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:
luating Emergency Core Cooling System Strainer Failure The applicable ECCS strainer failure criteria depend on several factors, including submergence and structural strength, and may be pump or system dependent. Figures A-3a, A-3b, and A-3c illustrate the three basic strainer configurations for fully submerged, partially submerged, and vented strainers. Although these figures show only vertical strainers with configurations that appear more consistent with PWR plants, the same designations generally apply to other strainer designs, including those used for BWRs. The key distinction between the fully and partially submerged configurations is that partially submerged or vented strainers allow equal pressure above the water surface on both sides of the strainer. Fully submerged strainers have a complete seal of water between the pump inlet and the containment atmosphere along all water paths passing through the sump screen. The following sections describe the effect of this difference on the evaluation of the sump failure criterion. (The reader should also refer to NUREG/CR-6762, Volume 1, Section 1.4.) For all of these configurations, entrainment of gases or voids at the pump suction should be evaluated. Note that vortexing may occur inside a vented or partially submerged strainer. 2 The value of 1.7 represents the mutual judgment of industry and Office of Nuclear Reactor Regulation staff representatives. See Section 1.4 of “Guidance to NRC/NRR/DSS/SRXB Reviewers for Writing Temporary Instruction (TI) 2515/177 Suggestions for the Region Inspections,” Revision 11, dated May 23, 2011 (Ref. A-7), for additional information and qualification. DG-1385, Appendix A, Page A-9 A-4.1 Fully Submerged Sump Strainers Figure A-3a presents a schematic of a fully submerged strainer. Potential failure modes considered for systems with this strainer configuration include (1) structural failure of the strainers caused by excessive differential pressure and (2) cavitation of the pump