Part 21 Report - 1997-571

ACCESSION #: 9708250224 NSD-NRC-97-5267 Westinghouse Energy Systems Nuclear Services Division Electric Corporation Box 355 Pittsburgh Pennsylvania 15230- 0355 August 19, 1997 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Attention: NRC Operations Center Subject: Notification of the Potential Existence of Defects Pursuant to 10CFR21.21 Westinghouse has identified a possible defect in a basic component that could potentially create a substantial safety hazard and therefore is deemed reportable under 10CFR21.21. Background/Evaluation Three HMCP (Motor Circuit Protectors) molded case circuit breakers were recently returned to Westinghouse's vendor, Cutler-Hammer when the utility determined that some of the poles were tripping outside the setpoint calibration range. These breakers were verified to be within specification before shipment as part of the Westinghouse commercial dedication process, but two tested out of specification before installation at the plant and one tripped in service when the motor was started. All were found with at least one pole out of specification when returned. HMCP Series C breakers, through magnetic trip action, provide instantaneous short circuit protection for motor circuits. These breakers have ratings from 3 amps to 600 amps in three frame sizes. The three breakers returned were all 400 amp. Safety Significance The setpoint on an HMCP breaker is selected to provide circuit protection without tripping on motor starting current. Several trip ranges are available for selection on each breaker. If the setpoint is not within the selected range, the possibility exists that the circuit will open preventing a safety-related motor from starting. However, confidence in continued system performance can be established by a history of successful motor start tests even if the breaker was not tested at the plant prior to installation. Plant Applicability The recommended actions apply to all plants that utilize these breakers for safety-related motor circuits. [Illegible] NSD-NRC-97-5267 2 August 19, 1997 Recommendations/Corrective Action Although setpoints of HMCP breakers are verified during the commercial dedication process, Westinghouse will recommend that the setpoint for breakers in safety-related motor circuits be verified prior to installation at the plants in addition to periodic surveillance testing. Limited feedback from utilities indicates that this verification is a typical practice. If you have any questions regarding the notification, please call me at 412/374-5282. Sincerely, H. A. Sepp, Manager Regulatory and Licensing Engineering 2508C-RBM-2:081197 *** END OF DOCUMENT ***

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