Document: NRC Regulatory Guide
Document ID: 6f0a99f2-d25a-44e3-b7f2-3286449a9752
Document Type: regulatory_guide
Title: Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident (Rev. 5)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2126/ML21266A185.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.82
CFR Part: 
CFR Title: 

Content:
ool fill, licensees should provide an adequate theoretical and experimental basis to demonstrate that such settling is prototypical of plant conditions. This settlement analysis should account for the possibility that natural convection through the water column will provide a motive force to keep the material in suspension. 1.3.4.7 Rather than perform detailed analyses for each transport mode, licensees may conservatively assume that 100 percent of the debris being considered during a specific transport phase is transported. For example, they may assume that all debris generated is transported to the pool, or that all debris entering or originating in the sump or suppression pool is transported to the ECCS strainers. 1.3.4.8 The effects of floating or buoyant debris on the integrity of the ECCS strainers and on strainer head loss should be considered during the initial filling of the sump (if applicable) and during recirculation. For strainers that are not fully submerged or are only shallowly submerged, floating debris could contribute to the debris bed head loss. Floating debris could be deposited onto the strainer and remain there because of the flow through the strainer surface. Entrapped air may cause some types of debris to float temporarily; the debris may then be transported by surface currents to the vicinity of the ECCS strainers, where it may sink or be drawn to the top surface of the strainers. A design feature (e.g., use of trash racks and solid cover plate) that keeps floating debris from reaching the sump or suppression pool strainer could reduce head loss caused by floating or buoyant debris. DG-1385, Page 26 1.3.4.9 Use of Debris Interceptors a. Credit for the performance of debris interceptors upstream of the ECCS strainers should be based on results of tests that are demonstrated to be either conservative or representative of the plant conditions. b. If the interceptors are credited with capturing fine debris to reduce the ECCS strainer debris