ML20096E651

Part 21 Rept Re Failure of MOV Motor Pinion Gear Mfg by Limitorque at Byron Station.Replacement & Insp Activities Initiated for Potentially Impacted Populations of MOVs at Byron & Braidwood Stations

ML20096E651
Person / Time
Site:	Byron, Braidwood
Issue date:	01/18/1996
From:	Graesser K COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-96 BYRON-96-0016, BYRON-96-16, NUDOCS 9601220338
Download: ML20096E651 (5)

Text

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POWER RENCTORE EVENT NUMBER: 29853 1

FACILITY: BYRON REGION: 3 NOTIFICATION DATE: 01/18/96 UNIT: [1] [2] [] 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) 1 NRC NOTIFIED BY: D PETERS'ON 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 i UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX MODE I

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. 3600 RPM, 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. l 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 l USED FOR THIS SIZE OPERATOR. AISI 11B44 MATERIAL IS A FREE-MACHINING, i RE-SULFERIZED, BORON-BEARING CARBIDE STEEL. BASED ON THE RESULTS OF THE I MATERIAL ANALYSIS, IT APPEARS AS IF THE FAILED MOTOR PINION GEAR WAS MACHINED FROM CAST STOCK. THE MOTOR PINION GEAR FAILURE WAS ATTRIBUTED TO l THE POOR MECHANICAL PROPERTIES OF THE PART AND THE INABILITY OF THE GEAR TO I SUSTAIN SERVICE LOADS. THE USE OF THE IMPROPER MATERIAL IN THE MOTOR PINION l 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). j PART 21 WAS FACSIMILED TO VERN HODGE NRR/PCEB.

9601220338 960118 PDR ADOCK 05000454 S PDR gq Ut  ;

SENT BY; 1-18-36 1:04PM : COM ED CENTRAL FILE- 301 8165151:: 1 o.ininonwc.ath toron i.o.nn.iny Hyron Genenstute Stacit.o

+ 40 NonlHiennan t:hurch Rimi il 3nm. II.C.inin 9M s Tei m . n r .i .

January 18.1996 I

l LTR: BYRON 96-0016 FILE: 2.01.0703 U. S. Nuclear Regulatory Commission Washington, DC 20555 1

l

Attention

Document Contml Desk l l

[

Subject:

Byron Station Units I and 2 '

Braidwood Station Units 1 and 2 j 10 CFR Part 21 Notification i improper Material in Motor Operated Valve Motor Pinion Gear NCR Dockets 50-454 and 50-455 l l

NCR Docketr 50-456 and 50-457 Applicability This notification is submitted in accordance with the requirements of 10 CFR Part 21, Section 21.21(b),21.3a(3), and 21.3d(4).

Identification of Facilities and Comnonents -

Byron Nuclear Generating Station Units 1 and 2 Braidwood Nuclear Generating Station Units 1 and 2 Motor Pinion Gears used in Motor Operated Valves (MOVs) procured from Westinghouse Electric Corporation and supplied to Westinghouse by I.imitorque Corporation.

Actuator Size: SB-0 Motor: 25 Ft.-lb. 3600 RPM Motor Pinion: 34 tooth part #60-415-0100-1 Identifiention of Comnonent Manufacturer /Sunolier Limitorque Corporation 5114 Woodall Road BYRON NUCLEAR POWER STATION j,a p,a-G P.O. Box 11318

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'SENT BY: 1-18-96 : 1:04PM : COM ED CENTRAL FILE- 301 8165151:e 2-Byron Ltr. 96-0016

Page 2

, January 18,1996 Nature of Defect The defect is related to the failure of a motor pinion gear at Byron Stadon. On 10/25/95, the ICV 8105 motor operated valve (MOV) at Byron Station failed mid-stroke when it was being closed during normal plant operations. Subsequent troubleshooting indicated that the failure was due to a sheared motor pinion gear. Material analysis of the failed motor pinion gear determined that the gear was made of an improper material. The  !

material used was 11 B44 versus the 4140,4320, or 86L20 material that should have been used for this size operator. ATSI 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 l

led to the failure of the ICV 8105 valve to operate.

Time of Discovery The failure of the ICV 8105 valve ocO2rred on 10/25/95. Comed determined that the failure was a potential defect subject to the provisions of 10CFR21 on 11/21/95. Final determination that the defect was reportable per 10CFR21 was made on 1/12/96. i l

Ntimber and Location of All Defective ComponenlE l

The only known defective motor pinion gear was identified in the 1CV8105 valve at  ;

i

. Byron Station. The 1CV8105 valve at Byron Station was one (1) of 12 MOVs that were l

purchased as a group from Westinghouse Electric Corporation for Comed's Byron and I Braidwood Stations (6 MOVs for cach station). The actuators / motors for these twelve (12) valves were purchased from Limitorque Corporation by Westingbouse and supplied to Comed.

l Corrective Actions:

l l Comed initiated replacement and inspection activities for the potentially impacted l population of MOVs at Byron and Braidwood Stations including testing of 14 spare I

replacement motor pinion gears in Comed Stores of that particular gear size. To date,20 of 21 gears tested have been determined to be of the correct material. The only identified use of the improper material was in the motor pinion gear that was removed from the ICV 8105 valve at Byron Station. Two (2) MOVs at Braidwood Station from the suspect purchase order were subsequently determined to have different gear ratios and not be impacted by this defect. From the original lot of MOVs purchased together, two (2)

MOVs at Byron Station and one (1) MOV at Braidwood Stadon remain to have their motor pinion gears replaced and inspected. These MOVs are on operating units at the respective stations.

I l . . . . . .. .

SENT BY: 1-18 96 1:04PM :_bOhEDCENTRALFILE- 301 8165151:# 3 Byron Ltr. 96-0016 Page 3 January 18,1996 i

The inspection and replacement activitics will take place prior to or during the next l -outage on each unit. These actions are being tracked by the station's respective corrective

! action programs.

At this time, based on conversations with the vendor, Limitorque Corporation, and the positive inspection results of other potentially impacted components, Comed believes that the presence of the defective material in the ICV 8105 valve at Byron Station was an isolated incident. Beyond the inspection of'the thrc'e (3) remaining motor pinion gears at

^

Byron and Braidwood Stations, no further actions are anticipated. However, it is Comed's understanding that the vendor is currently evaluating this defect for any generic applicability and will notify licensees, as appropriate. .

10 CFR 21 Evalmtian The 1CV8105 valve at Byron Station is a safety related valve in the Chemical and Volume Control System (CVCS) that is used as an isolation valve during nonnal charging activities. The specific failure of the 1CV8105 valve on 10/25/95 did not lead to an incident of significant magnitude. However, there was a potential for a more significant event. There is a redundant valve (ICV 8106)in series with the 1CV8105 valve that is capable of performing the same design function. However, the presence of  !

the improper material'in the ICV 8105 did represent a reduction in the inherent design margin of the system.

Therefore, Comed has determined that the procurement of the motor pinion gear with the improper material does constitute a defect per the fcquirements of 10CFR21 and is providing this notification to the NRC.

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!SEhTBy:.- 1-18-96 1:05PM : COM ED CENTRAL FILE- 301 8165151;# 4 i:

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l _ Byron Ltr 96-0016 Page 4 January 18,1996 i Contact Questions pertaining to this notification should be addressed to:

Bradley J. Adams Site Engineering

- Comed Byron Station -

4450 N. Gennan Chuich Road Byron, Illinois 61010 (815) 234-5441 x2979 Sincerely, K. L. Graesser Site Vice President t

Byron Nuclear Station l KLG/BAltp cc: H. Miller, Regional Administrator-RIII H. Peterson, Senior Resident inspector (Byron) i C. Phillips, Senior Resident Inspector (Braidwood)

G. Dick - NRR R. Assa - NRR Office of Nuclear Facility Safety - IDNS l

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