ML20138Q279

Part 21 Rept Re Notification on Model 763 Wire Failures.Itt Barton Presently Investigating Understanding of Situation & Intends to Identify Suitable Repair,Can Be Implemented in Field

ML20138Q279
Person / Time
Site:	Summer
Issue date:	12/13/1996
From:	Holdredge T ITT BARTON
To:	Fowlkes M SOUTH CAROLINA ELECTRIC & GAS CO.
References
REF-PT21-97 NUDOCS 9703060253
Download: ML20138Q279 (3)

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5euth Carolias Electric and Osa j P.O. Box 88 j Jenkinsville, South Caro!!aa,29365 i Attention: Mr. Mike Fowkes Managsr, Licensing subject: 10CFA21 Notification on Model 763 Wire Fallu:ss DearMr. Fowikes; Attached is our er:gir.ecring taput regreding the subject fa!!ure. ITT Banon has comnurted to supplyir.g SCE&O as well as the NRC with periodical updatas regarding our evaluation and eventual corrective action. l JTT Barton is compiling a listing of sIlimpacted customers whe will be nocified directly of the problem ecosistant with the requirements of 10CFR21.

This information is supplementary to the ICCTR21 Notficadon filed by the V.C. Summ:r Nu:l=ar Station (Docket Number c5000395) in their Licensing Event Repcrt (1.ER) Number 96-007, Rev. I sub: sit:ed to the U.S. Nuclear Reguistory by Scuth Carclina Electric and Gas letter nurnbar RC 96-0249 dated October 13,1996.

TIT Barton is continuin5 the invas:!gstion and undemandbg of the situation and intends to identify a suitable repair which can be haplanessed in the 6 eld. If you have additional questions, please do not hesitate to conteet the undersigned.

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Ted Holdredse , l wrM ns.or i irr1.du.i.  !

ITT Banon i Phone: (818) 9612547  ;

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10 CFR PART 21 NOTIFICATION -

(December 13,1996)

This NotiScation is provided as supplementa:y information to the 10 CFR Part 21 NotiScation filed by the V. C. Summer Nuclear Station (Docket Number 05000395) in their Licensing Event Report (LER)

Number 96-007, Rev. I submitted to the U.S. Nuclear Regulatcy Commission by South Carclina l Electric and Gas letter number RC-96-0249 dated October 18,1996.

TIT Barton supplies Model 763 and 763A Gage Preasure Electronic Transmitters to the commercial nuclear power industry for use in safety related applica: ions. More than 2000 Model 763 and 763 A transmittera have been manufactured by ITT Barton. We have recently discovered a situation that we believe represents a substantial safety hazard in some of thesem' struments that we have manufactured.

Until this time, all previously reported instances of:: rain gage lead wire failures in Model 763 and 763A transmitters (4 instances in the past ten years) were determined to have been caused as a result of mechanical damage to the very small wires during calibration effbrts. We now believe, based on evaluation of the three additiona! recently failed transmitters at V. C. Summer, that some of these reported problems may have involved wire embrittlernent which occurs during the wire soldering Operation.

Wire embrittlement can occur during the soldering of the seven strand #40AWO copper leads that connect the variable resistance strain gages to the remainder of the electronic circuit. This embrittlement involves a metallurgical reaction between the copper wire and the tin based solder used to make the connections. This reaction is common to the soldering of copper using tin based solders and involves t! e formation of an intermetallic phase ofmaterial (usually Cu.sns er Cu2Sn) formed at the solid-liquid interface. While a thin layer of this imermetallic compound is considered necessary to form the metallurgical bond, as the thickness of the layer increases, copper is consumed and the mechanical integrity of the joint is reduced. The dynamies of the intermetallic material growth are induenced by a number of factors which include the amount of tin and other elements in the solder, the soldering temperature and the dumtion of the heat exposure. This wire embrittlement process does not progressively worsen over time.

ITT Barten is concerned that instruments with excessive wire embrit:lement may now be in use for safery related applications which may fail when subjected to high vibra:ional stresses which could be experienced during nuclear power plant design basis events. Wh!!c each solder joint is subjected to signiScant mechanical stress during the instrument assembly process, historical evidence indicates tha:

this alone may not be adequate to ensure that any unit is capable of surviving the design basis events. It is not known to us hcw much residual strength may exist in the soldered connections of concern. We believe that the root cause of the problem is the decrease in the wire flexibility cansed by a reduction in the copper cross-sectional ares due to variations in the soldering process. ITT Barton believes that the situation can be remedied by the use cf additional extemal mechanical support fer the wires at the point of failure. This beliefis bued on the fact that there are no known failures of the S/G lead wires where extsrnal mechanical support for the connection is provided, including the opposhe end of the wires of concern in the Model 763 and 763 A transmitters (wires supported by the application of RTV materia!),

or other instruments that use the same wire with additional coatings / features that afford extra mechanical support.

ITT Barton is presently investigating our understanding of the situation and intends to identify a suitable repair which can be implemented in the Seld. We'll keep you infonned of our progress. If you have any questions please centact Theodore Hold. edge, Quality Assurance Manager, at (818) 951 2547 Ext. 363.

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U.S. Nuclear Regulatory -

m.: ( v.c. summer woeisar statina Docket Number 05000395 Licensing Event Raport Namber 96 007, Rev. I dated October 18.19H.)

D. Evans. GeneralManager. ITTBerton R.x=hmery, Diratororsosin orins.rrrmanon A. Luuler, Director of Operadens, rTr Banco l M. Larson, ITT Benon Nucieer & Government Product Engineering e J. Incontri. ITT Banan Director of Marketing S. Hoji, TITDarton N'- ASeirs Robert Justics, South Carohne Elec1ris and Gas j