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:
ense debris bed with low porosity that maximizes head loss. The thickness of the fiber layer necessary to filter fine particulate has not been generally defined, because it depends on several factors, including the strainer design, the strainer geometry and orientation, the approach velocity, the type and size of the fibrous debris, the type of particulate debris, and the presence of chemical effects. Appendix A, Section 6, in Ref. 13 provides testing methods acceptable to the NRC staff for evaluating thin-bed effects. c. Other testing and analyses have shown that the maximum debris loading case can also be a limiting head loss condition for strainers. Therefore, licensees should test for both the thin-bed and the maximum loading cases. If the maximum debris loading case could result in circumscribed debris accumulation, licensees should ensure that the strainer design and head loss test scaling account for this type of debris bed, which reduces the area through which the coolant flows. 1.3.11.1 Debris accumulation on the ECCS strainers for the head loss evaluation should be based on the amount of debris generated and the formation of different combinations of fibers and particulate mixtures (e.g., a fiber bed with a minimum thickness necessary to effectively filter particulate debris, as well as maximum debris loading), using the guidelines in DG-1385, Page 30 Section C.1.3.3, and on the debris transported to the strainers, in accordance with Section C.1.3.4. The evaluation should be based on plant-specific debris loads determined in accordance with these regulatory positions. 1.3.11.2 The degree of ECCS strainer submergence (full or partial) at the time of switchover to recirculation should be considered in calculating the available (wetted) screen area. For plants in which certain pumps take suction from the ECCS strainers before the switchover of other pumps, the NPSHa for these pumps should consider the submergence of the strainers at the time these pumps