ML19326B326

Deficiency Rept Re Paralleling of Vital Buses A3 & A4 During Integrated Engineered Safeguard Test.Caused by Error in Diagram of Automatic Restart Circuitry Mod.Diagram & Circuitry Corrected

ML19326B326
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/16/1974
From:	Phillips J ARKANSAS POWER & LIGHT CO.
To:
Shared Package
ML19326B321	List: ML19326B326
References
41688, NUDOCS 8004150709
Download: ML19326B326 (4)

Text

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ARK ANS AS POWER & LIGHT COMPA NY erH & LouisiAN A SrAEErS . LITrLE ROCeC A AK ANS AS 72203.(5013372-4311 May 16, 1974 Mr. D . F. Knuth Director of Regulatory Operations Of fice Of Regulation -

United States Atomic Energy Commission Washington, D. C. 20S45

Subject:

Arkansas Power & Light Company Arkansas Nuclear One-Unit 1 Docket No. 50-313 Paralleling of Vital Busses A3 and A4 m

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Dear Mr. Knuth:

(G On May 15, 1974, we reported to Mr. M. S. Kidd, Reactor Inspector, Region II, a possible significant deficiency regarding the paralleling of vital buses A3 and A4 during an Integrated Engineered Safeguard Test at Arkansas lluclear One-Unit 1. A written report describing this event is attached. 3 Very truly yours, ,

J. D. Phillips Senior Vice President JDP:lt Attachment -

cc: Mr. Norman C. Moseley -

Director Region II ,

Directorate of Regulatory Operations i United States Atomic Energy Commission i*!

f 230 Peachtree Street, N.W. , Suite 818 }' \

f-Atlanta, Georgia 30303 , ,

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800415o709 4 1888~ -

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-g STATE OF ARKANSAS )

) SS COUNTY OF PULASKI )

J. D. Phillips, being duly sworn, states that he is a Senior Vice President of Arkansas Power & Light Company; that he is authorized or the part of said Company to sign and file with the Atomic Enerciy Commission this Supplementary Informa-tion; that he has read all of the statements contained in _

such Information, and that all such statements made and matters set forth therein are true and correct to the best of his know-ledge, information and belief. ~

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J. D. Phillips s

4 SUBSCRIBED AND SWORN TO before me, a Notary Public in and for the County and State above named this [ day of ko,.a.,n, , 1974.

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} Attachment to Letter Phillips to Knuth May 16, 1974 j

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l Arkansas Nuclear One-Unit 1 ,

Paralleling of Vital Buses A3 and A4 Description of Incident During the conduct of the Integrated Engineered Safeguard Test on May 11, 1974, the service water pump motor PM4B was fed power simultaneously from redundant vital buses A3 and A4 resulting in a paralleling of these buses.- The _.

breakers feeding PM4B immediately reopened and buses A3 and A4 continued to supply power to engineered safeguard equipment. PM4B is one of three service water pump motors and can be fed fram either bus A3 or bus A4. The other two service water pump motors (PM4A and PM4C) can only be fed from one of the two buses.

Cause of Incident (h

i A modification had been made prior to the test to the auto- ._

matic restart circuitry of PM4B to allow automatic restart following loss of voltage without a concurrent ES signal.

A drawing error in one schematic diagram associated with the modification permitted the simultaneous closure of both supply breakers from the two vital buses.

4 s Safety Implications 1

The three service water pumps provide cooling water to plant systems during normal and emergency operations. Two redundant trains are provided, with one required for safe shutdown of the unit. PM4B can provide service water flow 3 to either of the redundant trains.

Since the incident occurred during the Preoperational Testing Phase, no safety hazard was created. Had the error in the .

circuitry gone undetected, the incident may have occurred during an emergency condition. If this had happnaed, the '

breakers feeding PM4B would have opened and PM4B would not start. PM4A and PM4C would be unaffected and would continue to function. One of these pumps would provide adequate cocl-ing water for the plant during the emergency condition.

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! Thus, the health and safety of the public would not be l affected by the failure of a service water pump to start in an emergency condition.

Corrective Action The electrical schematics related to the modification were reviewed and corrected. The circuitry was corrected on PM4B j and the Integrated Engineered Safeguard Test was rerun satisfac;orily.

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