ML20195H710

Discusses NRC Concerns Re Failures of Westinghouse Circuit Breakers Due to Lack of QC

ML20195H710
Person / Time
Issue date:	11/22/1988
From:	Murley T Office of Nuclear Reactor Regulation
To:	Caso C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 8811300584
Download: ML20195H710 (4)

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NOV 2198 Mr. Carlo L. Caso, General Manager Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, Pennsylvania 15230

SUBJECT:

FAILURES OF WE5TINGH0VSE CIRCUIT BREAKERS INDICATE LACK OF QUALITY CONTROL The NRC staff has become concerned about the quality of circuit breakers manu-factured by Westinghouse that are used in safety systems of nuclear power plants.

During the past several years, the NRC has evaluated a number of events at U.S.

nuclear power plants involving failures of Westinghouse circuit breakers. The failures are addressed in the NRC Bulletins and Information Notices listed in the enclosure. Many of the failures appear to be in part related to deficiencies in the circuit breaker manufacturing process.

For example:

• insufficient margin in the lifting (trip) force provided by the undervoltage trip attachment to move the breaker trip bar (08-50 breakers).

• brokenspringreleaselatchlevers(typeDSbreakers),

' excessive material in the rivet that holds the handle post to the operatingmechanism(moldeocasebreakers).

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• n.rocen welds and non-uniform surface on closing cam segments (M-416 breakers),

if spring tension due to deformation of the spring retainer in 11 switch spring return mechanism (W-2-type )reakers),

improper brazing of the pivot pin to the trip latch (05-416 breakers),

' improper weld technique and excessive misalignment of the main roller ontheclosecam(typeDSbreakers).

• miscellaneousweldfailures(DHP-50 breakers),and

• insufficient clearances between breaker moving parts and the breaker casing (05-416 breakers).

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Mr. Carlo Caso 2

160V 2 21988 The staff is concerned that the manufacturing process was not sufficiently controlled, and that the potential for the types of problems listed above was not detected under the product testing program.

The problems appear to involve quality control or manufacturing deficiencies that could cause coninon mode failures. The problems are germane to several different circuit breaker models and sizes and seem to indicate a breakdown of quality control.

The NRC is concerned that Westinghouse circuit breakers are not being properly fabricated, their dimensions and other critical attributes are not being in-spected (either when they are initially manufactured or when they are certified for Class 1E use), and hence their qualification for use in nuclear facilities is in question.

Therefore, I would like you and appropriate members of your staff to meet with me to discuss actions Westinghouse intends to take to improve the quality of its circuit breakers. Please contact Frank J. Miraglia of my staff at (301) 492-1274 to arrange a meeting time.

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Sincerely, Thomas E. Hurley, Director Office of Nuclear Reactor Regulation

Enclosure:

As stated e

Letter to Carlo Caso 3

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m ENCLOSURE INFORMATICN NOTICES AND BULLETINS ISSUED FOR WESTINGHOUSE CIRCUIT BREAKERS SINCE 1983 TITLE IEB 83-01 Failure of Reactor Trip Breakers (Westinghouse 08-50)

To Open on Automatic Trip Signal IEB 83-04 Failure of the Undervoltage Trip Function of Reactor Trip Breakers IEIN 83-18 Failures of the Undervoltage Trip Function of Reactor Trip System Breakers IEIN 83-50 Failures of Class 1E Safety-Related Switchgear Circuit Breakers to Close on Demand IEB 83-08 Electrical Circuit Breakers With an Undervoltage Trip Feature in Use in Safety-Related Applications Other Than the Reactor Trip System IEB 85-02 Undervoltage Trip Attachments of Westinghouse D8-50 Type Reactor Trip Breakers IEIN 85-93 Westinghouse Type DS Circuit Breakers, Potential Failure of Electric Closing Feature Because of Broken Spring Release Latch Lever IEIN 86-62 Potential Problems in Westinghouse Molded Case Circuit Breakers Equipped With a Shunt Trip NRCIN 87-35 Reactor Trip Breaker, Westinghouse Model 05-416, Failed to Open on Manual Initiation From the Control Room NRCIN 87-35 Supplement 1 - Same title NRCIN 87-61 Failure of Westinghouse W-2-Type Circuit Breaker Cell Switches NRCB 88-01 Defects in Westinghouse Circuit Breakers NRCIN 88-44 Mechanical Binding of Spring Release Device in Westinghouse Type DS-416 Circuit Breakers

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