United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9606200354

Commonwealth Edison Company
Dresden Generating Station
6500 North Dresden Road
Morris, IL 60450
Tel 815 942-2920
                                                                    ComEd

June 18, 1996

JSPLTR 96-0094

U. S.  Nuclear Regulatory Commission
Washington, D.C.  20555
ATTN: Document Control Desk

Subject:  Commonwealth Edison Company
          10 CFR Part 21 Final Report (File 9601)
          Deficiency of Model 12HGA17S63 Relays Manufactured by
          General Electric Company.

The purpose of this letter is to notify the NRC Staff of concerns by
Commonwealth Edison Company toward the failures of Model 12HGA17S63
relays manufactured by General Electric Company.  The suspect relays were
purchased from General Electric Supply, and qualified and, dedicated for
safety related use by Nutherm International Inc.  These relays were
installed in the reset logic for Primary Containment Isolation System
(PCIS) at Dresden Station Units 2 and 3.

ComEd has determined that the difference in the inside face to face
dimension of the phenolic contact finger carrier block made from mold
number 1 is small and under certain conditions provides friction between
it and the coil bracket at the pivot point.  This friction is believed to
be the cause of the relay's failure to open when de-energized.

Immediate Corrective Actions were to identify all defective relays on
Unit 3 by removing all relays from the plant subjecting each to special
testing at the corporate Materials Engineering test facility.  Only
relays which passed this test were reinstalled in the plant.  Replacement
relays were tested in a similar manner.

An operability evaluation was generated to document the acceptability of
similar relays installed in Unit 2.  This evaluation included
compensatory measures or additional operator actions to ensure isolation
valves would not open unexpectedly.

USNRC                                                             Page 2
June 17, 1996

The relays installed in Unit 2 have subsequently been tested and replaced
as required.

Provided as an attachment to this letter is ComEd's notification in
accordance with the requirements of 10 CFR Part 21.

As stated in the attached report, the defective component was identified
only at ComEd Dresden Station.  The Part 21 Notification has been
forwarded to other ComEd stations for their review.  If there are any
questions regarding this notification, please direct them to Frank
Spangenberg, Dresden Station Regulatory Assurance Manager, at (815) 942-
2920, extension 3800.

Very Truly Yours,

J. Stephen Perry
Site Vice President
Dresden Station

Attachment

cc:  H.  J.  Miller, Regional Administrator, Region III
     P.  L.  Hiland, Branch Chief, Division of Reactor Projects, Region
               III
     J.  F.  Stang, Project Manager, NRR (Unite 2/3)
     C.  L.  Vanderniet, Senior Resident Inspector, Dresden
     Office of Nuclear Facility Safety - IDNS
     File: Numerical

COMMONWEALTH EDISON COMPANY
10CFR PART 21 NOTIFICATION

General Electric 12HGA17S63 Series Relays

Part 21 File Number 9601, June 12, 1996

Applicability:

This notification is submitted in accordance with the requirements of
10CFR Part 21, section 21.1(b), 21.3a(3), and 21.3d(4).

Identification of Facility and Component:

This notification concerns Model 12HGA17S63 relays manufactured by the
General Electric Company.  The suspect relays were purchased from General
Electric Supply, and qualified and dedicated for safety related use by
Nutherm International Inc.  These relays were installed in the reset
logic for Primary Containment Isolation System (PCIS) at Dresden Station
Units 2 and 3.

A review of station stores data has indicated that Dresden is the only
ComEd Station which uses this type of relay in similar applications.
Notification of this event has been provided to other ComEd plants for
use in final determination of usage.

Identification of Component and Manufacturer:

Purchased, Qualified and Dedicated by:  Supplied by:
Nutherm International Inc:              General Electric Supply
501 South 11th Street                   PO Box 1230
Mt.  Vernon, IL 62864                   Fenton, MO 63026

Nature of Defect:

Relay part number 12HGA17S63 is a 15 cycle time delay relay with one
single pole double throw, and one normally closed contacts., It is a
surface mounted front connect unit (S) with a unit rating of 115 VAC 25
or 60 Hz (63).  The maximum pull in voltage for this unit is published as
46 VAC; the minimum drop out voltage, not published but measured during
testing, is 6.3 VAC.

The General Electric 12HGA17S63 relay is derived from the 12HGA11 series
relay with manufacturer installed modifications to achieve the nominal 15
cycle time delay.  The 12HGA17S63 timing element is a thick copper tube
which is inserted over the coil's core.  This tube, in effect, is a
single turn coil.  When the coil is de-energized, the collapsing field
induces a current in the tube which, in turn, develops a magnetic field,
This field holds in the armature for the stated 15 cycle time delay on
de-energization.  The strength of the magnetic field developed by the
copper tube is weak in comparison to the relay coil's field.  therefore,
armature return spring tension is reduced so as to not over compensate
for the weak induced magnetic field.  With only 6 volts required to hold
the armature in, the

COMMONWEALTH EDISON COMPANY
10CFR PART 21 NOTIFICATION

copper tube is capable of providing a 15 cycle delay.  This balanced
armature design is very sensitive to any binding that may occur in the
pivot area of the armature to the coil frame, the spring constant of the
armature return spring, contact wear or any residual magnetism present in
the coil assembly.

The armature assembly is made up of two contact fingers, one contact
finger hold-down spring block and name plate, one contact finger carrier
block, and the armature strike plate.  One machine screw holds the
assembly together.  Binding has been noticed to occur when the contact
finger carrier block rubs against she coil bracket that the armature
assembly hinges on.  Close examination revealed that the contact finger
carrier block is molded from one of two molds.  The dimension of the two
inside faces of the mold that can come in contact with the coil bracket
at the pivot point on relays with the identifier mold], is smaller than
the same dimension taken from mold number 2.

ComEd has determined that the difference in the inside face to face
dimension of the phenolic contact finger carrier block made from mold
number 1 is small and under certain conditions provides friction between
it and the coil bracket at the pivot point.  This friction is believed to
be the cause of the relay's failure to open when de-energized.  This
information has been provided to the relay manufacturer.  General
Electric and to Nutherm International Inc.  who performed qualification
testing on the relays at the time of installation.

Time of Discovery:

On May 15, 1996, two relays in the PCIS system on Dresden Station Unit 3
failed to reposition upon removing power from the relay coil.  In
response to this event, failure analysis testing was commenced.

On June 11, 1996, ComEd concluded that the failure of this relay was due
to differences in dimensional tolerances which occurred during the
manufacturing process.

On June 11, 1996, ComEd determined that although these relays were
installed in the reset portion of the isolation circuitry, and the
primary containment isolation would occur as designed, the failure could
affect the ability of the operator to maintain control of containment
isolation valves upon resetting an isolation signal.  If this situation
would have occurred with multiple concurrent relay failures, the result
would have been the opening of multiple valves without operator
intervention and thus could have complicated operator control of post
accident evolutions.  Therefore, ComEd concludes that this failure could
result in a substantial safety hazard.

COMMONWEALTH EDISON COMPANY
10CFR PART 21 NOTIFICATION

Number and Location of Defective Components in Use:

All defective components have now been removed from Dresden Station Units
2 and 3.  These components were originally installed in panels 902(3)-61
and 62 in the services listed below:

     Relay                    Associated Isolation Valve

     203-1AR2                 203-1A    MSIV
     203-1BR2                 203-1B    MSIV
     203-1CR2                 203-1C    MSIV
     203-1DR2                 203-1D    MSIV
     203-2AR2                 203-2A    MSIV
     203-2BR2                 203-2B    MSIV
     203-2CR2                 203-2C    MSIV
     203-2DR2                 203-2D    MSIV
     220-44R                  220-44    Steam Line Drain
     220-45R                  220-45    Steam Line Drain
     1301-17R                 1301-17   Isolation Condenser Vent
     1301-20R                 1301-20   Isolation Condenser Vent

Corrective Actions:

Immediate Actions were to identify all defective relays on Unit 3 by
removing all relays from the plant subjecting each to special testing at
the corporate Materials Engineering test facility.  Only relays which
passed this test were reinstalled in the plant.  Replacement relays were
tested in a similar manner.

An operability evaluation was generated to document the acceptability of
similar relays installed in unit 2.  This evaluation included
compensatory measures of additional operator actions to ensure isolation
valves would not open unexpectedly.

The relays installed in Unit 2 have been subsequently tested and replaced
as required.


Contacts:

F. A.  Spangenberg
Regulatory Assurance Manager
Commonwealth Edison, Dresden Station
6500 N.  Dresden Road
Morris, IL 60450
815 942-2920 ext. 3800

*** END OF DOCUMENT ***

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