ML20085C770

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Special Rept:On 910906,invalid Failure of Diesel Generator 1B Occurred & Sequencer Initiated Blackout Sequence & Restarted Generator,Resulting in Total Blackout.Failure Assigned to Util Significant Event Investigation Team
ML20085C770
Person / Time
Site: Catawba Duke Energy icon.png
Issue date: 10/07/1991
From: Tuckman M
DUKE POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9110110126
Download: ML20085C770 (2)


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DUKE POWER October 7,1991 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50-413 Special Report Invalid Failure of Diesel Generator IB Pursuant to Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Report concerning the Unit 1 Diesel Generator B (D/G 1B) invalid failure that occurred on September 6,1991.

Very truly yours, g T. h za M. S. Tuckman CRL/SR10791 Attachment xc. ' D. Ebneter

_segional Administrator, Region II W. T. Orders Senior Resident Inspector R. E. Martin, ONRR I

9110110126 91100'7 PDR ADOCK 05000413 l

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SPECIAL REPORT CATAWBA NUCLEAR STATION An invalid failure (Start #963) of D!esel Generator (D/G) IB occurred on September 6, 1991, while Unit I was at 100% power. D/G 1B was on a monthly test schedule at the time of the invalid failure. At the time of the invalid failure, there had been 0 valid failures in the last 20 valid tests and 1 valid failure in the last 100 valid tests on D/G 18.

D/G IB was declared inoperable on September 6,1991 at 10:40 A.M. for preplanned maintenance. Following the maintenance, Operations started D/G 1B (Start #962) per OP/1/A/6350/02 (Diesel Generator Operation) to perform a functional veriDeation of the maintenance performed. The rtm was successful and the D/G was secured. The D/G was restarted per PT/1/A/4350/02B (D/G 1B Operability PT). The D/G ran for approximately I hour at 5700 kW with no problems encountered. As per the procedure, the operatnr unloaded the D/G then mistakenly opened breaker IETB-3 (Essential Bus B Norial Incoming Feeder Breaker from 1 ATD) instead of IETB-18 (Diesel Generator IB Output Breaker). This resulted in the D/G carrying the ess.:ntial bus.

Next, the operator pushed the D/G 'Stop' button to secure the D/G. The sequencer circuitry, sensing a loss of voltage on the bus, initiated the blackout sequence & restarted the D/G. The operator noticed the D/G speed drop but returned back to normal. The operator then pushed the D/G 'Stop' button twice more in an attempt to secure the D/G.

Believing the D/G could not be secured by normal means, the operator then operated the emergency D/G 'Stop/Run' solenoid which ports air directly and extends the shutdown cylinder. At this time the D/G did shutdown and a total blackout occurred on IETB essential bus.

Once the D/G and essential bus were returned to normal alignment, D/G IB was restarted per PT/1/A/4350/02B (Start #964) and ran for approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> with no problems.

The D/G was then declared operable on September 7,1991 at 8:50 A.M.

D/G IB was inoperable for a total of 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> and 10 minutes. This time includes the period the D/G was removed from service for maintenance. During the time the D/G was inoperable, it was unavailable for a total of 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and 10 minutes.

Following this invalid failure, there are still 0 valid failures in the last 20 valid tests and I valid failure in the last 100 valid tests on D/G 18. Therefore, D/G IB will remain on a monthly test schedule as required by Technical SpeciDeations.

This failure has been assigned to a Duke Power Significant Event Investigation Team. Any corrective actions resulting from this review will be implemented at Catawba Nuclear Station.

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