Document: NRC Regulatory Guide
Document ID: 4a6ff506-3e14-471e-90ad-8c6b7081650a
Document Type: regulatory_guide
Title: Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal System Pumps
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739925.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.1
CFR Part: 
CFR Title: 

Content:
11/2/70 (Reprinted 12/1/70) SAFETY GUIDE 1 NET POSITIVE SUCTION HEAD FOR EMERGENCY CORE COOLING AND CONTAINMENT HEAT REMOVAL SYSTEM PUMPS A. Introduction Proposed General Design Criterion 41 re quires that the emergency cooling and contain ment heat removal systems be capable of ac complishing their required safety functions as suming partial loss of installed capacity. In cur rent designs the ability to accomplish these safety functions reliably depends in part on the proper performance of system pumps which, in turn, depends on the conditions under which the pumps must operate. One of these condi tions is suction pressure. This guide describes a suitable relationship between increases in containment pressure caused by postulated loss of coolant accidents and the net positive suc tion head (NPSH) of emergency core cooling and containment heat removal system pumps which may be used to implement General De sign Criterion 41. B. Discussion A significant consideration related to emer gency core cooling and containment heat re moval systems is the potential for degraded pump performance which could be caused by a number of factors, including inadequate NPSH. If the NPSH available to a pump is not suffi cient, cavitation of the pumped fluid can occur. This cavitation may reduce significantly the capability of the system to accomplish its safety functions. It is important that the proper performance of emergency core cooling and containment heat removal systems be independent of calcu lated increases in containment pressure caused by postulated loss of coolant accidents in order to assure reliable operation under a variety of possible accident conditions. For example, if proper operation of the emergency core cooling system depends upon maintaining the contain ment pressure above a specified minimum amount, then too low an internal pressure (re sulting from impaired containment integrity or operation of the containment heat removal systems at too high a rate) could