ML20084L741

AO 50-237/1974-31:on 740726,excessive Leakage Found on Reactor Bldg to Torus Vacuum Breaker 2-1601-31A.Caused by Binding Between Disc & Disc Arm.Valve Will Be Modified During Next Refueling Outage

ML20084L741
Person / Time
Site:	Dresden
Issue date:	08/02/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084L740	List: ML20084L739 ML20084L741 ML20084L744 ML20084L755
References
552-74, NUDOCS 8305230675
Download: ML20084L741 (2)

Text

~ - g h p% Comm^7ealth Edison d ; One Firkjcn.M Plua, Chicago. Ilhnois

'i, AJ/, Address Reply to: Post Ofhce Box 767

%V Chicago. !!hnoia 00600 BBS Ltr.0552-74 Dresden' Nuclear Power Station R. R. #1 Horris, Illinois 60450 August 2, 1974 Mr. J. F. O' Leary, Director Directorage .of Licensing ,

U. S. Atomic Energy Commission Washington, D. C. 20545

SUBJECT:

REPORT OF ABMON'AL__ OCCURRENCE PER SECTION 6.6 B OF THE _TP.CIUTICAL SPECIFICATIC is.

EXCCSSIVE LEAKAGE PAST REACTOR EUILDING TO TORUS VACtRRf BREAKER 2 -1601-31A .

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Tolephone: Mr. F. Maura, 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on July. 26,1974 Telegram: Mr. J. Keppler,1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> on July 26, 1974

3) Drawing Number M-25 y-Ecuusv h LatL 50-237/137'-31

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Report Date: August 2,.1974 h .s p },

4 Occurrence Date: July 26, 1974 ,

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Facility: Dresden Nucicar Power Station, Morris, Illinois- p( s"i ~

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IDE17FIFICATION OF OCCURRENCE -

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~At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on July 26, 1974, reactor building to torus vacuum breaker 2-1601-31A was found to have leakt.ge in excess of~the Technical Specification limits (4. 7. A.2. f(2)b) .

CONDITIONS PRIOR TO OCCURRENCE At.1400 houra 'on July 26,- 1974, Unit 2 was in the run taode with a steady-state power leve1 ~ of 2258 Ifdt and 7201No.

1 1]ESCRIPTION OF' OCCURRENCE

-At 1400 houro en July 26, 1974, a local leak rate . te.st was being conducted on the volter.a betwea va tyce A0 2-lG01-2CA and 2-1601-31A. nis -

test was' being conducted to 'lcak test t.hc rubber jea.q<d ventilation valve,

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Mr. J. F. O'Laary O O -

August 2, 1974 2-1601-20A. Excessive leakage was noted and was heard Icaking through the check valve,' 2-1601-31A. Upon looking into the pipe, it was noted that the disc was not centered and so didn't seem to be seating properly. The unit was shut down on July 27 due to the failure of valves 2-1601-21 and 2-1601-

22. On July 28, the valves were again tested af ter cycling valve 1601-31A.

The valves passed this test.

DESIGUATION OF APPARENT CAUSE OF OCCURRENCE The apparent cause of the occurrence would appear to be binding between the disc and the disc arm. This is probably caused by corrosion.

This is the same type of valve used for the torus to drywell vacuu:a breakers.

Special Report No. 23A dated August 1, 1973, covers this subject. The cycling of the valve was apparently enough to loosen the disc and the disc arm.

AMALYSIS 07 OCCURRENCE There were no safety consequences to the public or plant personnel as a result of this occurrence because valve 2-1601-20A, which is in series with valve 3-1601-31A, was operabic at all times.

CORRECTTWJCTIO11 This valve end valve 2-1601-31B will be included in the modifica-tion package along with the Unit 2 drywell to torus vacuun breakers. This package is described in Special Report No. 23A dated August 1, 1973. These valves will be modified during the next refueling outage.

In the interim, we will check these valves for operability monthly instead of the 3 month timing in the Technical Specifications.

FAILURE DATA This type of valve, Atwood and Morrill Co. 20" check valve, hr.s had a history of previous failures on the Unit 3 dryvell to torus vacuuu breaker cystem. The modification done to these valves should solve the problem.

Sincercly, Jr. .

M B. B. Stephenson Superintendent BBS:LD:do i

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