United States Nuclear Regulatory Commission - Protecting People and the Environment

Westinghouse Westinghouse
P.O. Box 355
Pittsburgh, Pennsylvania 15230-0355
USA


U.S. Nuclear Regulatory Commission Direct tel: (412) 374-5282
Document Control Desk Direct fax: (412) 374-4011
Washington, DC 20555-0001 e-mail: Sepp1ha@westinghouse.coin


Our ref: LTR-NRC-O3-8

March 14, 2003

Subject: Notification of the Potential Existence of Defects Pursuant to 1OCFR21

The following information is provided pursuant to the requirements to 10CFR 21to report the potential for the existence of a SUBSTANIIAL SAFETY HAZARD. This issue concerns failure of ABB medium voltage 4 KV circuit breakers to close and latch. Westinghouse supplied these breakers for safety-related applications at the Calvert Cliffs Nuclear Power Plant.

Background

Medium voltage (4 KV) 5VHKR/250 Model 80, 1200A circuit breakers were manufactured by ABB Inc. and commercially dedicated for Class lE applications by Westinghouse and shipped to the Calvert Cliffs Nuclear Power Plant with model 5 operating mechanisms installed Recently, Westinghouse had retrofitted the breakers with model 7 operating mechanisms manufactured by ABB Inc. Westinghouse validated that the original breaker qualifications (for Class lE applications) are still applicable with the model 7 operating mechanism installed. Two of these breakers failed to close and latch during testing at Calvert Cliffs. The first breaker failed to close and latch during acceptance testing on January 18, 2003. The second breaker failed to close and latch during its installation acceptance test in the breaker cubicle on January 27, 2003.

Evaluation

It is Westinghouse understanding that the direct cause of the failures is the result of out of tolerance primary and secondary trip latches in the ABB model 7 operating mechanism. The root cause investigation is on-going to determine if manufacturing, inspection and test procedures could have contributed to these failures. While breakers failed to close and latch on demand, a failure to trip on demand has not been seen during subsequent testing of these breakers

The extent of the out of tolerance parts has not been determined. ABB Inc. is currently investigating to determine if low voltage circuit breakers with the model 7 operating mechanism are affected by the out of tolerance parts.

Westinghouse has performed a seismic re-evaluation that documents that the breakers with the model 7 operating mechanisms installed will remain closed during a seismic event.




A BNFL Group Company

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Our ref: LTR-NRC-03 -8
March 14, 2003


Failure of the circuit breaker to close could be detected by observation of the breaker or monitoring lights.

Safety Impact

The out of tolerance parts could result in a common mode failure for redundant breakers in safety systems. Based upon testing of the failed breakers, the failure to close and latch condition is intermiffent. In the case of Calvert Cliffs, if both breakers failed to close when containment spray is required, the plant could be in a condition outside the accident analysis. Based upon past testing at ABB Inc. with the model 7 operating mechanism, breakers that have been operated 300 times or more and have not exhibited the failure to close and latch condition are expected to continue to close and latch as intended

Corrective Action

Upon discovery of the breaker out-of-tolerance parts, Calvert Cliffs took corrective actions to remove the breakers that are required to close or reclose to provide a safety function.

The extent of the out of tolerance parts has not been determined. ABB Inc. is currently investigating to determine if low voltage circuit breakers with the model 7 operating mechanism are affected by the out of tolerance parts.

Plant Applicability

This notification is applicable to Calvert Cliffs In addition, ABB Inc. is determining which utilities may have purchased or may have the model 7 operating mechanism installed in their circuit breakers.

Communications

ABB Inc. and Calvert Cliffs are aware of the out of tolerance primary and secondary trip latches. A Westinghouse Nuclear Safety Advisory Letter will be sent to all Westinghouse andCombustion Engineering power plants by March31, 2003.

Very truly yours,



H.A. Sepp,Manager
Regulatory and Licensing Engineering

cc: G. Shukla



A BNFL Group company

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