ML19273B957

Forwards ECCS Analysis of Small Breaks in Conjunction W/ Emergency Feedwater Flow Failures.Operator Has 20 Minutes to re-establish Feedwater Flow Prior to Core Uncovery

ML19273B957
Person / Time
Site:	Oconee
Issue date:	05/03/1979
From:	Bates A Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-SM-0106, ACRS-SM-106, NUDOCS 7906180583
Download: ML19273B957 (1)

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UNITED STATES fhb 2-2 E y',y E NUCLEAR REGULATORY COMMISSION

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0f ADVISORY COMMITTEE ON REACTOR SAFEGUARDS I*

WASHINoToN, D. C. 20S55 4

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May 3, 1979 ACRS Members B&W VERY SMALL BREAK ANALYSIS Attached is an analysis for the Oconee Units 1, 2, 3 for very small breaks where emergency feedwater is lost. W e report concludes that 20 minutes is available for the operator to re-establish feedwater flow prior to core uncovery.

Several items that appear to have contributed to the Three Mile Island incident are not addressed. Wese include:

i 1.

te information available to the operator to allow him to recognize the situation.

2.

te effect of break location upon the operators ability to recognize and respond to the situation.

3.

t e reactor pumps are assumed to have tripped. We ability to establish natural circulation cooling (needed water levels in the steam generator, steam bubble binding problems, etc.) were not addressed.

4.

We break is assumed to cause the reactor trip (low pressure) and subsequent feedwater pump trip. khat is the consequence of loss of feedwater prior to reactor trip?

5.

It is assumed that a break location that maximizes the loss of HPIS flow is the worst.

It is not clear that some other combination of break size and loca-tion may not produce significantly different system be-havior, i.e. how would a primary system break to the secondary system (OTSG) effect the depressurization rate of the reactor and the behavior of the secondary side instrumentation that controls the feedwater and emergency feedwater as well as the operator response.

Y. 0 5 A. Bates Reactor Engineer Attachment As Stated cc w/ attach: ACRS Technical Staff 2353 258 C. Michelson Z. Zudans 7906180583 n ki

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