ML17252B517

LER 78-032/03L-0 for Dresden, Unit 2 Re During Steady State Operation, Torus to Drywell Vacuum Breaker 2-1601-33E & F Were Found Inoperable During Routine Operability Surveillance

ML17252B517
Person / Time
Site:	Dresden
Issue date:	06/09/1978
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS LTR 78-949 LER 78-032/03L-0
Download: ML17252B517 (3)

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-June 9, 1978 BBS Ltr. #78-949 James G~ Keppler, Regional Director Directorate of Regulatory Operations - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Reportable Occurrence Report #78-032/031-0, Docket #050~237 is hereby submitted to your office in accordance with Dresden Nuclear Power Station Technical Specification 6.6.B.2.(b), conditions leading to*

operation in a degraded mode permitted by a limiting condition for operation.

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Station Superintendent Dresden Nuclear Power.Station BBS/deb Enclosure cc:. Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC

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NRC .FORM 366 U. s~ NUCLEAR REGULA TO.RY COMMISSION (7-771

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,~ I During steady state operation, torus. to drywe11 vacuum breakers 2-1601-33E & F were found ir~0perable during. routine operability surveillance. 2-1601-33E had an excessiv~

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((ill The valves*were secured closed and normal operation continued since 10 (9 required)*

[Qli] vacuum breakers were operable. As a* result, this event has little safety significancf?

~ I Similar events: S0-237 /77-77, 50-237 i78-8 and 50;..237 /74-11 & 27. I

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[J]JJ 1replacemenobronze bushings have been procured, they will be installed on future

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ATTACHMENT TO LICENSEE EVENT REPORT 78-032/031-0 COMMONWEALTH EDISON COMPANY (CWE)

DRESDEN UNIT-2 (ILDRS-2)

DOCKET llos0-237 During the torus to drywell vacuum breaker monthly operability surveillance, 2-1601-33E & 33F were found to be inoperable. During the surveillance (DOS 1600-9) it was :i.oted that both valves would not freely s~ing closed. An opening torque measurement was made on each of these valves and was found to be excessive for 2-1601-33E~ However, both valves were secured closed as required by Technical Specification 3.7.A.4. and normal operation continued since ten vacuum breakers (9 required) remained operable. Since the vacuum breakers were closed prior to the test and ten were operable, this event has little safety significance.

Whi~.e the unit was shutdown for maintenance, the stuffing boxes, which house.the teflon shaft bushings, on 2-1601-33E & 33F were pulled. It was found that one of the teflon bushings on 2-1601-33F and both bushings on 2-1601-33E had swelled reducing the bushing to shaft clearance and causing binding of the valve. The bushings were machined to the proper tolerance and the valves reassembled and tested satisfactorily.

As reported by LER 50-237/1974-27, new phosphor-bronze bushings were installed in valve 3-1601-33E on Dresden Unit 3 on a trial basis.

Since no problems have occurred with this. valve following installation of the phosphor-bronze bushings, the station will procure replacement: bronze bushings to be installed during future overhauls of the vacuum breakers. This will be done on both Units 2 and 3.