Information Notice 2002-34, Failure of Safety-Related Circuit Breaker External Auxiliary Switches at Columbia Generating Station

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Failure of Safety-Related Circuit Breaker External Auxiliary Switches at Columbia Generating Station
ML023300015
Person / Time
Site: Columbia 
Issue date: 11/25/2002
From: Beckner W
NRC/NRR/DRIP/RORP
To:
Hodge, CV, NRR/DRIP/RORP, (415-1861)
References
IN-02-034
Download: ML023300015 (7)
v • d • e


UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, DC 20555-0001November 25, 2002NRC INFORMATION NOTICE 2002-34:FAILURE OF SAFETY-RELATED CIRCUITBREAKER EXTERNAL AUXILIARY SWITCHES

AT COLUMBIA GENERATING STATION

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to informaddressees of failures of circuit breaker external auxiliary switches because of inadequate

maintenance of the associated switchgear. It is expected that recipients will review the

information for applicability to their facilities and consider actions, as appropriate, to avoid

similar problems. However, suggestions in this information notice are not NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

On February 14, 2002, at the Columbia Generating Station, the licensee initiated a requiredplant shutdown because of a mechanical problem in an emergency diesel generator (EDG)

output circuit breaker. Although the breaker was capable of closing and connecting the EDG to

its safety bus, its cubicle-mounted auxiliary contacts, called mechanism-operated cell (MOC)

switches, failed to change state as designed. The licensee determined that the MOC switch

failures associated with this breaker and other breakers of this type resulted in failure of various

electrical distribution system control functions, including some non-safety loads not being

removed from the EDG bus following an accident signal.On June 29, 2001, during a refueling outage at the same plant, after breaker replacement, astandby service water pump breaker MOC switch failed to reposition during breaker closure.

This failure recurred on November 19, 2001. A MOC switch contact prevented the pump

discharge valve from opening after a pump start, rendering the service water system and

supported systems, such as EDGs, inoperable.

DiscussionThe licensee believes the failure was caused by excessive resistance in the linkage betweenthe breaker and the MOC switches. The licensee had not performed periodic maintenance on

this linkage in the breaker cell housing. Over time, dirt and dust accumulated and grease

hardened to increase the resistance in the linkage mechanism. During the preceding refueling outage, ending in July 2001, the licensee replaced 22 safety-related 4160-volt circuit breakers, exchanging older design Westinghouse Type DHP-350 (air- magnetic) breakers with newer design, Westinghouse-dedicated, Cutler Hammer Type

DHP-VR (vacuum replacement) breakers using Sure-Close

TM mechanisms to operate the MOCswitches. In the DHP-VR, the Sure-Close

TM mechanism operates the MOC switches independently of thebreaker's main contacts so that the MOC switches can be operated at a slower speed to avoid

excessive kinetic energy and wear. In addition, the external MOC switch linkage drag won't

stall the main contacts, even if the linkage is poorly maintained. However, because the design

of the Sure-Close

TM mechanism intentionally limits the force on the linkage, it does not havesufficient force margin to overcome the excessive drag of poorly maintained MOC switch

linkages (for an explanation of Sure-Close

TM operation, see "DHP -VR SURE CLOSEMechanism: A Kinematic System Solution for Medium Voltage Circuit Breaker MOC Auxiliaries

Operation," U. S. Patent 5,856,643, Ronald E. Vaill, available from Cutler-Hammer Nuclear

Programs).The Columbia Generating Station experience illustrates that the newer design breakers with theSure-Close

TM mechanisms operating the MOC switches depend more heavily on the state ofmaintenance of the linkage than do the older design breakers coupled directly to the MOC

switches. Older design breakers will eventually cause damage to poorly maintained MOC

switches and linkages. In severe cases, poorly maintained MOC switches and linkages could

stall the older design breaker main contacts with potentially serious results.This information notice requires no specific action or written response. If you have anyquestions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate project manager from the NRC's Office of Nuclear Reactor

Regulation (NRR). /RA/William D. Beckner, Program Director

Operating Reactor Improvements Program

Division of Regulatory Improvement Programs

Office of Nuclear Reactor RegulationTechnical contacts:V. Hodge, NRRSteven Alexander, NRR301-415-1861301-415-2995 E-mail: cvh@nrc.govE-mail: sda@nrc.govAttachment: List of Recently Issued NRC Information Notices

ML023300015 DOCUMENT NAME: G:\RORP\OES\STAFF FOLDERS\Hodge\event reviews\col_brkr\21016 short col_brkr inf.wpdOFFICEOES:RORP:DRIPTech EditorIQMB:DIPMEEIB:DENAMECVHodgePKleene*SDAlexander*ASGillDATE11/07/200205/07200211/07/200211/19/2002OFFICEC:EEIB:DESC:RORP:DRIPPD:RORP:DRIPNAMEJACalvoTReisWDBecknerDATE11/20/200211/22/200211/25/2002

______________________________________________________________________________________OL = Operating License

CP = Construction PermitAttachment 1 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES

_____________________________________________________________________________________InformationDate of

Notice No. SubjectIssuanceIssued to

_____________________________________________________________________________________2002-33Notification of PermanentInjunction Against Neutron

Products Incorporated of

Dickerson, Maryland11/21/2002All teletherapy and radiationprocessing licensees. 2002-29(Errata)Recent Design Problems in Safety Functions of Pneumatic

Systems11/06/2002All holders of operating licensesor construction permits for

nuclear power reactors.2002-32Electromigration onSemiconductor Integrated

Circuits10/31/2002All holders of operating licensesfor nuclear power reactors except

those who have ceased

operations and have certified that

fuel has been permanently

removed from the reactor vessel.2002-31Potentially Defective UF

6Cylinder Valves (1-inch)10/31/2002All licensees authorized topossess and use source material

and/or special nuclear material for

the heating, emptying, filling, or

shipping of uranium hexafluoride

(UF 6) in 30- and 48-inchcylinders.2002-30Control and Surveillance ofPortable Gauges During Field

Operations10/30/2002All NRC licensees authorized topossess, use, transport, and store

portable gauges.2002-29Recent Design Problems inSafety Functions of Pneumatic

Systems10/15/2002All holders of operating licensesor construction permits for

nuclear power reactors.2002-28Appointment of RadiationSafety Officers and Authorized

Users Under 10 CFR Part 3509/27/2002All medical licensees.Note:NRC generic communications may be received in electronic format shortly after they areissued by subscribing to the NRC listserver as follows:To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the followingcommand in the message portion:subscribe gc-nrr firstname lastname


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