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Information Notice No. 82-54: Westinghouse NBFD Relay Failures in Reactor Protection Systems
SINNS No.: 6835 IN 82-54 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 December 27, 1982 Information Notice No. 82-54: WESTINGHOUSE NBFD RELAY FAILURES IN REACTOR PROTECTION SYSTEMS Addressees: All holders of a nuclear power reactor operating license (OL) or construction permit (CP). Purpose: This information notice is provided as an early notification of a potentially significant problem pertaining to a certain "batch" of Westinghouse (W) NBFD relays used in the reactor protection system and engineered safeguards systems. This problem may affect both PWR and BWR facilities. The Nuclear Regulatory Commission (NRC) staff is reviewing the problem and its effects. If the evaluation so indicates, the NRC may request further licensee action. In the interim, we expect the addressees of this information notice to review the information herein for applicability to their facilities and to take appropriate actions. No specific action or response is required at this time. Description of Circumstances: Wisconsin Electric Power Company (WEPC) issued Licensee Event Report 82- 026/OIT-0 on December 7, 1982, notifying the NRC that replacement relays and coils for W NBFD relays installed at Point Beach Unit 1 have experienced a higher-than-expected failure rate following post-installation tests. According to the licensee, failure was attributed to coil filler epoxy which flows during service into the plunger cavity, inhibiting or preventing the relay from moving to a de-energized position after power is removed. The relays had been replaced to correct deficiencies discussed in IE Information Notice 82-02. After reviewing the above problem, Westinghouse has issued a technical data letter via an electronic mailgram to all sites having a W Resident Engineer, and has made telephone contact with those W PWRs that do not have a permanent W Resident Engineer. An extract from the latest version of this technical data letter is attached for your information and appropriate use. The technical data letter discusses the problem and provides inspection and test methods for verifying operability of normally energized and de-energized NBFD relay applications in safety-related systems. The technical data letter recommends that after completing the initial inspection/test of all NBFD relays received after October 29, 1981, these normally energized relays be retested weekly until the "sticking" problem is resolved. The technical data letter also provides the relay coil style number to facilitate identification of the potentially affected relays. 8208190275 . IN 82-54 December 27, 1992 Page 2 of 2 Since the NBFD relay is not unique to W PWR power plants, the problem may also exist at other nuclear power plants. Therefore, we advise all nuclear plants to review their safety-related systems to ascertain whether NBFD relays received after October 21, 1981 have been installed, or are being held as spare parts. If you have any questions regarding these matters, please contact the administrator of the appropriate Regional Office or this office. Edward L. Jordan, Director Division of Engineering & Quality Assurance Office of Inspection and Enforcement Technical Contact: V. D. Thomas 301-492-4755 Attachments: 1. Extract from Westinghouse Technical Letter 2. List of Recently Issued IE Information Notices . Attachment 1 IN 82-54 December 27, 1982 Page 1 of 2 EXTRACT FROM WESTINGHOUSE TECHNICAL DATA LETTER "NBFD RELAYS" DATED DECEMBER 9, 1982. ALL PLANTS WITH NBFD RELAYS IN I&C PROTECTION SYSTEM The following information is provided as a recommendation from Westinghouse as to a representative procedure which may be conducted to assure proper operation of certain NBFD relays. You may have additional information concerning previous operational history of the subject relays coupled with comparable testing programs that are already implemented and would provide you sufficient assurance of proper operations. Response time testing of the relays which you may have included in your test program would also provide important information to support your evaluation of the performance of these relays. Whichever choice you make with regard to testing of these relays, please forward the test data and program information to Westinghouse for our information during our continuing review of this problem. We will keep you advised of our progress and the outcome of our evaluation. Recent information indicates that there is a possibility of sluggish operation of NBFD relays when they are de-energized. The following are Westinghouse interim recommendations pending final resolution of this possible problem with the NBFD relay coils. They apply to all plants having: 1. Installed NBFD relay coils bearing style No. 1293C51G01 2. Installed NBFD relay coils received after October 29, 1981: or 3. Installed NBFD relay coil whose vintage cannot be identified. Previous information or instructions provided concerning this potential problem with NBFD relays is superseded by this notice. IMMEDIATE ACTION Perform a complete test of the reactor trip system in accordance with surveillance test procedures to confirm operability of normally energized NBFD relays which open the reactor trip breakers or which provide power level permissive signaling such as P-7. At that step in the procedure where the relay is de-energized, manually depress and release the contact block actuation buttons several times. The movement should be positive, free and unrestricted. Any abnormal resistance during depression of the buttons or sluggish non-snapping return of the buttons upon release should be considered evidence that the plunger is binding. In such cases refer to the CORRECTIVE ACTION section of this notice. In conjunction . Attachment 1 IN 82-54 December 27, 1982 Page 2 of 2 with the relay functional tests, all relay cabinets should be visually examined for indications within the rack of molten or soft epoxy flowing out of the relay housings. All normally energized reactor trip and permissive relays in this system must be tested. During this interim period, all tests on these relays should be conducted weekly. Normally de-energized NBFD relays associated with initiation of safeguards should be manually tested and visually examined as described above, but with proper coordination with plant operators to block actuation of the final device where necessary. The weekly tests on normally energized relays should not be required for the safeguards normally de-energized relays. However, in the event that the normally de-energized relays are energized for an extended period of time, the possibility exists for the plunger to bind and prevent smooth, quick return to the de-energized mode. Station operators should be alerted to the potential need for manual intervention should a safeguards relay bind up and fail to return to the de-energized state. In the event that battery equalizing is necessary during this interim period, the tests of the normally energized reactor trip and permissive relays should be conducted immediately following the battery equalization cycle. CORRECTIVE ACTION Any relay coil found to have sluggish or restricted plunger travel or any evidence of uncured epoxy must be replaced. Before installing any replacement coil with style #1293C51G01, the coil should be oven heated at no less than 200 degrees Fahrenheit for no less than 2 hours and visually inspected for evidence of flow of the black filler epoxy. The coil bore should also be carefully inspected. After installation of oven heated coils into the relay assembly, electrical and manual tests should be conducted periodically to confirm proper operation. All suspect coils may be returned to Westinghouse for replacement. Westinghouse plans to test our current stock for use in replacing previously shipped suspect coils.
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