ML19326C333

Submits Info Re Util Review of Potential for Boron Dilution Accident Requested by NRC 770915 Ltr.Operating Procedures Changed to Require Closing of Valve CA49 in Addition to CA61 & CA62 During Sodium Hydroxide Control Valve Testing

ML19326C333
Person / Time
Site:	Arkansas Nuclear
Issue date:	12/22/1977
From:	David Williams ARKANSAS POWER & LIGHT CO.
To:	Desiree Davis Office of Nuclear Reactor Regulation
Shared Package
ML19326C335	List: ML19326C333
References
1-127-17, NUDOCS 8004220883
Download: ML19326C333 (3)

Text

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FE0M DOCE FillC00 H EL PIN G BUILO A R KA N S A S A R K A N S A S P O W E R & LI G H T C: O M P A N Y P C. SCX 5S1 LITTLE AOCK. A AK ANS AS 72203.(501)371-4000 December 22, 1977 1-127-17 7 'N Director of Nuclear Reactor Regulation '

ATTN: Mr. D. K. Davis, Acting Chief Operating Reactor Branch #2

U. S. Nuclear Regulatory Commission Washington, D. C. 20555 hp , .j j: '

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Docket No. 50-313 \ .A/

License No. DPR-51 j Inadvertent NaOH Addition to RCS (1 to 3 .dy (File: 1510)

Gentlemen:

By letter dated September 15, 1977, you informed us of a limited boron dilution incident at an operating PWR facility due to the inadvertent injection of a portion of the contents of the sodium hydroxide (NaOH) tank into the reactor coolant system while the reactor was in the cold shutdown condition. Your letter requested we provide an analysis of the potential for and consequences of a boron dilution accident at Arkansas Nuclear One-Unit 1 (ANO-1).

Our review of this potential incident indicated that ANO-1 operates with two isolation valves closed between the NaOH Engineered Safeguards (ES) control valves and the decay heat removal (DHR) pumps when we are in the DHR mode of operation and testing the NaOH control valves. Therefore, for that mode of operation, no single valve failure would allow a boron dilution accident due to NaOH injection in the reactor coolant system.

Also, our review indicated that only one valve would isolate the NaOH tank from the reactor core when filling the refueling canal by way of the low pressure injection (LPI) system when testing the NaOH control valves. Although the possibility of that valve failing at that time is very remote, we have changed our operating procedures to require that valve CA49 be manually closed in addition to valves CA61 and CA62 during NaOH control valve testing.

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, Mr. D. K. Davis December 22, 1977 1-127-17 Based on the above, we contend that adequate measures exist to preclude the possibility of a postulated boron dilution accident. Should you require additional information, please advise.

Very truly yours, aniel H. Williams Manager, Licensing DHW:DGM:dr O

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