IE Circular No. 79-17 - Contact Problem in SB-12 Switches on General Electric Company Metalclad Circuit Breakers
CR79017 August 9, 1979 MEMORANDUM FOR: B. H. Grier, Director, Region I J. P. O'Reilly, Director, Region II J. G. Keppler, Director, Region III K. V. Seyfrit, Director, Region IV R. H. Engelken, Director, Region V FROM: Harold D. Thornburg, Director, Division of Reactor Construction Inspection, IE SUBJECT: IE CIRCULAR NO. 79-17 - CONTACT PROBLEM IN SB-12 SWITCHES ON GENERAL ELECTRIC COMPANY METALCLAD CIRCUIT BREAKERS The subject circular should be dispatched for action to all power reactor licensees with a construction permit and/or operating license no later than August 14, 1979. The text of the circular and draft letter to licensees are enclosed for this purpose. Harold D. Thornburg, Director Division of Reactor Construction Inspection Office of Inspection and Enforcement Enclosures: 1. Draft Transmittal Letter 2. IE Circular No. 79-17 CONTACT: W. Laudan, IE 49-27551 . (Draft letter to all holders of Reactor Operating Licenses and Construction Permits) IE Circular No. 79-17 Addressee: This Circular is provided as an early notification of a possible significant matter. It is expected that recipients will review the information for possible applicability to their facilities. No specific action or response is requested at this time. If further NRC evaluations so indicate, an IE Bulletin will be issued to recommend or request specific licensee actions. If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office. Sincerely, Signature (Regional Director) Enclosures: 1. IE Circular No. 79-17 2. List of IE Circulars Issued in the Last 12 Months . Accession No: 7908090272 SSINS: 6830 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 August 14, 1979 IE Circular No. 79-17 CONTACT PROBLEM IN SB-12 SWITCHES ON GENERAL ELECTRIC METALCLAD CIRCUIT BREAKERS The General Electric Company, Switchgear Department in Philadelphia, reported to the NRC on July 3, 1979, an intermittent contact problem in SB-12 switches. This intermittent contact problem will cause a lack of continuity through the "a" contact of the switch that is used to energize the trip coil of the circuit breaker. Investigation disclosed that a die used to form a hole in the contact arms of the switch had worn, resulting in elongated holes. This condition could permit the contact bridge member to move laterally relative to the contact arm, occasionally resulting in improper "a" contact wipe. The worn die has been corrected, and all switches shipped on or after July 1, 1979, include this correction. A review of the history of these components indicates that switches shipped in the time period of August 1, 1978, to July 1, 1979, could have this problem. The trip coil and auxiliary switch portion of the trip circuit is monitored for continuity by a red light on the front door of the switchgear. This light is lit when the breaker is closed and the control circuits are energized. If the red light is lit, this indicates that the "a" contacts of the switch are closed, and that a trip signal will trip the breaker. Based on the above, the licensees are advised to do the following: 1. Insure that all General Electric Company Metelclad Circuit Breakers shipped to your facilities during the period from August 1, 1978 to July 1, 1979 and used in or affecting the operation of safety related equipment are furnished with new SB-12 control switches as promptly as possible. 2. Pending replacement of SB-12 control switches administrative controls should be initiated to assure the red light which demonstrates contact continuity, is lit and remains lit each time these circuit breakers are closed. No written response to this circular is required. If you require additional information regarding this subject, contact the Director of the appropriate NRC Regional Office.
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