Part 21 Report - 1997-120
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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