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:
abrasion of surfaces (e.g., pump running surfaces) and heat exchanger tubes and orifices, and (3) blockage of flowpaths through fuel assemblies. 1.3.8.2 The quantity and size characteristics of debris that penetrates the strainer will be unique to each strainer design and plant-specific debris mixture and should be determined during strainer head loss tests. WCAP-16406-P-A and the staff SE (Ref. 32) provide a method that the NRC considers acceptable for PWR licensees to use in evaluating the downstream impact of sump debris on the performance of their ECCSs, CSSs, and other components following a LOCA. Section C.1.3.12.7 discusses methods for evaluating the amount of debris that may pass downstream of the strainer. The NRC-approved Westinghouse report WCAP-16793-NP-A, Revision 2, gives a method for evaluating the impact of debris on fuel in the reactor vessel following a LOCA for PWR licensees whose plants are bounded by its assumptions, subject to the conditions and limitations specified in the NRC SE. The acceptance criteria for WCAP-16793-NP-A as originally approved by the NRC SE had a relatively low fiber limit. Some PWR licensees could not demonstrate that the amount of fiber entering the core was bounded by this acceptance limit. The Pressurized-Water Reactor Owners’ Group conducted a program of testing and analysis, which it submitted to the NRC for review and approval, to justify an increase the in-vessel fiber limits based on DG-1385, Page 28 plant-specific parameters. This program was ultimately documented in WCAP-17788-P, Revision 1. The NRC did not approve the topical report but considered that it provided significant information and understanding of the phenomena associated with debris in the reactor vessel. Based on the topical report and extensive staff analysis, the NRC developed guidance on PWR in-vessel debris evaluations, provided in “U.S. Nuclear Regulatory Commission Staff Review Guidance for In-Vessel Downstream Effects Supporting Review of