Bulletin 73-02: Malfunction of Containment Purge Supply Valve Switch
IEB 73-02 UNITED STATES ATOMIC ENERGY COMMISSION DIRECTORATE OF REGULATORY OPERATIONS REGION II - SUITE 818 230 PEACHTREE STREET, NORTHWEST ATLANTA, GEORGIA 30303 July 13, 1973 Gentlemen: The attached Directorate of Regulatory Operations Bulletin No. 73-2, "Malfunction of Containment Purge Supply Valve Switch," is sent to you to provide you with information we received from the Wisconsin Electric Power Company concerning the Point Beach 2 pressurized water reactor facility. This information may relate to the design and performance of certain equipment at your facility. Action requested on your part is identified in Section B of the bulletin. Very truly yours, Norman C. Moseley Director Enclosure: RO Bulletin 73-2 . July 15, 1973 RO Bulletin 73-2 MALFUNCTION OF CONTAINMENT PURGE SUPPLY VALVE SWITCH We recently received information from the Wisconsin Electric Power Company concerning a problem found during functional testing following maintenance at the Point Beach 2 pressurized water reactor which may relate to the design and operation of the control circuit for containment purge valves at your facility. Pertinent details relating to this problem are contained in Section A below. Action requested by this Bulletin is contained in Section B. A. Description of Circumstances During the performance of functional testing of one of the Unit 2 containment purge valves following maintenance, the valve opened when the manual control switch was moved to the open position but failed to close when the switch was placed in the closed position. In the Point Beach facility design, the redundant pneumatic operated, air to open containment purge supply valves are manually controlled by a signal switch. For testing purposes during facility operation, instrument air is secured to one valve that remains closed to maintain containment integrity while the other valve is being tested. Subsequent investigation by the licensee revealed that a small screw which secures the contact closing cam to the manual portion of the switch had loosened. This permitted the cam to stay in the "Contacts Closed" position and prevented further manual operation of the switch from opening the contacts and closing the valve. A followup review of electrical drawings also revealed that in the event of a similar switch failure open redundant purge valves would not close on receipt of a containment isolation signal. The corrective action for this apparent design deficiency consisted of modifying the control circuit such that each individual valve is operated by a separate switch. Thereby, a malfunction of a single switch can result in one valve failing to close with containment integrity maintained by the redundant valve. B. Action Requested of the Licensee It is requested that you review the design of the control circuit for the containment ventilation system isolation valves installed at your facility to determine whether the failure of a single . - 2 - control switch could result in the simultaneous failure of the redundant supply valves or redundant exhaust valves and provide this office with your findings. If the results of your review indicate that the simultaneous failure of the redundant containment purge valves could exist under the conditions described above, please include in your response a description of the corrective action taken or planned and the date of scheduled completion of your corrective actions. This information should be provided to this office, in writing, within 45 days of your receipt of this letter.
Page Last Reviewed/Updated Friday, May 22, 2015