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:
ould choose a suction strainer design (i.e., size and shape) that will prevent unacceptable loss of NPSH margin from debris accumulation during the period that the ECCS and CSS are required to operate to maintain long-term cooling. 1.1.1.9 Licensees should assess the possibility of debris clogging narrow flow passages downstream of the ECCS strainer, to ensure adequate long-term recirculation cooling, containment cooling, and containment pressure control capabilities. The size of the openings in the strainer should be determined by considering the flow restrictions of systems served by the containment pool. Licensees should consider the possibility that long, thin debris pieces will pass axially through the suction strainer, then reorient and clog downstream flow restrictions. 1.1.1.10 Licensees should consider the effects of debris and chemical reaction products at downstream locations, including containment spray nozzle openings, HPSI throttle valves, coolant channel openings in fuel assemblies, fuel assembly inlet debris screens, ECCS pump seals, bearings, and pump impeller clearances. The design of the ECCS pumps is a significant factor in the sensitivity of the pump operability to debris ingestion. Three aspects of pump operability— hydraulic performance, mechanical shaft seal assembly performance, and pump mechanical performance (vibration)—should be considered when evaluating the ECCS pumps for operation with debris-laden water. Westinghouse Commercial Atomic Power (WCAP)-16406-P-A, Revision 1, “Evaluation of Downstream Sump Debris Effects in Support of GSI-191,” 3 issued March 2008 (Ref. 31), and its SE (Ref. 32) provide evaluation methods and criteria that the NRC considers acceptable for ex-vessel downstream evaluations. If wear or internal blockage evaluations indicate that a component may not be able to fulfill its design function throughout its mission time, and that it is not practicable to install a suction strainer with openings small enough