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:
ough the strainer and any associated connecting pipes and plenums) should consider the distribution of flow through the strainer that produces the highest head loss. For some curvilinear-type strainer designs, this occurs with a filtering debris bed near the strainer outlet and a clean strainer where the unobstructed flowpath is longer. If the strainer were partially covered with a filtering debris bed, much of the strainer flow could occur through the unblocked strainer surfaces, which could be more limiting for some designs. 1.3.1.8 Licensees should refer to Sections C.1.3.10 and C.1.3.11 for guidance on determining strainer head loss caused by blockage from LOCA-generated debris and its chemical reaction products or from foreign material in the containment that is transported to the suction intake screens. 1.3.1.9 Licensees should calculate NPSHa as a function of time until it is clear that the NPSHa will not decrease further. 1.3.2 Pipe Break Selection a. Licensees should consider a sufficient number of high-energy pipe break locations that could result in ECCS recirculation, so that variations in debris size distributions, quantity, and types are bounded. The objective of the break selection process is to identify the break location and size that results in debris generation that produces the maximum head loss across the sump screen. Licensees should consider all aspects of the accident scenario for each postulated break location, including debris generation, debris transport, latent debris, coating debris, chemical effects, upstream and downstream effects of debris accumulation, and sump screen head loss. b. The objective of strainer head loss testing is to simulate the debris from the break location that transports the maximum amount of debris or the combination of debris types that produces the maximum head loss to the sump strainer. At a minimum, licensees should consider the postulated break locations and pipe break characteristics described in the