ML20087H251

Special Rept:On 950726,non-valid Failure of E-3 EDG Occurred Due to Dead Spot on E-3 EDG Motor Operated Potentiometer (MOP).E-1 & E-3 EDG Mops Will Be Replaced W/New Type Mop During Future Mod Outages

ML20087H251
Person / Time
Site:	Peach Bottom
Issue date:	08/14/1995
From:	Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9508170380
Download: ML20087H251 (2)

Text

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Ccrrett C E' war:33 y' ,,

• - Plant Manager Peach Bottom Atomic Power fataaon O

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EN RGY ecco tee,0< ceene",

FID 1, Box 208 DeKa, PA 17314-9739 717 450 4244 August 14, 1995 Docket Nos. 50-277 50-278 Ucense Nos. DPR-44 DPR-56 Document Contrc.' Desk U. S. Nuclear Regulatory Commission Washington, DC 20555

SUBJECT:

Peach Bottom Atomic Power Station - Unit 2 & 3 Special Report for a Non-Valid Failure of the E-3 Emergency Diesel Generator on 7/26/95

REFERENCE:

Peach Bottom Atomic Power Station Technical Specification (Tech Spec) 4.9.A.1.2.L and M This Special Report is submitted pursuant to the requirements of Tech Spec 4.9.A.1.2.M. This Surveillance Requirement requires reporting of all emergency Diesel Generator (D/G) failures, valid or non-valid, within 30 days. This report is required to include the information recommended in Regulatory Position C.3.d of Regulatory Guide (RG) 1.108 " Periodic Testing of Diesel Generator Units as Onsite Electric Power System at Nuclear Power Plants", Revision 1, August 1977.

On 7/26/95 at approximately 0130 hours0.0015 days <br />0.0361 hours <br />2.149471e-4 weeks <br />4.9465e-5 months <br />, with Unit 2 at 100% power and Unit 3 at approximately 70% power, during the performance of a Surveillance Test (ST),

the E-3 D/G Output Rreaker (E-32) tripped open while the operator was attempting to increase load on the unit. Troubleshooting revealed that the E-3 D/G Motor Operated Potentiometer (MOP), used for manually increasing load on the D/G ,

during testing activities, had a dead spot. This dead spot on the potentiometer i affected the E-3 D/G controller output signal thus causing the fuel racks to close i and the D/G Output Breaker to trip open. At approximately 2312 hours0.0268 days <br />0.642 hours <br />0.00382 weeks <br />8.79716e-4 months <br />, the E-3 l D/G was returned to an operable status following MOP replacement and successful D/G testing.

The E-2 and E-4 D/G MOPS were just replaced with a new type MOP during the .

recent D/G modification outages. The E-1 D/G MOP was just successfully used CCN 95-14068 0 ho PDR 77 $

S f L

I j a. .Q y t 1

U. S. Nuclear Regulatory Commission Pa'ge 2 w l for testing on 7/25/95. In addition, the E-1 and E-3 D/G MOPS will be replaced .

with the new type MOP during future modification outages.  :

1 The E-3 D/G failure was classified as a non-valid failure using the guidance of RG 1.108, Revision 1,1977. Because this occurrence was classified as a non-valid. ,

failure, the current surveillance testing interval will remain at once per 31 days  :

which is in conformance with RG 1.108, Revision 1, Section C.2.d.

During this event,- the E-3 D/G was unavailable for operation approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The MOP is used for testing purposes only so that part of the logic which  ?

contains the MOP is normally bypassed on a D/G automatic start signal.- ,

Therefore, the MOP failure would not have prevented tha D/G from performing its  :

safety function. In addition, the remaining D/Gs were operable and would have l provided adequate AC power to safety related loads in the event of an actual loss  ;

of offsite power. ,

If you have any questions or require additional information, please do not hesitate .;

to contact us.

i 1

Sincerely, l

1 GDE/GAJ:gaj cc: R. A. Burricelli, Public Service Electric & Gas  ;

R. R. Janati, Commonwealth of Pennsylvania T. T. Martin, US NRC,~ Region I ,

R. l. McLean, State of Maryland ,

W. L Schmidt, US NRC Senior Resident inspector ~

H. C. Schwemm, Atlantic Electric .l A. F. Kirby lil, DelMarVa I

CCN 95-14068 1

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