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SSINS No.: 6870 Accession No: 8006190040 IN 80-31 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 August 27, 1980 Information Notice No. 80-31: MALOPERATION OF GOULD-BROWN BOVERI 480 VOLT-TYPE K-600S AND K-DON 600S CIRCUIT BREAKERS Description of Circumstances: The Cincinnati Gas & Electric Company reported problems with the Gould-Brown Boveri Type K-600S and K-DON 600S circuit breakers used in 480 volt a.c. circuits at the William H. Zimmer nuclear stations. The problem involved inadvertent circuit breaker closure during operation of the breaker charging springs when the breaker was racked out to the test position. The problem resulted from the use of undersized bushings in the circuit breaker secondary close latches. The undersized bushings caused the secondary close latch to hang-up on the shunt trip device resulting in an inadvertent circuit breaker closure when the spring charging motor was energized. The vendor has stated that the problem does not exist during normal operations with the circuit breaker in the connected position. Recommended Action for Licensees and Holders of Construction Permits: All licensees of operating nuclear power reactors and holders of construction permits should be aware of the potential problems described above. The vendor has stated that a small number of circuit breakers were assembled with undersized secondary latch bushings between 1969 and 1977. It is recommended that the following actions be taken: (1) Determine if the subject circuit breakers are installed in any safety- related application at your facility. The affected circuit breakers are manufactured by Gould-Brown Boveri and are types K-600S and K-DON 600S, 480-volt a.c. electrically operated, drawout type with static trip device. (2) If it is determined that your facility has the circuit breakers described in Item (1) above, perform the K-600S, K-DON 6005 Field Test Procedure attached to this information notice (Gould-Brown Boveri I.B.-9.1.7-6 Issue F, Addendum 2, dated March 4, 1980). (3) If maloperation of the circuit breaker occurs during performance of the field test procedure described in Item (2) above, perform the corrective action described in the attached field test procedure (installation of a 0.050 shim to the secondary close latch and retest of the circuit breaker). . IN 80-31 August 27, 1980 Page 2 of 2 No written response to this information notice is required; however, if additional information is required, contact the Director of the appropriate NRC Regional Office. Enclosure: Excerpt from Gould-Brown Boveri Letter to NRC Region III dated June 2, 1980.
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