ML19296D513

Part 21 Rept:On 800131,util Telephoned Rept to Region 2 of Potential Problem in safety-related Overcurrent Relays. Component,sodium-cooled Reactor,Within Overcurrent Relay Failed,Causing Circuit Breaker to Open

ML19296D513
Person / Time
Site:	Catawba
Issue date:	02/11/1980
From:	Duvall D GOULD-BROWN BOVERI
To:
References
REF-PT21-80-196-000 NUDOCS 8003040707
Download: ML19296D513 (2)

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$f 6 -l ? b " 0 0 0 February 11, 1980 Mr. Victor Ftello, Jr. Director Office of Inspection & Enforcement U.S. Nuclear Regulatory Cornission g ,4/gy/p Washington, DC 20555

Dear Mr. Ptello:

On January 31, 1980, Duke Power Cocpany telephoned a report to the office of the Director, I & E Region II of a potential problem in safety related over-current relays furnished by Gould-Brown Boveri. This report indicated that a component, an SCR, within an overcurrent relay had failed, causing a circuit breaker to open at the Catawba Nuclear Station.

The purpose of this letter is to advise your of fice that a potential problem may exist in some solid-state devices produced by Gould-Brown Boveri, Horsham, PA. These devica ; include: Type CRS, Ground Fault Relay; Type ITE50, Over-current Relay; Type ITE51, Overcurrent Relay;and Solid State Trip Device.

As part of our investigation into some random failures of Motorola Inc. SCR's (Types 1379 and 1235), three units were returned to the supplier where they were examined by a scanning electron microscope. These units were determingd to have failed due to the nigration of copper from the top metal system into the bulk silicon material. Small pin holes in a chrome metal barrier that separates the copper from the silicon permitted the copper to migrate into the silicon as a direct funct*on of temperature and time, resulting in the failure. The inspection and screening methods used by Motorola Inc. were thought to be suf ficiently comprehensive to preclude the use of SCR's with susceptibility to this copper migration problem.

As an immediate corrective action, Motorola has identified an additional high temperature screening test which will be ef fective in identifying units that are susceptible to copper nigration. This test requires baking the units at 150*C for two weeks to identify units that would be susceptible.

Currently, both Gould-Brown Boveri and 'Motorola are screening SCR's by means of the high te=perature bake to obtain SCR's known to be free of the copper migration. problem.

COPY SENT REGION [&

- - GOULD-BROWN BOVE.

These SCR's vill then be used to change out SCR's in selected devices at Duke Power Co=pany. The SCR's removed from the selected devices at Duke Power Company will then be subjected to detailed cza=ination, so that we may more accurately determine the scope of this potential probles.

It is esHmted the _ SCR screening vill take approximately 3 weeks, and the change out of SCR's at Duke Power vill take approximately 3 weeks, followed by 3 to 4 weks of detailed exanination to fully evaluate the situation. At this peint in tirne, then ve can detemine if the problem is batch or lot re-lated, or if the failures were purely randotn. This plan of action should be co=pleted by early April 1980.

In discussions with Motorola, we have determined that other users of SCR's have not identified similar failures, even where the units are exposed to much higher a=bient te=peratures than in switchgear applications. The SCR's are rated at 125'c and normally do rot experience an operating ambient above 50*C in a svitchgear overcurrent relay environment.

To date ve have only three positively identified SCR field failures attrib-utable to copper migration and only one of these was returned from Duke Power vith the other two from cet=oercial operation.

We vill keep ycu appraised of our progress and findings in this matter.

Very Truly Yours, a C>- ' /k-D. D. Duvall Vice President and General Manager Switchgear Syste s Division DDD/jin cc:

A. Loe:ticher B. Cochran b'RC REG II R. Conrad D. Dalas ta R. Ianaozzi- --

W. Laubach J. Lipnit:

E. Rhoads W. Wagner 5205 9