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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