Bulletin 78-05: Malfunctioning of Circuit Breaker Auxiliary Contact Mechanism - General Electric Model CR105X
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 April 14, 1978 IE Bulletin No. 78-05 MALFUNCTIONING OF CIRCUIT BREAKER AUXILIARY CONTACT MECHANISM - GENERAL ELECTRIC MODEL CR105X Description of Circumstances: The Sacramento Municipal Utility District recently reported a problem encountered with the operation of the GE Model CR105X auxiliary contact mechanism installed in a 480 volt circuit breaker. Investigation into the cause for the inability to shutdown a booster supply fan (SF-A-7) in the control room emergency air conditioning system revealed that an auxiliary contact (GE Model CR105X) had failed in the closed position, preventing the fan's power supply circuit breaker from opening. The specific cause for failure was binding of the plunger arm due to burrs and nicks on its surface. An investigation was conducted by the licensee to determine the extent of usage of this type auxiliary contact in other circuits throughout the reactor power plant. Approximately fifty (50) positions in the nuclear service motor control centers were identified as having a similar type auxiliary contact mechanism. It was also determined that many of the affected systems which require contact operation similar to that described above, either permit or provide a safety feature function during emergency conditions. An example of this type application is auxiliary contacts that must open to permit closing of certain safety related valves from 480 volt motor control centers. The attached GE Service Advice Letter and associated instruction/drawing sheet were sent to all nuclear power reactor facilities by GE Field Service Offices. The letter, together with the instruction/drawing sheet identifies the problem and provides the recommended corrective action. Action To Be Taken By Licensees: For all power reactor facilities with an operating license or construction permit: 1 of 2 . IE Bulletin 78-05 April 14, 1978 1. If you have received the enclosed General Electric letter and instruction/drawing sheet addressing the auxiliary contact mechanism problem, and if you have these devices in use at your facility, it is requested that you describe what corrective action you have taken. 2. If you have not received the enclosed GE documents before, it is requested that you describe what action you plan to take if the GE CR105X auxiliary contact mechanism is in use or planned for use in safety systems at your facility(ies). 3. Facilities having an operating license should report in writing, within 45 days, and facilities with construction permits within 60 days, the results of action taken or planned with regard to Items 1 and 2 above. Your written reply should also include the date when such actions were or will be completed. Reports should be submitted to the Director of the appropriate NRC Regional office and a copy should be forwarded to the U. S. Nuclear Regulatory Commission, Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Office of Inspection and Enforcement, Washington, D, C, 20555. Approved by GAO, B180225 (R0072); clearance expires 7/31/80. Approval was given under a blanket clearance specifically for identified generic problems. Attachments: 1. GE Letter 2. GE Control and Instruction Sheet 2 of 2
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021