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:
ance described below should be used in a plant-specific evaluation to ensure that any implementation of a combination of the features and capabilities listed in Section C.1.1 is adequate to ensure the availability of a reliable water source for long-term recirculation following a LOCA. These assumptions and guidance can also be used to develop conditions for suction strainer testing. b. To ensure that long-term recirculation cooling can be accomplished following a LOCA, licensees should evaluate (1) ECCS strainer hydraulic performance (e.g., geometric effects, air ingestion, flashing, and gas void accumulation), (2) debris effects (e.g., break selection, debris generation, debris transport, latent debris, chemical precipitation, upstream effects, downstream effects, interceptor blockage, strainer head loss, and structural integrity), and (3) the combined impact on NPSHa at the pump inlet. Such an evaluation should demonstrate adequate strainer and pumping performance (e.g., adequate pump NPSH margins, adequate strainer structural strength, and no excessive air ingestion). Licensees should also assess the susceptibility of the containment drainage flowpaths to the recirculation sump or suppression pool to debris blockage. A holdup of water assumed to reach the pool could affect the NPSHa, flashing, and/or air ingestion evaluations. In addition, licensees should assess the structural adequacy of any interceptors or trash racks used to prevent debris blockage of these flowpaths to protect against a reduction in NPSHa if substantial amounts of water are held up or diverted away from the sump or suppression pool. Licensees should also assess the potential for failure of the flowpaths and components downstream of the strainers, to ensure that debris blockage and particulate ingestion do not prevent the components from performing their required functions. The assessment should include abrasive effects to ensure that long-term degradation of the equipment does not occur.