United States Nuclear Regulatory Commission - Protecting People and the Environment


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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