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:
ees may demonstrate that the pump can be secured by operator action before significant effects on debris transport and strainer performance occur. 1.3.12.9 The time dependence of debris arrival at the strainer is difficult to model in a practical number of head loss tests. A conservative assumption is that all of the LOCA debris is present on the strainer at the beginning of recirculation. This debris should include that generated from the LOCA blowdown, failed unqualified coatings, eroded fine debris, chemical precipitates, and all other debris predicted to be transported to the strainer. Licensees may be able to demonstrate that the arrival of some debris will be delayed and account for this in the analyses. 1.3.12.10 In some cases, head loss testing for complex combinations of debris that typically result from limiting plant debris loads has shown significant variation for the same debris loading. Licensees should therefore ensure that head loss test results have been demonstrated to be sufficiently repeatable, in light of known margins, uncertainties in debris quantities, the collective body of knowledge from tests on similar strainers, and other relevant information. 1.3.12.11 Debris introduction procedures should consider the fact that variations in the sequence and rate of debris introduction can affect the head loss measurement. One acceptable approach is to introduce the debris slowly into the test tank with the pump running and prototypical hydraulic conditions established. The most transportable debris should be added first and the least transportable last. Licensees may also use other approaches, if justified. Testing that takes credit for nearfield settlement should either realistically or conservatively simulate the strainer upstream flow and turbulence conditions. Licensees should conduct a proper analytical evaluation of the similarity of the test tank and the actual plant conditions. The NRC staff considers CFD codes to be useful tools in such