ML20140J198

Part 21 Rept Re Failures of GE Type CR120AD Relays Dedicated for SR Use.Resulting High Current Through Short Circuit Caused Magnet Wire to Fuse & Produced Energetic Arc at Failure

ML20140J198
Person / Time
Site:	Oyster Creek
Issue date:	06/12/1997
From:	Broughton T GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-97 6730-97-2176, NUDOCS 9706190261
Download: ML20140J198 (3)

Text

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j GPU Nuclear, Inc.

( One Upper Pond Road NUCLEAR Persippany, NJ 070541095 Tel201316 7000 June 12, 1997 6730-97-2176 .

U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen:

Subject:

10CFR Part 2130-Day Repon i Oyster Creek Nuclear Generating Station Docket No. 50-219 Potential Failure of General Electric Type CR120AD Relays Oyster Creek has experienced failures of the General Electric Type CR120AD relays. The failure mechanism was identified as a manufacturing defect; specifically, part of the stan-end pigtail of the relay coils was off the insulating lead pad and, therefore, lying directly on the outer  !

layer of the winding. This configuration placed insulation on the afTected length of magnet wire in a high-electrical-stress condition that led to dielectric breakdown at the failure site, thus effectively short circuiting the coil.

Although our evaluation of all ten potentially defective relays installed at Oyster Creek i concluded that their fail-safe mode does not impact plant safety, this potential defect is being conservatively reported in accordance with 10 CFR Part 21.21, (d) (3)(ii). l Should you have questions regarding this matter, please contact Yosh Nagai of our staff i at (201) 316-7974.

Sincerely, I

$W h li ,

T. G. Broug/hton \

President ,-

YN/ pip ' l((

c: Administrator, Region 1 NRC Resident inspector Oyster Creek NRC Project Manager 9706190261 970612 PDR 8 ADDCK 05000219 PDR ^

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l 10 CFR 21 - 30 DAY WRITTEN REPORT CONCERNING POTENTIAL FAILURE OF

. GENERAL ELECTRIC TYPE CR120AD RELAYS

1. Name and Address Of The Individual Informing The Commission:

Name: T. G. Broughton President ,

Address: GPU Nuclear, Inc.

One Upper Pond Road l' Parsippany, NJ 07054-1149

11. Basic Component Affected: j General Electric Type CR120AD Relays Ill. Firm Supplying Components:

l General Electric Nuclear Energy 175 Curtner Avenue San Jose, California 95125 IV. Nature of the Potential Defect:

On March 26,1996 Oyster Creek Generating Station issued a deviation report which identified an open coil in three CR120AD relays dedicated for safety-related use: one relay failed immediately after the installation when energized, another relay failed within two days during startup test and a third failed some months later during a surveillance test. Following these incidents a coil from one of the failed relays was sent to General Electric (GE) for analysis and the two remaining relays were sent intact to an independent research laboratory (Southwest Research Institute) for failure analysis.

After the analysis, Southwest Research Institute concluded that the principal problem observed in both relay coils was a manufacturing defect: specifically, part of the start-end pigtail of the coil was off the insulating lead pad and, therefore, lying directly on the outer layer of the winding, which was near the finish end of the coil. This configuration placed insulation on the affected length of magnet wire in a high-electrical-stress l condition that led to dielectric breakdown at the failure site, thus efTectively short l circuiting the coil. Resulting high current through the short circuit caused the magnet wire to fuse and produced an energetic arc at the failure site.

e There are ten (10) potentially defective relays installed at Oyster Creek. GPU Nuclear ,

has concluded that their fail-safe mode does not impact plant safety. However, there may be other nuclear facilities with these relays installed or kept in their warehouse without knowing of or about this potential failure.

V. Date on which Potential Defect Was Identified.

1 We determined on May 8,1997 that this potential failure of the GE relay CR120AD '

could have a generic implication and it was reported to NRC Operations Center, by phone, on May 9,1997.

VI. Number and Location of Components.

There are ten (10) potentially defective relays installed at Oyster Creek.

l Vll. Corrective Actions Taken if a premature failure of any of these relays occurs, with an "open" coil as the failure  ;

mechanism, we may consider replacing the remaining nine relays. However, replacement I

of the ten relays is not scheduled at this time for the following reasons:

i) The previous failures of the CR120AD relays at Oyster Creek occurred either i immediately upon energization or within a few months of operation. Also, none of I the installed relays have failed since their installation approximately seven months l

l ago.

i ii) The probability of these relays having a potential manufacturing defect is extremely low.

iii) Our evaluation concluded that there is no impact to plant safety due to their fail-l safe mode feature.

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i l GPU Nuclear, Inc.

i A One Upper Pond Road l NUCLEAR Parsippany, NJ 070541095

[ Tel 201316 7000

! June 12, 1997 '

6730-97-2176 l

U. S. Nuclear Regulatory Commission Attention: Document Control Desk j

, Washington, DC 20555 l

l Gentlemen: .

Subject:

10CFR Part 2130-Day Report l Oyster Creek Nuclear Generating Station i l- Docket No. 50-219 Potential Failure of General Electric Type CR120AD Relays Oyster Creek has experienced failures of the General Electric Type CR120AD relays. The I failure mechanism was identified as a manufacturing defect; specifically, part of the start-end  !

pigtail of the relay coils was ofTthe insulating lead pad and, therefore, lying directly on the outer laycr of the winding. This configuration placed insulation on the afTected length of magnet wire  :

in a high-electrical-stress condition that led to dielectric breakdown at the failure site, thus ' i effectively short circuiting the coil.

l Although our evaluation of all ten potentially defective relays installed at Oyster Creek concluded that their fail-safe mode does not impact plant safety, this potential defect is being conservatively reported in accordance with 10 CFR Part 21.21,(d)(3)(ii).

- Should you have questions regarding this matter, please contact Yosh Nagai of our staff at (201) 316-7974.

Sincerely, MbMA l i T. G. Broughton President YN/ pip 4

i c: Administrator, Region 1 l NRC Resident inspector Oyster Creek NRC Project Manager

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10 CFR 21 - 30 DAY WRITTEN REPORT CONCERNING POTENTIAL FAILURE OF GENERAL ELECTRIC TYPE CR120AD RELAYS

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1. Name and Address Of The Individual Informing The Commission:

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l l Name: T. G. Broughton l

l President  !

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Address: GPU Nuclear, Inc.

One Upper Pond Road Parsippany, NJ 07054-1149

11. Basic Component Affected: l l

l General Electric Type CR120AD Relays Ill. Firm Supplying Components:

General Electric Nuclear Energy 175 Curtner Avenue  !

San Jose, California 95125 '

l IV. Nature of the Potential Defect: l l

On March 26,1996 Oyster Creek Generating Station issued a deviation repon which identified an open coil in three CR120AD relays dedicated for safety-related use: one l relay failed immediately after the installation when energized, another relay failed within l two days during startup test and a third failed some months later during a surveillance test. Following these incidents a coil from one of the failed relays was sent to General

! Electric (GE) for analysis and the two remaining relays were sent intact to an independent I l research laboratory (Southwest Research Institute) for failure analysis.

! After the analysis, Southwest Research Institute concluded that the principal problem observed in both relay coils was a manufacturing defect: specifically, part of the start-end pigtail of the coil was off the insulating lead pad and, therefore, lying directly on the outer layer of the winding, which was near the finish end of the coil. This configuration placed insulation on the affected length of magnet wire in a high-electrical-stress condition that led to dielectric breakdown at the failure site, thus efTectively short 4 circuiting the coil. Resulting high current through the short circuit caused the magnet wire to fuse and produced an energetic arc at the failure site.

1 . ___ _. __

i I

There are ten (10) potentially defective relays installed at Oyster Creek. GPU Nuclear {

has concluded that their fail-safe mode does not impact plant safety. However, there may l l

be other nuclear facilities with these relays installed or kept in their warehouse without l

' knowing of or about this potential failure. I V. Date on which Potential Defect Was Identified.

We determined on May 8,1997 that this potential failure of the GE relay CR120AD could have a generic implication and it was reported to NRC Operations Center, by l

phone, on May 9,1997.

l VI. Number and Location of Compnents.

There are ten (10) potentially defective relays installed at Oyster Creek.

Vll. Corrective Actions Taken

if a premature failure of any of these relays occurs, with an "open" coil as the failure i i

mechanism, we may consider replacing the remaining nine relays. However, replacement i of the ten relays is not scheduled at this time for the following reasons:

l l i) The previous failures of the CR120AD relays at Oyster Creek occurred either immediately upon energization or within a few months ofoperation. Also, none of the installed relays have failed since their installation approximately seven months I ago. ,

i ii) The probability of these relays having a potential manufacturing defect is l extremely low.

l iii) Our evaluation concluded that there is no impact to plant safety due to their fail-safe mode feature.

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