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:
hen the suction pressure or the NPSHa is decreased from the value corresponding to cavitation inception, the region of cavitation grows. If the decrease in NPSHa is significant, then noise, cavitation erosion of pump parts (mainly the impeller), and pump performance degradation will occur. Figure B-1 Illustration of NPSH test with flow rate held constant DG-1385, Appendix B, Page B-3 B-2 The Role of Emergency Core Cooling System and Containment Heat Removal Pumps Boiling-Water Reactor Pumps The boiling-water reactor (BWR) pumps for which licensees may use CAP in determining the NPSH margin are the residual heat removal (RHR) system and core spray (CS) system pumps. The RHR pumps are typically single-stage, high-capacity, low-discharge-head pumps. They have several modes of operation, including but not limited to the following: • cooling of the reactor coolant system during normal reactor shutdown • suppression pool cooling during normal plant operation if heat is added to the suppression pool • emergency coolant injection into the reactor vessel following a loss-of-coolant accident (LOCA) • suppression pool cooling following a postulated accident (e.g., LOCA) or special event (e.g., Appendix R fire, station blackout (SBO), or anticipated transient without scram (ATWS)) • CS (drywell spray and wetwell spray) for containment cooling and fission product removal During normal operation, the RHR pumps are in standby and configured for safety injection. They may be operated for suppression pool cooling during normal operation and for surveillance testing in accordance with the American Society of Mechanical Engineers (ASME) Code and the plant’s technical specifications (TS). BWR CS pumps are typically single-stage, low-head, high-flow-rate pumps. Their function is to spray water from the suppression pool into the core following a LOCA. During normal operation, they are in standby except for surveillance testing in accordance with the ASME Code and the