Document: NUREG-0800
Document ID: c12e6057-2586-4b17-91eb-dad71349982d
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:
Revision 4 – September 2013 and associated data become available to better quantify the in-structure response reductions due to ground motion incoherency effects. The EPRI performed analytical studies which formed the basis for the staff’s guidance in DC/COL-ISG-01. These studies compared coherent ISRS results to incoherent ISRS results, based on the NRC-accepted coherency function. The structural model used has stick model representations of the AP1000 steel containment vessel, shield building, and containment internal structures, sitting on a large basemat. Review of the comparisons indicated that the ISRS are generally similar up to about 10 Hz. Above 10 Hz, there is generally a gradually increasing difference. Above 30 Hz, differences as high as 40-50 percent can be observed. The staff has accepted this level of reductions on a case-by-case review along with independent confirmatory analysis. Based on the uncertainties associated with the coherency function described above and the limited experience in its implementation to date, the staff has determined that it is reasonable to impose limits on the maximum acceptable reductions between coherent results and incoherent results. These reductions generally are in line with the Electric Power Research Institute (EPRI) studies. It should be noted that the proposed criteria allows for larger ISRS reductions than the specified limits if sufficient technical information is provided to support the larger reductions. The staff reviews and accepts the technical justifications for larger reductions on a case-by-case basis. 8. Enhanced SRP Section 3.7.2 II.8 “Interaction of Non-Seismic Category I Structures with seismic Category I SSCs” by revising acceptance criteria related to Criterion C. The technical rationale for this change is as follows. The objective of Criterion C is to demonstrate that failure under SSE conditions will be prevented. What constitutes “failure” is dependent on the proximity of the