ELV-02215, Special Rept 2-90-04:on 901009,invalid Diesel Generator Failure Occurred

Special Rept 2-90-04:on 901009,invalid Diesel Generator Failure Occurred

ML20065J984
Person / Time
Site:	Vogtle
Issue date:	11/08/1990
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2-90-04, 2-90-4, ELV-02215, ELV-2215, NUDOCS 9011150034
Download: ML20065J984 (3)

Text

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1 e Georgia Power Company 333 P.edmont Annue Atianta. Georgia 30308 f

Jo;ephono 404 526 31D5 Ma4ing Addrent ,

40 insornet.s Center Parkwar ~, t

. Post O'fce Don 1295 1

Dirrrungham Alatama 35201 To!cphore 205 868 5581 November 8, 1990- ,, ,,,,,.,, ,y,, j W. G. Hairston, m l Sonor Vce Presidert  ;

Nucicar Operations r ELV-02215 f 0678 l

Docket No. 50-425 l b U. S. Nuclear Regulatory Commission  !

ATTN: Document Control. Desk j Washington, D. C. 20555 ,

Gentlemen: -l V0GTLE ELECTRIC GENERATING PLANT 4 SPf',IAL REPORT i INVALID DIESEL GENERATOR FAILURE l

In accordance with the requirements of the Vogtle Electric Generating Plant:  :

Technical Specifications,. Sectiont 4.8.1.l.3 and 6.8.2, Georgia Power Company hereby submits the enclosed Speci.1 Report .concerning an -invalid diesel. j generator failure.  ;

i Sincerely,  ;

K]. h h ! A- W W. G. Hairston,-III-  :

WGH,III/NJS/gm  !

Enclosure:

Special Report 2-90-04  !

xc: Georaia Power Comoany '

Mr. C. K. McCoy  ;

l- Mr. W. B. Shipman  !

! Mr. P. D. Rushton  ;

i Mr. R. M. Odom  !

L NORMS  ;

J, U. S. Nuclear ~ Reaulatory Commission i Mr. S. D. Ebneter, Regional Administrator- .

i Mr. D. S. Hood, Licensing Project Manager, NRR.

Mr. B.. R. Bonser. ' Senior Resident Inspectore Vogtle- i i

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9011150034 90110s PDR 7 j%y y-

, S ADOCK 0500C425 '

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i V0GTLE ELECTRIC GENERATING PLANT - UNIT 2 TECHNICAL SPECIFICATION SPECIAL REPORT 2-90-4 ,

l INVALID DIESEL GENERATOR-FAILURE l

l A. REQUIREMENT FOR REPORT This report is required in accordance with the Vogtle Electric Generating; Plant Technical Specifications, Section 4.8.1.1.3. This section of the }

Technical Specifications requires ths.t all Diesel Generator-(DG)' failures, ,

valid or non-valid, be repurted to the Commission in a Special Report pursuant to Technical Specification 6.8.2.

B. DESCRIPTION OF INVALID FAILURE OF DIESEL GENERATOR 2A  !

On 10-9-90, Unit 2 was in Mode.6 (Refueling) during a scheduled refueling  !

outage and DG 2A was undergoing a planned engine overhaul.1 At 0211 CDT,.DG 2A was started for a 24-hour run as a part of the Engineered Safety Features .

Actuation System (ESFAS)-testing. At 0331 CDT,. operators observed a."DG 2A,  :

Vibration Trip" annunciator light on the local control panel, but the DG did not trip. Operators reduced the DG electrical load and immediately began

, troubleshooting by resetting-the four. vibration. sensors' and taking vibration readings. At 0407 CDT, while troubleshooting was in progress, a DG trip occurred with no annunciator indicating the reason for the trip, t An investigation into this failure identified'that one of the four vibration sensors had actuated below its trip setpoint and initiated,a trip signal to  !'

i the air logic trip circuit. This circuit trips the DG when air' pressure-l drops below 20 psi. The circuit was activated, but the trip did not occur .

dus to an inadequate design which allowed circuit air. pressure to remain above 20 psi following the sensor trip. During the event,.the four sensors were reset, but the trip circuit retained the trip signal. When circuit air pressure fluctuations caused air pressure to fall below the 20 psi setting, the DG tripped with no annunciation on the control panel. The faulty sensor has been returned to the vendor for examination. An orifice in the shutdown air logic circuit board'has been replaced with an orifice having a smaller opening. This will allow the logic circuit air pressure to drop below 20 psi and initiate a DG trip when a valid signal'is ) resent,< thus correcting l the inadequacy noted above. Similar orifices-in tie other DG'sthave been '

replaced. DG 2A was taken out of service for a scheduled overhaul at 2220 i CDT on 9-25-90, and was returned to service at 2314 CDT on 10-16-90.

1 In addition, further investigation revealed that another of the sensors  :

would not initiate a trip. Upon consultation with the vendor, Georgia Power ,

Company learned that these vibration sensors.have been subject:to failures  !

which could be attributed to a design defect. The vendor has modified the ,

design of the sensor to' eliminate the. defect, and 'all of the potentially defective sensors at Plant Vogtle have been replaced with the modified version. The sensor which would not initiate a trip has.been returned to -

the vendor for examination.

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i o C. SUPMARY This event is classified as an invalid failure per Regulatory Guide 1.108 Section C.2.e. because vibration trip signals are not active in the emergency mode. There have been a total of 56 valid tests of DG 2A'and 5 valid failures. The test frequency for DG 2A remains at once per 7 days in accordance with Table 4.8-1 of the Technical-Specifications.

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