ML19329B089

Interim Deficiency Rept Re Zener Diode Failure Mode for GE Breaker Power Sensors.Ge Re Potential for Same Encl.All GE Power Sensor Power Supplies & Logic Units to Be Replaced

ML19329B089
Person / Time
Site:	Davis Besse
Issue date:	08/06/1976
From:	Roe L TOLEDO EDISON CO.
To:
Shared Package
ML19329B081	List: IR 05000346/1976019 ML19329B079 ML19329B083 ML19329B089 ML19329B094 ML19329B095 ML19329B096 ML19329B097 ML19329B101
References
NUDOCS 8001300677
Download: ML19329B089 (3)

Text

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TOLEDO

% sisG;u 1.OWELL E. ROE August 6, i976 v.e. em.em r

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m Docket No. 50-346 casi ess-sm 1

Mr. James C. Keppler q

Regional Director, Rcgion III Directorate of Regulatory Operations U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 i

d

Dear Mr. Keppler:

This letter is submitted as an interim report regarding the Davis-Besse 1

Nuclear Power Station Unit No. 1, Gencial Electric, 400 volt AC breaker power sensors, related in person to Mr. D. Hayes, Office of Inspection and Enforcement, Region III on May 13, 1976.

We are inclGding a copy of General Electric letter dated May 12, 1976 which describes a potential zoner diode failure mode for the subject power sensors.

The content of the May 12, 1976 letter was the subject of a meeting between General Electric and Toledo Edison on May,17,1976.

/

The result of this meeting uns a program where Toledo Edison will replace all General Electric pouer sensor pouer supplies and logie units at Davis-Besse Unit No. 1.

Although not directly related to the zener problem, Toledo Edison will also be adding concurrently more selective ground fault coordinations to motor control feeder breakers.

Toledo Edison and' General Electric are now developing the details of the program which include delivery of materials, preparation of and approval of procedures, and schedule for rework.

The foregoing items are currently under review by Toledo Edison.

Upon completion of the establishment corrective action and verification of its results, a definitive report of the deficiency, analysis of the safety implications and the corrective action taken will be submitted to your office in accord with 10 CFR Part 50.55 (e).

Yours very truly, y

LER:ss O

(") cc:

Dr. Ernst Volgonau, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 8001300 7

Washington, D.C.

20555 l

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[' s.'i SERVICE g

Elf G IN EERIN G inAt. CtECTNC COMPANY 3450 WEST CENTRAL. AVENUE, TOLEDO. CHIO 43C00 D E P A R Tl.1 E N T

.s Phono (410) 5314C03 May 12, 1976 RECEIVE',.

>1edo Edison Company N'

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0. Madison Avenue

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POY!im ENG.

ledo, Ohio 43652

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Mr. E.

C. Novak telemen :

wi s ti t o 'c a ll to the attention.of users of our products with icar station responsibility, a condition that tain cir,cumstances may occur under with power supplies.used in the Power Sensor ton ofcAK circuit breakers.

g-ent' analysis of power supplies. indicates t ha t a V Zence may occur when two independent conditions exist simul-failure of the

ously.

First, the load current through the circuit b rea k e r to be less than 15% to 20% of the frame s i z e. current rating, snd, the gate current requirement of the shunting SCR'n has to it the median to upper ra n ge of the s p ec i f ica t. ion limi s.

When ic two conditions exist simultaneously

.the thermal rating of

7. c n c r ' i s excceded, w h i c h m a y -1 c a d to failure of the Zoner.

cr of the conditions alonc does not result in Zonor.

overstressing ure of the Zener could occur in two modes, either short cir-ed or open, circuited.

If the f a ilu r e is a short circuited

• r, the power supply voltage is li cii t e d to less than 30V. in-icient to trip the circuit breaker when i t should.

If the

' re in an open circuited Zence, the power supply voltage rises u

50V[)more.

Although the circuit breaker retains trip cap-ity G )c overvoltage is impressed on components in both the O

e O

U power supply and the logic unit, with possibic further component

'do te rio ra tion.

We arc, therefore, recommending replacement of power supplics and logic units.

9xtensive reviev of field test data and ficid failure analysis ao shoun that a very small number of Zener failures have been-otected, approximately 0.4% of the units shipped between 1967 nd September 1975.

We are unauare of any cases where oner has a failed resulted in personal inj ury or property damage, a

nits nou being shipped include a power supply. circuit redesigned o climinate the Zence diode failure mechanism.

If you have Power ensor equipped circuit breakers a t your nucicar site, the General lectric Corpany is prepared to replace the power supplies and ogic units.

Removal of original units and installation of re-lacements vill be at our expense, with Installation and Service ngineering providing logisticni, technical and test support, and 1so peturning the replaced units to the' factory..

Very truly y,ours, YAU Y b h rgil L. Roberts,

<ca Engineer R:j ob Mr. J. G. Evans Mr. J. D. Lonardson

'Ioledo Edison Company 300 Madison Avenue Toledo, Ohio 43652 Mr. P.

P. Anas 13cchtel Company P. O.

11ox 607 V'j0 Shady Grove Road

( g ersburg, Maryland 20760 h

Mr. P. V. Martin General Electric Company 300 Madison Avenue R:om 1510 w

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