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:
and functionality, the top of the ECCS strainer structures should be a solid cover plate that is designed to be fully submerged after a LOCA and completion of the ECCS injection phase. The cover plate protects the strainer from LOCA-generated loads and from water drainage from upper containment. The design should also provide a means for venting any air trapped under the cover. 2.2 Chemical Reaction Effects 2.2.1 For PWRs, the Westinghouse report WCAP-16530-NP-A and the limitations discussed in the associated SE (Ref. 36) provide an acceptable approach to evaluating chemical effects that may occur in a post-accident containment sump pool. 2.2.2 Plant-specific information should be used to determine the projected post-LOCA chemical precipitate quantity. The plant-specific chemical effects evaluations should use a conservative analytical approach. The report “NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Plant-Specific Chemical Effect Evaluations” (Ref. 48) provides a general approach to these evaluations for PWR licensees. 2.2.3 WCAP-16793-NP-A and its SE (Ref. 33) provide guidance for evaluation of chemical debris within the reactor for those PWRs in which a limited amount of fibrous debris reaches the core inlet. In addition to the acceptance criterion for fiber mass limit per fuel assembly, evaluations using WCAP-16793-NP-A also determine deposition thickness on the fuel rods and the resulting peak clad temperature. Another method of evaluating the effects of fibrous debris, particulate, and chemical precipitates in the reactor vessel can be found in WCAP-17788-P, Revision 1. Volume 5 of WCAP-17788-P, Revision 1, was not approved by the NRC but nevertheless contains considerable information on the timing of chemical precipitates based on simulated plant-specific post-LOCA environments. The memorandum “U.S. Nuclear Regulatory Commission Staff Review Guidance for In-Vessel Downstream Effects Supporting Review of Generic