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:
analysis, the NRC developed guidance on PWR in-vessel debris evaluations, provided in “U.S. Nuclear Regulatory Commission Staff Review Guidance for In-Vessel Downstream Effects Supporting Review of Generic Letter 2004-02 Responses” (Ref. 9). For BWRs, the BWROG and the NRC staff performed deterministic and risk-informed analyses of the in-vessel issue. The NRC evaluation of the BWR in-vessel issue can be found in a staff technical evaluation issued May 2018 (Ref. 24). 1.3.9 Strainer Structural Analysis (This regulatory position also applies to trash racks and debris interceptors, if used.) 1.3.9.1 Items that should be considered in the structural analyses include (1) verification of maximum differential pressure caused by the combined clean strainer and worst-case debris scenario at rated flow rates or maximum realistic flow rates, whichever are greater, (2) geometry concerns (i.e., mesh and frame versus perforated plate), (3) ECCS strainer material selection for the post-accident environment (i.e., corrosion-resistant materials that can withstand the post-LOCA environment), and (4) hydrodynamic loads. 1.3.9.2 Licensees should compute structural loads on a strainer using the maximum pressure drop across the strainer. This is accomplished by evaluating the limiting conditions corresponding to the break location and debris source term that induce the maximum total head loss at the ECCS strainer. 1.3.9.3 For some licensees, the minimum structural design criterion for the ECCS strainer may depend on the plant’s NPSH margin. That is, the crush pressure of the strainer must support the required NPSH margin by ensuring that the strainer does not fail structurally before other parameters result in a failure. Plant-specific licensing bases may dictate the structural capacity of the ECCS strainer to support water flow through the strainer and debris bed under limiting flow rates. The criteria will depend on strainer geometry (i.e., fully submerged versus partially