ML20011F426

LER 90-002-00:on 900117,hold Down Screws on Sylvania Contactors in Motor Control Ctrs Found Loose.Caused by Mfg Deficiency.Contactor Screws Tightened.All Hold Down Screws Will Be Replaced W/Another type.W/900223 Ltr

ML20011F426
Person / Time
Site:	McGuire
Issue date:	02/16/1990
From:	Mcconnell T, Sipe A DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-002-02, LER-90-2-2, NUDOCS 9003060015
Download: ML20011F426 (8)

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, bake her Conpany 000MM J: ,

, McGuirr Nuclear Station ,*

12700 Hagers krry Road -

Huntersville, AC280iH985 DUKE POWER t

February 23, 1990 i

4 U.S. Nuclear Regulatory Commission  !

Document Control Desk

! Washington, D.C. 20555  :

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h Subjecta McGuire Nuclear Station Units 1 and 2 l Docket No. 50-369  :

L: Licensee Event. Report 369/90-02 J i i.

! Gentlemen:

Pursuant.to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Evenc e Report 369/90-02 concerning loose holddown screws on Sylvania contactors in Motor =

Control Centers. This report is being submitted.as a voluntary report. This event is considered to be of no significance with respect to the health and safety of ,

the public. ,

Very truly yours, b (- DL"> '

7L j T.L. McConnell DVE/ADJ/cb1 ,

Attachment xc: Mr. S.D. Ebneter American Nuclear Insurers Administrator, Region II c/o Dottie Sherman, ANI Library U.S. Nuclear Regulatory Commission The Exchange, Suit 245 101 Marietta St., NW, Suite 2900 270 Farmington Avenue Atlanta, GA 30323 Farmington, CT 06032 INPO Records Center Mr. Darl Hood Suite 1500 U.S. Nuclear Regulatory Commission  ;

I- 1100 Circle 75 Parkway Office of Nuclear Reactor Regulation Atlanta, GA 30339 Washington, D.C. 20555 M&M Nuclear Consultants Mr. P.L Van Doorn 1221 Avenue of the Americas NRC Resident Inspector ,

New York, NY 10020 McGuire Nuclear Station

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! bxc: B.W. Bline ll A.S. Daughtridge J.S. Warren 7 R.L. Gill R.M. Glover (CNS)

T.D. Curtis:(ONS) i P.R. Herran

.S.S. Kilborn (W)

R.E. Lopez-Ibanez

, M.A. Mullen

[ R.O. Sharpe (MNS)  ;

G.B. Swindlehurst (

l- K.D. Thomas  !

M.S. Tuckman o L.E. Weaver '

f R.L. Weber J.D. Wylie (PSD)-

3 J.W. Willis

-QA Tech. Services NRC Coordinator (EC 12/55)

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McGuire Nuclear Station, Unit 1 o is to ro lol3 i6 l 9 t lor l 0l6 l Hold Down Screws On Sylvania Contactors In Motor Control Centers Were Found Loose Because Of A Manufacturina Deficienev ivtant Dart (81 Ltn asuaabtR lei htP0mt Dart (t) OTMth 8 ACILiteit INv0LytD (4) 88$yi$

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On January 17, 1990, McGuire Nuclear Station (MNS) personnel were notified by Catawba Nuclear Station (CNS) personnel of a problem identified at CNS with hold down screws on Sylvania (Clark) Contactor types TM 00, TM 1, and TM 2 becoming loose. This problem could potentially cause improper contactor operation. Based on this information, MNS Maintenance Engineering Services, and Instrumentation and Electrical personnel initiated an inspection of the Safety Related Motor Control Centers at MNS to identify any contactors with loose hold down screws. Subsequent inspection revealed 14 contactors with loose hold down screws. However, no safety l related contactors were found to be inoperable. This incident has been assigned a

! cause of Manufacturing Deficiency because of poor material selection. Unit I was l in Mode 5 (Cold Shutdown) and Unit 2 was in Mode 1 (Power Operation) at 100% power l

at the time this incident was discovered. All contactor screws found loose were tightened according to manufacturer recommendations after inspection. All hold down screws will be replaced with another type to prevent recurrence of this problem. This report is being submitted as a voluntary LER.

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EVALUATION:

Background

-The 600 volt Essential Motor Control Center (EPE) system [EIIS:ED) is made up of two completely redundant and independent networks, designated Tre.in A and Train B.

Train A and Trais B feed identical loads that perform the same #. unction. Either  :

the Train A or Train B EPE system can power all of the necessary essential loads.

The Motor Control Centers (MCCs) are made up of breaker compartments containing combination full voltage reversing and non-reversing starters, combination full volt ge non-reversing contactors (EIIS:CNTR), and feeder breakers [EIIS:52] which feed the various loads, The combination full voltage non-reversing contactor is a remote control magnetic switching device used to energize electrical equipment. The contacts are mounted on a moveable carrier held in place by two hold down screws. Spring tension holds the contacts in the open position until a remote signal energizes a magnetic coil to close them and therefore, energize the equipment.

Description of Event On January 4, 1990, CNS personnel discovered a problem with Sylvania (Clark)

Contactor hold down screws becoming loose. This problem was addressed by CNS Problem Investigation Report (PIR) number 0-C90-0008. -

6.

On January 17, 1990, MNS personnel were notified of the problem and the possibility for improper operation of similar contactors at MNS. Based on this information,

Maintenance Engineering Services (MES) personnel initiated work requests 69765, 69766, 69767, and 69768 to perform a visual inspection of the two contactor hold down screws on Sylvania (Clark) MCC Contactor types TM 00, TM 1, and TM 2 to ensure that they were tight. This inspection was to be performed on all safety related

! contactors of this type at MNS.

At 1430 on January 17, 1990, Instrumentation and Electrical (IAE) personnel discovered one of the contactor hold down screws on cubical R02F at MCC 2EMXF to be backed out approximately one inch and the other screw to be loose. The loose screws were on a normally open contactor which controls valve [EIIS:V] 2RN-174B, Diesel Generator [EIIS:DG) 20 Meat Exchanger (EIIS:HX] Control. Emergency Work Request 69764 was generated to repair the problem with the contactor.

l MES personnel also initiated PIR 0-M90-0024 to resolve the problem of loose I

contactor hold down screws.

IAE personnel tested the operation of the contactor in question by first taking resistance readings across the contacts and then having Operations personnel close the breaker and cycle the valve. No problems were noted. IAE personnel then torqued the hold down screws per manufacturer recommendation. Again, IAE personnel took resistance readings and had the valve cycled. No differences were noted.

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Subsequent inspections were periormed by 1AE personnel of all safety related MCC '

compartments with Sylvania (Clark) type TM 00, TM 1, and TM 2 contactors. The following is a list of the compartments found with loose hold down screws and the corrective work request number for each. '

i MCC Inspection Corrective Cubical Work Reg. No. Work Req. No.

1 UNIT 1 Train 1A a 1EMXH-5A 69765 69774 1EMXA4-2A 69765 69776 1EMXH1-1B 69765 69777 1EMXA2-3A 69765 69775 IEMXA2-3B 69765 69775 3

Train IB .

1EMXB2-F3C 69766 69785 UNIT 2 Train 2A 2EMXE-R2D 69767 69786 2EMXE-F3D 69767 69786 Train 2B 2EMXB2-F3A 69768 69770 2EMXB2-R2C 69768 69771 2EMXB2-RIA 69768 69772 2EMXB2-F3C 69768 69769 2EMXH-R3D 69768 69773 2EMXF-R2F 69768 69764 All contactors were repaired and the inspection was completed on January 22, 1990.

Design Engineering (DE) personnel reviewed the actions taken by MES and IAE personnel and stated that they had uatisfactorily tested the contactors and proved operability prior to correcting the problem. DE personnel also performed a seismic

) operability calculation and concluded that the contactors were operable.

Project Services personnel generated McGuire Exempt Variation Notice (MEVN) 2174 to add attachments to Nelson Electric Vendor Manual, MCM-1314.01-166, to specify vendor supplied torque specifications for Sylvania (Clark) contactor hold down screws. . This facilitated repair of the loose screws.

New screws with a 1/4 inch nylon patch on the bottom threads were ordered as a replacement for all the hold down screws presently in use. These screws should prevent recurrence of the problem since the nylon patch on the bottom threads will prevent the screw from becoming loose, g$4awsena .v. .. m, i ...noo.., oev o

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Conclusion 1 l

This incident is assigned a cause of Manufacturing Deficiency because the contactor 1 hold down screws used in the original design of the Sylvania (Clark) type TM 00, TM 1, and TM 2 contactors were not adequate fasteners. Therefore, the potential exists for vibration to cause the hold down screws to back out of position over a i period of time.

l CNS personnel discovered a contactor which had both hold down screws out and, j therefore, had allowed the cor. tact carrier to fall out of position rendering the  ;

contactor inoperable. No safety related contactors were found in this condition at i MNS. This is probably because MNS has a preventative maintenance program ongoing >

which should correct many of these problems. This preventative maintenance assures that all screws are tight at the time it is performed. However, the Preventative  ;

Maintenance inspections, while adequate under norma'l circumstances, are performed '

at long enough intervals (5 years) to have al W d roite of the screws to loosen.

All safety related contactors inspected at HNS were found to be operable and any screws found loose were tightened and torqued based on additional information obtained from the vendor.

Prior to the discovery of the problem by CNS personnel, MNS personnel who are experienced with the contactors in question stated that on several occasions hold down screws had been found backed out at MNS. These incidents were few and l occurred over a long period of time. Therefore, the problem was not considered to be recurring and no PIR was % erated. Immediately on finding the inoperable  ;

contactor at CNS, a PIk was generated at CNS and a follow-up inspection was l initiated at MNS.

As a result of this incident, work requests were written to replace all hold down screws in safety related contactors of this type with screws having a 1/4 inch j nylon patch to prevent them from backing out. Also, torque requirements were added to the Nelson Electric Vendor Manual, MCM-1314.01-166. This will ensure that all screws will be tightened properly in the future and should prevent recurrence of this problem. In addition, an inspection is in progress of all non-safety related contactors of this type to correct any discrepancies of a similar nature.

A review of the Operating Experience Program data base for the past twelve months prior to this incident revealed 3 events that were assigned a root cause of Design, Manufacturing, Construction / Installation Deficiency because of poor material design selection. These events involved material selection deficiencies by DE personnel and not by the manufacturer. Therefore, the incident is not considered to be recurring.

This incident is not Nuclear Plant Reliability Data System (NPRDS) reportable.

4 There were no personnel injuries, radiation overexposures, or uncontrolled releases of radioactive material as a result of this incident.

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Immediate: 1) IAE personnel began inspection of all safety related Sylvania (Clark) contactor types TM 00, TM 1, and TM 2. 1

2) MES and 1AE personnel initiated emergency werk requests to repair contactors found with loose hold down screws. >

3) IAE personnel tightened and torqued loose hold down screws according to manufacturer specifications.

Subsequent: 1) DE personnel performed an evaluation of the action taken by MNS  :

personnel and concluded that they had performed adequate testing to ensure operability of the contactors.

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2) DE personnel performed a seismic operability evaluation and '

concluded that the contactors were operable with one screw loose.

3) MES personnel initiated work requests to replace the present '

contactor hold down screws with screws having a 1/4 inch nylon patch to prevent recurrence of the problem.

! 4) Project Services personnel generated MEVN 2174 to add l attachm ts to Nelson Electric Vendor Manual, MCM-1314.01-166 ,

l to speci torque requirements so that repair of the loose I contactor hold down screws could be completed.  ;

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Planned: 1) IAE personnel will replace contactor hold down screws on safety l

related contactors for Unit 1 presently in use with new ones I

incorporating a 1/4 inch nylon patch on the bottom threads.

2) IAE personnel will replace contactor hold down screws on safety related'contactors for Unit 2 presently in use with new ones incorporating a 1/4 inch nylon patch on the bottom threads.

3) MES and IAE personnel are in the process of inspecting and repairing similar non-safety related contactors for botb units.

SAFETY ANALYSIS:

The EPE system contactors in question supply voltage to feed various safety related equipment. There were no safety related contactors found during the course of this inspection to be inoperable or in any way incapable of supplying voltage to their respective devices. The worst case found was that one safety related contactor hold down screw was backed out approximately one inch and the other screw was loose. Upon evaluation and after testing, it has been proven that the operability of the contactor carriage plate does not change because one screw is missing. The reason for this is that the carriage plate is captured within a support system that l

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only allows motion in and out and not from side to side. Therefore, this incident had no.effect on the' operation of any safety related device.

This incident'did not affect the health and safety of the public. I

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