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:
e ingestion do not prevent the components from performing their required functions. The assessment should include abrasive effects to ensure that long-term degradation of the equipment does not occur. 1.3.1 Net Positive Suction Head of the Emergency Core Cooling System and Containment Heat Removal Pumps 1.3.1.1 The design of the ECCS and containment heat removal system should ensure that sufficient NPSHa is provided to the system pumps, assuming the maximum expected temperature of the pumped fluid and no increase in containment pressure from that present before the postulated LOCA. Appendix B implements the staff requirements memorandum for SECY-11-0014, “Staff Requirements—SECY-11-0014—Use of Containment Accident Pressure in Analyzing Emergency Core Cooling System and Containment Heat Removal System Pump Performance in Postulated Accidents,” dated March 15, 2011 (Ref. 37), by providing guidance on the use of CAP for determining the NPSH margin for the ECCS and containment heat removal pumps in BWRs and PWRs. DG-1385, Page 20 a. It is conservative to assume that the containment pressure equals the vapor pressure of the pool water. This ensures that credit is not taken for containment pressurization during the transient. b. For PWR sub-atmospheric containments, this guidance should apply after termination of the injection phase. For these sub-atmospheric containments, before termination of the injection phase, NPSH analyses should include conservative predictions of the containment atmospheric pressure and sump water temperature as a function of time. 1.3.1.2 For certain operating reactors in which it is not practicable to alter the design, conformance with Section C.1.3.1.1 may not be possible. In these cases, the determination of NPSHa should not include containment pressure above that which is necessary to preclude pump cavitation. In the determination of NPSHa for this situation, the calculation of available containment pressure and sump/pool water