United States Nuclear Regulatory Commission - Protecting People and the Environment

LICENSEE: SOUTH CAROLINA ELECTRIC & GAS CO.
SITE: SUMMER 1 EN NUMBER: 35677
DOCKET: EVENT DATE: 05-02-99
RX TYPE: PWR EVENT TIME: 18:00
VENDORS: W-3-LP NOTIFY DATE: 05-05-99
EMERGENCY CLASS: N/A REGION: 2 STATE: SC TIME: 10:17
OPS OFFICER: LEIGH TROCINE
10 CFR SECTION: CCCC UNSPECIFIED PARAGRAPH

UNIT
SCRAM
CODE
RX
CRIT
INIT
PWR
INITIAL
MODE
CURR
PWR
CURRENT
MODE
1 N N 0 Refueling 0 Refueling

GENERIC CONCERNS REGARDING A COMMON MODE FAILURE FOR MAGNE-BLAST BREAKERS

The following text is a portion of a facsimile received from the licensee:

"This is report is being made pursuant to 10CFR21.21 to identify a Substantial Safety Hazard with General Electric 7.2-kV Magne-Blast Breakers."

"On April 15, 1999, V.C. Summer Nuclear Station submitted a potential Substantial Safety Hazard report due to 7.2-kV breakers which failed to close. After further investigation and testing, it has been determined that a Substantial Safety Hazard could exist with this failure to close. The identified problem deals with a cotter pin striking the latch check switch mounting bracket and bending it forward. This removes the factory set clearance between the bracket and the switch actuating paddle.

This results in the paddle, which is bolted to the trip shaft, rolling the trip shaft to the trip position when the breaker attempts to close. The cotter pin problem is considered a defect in repair. This condition represents a potential for a common mode failure for safety-related Magne-Blast breakers."

"V.C. Summer Nuclear Station utilizes these breakers in many applications, including the 7.2-kV Emergency Diesel Generator electrical buses."

"The function of the latch check switch is to enable rapid repeated breaker closures, which is not required in the V.C. Summer application of these breakers. Engineering has determined that removal of the latch check switch, the latch switch mounting bracket, and the actuating paddle will prevent recurrence of this problem in the future."

The licensee stated that this action has already been taken on all of the safety-related Magne-Blast breakers. However, this action has not been taken for the non-safety-related Magne-Blast breakers located in the balance of plant. These breakers are normally closed and stay closed throughout the cycle. The licensee stated that these are not restart items. All have been done with the exception of four, which feed the transformers for the 480-V switchgear.

The licensee notified the NRC resident inspector

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