Information Notice No.80-31 - Maloperation of Gould-Brown Boveri 480 Volt-type K-600s and K-DON 600s Circuit Breakers
SSINS No.: 6870
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
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
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
(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).
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.
Excerpt from Gould-Brown Boveri
Letter to NRC Region III dated
June 2, 1980.
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