ML19326C787

Forwards Responses to Questions Requested in Telcons W/ J Burdoin & R Snaider Re re-evaluation of ECCS Performance

ML19326C787
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/20/1978
From:	David Williams ARKANSAS POWER & LIGHT CO.
To:	Desiree Davis Office of Nuclear Reactor Regulation
References
1-018-17, 1-18-17, NUDOCS 8004280722
Download: ML19326C787 (5)

Text

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REGULATORY INGOFNATION DISTRIBUTION SYSTEM (RIDS)

DISTRIBlJTION-FOR INCOMING HATERIAL 50-31?

$EC: DAVIS D.K ORG: WILLIAMS D H DOCDATE: 01/20/78 lNRC AR PWR L LIGHT DATE RCVD: 01/31/79 MCTYPE:' LElTER NOTARIZFD: NO COPIES RECEIVED UBJECT: .

LTR 1 ENCL 40 sNCL RESPONSES TO SEVERAL QUESTIONS CONCERNING THE RE-EVALUATION OF THE ECCS SERFORMANCE.

fLANT - NAME: ARKAN3 AS -' UNIT.1 REVIEWER INITIAL: X9T DISTRIEUTOR INITIAL:

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FOR AC 1 ION: ERANCH CHIEF DAVIS **W/7 FNCL

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s H G L PI N G BUILO ARKANSAS ARK ANS AS POWER & LIGHT COMPANY A 0. Box 551 UTTLE AOCK. A AK ANS AS 72203*(5011371-4000 January 20, 1978 1-018-17

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Director of Nuclear Reactor Regulation ATTN: Mr. D. K. Davis, Acting Chief

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U. S. Nuclear Regulatory Commission 'h r4Sl'8 .l_ i9'g >

Washington, D. C. 20555 .

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Subject:

Arkansas Nuclear One-Unit 1 \- j Docket No. 50-313 y-License No. DPR-51 4 p 7 g .-? L, ,,

Re-Evaluation of ECCS Perfomance (File: 0930, 1510)

Gentlemen:

In telecons with your Mr. J. Burdoin and R. Snaider, several questions have arisen concerning the above captioned subject. Attached find our responses to those questions.

If you have any questions and/or comments, please advise.

Very truly yours,

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7/. t Daniel H. Williams Manager, Licensing DHW:RMC:nf Attachment 0 , '7 0 7 d

II E'f T A x P AYING. INVESTQ A OWNE O MEMSE A MlOOLE SOUTH U T I L I TI E S S Y a.,

Question 1 Are the raceways, -limit switches, etc. for submersible valves CV-1414, CV-1415, CV-1410 an

• CV-1050 also submersible? *

Response

Yes, or are above flood elevation 345'3".

Question 2 Explain the utili:ation of fuse co-ordination to maintain bus integrity in case of a fault.

480 Volt Power Circuit Protection Referring to Fig. 1 each breaker is looking at current out in the system (i.e. current on its load side). Thus each breaker (1,2,3 and 4) effee-tively " sees" the current being supplied to the load M1. At a given fault current at point X breaker 1 is set to trip faster than breaker 2, breaker 2 faster than breaker 3, etc. Thus for a fault at point X breaker 1 would trip first clearing the fault and 1 caving the rest of the system intact.

The breakers have been and are periodically tested against the calculational curves providing operational- assuredness.

120V AC 12SV DC Instrument Protection Instrument Protection Fig. 2 is similar to the Power Protective Circuits with the exception that fuses are used to protect loads. For a fault at point X, the fuse has a faster clearing time than breaker 1.etc. Thus selective tripping is assured.

Question 3 llow long can a submersible valve be depended upon to be operable during sub-mergence?

Response

The submersible rotork operators can be depended on to operate a minimum of 30 days in a submersed condition. Rotork has tested this type operator at 70 psi and 50 F submersed in a solution of the same chemistry as our Reactor Building Spray for 30 days with no failure.

L Question 4 Look at providing protection for the service water system by locking CV-3823 open or closed similar to that utili:cd for CV-3824 and delineated in our. July 9,' 1975 letter.

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R;sponsa ^

CV-3823 will be locked open (opening the breaker) when the plant is utili-ing the Emergency Cooling Pond for the service water system. This procedure, in ronjunction with-locking CV-3824 closed as previously discussed in our July 9,1975, . letter, will ensure that a single failure in this valve will not eliminate a discharge path from the plant for service water.

The need to lock CV-3823 closed when CV-3824 is locked open is non-existant in that a single failure will only provide another discharge pcth for se rvi ce water.

We can see no safety problem in discharge water from the service water system going to the Emergency Cooling Pond. Therefore no procedure will be initiated to require locking CV-3823 closed when CV-38I4 is locked open .

Question 5 Look at providing an interlock between CV-3823 and CV-3824 to prevent these valves from being open or closed concurrently.

Response

We believe our response to Question 4 above and the administrative proce-dures provided for racking out valves and returning them to service satis-fies this concern without providing an interlock.

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