United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9703060253



ITT Industries                          ITT Barton

AUTOMOTIVE                              870 S. Turnbull Canyon Rd.

DEFENSE & ELECTRONICS                   P.O. Box 1582

FLUID TECHNOLOGY                        City of Industry, CA 31749-1882

                                        Tel: (818)  961-2547

                                        Fax: (818) 333-7241

                                        Email:itt (illegible)



December 13, 1996



South Carolina Electric and Gas

P. O. Box 88

Jenkinsville, South Carolina, 29065



Attention:  Mr. Mike Fowlkes

            Manager, Licensing



Subject:    10CFR21 Notification on Model 763 Wire Failures



Dear Mr. Fowlkes:



Attached is our engineering input regarding the subject failure.  ITT

Barton has committed to supplying SCE&G as well as the NRC with

periodical updates regarding our evaluation and eventual corrective

action.



ITT Barton is compiling a listing of all impacted customers who will be

notified directly of the problem consistent with the requirements of

10CFR21.



This information is supplementary to the 10CFR21 Notification filed by

the V.C. Summer Nuclear Station (Docket Number 05000395) in their

Licensing Event Report (LER) Number 96-007, Rev. 1 submitted to the U. S.

Nuclear Regulatory by South Carolina Electric and Gas letter number RC-

96-0249 dated October 18, 1996.



ITT Barton is continuing the investigation and understanding of the

situation and intends to identify a suitable repair which can be

implemented in the field.  If you have additional questions, please do

not hesitate to contact the undersigned.



Regards,



Ted Holdredge

Quality Manager

ITT Industries

ITT Barton

Phone: (818) 961-2547



    Check us out on IndustryNet at http:/www:industry.noc/itt/barton



                       10 CFR PART 21 NOTIFICATION

                           (December 13, 1996)



This Notification is provided as supplementary information to the 10 CFR

Part 21 Notification filed by the V.  C.  Summer Nuclear Station (Docket

Number 05000395) in their Licensing Event Report (LER) Number 96-007,

Rev.  1 submitted to the U.  S. Nuclear Regulatory Commission by South

Carolina Electric and Gas letter number RC-96-0249 dated October 18,

1996.



ITT Barton supplies Model 763 and 763A Gage Pressure Electronic

Transmitters to the commercial nuclear power industry for use in safety

related applications.  More than 2000 Model 763 and 763A transmitters

have been manufactured by ITT Barton.  We have recently discovered a

situation that we believe represents a substantial safety hazard in some

of these instruments that we have manufactured.  Until this time, all

previously reported instances of strain 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 efforts.  We now believe, based on

evaluation of the three additional recently failed transmitters at V.  C.

Summer, that some of these reported problems may have involved wire

embrittlement which occurs during the wire soldering operation.



Wire embrittlement can occur during the soldering of the seven strand #40

AWG copper leads that connect the variable resistance strain ages 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 the formation of an

intermetallic phase of material (usually Cu sub 6 Sn sub s or Cu sub 3

Sn) formed at the solid-liquid interface.  While a thin layer of this

intermetallic 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 dynamics of the

intermetallic material growth are influenced by a number of factors which

include the amount of tin and other elements in the solder, the soldering

temperature and the duration of the heat exposure.  This wire

embrittlement process does not progressively worsen, over time.



ITT Barton is concerned that instruments with excessive wire

embrittlement may now be in use for safety related applications which may

fail when subjected to high vibrational stresses which could be

experienced during nuclear power plant design basis events.  While each

solder joint is subjected to significant mechanical stress during the

instrument assembly process, historical evidence indicates that this

alone may not be adequate to ensure the any unit is capable of surviving

the design basis events.  It is not known to us how 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 caused by a reduction in the copper cross-sectional area due

to variations in the soldering process.  ITT Barton believes that the

situation can be remedied by the use of additional external mechanical

support for the wires at the point of failure.  This belief is based on

the fact that there are no known failures of the S/G lead wires where

external mechanical support for the connection is provided, including the

opposite end of the wires of concern in the Model 763 and 763A

transmitters (wires supported by the application of RTV material), 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

field.  We'll keep you informed of our progress.  If you have any

questions please contact Theodore Holdredge, Quality Assurance Manager,

at (818) 961-2547 Ext.  363.



cc:

U. S. Nuclear Regulatory

Re: (V. C. Summer Nuclear Station

Docket Number 05000395

Licensing Event Report Number 96-007, Rev. 1

dated October 18, 1996.)



D.  Evarts, General Manager, ITT Barton

R.  Krechmery, Director of Engineering, ITT Barton

A.  Lussier, Director of Operations, ITT Barton

M.  Larson, ITT Barton Nuclear & Government Product Engineering

J.  Incontri, ITT Barton Director of Marketing

S.  Noji, ITT Barton Consumer Affairs



Robert Justice, South Carolina Electric and Gas



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