ML20085J922

Ao:On 740515,during Local Leak Rate Testing of Msivs,Valves 1B & 2B Found W/Leak Rate Above Allowable Limit.Caused by Warped Valve Seat & Hairline Cracks in Stellate Overlay on Disc.Seating Surfaces of 2B Reinstalled

ML20085J922
Person / Time
Site:	Dresden
Issue date:	05/21/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085J926	List: ML20085J922 ML20085J927 ML20085J933
References
365-74, NUDOCS 8310190206
Download: ML20085J922 (2)

Text

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f.g Ccmmopy/ealth Edison t ni One First/ pal Plaza. Cnicago. Imnois i~% / Addrcss f~rdy to: Post Olkco Box 767 *

' e: Chicago, !!!ihois 60690 BBS Ltr.#365-74 Dresden Nucicar Power Station R. R. #1 Morris, Illinois 60450 May 21, 1974

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SUBJECT:

EICENSE DPR-25, DRESDEN i:UCLEAR PO'JER STATION. UNIT #3, REPORT OF AENOFAL OCCURRENCE PER SECTION 6.6.B. I.a OF THE TECHNICAL SPECIPICATIONS.

_ EXCESSIVE LEAKAGE TilRU MSIV 3-202-1B.

References:

1) Notification of Region III of AEC Regulatory Operations Telephone: F. Maura , 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on May 16, 1974 Telegram: J. Keppler, 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> on May 16, 1974

2) Dwgs: P&ID M-345

Dear Mr. O' Leary:

liais letter is to report a conoition relating to the operation or the unit on May 15, 1974. On this date, during local leak rate testing of

. the tuain steam isolation valves, valve IB was found to have leakage of 24.8 scf/hr. This malfunction is contrary to section 4.7.A.2.f(2)(c) of the Technical Specifications which requires that the maximum allowable leakage for any one main steam line isolation valve is 11.5 scf/hr @ 25 PSIG.

PROBLEM On Iby 15, 1974, local leak rate-tests were being conducted on Unit 3 main steam isolation valves. A test on valves 13 and 2B revealed a'lcakage rate of 30.8 sef/hr. On March 14, 1974,'2B was tested and found to have a leakage rate of 6.0 scf/hr. This implies 1B has a leakage rate of 24.8 scf/hr.

At the time of the occurrence, Unit 3 was in its second :r.ajor outage and primary containment was not required.

INVESTICATION'

. It was decided that both valves 203-1B & 2B internal components would be inspected to determine the source of the leakage. Upon inspection, valve 203-2B was found to'have a warped valve seat and valve IB was checked and found to have hairline cracks in the stellite overlay on the disc.

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May 21, 1974 CORRECT 1'E ACTIONS The corrective actions taken on MSIV 2B was to lap the seating surfaces and reinstall. As a result of the hairline cracks, MSIV IB will be fitted with a new disc which will be lapped and reinstalled. The leak test for these valves will be included in the pri: nary containment leak rate test report to be submitted for this outage. The other six MSIV's have been leak tested and found satisfactory.

, EVALUATIONS The failure of MSIV 1B did not offect the safety of plant personnel or the public because the back-up valve in this line, M31V 2B, had leakage within Technical Specification limits. A review of MSIV probleus has verified that this is the first failure of this type. It is therefore concluded that the corrective action stated above is adequate.

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B.'E. Stephenson Superintendent LLs;ii:du l