not mandated by regulation, a number of reactor designs have specified a shear wave velocity of 1000 fps as the definition of competent material, which is considered acceptable. If non- 3.7.1-8 Draft Revision 4 - December 2012 competent material is present, any excavation and/or backfilling should not alter the development or location of the site-specific GMRS. However, the soft soil or backfill material needs to be considered in the SSI or other analyses. Additional guidance on the development of the GMRS on the ground surface or as free-field outcrop motions and the GMRS at the foundation level in the free-field, referred to as the foundation input response spectra (FIRS), is provided in ISG-01 and ISG-17. According to Appendix S to 10 CFR Part 50, the minimum peak ground acceleration (PGA) for the horizontal component of the SSE at the foundation level in the free-field should be 0.1g or higher. The response spectrum associated with this minimum PGA should be a smooth broad-band response spectrum (e.g., RG 1.60, or other appropriate shaped spectra if justified) and is defined as an outcrop response spectrum at the free-field foundation level. This response spectrum anchored