ML20057B351

Special Rept 93-10:on 930813,valid Failure Occurred on DG 2B.Cause of Event Could Not Be Determined.Dg Start Circuit Will Be Changed Such That Control Air Will Not Be Needed to Start or Maintain DG Running

ML20057B351
Person / Time
Site:	Mcguire
Issue date:	09/13/1993
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
93-10, NUDOCS 9309210227
Download: ML20057B351 (3)

Text

..

ll l Duke fbuer Cornpany (74g7 g

.o Akf iarre NuclearStatson 12700 llegers ferry Rc>ad flunt,erwille, NClSO784M5

. DUKE POWER September 13,1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station Unit 2 Docket No. 50-370 Diesel Generator Special Report No. 93-10 Gentlemen:

Pursuant to McGuire Technical Specifications 4.8.1.1.3.c and 6.9.2, find attached a special report concerning a valid failure of Diesel Generator 2B.

Should there be any questions, please contact Terry Pederson at (704) 875-4487.

Very truly yours,

.C.

v McMeekin 4

TLP/bcb Attachment xc: Mr. S.D. Ebneter INPO Records Center Administrator, Region II Suite 1500 U.S. Nuclear Regulatory Commission 1100 Circle 75 Parkway 101 Marietta St., NW, Suite 2900 Atlanta, GA 30339 Atlanta, GA 30323 Mr. Victor Nerses Mr. George Maxwell U.S. Nuclear Regulatory Commission NRC Resident Inspector Office of Nuclear Reactor Regulation McGuire Nuclear Station Washington, D.C. 20555 9309210227 930913 7% i c .

PDR ADOCK 05000370 .t z

. /1 }

S PDR ius gy)

n. m.> ,o, c cw

9-

. DUKE POWER COMPANY .I McGUIRE NUCLEAR STATION l Diesel Generator Special Report Number 93-10 PIP 2-M93-0762 September 9, 1993 On August 13, 1993 at 1656, a Valid Failure occurred on Diesel Generator (DG) 2B. Unit 2 was in Mode 6 (refueling outage 2EOC8). DG start attempt number 993 was performed during PT/2/A/4350/15B (DG 2B Periodic Test, 18 month frequency). DG 2B started; however, the time to 95% speed was 11.5 seconds and the time to 4160V was 12.5 seconds verses the Tech Spec requirement of 11 seconds for each.

This was the first Valid Failure in the last 20 Valid Tests and the second Valid Failure in the last 100 Valid Tests for DG 2B.

On a unit basis, this is the third Valid Failure in the last 100 Valid Tests of DG 2A and 2B combined. Surveillance frequency '

remains monthly.

Start 994 was performed on August 13, 1993 at 1722 to  ;

troubleshoot the previous slow start. The start times were normal (8.4 seconds to 95% speed and 9.7 seconds to 4160V). Work Order 93059393 was initiated to investigate the slow start.

Start 995 was performed on August 14, 1993 at 1100 to monitor for ,

control air leakage and relay operation. The start times again '

were normal (8.8 seconds to 95% speed and 9.7 seconds to 4160V).

Significant control air leakage was noted at three locations in the pneumatic control air circuit which provides pressure from ,

the starting air tanks to the engine run/ shutdown cylinders.

Leakage in this loop has been found to cause slow starts in the past. The leaks were repaired by replacing the-shutdown valve,  ;

the control air valve and a leaking fitting. Solenoid valve 2MVGSV5173 was also replaced as a precaution because it had stuck partially open on a previous break-in run (it later reseated and no further problems were noted with this valve on other treak-in runs).

Three starts were performed following the maintenance work and all start times were very good. The results were as follows: ,

Start # 95% speed (sec.) 4160V (sec.)

996 8.3 9.4 997 8.3 9.5 998 8.3 9.6 t The root cause of the slow start on attempt # 993 could not be  !

determined because the start times for attempts 994 and 995 were i good. However, it is thought that the control air leakage and a possible sticking of 2MVGSV5173 was likely the reason for the slow start.  ;

f

Diesel Generator Special Report PIP 2-M93-0762 September 9, 1993 Page 2 of 2 As a result of this event, control air leakage for the other DGs was monitored and found to not be excessive. Long-term, modifications NSM 12279 (Unit 1) and 22279 (Unit 2) will change the DG start circuit such that control air will not be needed to start or maintain the DG running. The portion of the pneumatic loop that was leaking will be eliminated. These modifications are scheduled for the EOC9 refueling outages.

p

//,7 pf_ s nr R.M. Roberts DG System Engineer cc: R.A. Johansen J.A. Kisner W.E. Thomas D.G. Gardner W.W. Gallman R.E. Hunning B.T. Harkey R.C. Norcutt N.E. Kunkel A