ML19325F182

LER 89-012-00:on 891010,in-core Instrumentation Guide Thimble Tubes Identified W/Degradation in Excess of 60% Wall Thickness.Caused by Mechanical Wear of Thimbles Against Reactor Vessel Internals.Tubes isolated.W/891108 Ltr

ML19325F182
Person / Time
Site:	Beaver Valley
Issue date:	11/08/1989
From:	Noonan T DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-012-01, LER-89-12-1, ND3MNO:1987, NUDOCS 8911150226
Download: ML19325F182 (4)

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4 gR Ng Y Tceson. 9 m 3934,a3a gw,c,<oup s,..,,n,,- ... , w 7, .m November 8, 1989 ND3MNOt1987 Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 LER 89-012-00 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555-Gentlement In accordance with Appendix A, Beaver Valley Technical Specifications, the following Licensee Event Report is submitted:

LER 89-012-00, 10 CFR 50.73.a.2.ii, "Incore Instrumentation Thimble Tube Wear".

Very truly yours, T. P. oonan General Manager Nuclear Operations cj Attachment 8911150226 891108 PDR ADOCK 05000334

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October 20, 1989  !

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cc Mr. William T. Russell f Regional Administrator  !

United States Nuclear Regulatory Commission j Region 1  :

475 Allendale Road i King of Prussia, PA 19406 C. A. Rotock, Ohio Edison  ;

i Mr. Peter Tam, BVPS Licensing Project Manager  ;

United States Nuclear Regulatory Commission I Washington, DC 20555  !

Beall, Nuclear Regulatory Commission,  ;

J.

BVPS Senior Resident Inspector  ;

Dave Amerine Centerior Energy i 6200 Oak Tree Blvd.  ;

Independence, Ohio 44101 INFO Records Center  :

Suite 1500 1100 circle 75 Parkway l Atlanta, GA 30339 ,

G. E. Muckle, Factory Mutual Engineering, Pittsburgh Mr. J. N. Steinmetz, Operating Plant Projects Manager Mid Atlantic Area Westinghouse Electric Corporation Energy Systems Service Division Box 355 Pittsburgh, PA 15230 Anorican Nuclear Tasurers c/o Dottie Sherman, ANI Library The Exchange Suite 245 270 Farmington Avenue ,

Farmington, CT 06032 Mr. Richard Janati Department of Environmental Resources P. O. Box 2063

, 16th Floor, Fulton Building Harrisburg, PA 17120  ;

Director, Safety Evaluation & Control

. Virginia Electric & Power Co.

• l P.O. Box 26666 One James River Plaza Richmond, VA 23261

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$V8MilliON vtS 819 ves. sempsee i APIC110 Sv0MISS104 DA TU NU l l l L95 TRACT ILnit80 1000 nonces o e , opensanew'r rowen om,'e neece treewroren kneet i14I On 10/10/89, while the unit was in its seventh refueling outage, eddy current testing identified nine incore nuclear instrumentation guide thimble tubes with degradation in excess of specified limits. The analysis also projected degradation in excess of 60% wall thickness for an additional nine tubes by the end of the next fuel cycle. This degradation is apparently due to mechanical wear of the thimbles against reactor vessel internals induced by the coolant flow characteristics through the vessel.

Finite element analysis has determined that, based on ASME Code allowable stress limits, tube degradation of up to 60% is acceptable. The nine tubes with degradation beyond specified lim.tts were removed from service and isolated to prevent leakage.

The nine tubes with projected degradations in excess of 60% were repositioned to prevent unacceptable wall thinning. There were no safety implications due to this event. Failure of a guide thimble tube is bounded by Beaver Valley Unit 1 UFSAR Analysis section 14.3, " Loss of Coolant Accident."

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o] 2 0F 0l2 nn a na. mn e man un ename nnc o avewn Descriotion of Event on 10/10/89, while Beaver Valley Unit 1 was shutdown for its  !

Ceventh refueling outage, eddy current test results identified a ]

total of nine incore nuclear instrumentation guide thimble tubes  ;

with degradation in excess of 50% of their initial wall thickness. The degraded tubes were located in core positions J15, l B05, B10, F08, Di{, EOS, H06, LO4 and J05. (The tube at J15 had i been identified as degraded during the previous refueling outage )

and had been isolated during the entire last fuel cycle.)  ;

l Additionally, there were nine tubes which had less than 50%

degradation but which the analysis projected would have in excess )

of 60% degradation by the end of the next fuel cycle. The tubes i with projected degradations of greater than 60% were located Lt ,

core positions C08, B08, G14, G09, N12, LO6, J07, N07 and N05.  !

Cause of Event

The guide tube wall thinning is apparently due to mechanical wear induced by reactor coolant flow characteristics. Turbulent coolant flow through the reactor vessel caused guide thir.ble tube ,

vibration. The mechanical wear resulted when the vibrating tube  !

contacted the vessel internals. l l

Corrective Actions l All tubes with degradation in excess of 50% were removed from cervice and isolated to prevent leakage in the event of a tube failure. The tubes with a projected 60% degradation were  ;

repositioned in order to-prevent additional wear in the locations where the wall thinning was occurring.

I Er.evious Similar Events j There has been one previous similar event (LER 88-010-00) )

involving guide thimble degradation. This report documents the I cupplemental report identifiod in LER 88-010-00. ]

Safety Analysis There were no safety implications due to this event. Failure of a )

guide thimble tube is bounded by Beaver Valley Unit 1 UFSAR Analysis section 14.3, " Loss of Coolant Accident." Westinghouse J cnalysis has shown that a tube with up to 60% degradation is l structurally acceptable. I i

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