ML003739925

Safety Guide 1, Net Positive Suction Head for Emergency Core Cooling & Containment Heat Removal System Pumps

ML003739925
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Issue date:	12/01/1970
From:	Office of Nuclear Regulatory Research
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Download: ML003739925 (1)

Text

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 possible accident conditions. For example, if proper operation of the emergency core cooling Proposed General Design Criterion 41 re system depends upon maintaining the contain quires that the emergency cooling and contain ment pressure above a specified minimum ment heat removal systems be capable of ac amount, then too low an internal pressure (re complishing their required safety functions as sulting from impaired containment integrity suming partial loss of installed capacity. In cur or operation of the containment heat removal rent designs the ability to accomplish these systems at too high a rate) could significantly safety functions reliably depends in part on the affect the ability of this system to accomplish proper performance of system pumps which, its safety functions by causing pump cavita in turn, depends on the conditions under which tion. In addition, the deliberate continuation of the pumps must operate. One of these condi a high containment pressure to maintain an tions is suction pressure. This guide describes adequate pump NPSH would result in greater a suitable relationship between increases in leakage of fission products from the contain containment pressure caused by postulated loss ment and higher potential offsite doses under of coolant accidents and the net positive suc accident conditions than would otherwise result.

tion head (NPSH) of emergency core cooling Changes in NPSH for emergency core cool and containment heat removal system pumps ing and containment heat removal system which may be used to implement General De pumps caused by increases in temperature of sign Criterion 41.

the pumped fluid under loss of coolant accident B. Discussion conditions can be accommodated without reli ance on the calculated increase in containment A significant consideration related to emer pressure. Adequate NPSH can be assured by gency core cooling and containment heat re locating pumps at- suitable elevations with re moval systems is the potential for degraded spect to the storage volumes connected to their pump performance which could be caused by a suction sides, by using multistage or booster number of factors, including inadequate NPSH.

pumps, by a combination of these methods, or If the NPSH available to a pump is not suffi by other techniques.

cient, cavitation of the pumped fluid can occur.

This cavitation may reduce significantly the C. Regulatory Position capability of the system to accomplish its safety Emergency core cooling and containment functions. heat removal systems should be designed so It is important that the proper performance that adequate net positive suction head (NPSH) of emergency core cooling and containment is provided to system pumps assuming maxi heat removal systems be independent of calcu mum expected temperatures of pumped fluids lated increases in containment pressure caused and no increase in containment pressure from by postulated loss of coolant accidents in order that present prior to postulated loss of coolant to assure reliable operation under a variety of accidents.

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