ML19329B089

Interim Deficiency Rept Re Zener Diode Failure Mode for GE Breaker Power Sensors.Ge 760512 Ltr 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: ML19329B083 ML19329B089 ML19329B094 ML19329B095 ML19329B096 ML19329B097
References
NUDOCS 8001300677
Download: ML19329B089 (3)

Text

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• o TOLEDO

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

- r . o. m casi ess-sm Docket No. 50-346 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 l 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 l O

• I l

(") cc: Dr. Ernst Volgonau, Director Office of Inspection and Enforcement

• l

. U.S. Nuclear Regulatory Commission l Washington, D.C. 20555 .

8001300 7 l

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SERVICE '

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• Elf G IN EERIN G .

inAt. CtECTNC .s COMPANY 3450 WEST CENTRAL. AVENUE, TOLEDO. CHIO 43C00

, D E P A R Tl.1 E N T .

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

>1edo Edison Company N' d' ~

0. Madison Avenue ledo, Ohio 43652 " POY!im ENG. -

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tE: Mr. E. C. Novak '

telemen :

wi s tistation icar t o 'c aresponsibility, ll to the attention.of users of our products with tain cir,cumstances a condition that may occur under ton ofcAK g- circuit breakers.

with power supplies.used in the Power Sensor '

ent' analysis of power supplies . indicates t ha t a V:ously.Zence may occur when two independent conditions failure exist ofsimul- the 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 Zonor. conditions alonc does not result in overstressing ureorofopen, ed the Zener circuited. could occur in two modes, either short cir-r, the power supply voltage If theisf ali cii ilu tr ee distoa less shortthan circuited 30V. in- * -

uicient to trip the circuit breaker when i t should. If the

'50V[)more.

re in an open circuited Zence, the power supply voltage rises ity G )c overvoltage Although the circuit breaker retains trip cap- ,

is impressed on components in both the O e O

U power

'do te riosupply ra tion. and the logic unit, with possibic further component power supplics and We arc, logictherefore, units. recommending replacement of 9xtensive ao shoun that reviev of field test data and ficid failure analysis a very small number of Zener failures have been- '

otected, nd September approximately 1975. We0.4% of the units shipped between 1967 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 ogic units. Corpany is prepared to replace the power supplies and 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, h Maryland 20760 Mr. P. V. Martin - '

General Electric Company -

300 Madison Avenue w

R:om 1510 ~ -

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