ML17252A906

Letter Reporting a Condition Concerning Excessive Leakage Through MSIV 3-202-1B - Dresden Unit 3

ML17252A906
Person / Time
Site:	Dresden
Issue date:	05/21/1974
From:	Stephenson B Commonwealth Edison Co
To:	O'Leary J US Atomic Energy Commission (AEC)
References
BBS Ltr. #365-74
Download: ML17252A906 (2)

Text

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CommonweAEdison One First Nation'Kza, Chicago, 11n.fiofs'* "

Address Reply to: Post Office Box 767 Chicago, Illinois 60690 BBS Ltr.-#365-74 Mr. J. F. O'Leary, Director Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C.

20545 Dresden Nuclear Power R. R. #1 Morris, Illinois.

May 21, 1974 50.-**2 4 9

SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, REPORT

• op ABNORMAL OCCURRENCE PER SECTION 6.6.B.l.a OF THE TECHNICAL SPECIFICATIONS.

EXCESSIVE LEAKAGE THRU MSIV 3*202-lB.

References:

1) Notification of Region Ill of AEC Regulatory Oper 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, 197

2) Dwgs: P&ID M-345

Dear Mr. O'Leary:

This letter is to report a condition relating to the operation of the unit on May 15, 1974.

On this date, during local leak rate testing of the main steam isolation valves, valve lB 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 F$IG.

PROBLEM On May 15, 1974, local leak rate tests were being conducted on Unit 3 main steam isolation valves. A test on valves lB and 2B revealed a leakage rate of 30.8 scf/hr.

On March 14, 1974, 2B was tested and found to have a leakage rate of 6.0 scf/hr. This implies lB has a leakage rate of 24.8 scf/hr.

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

INVESTIGATION It was decided that both valves 203-lB & 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 lB was checked and found to have hairline cracks in the stellite overlay on the disc.

REGULATORY DOCKET FILE COPY

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Mr. J. F. O'Leary CORRECTIVE ACTIONS May 21, 1974 The corrective actions taken on MSIV 2B was to lap the seating surfaces and reinstall. As a result of the hairline cracks, MSIV lB will be fitted with a new disc which will be lapped and reinstalled.

The leak test for these valves will be included in the primary 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 lB did not effect the safety of plant personnel or the public because the back-up valve in*this line,* MSIV 2B, had leakage within Technical Specification limits. A review of MSIV problems 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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