ML19324C317

LER 89-020-00:on 891011,HPCI F006 Valve Motor Control Ctr Indicating Light Socket Shorted & Blew Control Power Fuse for Valve.Caused by Inward Force Applied to Bulb During Removal.Lamp,Socket & Fuse replaced.W/891107 Ltr

ML19324C317
Person / Time
Site:	Brunswick
Issue date:	11/07/1989
From:	Harness J, Harris T CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-89-1002, LER-89-020, LER-89-20, NUDOCS 8911160126
Download: ML19324C317 (5)

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i' Carolina Power & Light Crsmpany '  :

' Brunswick Nuclear Project P. O. Box 10429.

Scuthport. NC 28461-0429 i,

November'7, 1989 t t y

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i FILE: B09,135100- 10CFR50.73  :

SERIAL: BSEP/89-1002 U.S.' Nuclear Regulatory Commission  ;

. ATTN: Document' Control Desk Washington, DC 20555 {

BRUNSWICK STEAM ELECTRIC PLANT UNIT 1 SOCKET NO. 50-325 y LICENSE NO. DPR-71 LICENSEE EVENT REPORT 1-89-020 ,

Gentlemen: I In accordance with Title 10 to the Code of. Federal Regulations, the enclosed ,

Licensee Event Report is submitted. This report fulfills the requirement for

.t a-written report within thirty (30) days of a reportable occurrence and is in l, accordance with the' format set forth in NUREG-1022, September 1983.

J Very truly yours, >

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I J. L. Harness, General Manager Brunswick Nuclear Project 1 TH/mcg 1

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At 1035 on 10/11/89, with Unit 1 at 100'. power, the HPCI F006 injection value Motor Control Center indicating light socket shorted and blew the control power fuse for the F006 valve as the bulb was being removed. This resulted in j a loss of centrol power to the F006 valve, which would have prevented the valve i from automatienlly opening if the HPCI system was needed.

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The event was caused by movement of the negat.ive socket coil into contact with  !

the positive scchet tab during bulb removal. The coil movement during removal l" 1s attributed to inward force applied to the bulb during removal. When the coil came into contact with the tab the resulting short caused the loss of i control power to the F006 valvo. 1

- Corrective actions include replacement of the lamp, socket and fuse and a sampling of various plant MCCs for similar coil distortion. As a result of this inspection, additional corrective actions were identified, including a review of the event wit.h appropriate operating personnel, evaluation of the feasibility of replacing the current socket with a different type socket, and .

development of an inspection plan for safety related MCCs and Transformer l sockets in the switchyard area. This event would not be considered more l significant under reasonabic and credible alternative conditions.

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Event i

Loss of control power and operability of 1-E41-F006 valve while removing the

, indicator light bulb from the MCC breaker compartment.

Initial Conditions Unit 1 Reactor was at 100*; powe r . The Residual llent Removal / Low Pressure Coo'lant Injection (RllR/LPCI) System (EIIS/110), Core Spray System. (Ells /BM),

Reactor Core Isolation Cooling (RCIC) System (EIIS/BN) and the Automatic Depressurir.ation System (EIIS/*) were in standby readiness.

Event Description At 1035 on 10/11/89, the llPCI (E41)-F006 valve Motor Control Center (MCC) indicating light sock'et (Ells /BJ/INV/IL/**), General Electric Model CR2940 shorted and blew the control power fuse to the F006 valve au the blown bulb was being removed from the socket by an Auxiliary Operator (AO). This resulted in a loss of control power to the 1-E41-F006 IIPCI irijection valve (EIIS/BJ/INV). This loss of control power would have prevented the valve from automatically opening if the HPCI System was needed. An LCO was initiated on the system due to this condition, and the fuse and lamp sccket were replaced.

The system was returned to r;ervice on 10/11/89 at 2036.

Event Investigation The cause of this event was the positive tab of the light bulb socket coming int.o contact with the negative coil of the socket, causing a short which resulted in the blown fuse. The negative coil is used as the thread for the light in the socket. The exact cause of the tab coming into contact with the coil is not known; however, during the investigation into possibic mechanisms for the contact between the coil and the t.ab, it was noted that numerous sockets for indicating lights in various MCOs had coils that were closer to the j tab than in a new socket. The reason for this closeness is possibly due to I

inward force being exerted on the coil during removal of bulbs. It is speculated that the coil moved closer to the tab as a result of this inward force, and as I the A0 was removing tha bulb, the coil came into contact with the tab, fusing i the two together, j

The investigating engineer for this event noted that if an inward pressure was i applied and maintained while removing a bulb from a typical socket, the coil '

may be distorted inward, closer to the positive tab. It was also noted during

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1 field inspection of in-service sockets that the presence of corrosion on the socket coll / tab areas or the lamp base makes removal of the bulb difficult, often requiring inward force to be applied to the lamp during removal. +

The coil in the type socket involved in this failure is secured only at one side of the socket. This allows inward movement of the coil toward the tab when inward pressure is applied during removal.

The vendor (GE) has been contacted to find out if similar occurrences of shorted sockets have been experienced by other facilities. No other similar socket failures were identified by the vendor.

Exact determination of the root cause of the mechanism for the shortin's has been hampered by the fact that the original faulted socket, fuse and bulb were l discarded prior to an in-depth analysis. The conclusion documented herein is a result of field inspections of in-service sockets, detailed breakdown, inspection and testing of a new socket and discussions with the A0 and Instrumentation and Control (16C) technicians involved with the incident.

Corrective Actions Which llave Been Taken i i

The lamp, socket and fuse have been replaced. Technical Support engineers i have performed a random sampling of HCC indicating light sockets in order to i determing if the distortion of the coil could be a generic problem. s Preliminary results from this investigation (approximately 70 sockets were inspected in the Reactor Building, Turbine Bui? ding, Radwaste Building, and main transformer area) support the conclusion that coil distortion is a i potential generic effect from bulb removal, especially where corrosion is involved.

A memorandum has been issued to the Plant Management group, using this event l

as an example, defining the responsibility of site personnel in preserving physical evidence for investigations until the completion of the ,

l investigation, per the direction of Regulatory Complience Instruction  ;

(RCI)-06.6, Site Event Investigation Process.

Corrective Actions to be Taken to Prevent Recurrence The following corrective actions will be taken:

1. Review of this event with appropriate Operations personnel. This item 1 will be completed by the end of the first quarter of 1990.

2. Technical Support will investigate the feasibility of replacement of the currently stocked General Einctric Model CR2940 socket with a Westinghouse bayonet type socket.

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3. An inspection plan will be developed and implemented for safety related MCCs for socket degradation. This inapection will be limited to MCCs which could produce a system failure due to a single socket failure.

Development of this plan will be completed by the end of the first quarter of 1990.

4. Transformer sockets in the plant switchyard area have been identified to be more susceptible to corrosion due to tha outside environment.

Technical Support will coordinate with the Wilmington Transmission

. Department the-inspection / replacement of the sockets in the plant switchyard transformers as necessary.

Event Assessment As a result of this event, the IIPCI F006 valve would not have been able to 1 automatically open u} ion receipt of an initiation signal due to the loss of control power, which would have prevented the system from automatically injecting into the vessel. This is mitigated by three factors:

1. The valve is accessible and could have been manually operated if required.

2. The ADS /LPCI systems combination serves as a backup to !!PCI for safe shutdown and accident conditions. These systems were operable for the i duration of this event.

L 3. The plant is analyzed for a llPCI failure.

l l As a result of the above, this event would not be considered more significant l under reasonable and credible alternative conditions.

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