Bulletin 75-06: The Westinghouse Electric Corporation
BL75006 Inspection and Enforcement Bulletin No. 75-06 May 30, 1975 DEFECTIVE WESTINGHOUSE TYPE OT-2 CONTROL SWITCHES DESCRIPTION OF CIRCUMSTANCES: The Westinghouse Electric Corporation recently reported to the NRC the finding of a number of defective Westinghouse type OT-2 electrical switches in the main control board of the Sequoyah Station. The defective switches were found during installation of the main control board of the Sequoyah Station, which is currently under construction. The defective switches are of a spring-return-to-neutral type. Manual operator action of the switch involves rotating the switch clockwise or counterclockwise, and an internal spring force returns it to the central neutral position. Westinghouse reported that internal friction caused some switches to bind and fail to return to the neutral position, due to an adverse tolerance stack-up on internal switch components. Corrective action has been taken to replace the defective switches in the Sequoyah Station. Westinghouse has issued a Technical Bulletin to utilities with Westinghouse NSSS's in operation, advising them of the potential for similar defective switches in these facilities. These switches may also be installed in other nuclear power facilities. In case of uncertainty, licensees are advised to contact the Westinghouse Control Products Division regarding test instructions and replacement procedures for these switches. ACTION TO BE TAKEN BY LICENSEES: For all power reactor facilities with operating license or construction permit: 1. Determine if switches of the type described above are in use, or planned for use, in safety related systems of your power reactor facility(ies). . -2- 2. Notify this office in writing, within 30 days for facilities with an operating license and within 60 days for facilities with a construction permit, of the results of your findings with regard to item 1, above. 3. If switches of the type described are in use or planned for use in Safety related systems, include in your written reply to this Bulletin the extent of their use and the actions you have taken or plan to take to prevent malfunction of the type described above. Your written reply should include the date(s) when your actions in response to this Bulletin were or will be completed.
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