ML20084L786

AO 50-237/1974-27:on 740720,during Routine Surveillance Testing of torus-to-drywell Vacuum Breakers,Valve 2-1601-33E Found Binding Open.Caused by Swelling of Teflon Bushings. Valve Willbe Remachined.Study Initiated

ML20084L786
Person / Time
Site:	Dresden
Issue date:	07/29/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084L783	List: ML20084L782 ML20084L786 ML20084L789
References
543-74, NUDOCS 8305230722
Download: ML20084L786 (3)

Text

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One First bbonal Para. CNeago. Illinois Address Reply to: Post 0;fece Box 767 Chicago, tihnois 60690 v.

BBS Ltr.#543-74 Dresden Nuclear Power Station

' R. R. 41 Morris, Illinois 60450 go) j July 29, 1974

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50-237 Anel GP Mr. J. F. O' Leary, Director

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Directorate of Licensing

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SUBJECT:

REPORT OF ABNORMAL OCCURRENCE PER SECTION 5.6.B.3 OF THE TECHNIC (~

SPECIFICATIONS.

BEDI!iG OF UNIT #2 D'RYWELL TO TORUS VACUUM BREAKER.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura,1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on 7/22/74 Tclegram: Mr. J. G. Keppler,1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on 7/22/74

3) Drawing Number: M-25 Reoort Number: 50-237/1974-27 Report Date: July 29,,1974 0'ecurrence Datet July 20, 1974 Facility: Dresden Nuclear Power Station, Morris, Illinois IDr.NTIFICATION OF OCCURRENCE' During routine surveillance testing of the Unit #2 torun-to-drywell vacuum breakara (1600-S-XII), it was discovered that valve 2-1601-33E was binding open. This is contrary to section 3.7.A.4.a(2) of the Technical Snecifications which etates that for a vacuum breaker to be operabic, it must close by gravity when released af ter being cpened by r.utnual means.

_CONDITIOE PRIOR TO OCCURRENCE Unit #2 was at steady state operation at 724 MWe, 2265 MWt in the run mode.

Core flow uss 97.50 x 100 lba/hr and feed flow was 8.7 x 106 lba/hr. One torus-to-drywell vacuu:n breaker (2-1601-33C) was wired shut. Routint. surveillance was being conducted.

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Mr. J. F. O'Le July 29, 1974

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DESCRIPTION OF OCCURRENCE This abnormal occurrence was discovered during routine surveillance testing conducted on July 20, 1974. At 0455, operations discovered the problem with valve 2-1601-33E. Af ter the operator manually opened the valve and released the operating arm, he discovered the binding problem. He then notified his shift supervisor and made preparations to wire the valve shut.

At 0700, the valve was wired shut. Work Request Number 5974 was issued to repair the valve.

DESIGNATION OF APPARENT _ CAUSE OF OdCURRENCE This problem has occurred in the past. The cause of the sticking problem is the " growing" or " swelling" of the teflon bushings which in turn cause valve shaft binding.

. ANALYSIS OF OCCURRENCE Since the valves were verified in the closed position prior to the test, no leakage path existed from the drywell to the top of the torus.

Any steam, that could have been in the drywell as a result of a pipe break, would have been forced into the torus water through the centipede legs.

Also, Technical Specifications only require that 9 of ths 12 vacuum breakers La uge t a'ulu. an.d 1G ute a6111 uuesablu.

Ihun the health and naiety of plani.

personnel and the general public was in no way jeopardized.

CORRECTIVE ACTION To solve 'the sticking problem, a study is underway on a new type bushing. Phosphorus-bronze bushings have been installed in valve 3-1601-33E on Unit #3.

If the new bushing works natisfactorily, all vacuum breakers will receive this modification.

However, in the interim, the valve shall be kept out of service until the fall refueling outage. At that time, the bushings shall be remachined to specifications.

FAILURE DATA Previous failures of a similar type have occurred on valves 2-16'J1-33C on December 3,1973, 2-1601-32D and 2-1601-33A on thy 18, 1974.

Valves 2-1601-32D and 2-1601-33A were lubricated, Icak tested and placed back in service in June, 1974. Valve 2-1601-33C will be worked on during the fall refueling outage.

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Mr. J. F. O'Letry July 29, 1974

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As mentioned earlier in this letter, the failure occurred in the teflon bushing of the 18" ANSI 150 lb. vacuum breaker 2-1601-33E manufact-ured by Atwood & Morrill Co:npany.

Sincerely,

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i B. Stephenson Superintendent i

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