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:
spect to penetration that could occur in the plant. Penetration testing is conducted only for fibrous debris. In general, head loss testing guidance applies to penetration testing. Penetration testing usually involves only fine fibers, which are introduced in small batches to prevent formation of a filtering bed faster than might occur in the plant. If larger debris is included, it should be introduced after the fines. Particulate debris is generally excluded, because it is difficult to separate it from fibrous debris when quantifying penetration. A test may attempt to determine the maximum amount of fiber that may penetrate the strainer, or to determine a load-dependent fiber penetration curve. The latter is done by batching in fiber while collecting fiber downstream of the strainer, allowing time for the system to stabilize, collecting the penetrated fiber from that batch, aligning a new collection filter, then repeating the process. These steps may be iterated several times; the results can be used to generate a penetration model that is dependent on fiber load at the strainer. Load-dependent models may be useful in determining the amount of fiber that reaches the core if credit is taken for flow through the CSS, if different fiber load cases are considered, or if other scenarios require analysis of penetrated fiber. Penetrated debris should be collected in full flow filters. If incremental penetration data are desired, the system and test procedure should allow for swapping of collection filters without perturbing the flow rate through the test strainer. Filters should be fine enough to collect all penetrated fiber. Penetration testing and its extrapolation to the plant strainer should consider flow velocity through the strainer and the velocity profile through the strainer. Testing and extrapolation to the plant scale should also consider sacrificial strainer area, the number of strainers in service, and the flow through each strainer. In general, testing