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:
culations should be performed to ensure that the most limiting conditions are chosen and that the results are conservative. The calculation of NPSH margin should include head loss caused by debris, by subtracting the total debris-laden strainer head loss from the available hydraulic head. The total debris-laden strainer head loss, including chemical reaction products, should be determined by prototypical strainer testing. The strainer testing assumptions and methodology should be similar to those used for the resolution of Generic Safety Issue (GSI)-191, “Assessment of Debris Accumulation on PWR Sump Performance” (Ref. 11), and GL 2004-02, “Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors,” dated September 13, 2004 (Ref. 12). Section C of this guide and the document “NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing,” issued March 2008 (Ref. 13), discuss this issue in more detail. The analyses and testing for head loss effects should include all debris and chemical reaction products that are transportable to the ECCS strainer. Fine debris that is small enough to pass through the strainer should be included for head loss effects if it can be filtered by the debris bed on the strainer. ECCS components and flow restrictions inside the reactor vessel should be evaluated for erosion, wear, and blockage that may be caused by the debris and chemical precipitates that penetrate the strainers. Blockage of the ECCS strainer and other debris interceptors is a function of the types, combinations, sizes, shapes, and quantities of debris that can be transported to these components. The size of the openings in the strainer should be appropriate for any physical restrictions in the systems supplied with coolant from the ECCS sump, including openings in the containment spray nozzles, coolant channel openings in the core fuel