United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9507280064

To: NRC Operations Center
      FAX: (301) 816-5151

From: Foxboro, J. T. Keiper
      FAX: (508) 549-6580
      TEL: (508) 549-6332

Date: 7 July 1995

Subj:  Potential 10CFR21 Notification for Custom N-2AO-V2H SPEC 200
Analog Output Module

Attached is a copy of a letter written to Northeast Utilities regarding
two potentially defective modules shipped to the Connecticut Yankee
plant. These custom modules were shipped to the site for installation by
the utility; so we do not know the application in which the modules were
used.

The same type of custom modules are in use at the D C Cook plant.  D C
Cook personnel discovered the original problem and have been working with
Foxboro to develop a solution.

There are no other nuclear plants using these custom modules.

If you have any further questions please contact me.

James T. Keiper
Industry Consultant
Nuclear Power Systems
Electric Utility Division

FOXBORO   The Foxboro Company

Foxboro, MA U.S.A. 02035-2099           Telephone: 508-543-8750
Telex: MCI-6817560                      Fax 508-549-6770

July 6, 1995

Northeast Nuclear Energy Company
107 Seldon Street
Berlin, CT 06037

Attention:     Mr. T. J. Dente
               Manager,
               Nuclear Operations Services

Subject:  Potential Problem with SPEC 200 N-2AO-V2H Custom 10 to 50 mA
Output Converter Module

Gentlemen:

This letter is to notify you of a potential problem in the operation of
the model number N-2AO-V2H Custom per N-ECEP-90089, 10 to 50 mA isolated
output converter.  The D C Cook Nuclear Power Plant has reported high
failure rates of the DC/DC converter that was added to the standard N-
2AO-V2H module to provide 1E to non-1E isolation for the output module.

Most of the reported failures were characterized by an abnormal power
draw by the DC/DC converter that ultimately resulted in component failure
within the DC/DC converter or a blown fuse on the module.  This resulted
in a loss of one or both of the two output channels on the module.  At
least one failure resulted in a blown fuse on the nest power distribution
module, N-2AX+DP11 which in turn resulted in a loss of power to all
modules in the nest.

Recently D C Cook experienced two failures that affected other custom N-
2AO-V2H output modules prior to failure of the module.  D C Cook reported
perturbations in the 10 to 50 mA outputs from other custom N-2AO-V2H
output modules.  The failing module apparently fed back voltage
fluctuations to the nest power distribution busses that affected the
DC/DC converters on other output modules on the same bus.  There was no
evidence that modules other than the custom N-2AO-V2H modules were
affected, though we cannot eliminate that possibility.

FOXBORO

Foxboro is designing a replacement DC/DC converter and is prepared to
receive your custom N-2AO-V2H modules in approximately 12 weeks to carry
out the retrofit of the suspect component in our factory.  Meanwhile it
is recommended that you notify your operators of the potential anomalous
behavior of the custom N-2AO-V2H module.

Our records indicate that you have purchased two of these modules on PO
265983 for the Connecticut Yankee Atomic Power Company Haddam Neck Plant.
However, we cannot assess the potential 10CFR21 impact for your
particular application.  We have notified the NRC concerning this matter.

If you have any questions concerning this issue please contact Mr. James
Bright at (508) 549-2660 or Mr. James Keiper at (508) 549-6332.

Very truly yours,
THE FOXBORO COMPANY

Truman L. King
Corporate Director
Product Safety and Quality Assurance

Copy:

Connecticut Yankee Atomic Power Company
362 Injun Hollow Road
East Hampton, CT 06424

Attention: Mr. J. Chiarella

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