Part 21 Report - 1996-170
ACCESSION #: 9601220338
POWER REACTOR EVENT NUMBER: 29853
FACILITY: BYRON REGION: 3 NOTIFICATION DATE: 01/18/96
UNIT: [1] [21 [ I STATE: IL NOTIFICATION TIME: 14:04 [ET]
RX TYPE: [1] W-4-LP,[2] W-4-LP EVENT DATE: 01/18/96
EVENT TIME: 14:00[CST]
NRC NOTIFIED BY: D PETERSON LAST UPDATE DATE: 01/18/96
HQ OPS OFFICER: JOHN MacKINNON
NOTIFICATIONS
EMERGENCY CLASS: NOT APPLICABLE
10 CFR SECTION:
CDEF 21.21(b)(2) DEFECTS/NONCOMPLIANCE
UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX MODE
1 N N 0 0
2 N N 0 0
EVENT TEXT
FAILURE OF A MOTOR PINION GEAR AT BYRON STATION.
MOTOR PINION GEARS USED IN MOTOR OPERATED VALVES PROCURED FROM
WESTINGHOUSE ELECTRIC CORPORATION AND SUPPLIED TO WESTINGHOUSE BY
LIMITORQUE CORPORATION. ACTUATOR SIZE:SB-0, MOTOR: 25 Ft-lb. 3600RPM,
MOTOR PINION: 34 TOOTH PART #60-415-0100-1.
THE DEFECT IS RELATED TO THE FAILURE OF A MOTOR PINION GEAR AT BYRON
STATION. ON 10/25/95, THE 1CV8105 MOTOR OPERATED VALVE AT BYRON
STATION
FAILED MID-STROKE WHEN IT WAS BEING CLOSED DURING NORMAL PLANT
OPERATIONS. SUBSEQUENT TROUBLESHOOTING INDICATED THAT THE FAILURE
WAS
DUE TO SHEARED MOTOR PINION GEAR. MATERIAL ANALYSIS IF THE FAILED
MOTOR
PINION GEAR DETERMINED THAT THE GEAR WAS MADE OF AN IMPROPER
MATERIAL.
THE MATERIAL USED WAS 11B44 VERSUS 4140, 4320, OR 86L20 MATERIAL THAT
SHOULD HAVE BEEN USED FOR THIS SIZE OPERATOR. AISI 11B44 MATERIAL IS A
FREE-MACHINING, RE-SULFERIZED, BORON-BEARING CARBIDE STEEL. BASED
ON THE
RESULTS OF THE MATERIAL ANALYSIS, IT APPEARS AS IF THE FAILED MOTOR
PINION GEAR WAS MACHINED FROM CAST STOCK. THE MOTOR PINION GEAR
FAILURE
WAS ATTRIBUTED TO THE POOR MECHANICAL PROPERTIES OF THE PART AND
THE
INABILITY OF THE GEAR TO SUSTAIN SERVICE LOADS. THE USE OF THE
IMPROPER
MATERIAL IN THE MOTOR PINION GEAR DIRECTLY LED TO THE FAILURE OF THE
1CV8105 VALVE TO OPERATE. BRAIDWOOD STATION ALSO PURCHASED 6 OF
THESE
MOTOR PINION GEARS (IDENTIFIED IN THE 1CV8105 VALVE).
PART 21 WAS FACSIMILED TO VERN HODGE NRR/PCEB.
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