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:
separate tests to credit reductions in debris transport to the strainer (i.e., settling) under conditions that are conservatively or prototypically scaled to the plant conditions. Head loss or debris settlement testing that credits or evaluates lack of transport due to settling should include careful evaluation of the flow characteristics (e.g., velocity and turbulence) in the test to ensure that the simulated flows are prototypical or conservative with respect to the plant conditions. In evaluating how potential accumulation of debris in areas of flow restrictions may affect debris transport, licensees should consider scaling of debris per unit area of floor in the flume versus debris per unit floor area of the plant. The quantity of debris per unit width of the flume relative to the flow passages in the plant is another important scaling parameter. Licensees should also consider the adequacy of other aspects of the test protocol, such as debris preparation, addition sequencing, debris concentration in the flume, and test flume geometry, when designing tests. They should ensure that the amounts of debris settling in the plant containment will be similar to or larger than the amounts in the test. They should also consider how debris settlement during a head loss test could affect other aspects of the analysis. For example, allowing debris settlement in the test tank may not account for erosion of the settled debris in the analysis. Because it is impractical to simultaneously scale the multiple complex phenomena associated with debris transport and head loss in a rigorous way, licensees should apply conservatism to tests that model both transport and head loss. Section 5.7.4 of NUREG/CR-7172 provides more details on this topic. 1.3.12.7 Licensees may sample the flows downstream of the test strainer to determine the amount of debris passing through the strainer. The sampling should be performed with a frequency that ensures adequate characterization of the total