ML20086C255

Forwards Analyses & Technical Info Supporting Discretionary Enforcement Action

ML20086C255
Person / Time
Site:	Mcguire
Issue date:	06/29/1995
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20086C257	List: ML20086C255 ML20086C258
References
NUDOCS 9507060387
Download: ML20086C255 (7)

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DukeIbwerCompany T.C Alcttam bicGuire Nudear Generation Depaenent ticePre:ident 1270()Hagen ferryRoad(h1GolVP)

(704)87M800 Huntenville, NC280784985 (704)8iM809Far i

DUKEPOWER June 29,1995 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

McGuire Nuclear Station Docket Nos: 370 Discretionary Enfomement Request - Unit 2 EDG Turbocharger Failures

Dear Sir:

Attached is the analyses and technical information supporting the McGuire Unit 2 discretionary enforcement action of 6/28/95.

We believe this discretionary enforcement was in the best nterests of nuclear safety. The TS action statements required Unit 2 to be i

in HOT STANDBY within six hours, thus your prompt action was necessary and was appreciated.

Regarding, current status (1200,6/29/95)

- Unit 1 is in Mode 4 with the unit cooldown continuing to Mode 5 per TS requirements. Our current schedule for the forced outage indicates Unit I will be back online appr. 7/5/95 after repairs to EDG 1 A and 1B are complete.

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- Following approval of the NOED yesterday, the TS required shutdown of Unit 2 was terminated. After discussion with Operations and management personnel, Unit 2 was returned to appr. 45% power level while EDG 2B repairs were ongoing. The 45% power level was chosen to minimize unit vulnerability to secondary system transients, e.g. loss of one feedwater pump or unit runback capability in the case of a LOOP cvent.

- EDG 2B repairs have now been completed and its operability run was completed i

and it was declared operability at 0730 AM today. Unit 2 will retum to full power I

on a normal power escalation scheduk. Repair to EDG 2A are underway on a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> basis.

1 05 CGS;3 9507060387 950629 PDR ADOCK 05000370 P

PDR ip,

4 June 29,1995

Subject:

McGuire Nuclear Station Docket Nos: 370 Discretionary Enforcement Request - Unit 2 EDG Turbocharger Failures 1

We will keep your informed regarding our progress in investigating this EDG equipment failure through our normal communication channels.

If you require further information, please contact James E. Snyder at (704)875-4447.

I Very truly yours, i

l Mci T. C. McMeekin 1

US Nuclear Regulatory Commission June 28,1995 Page 2/2.

xc: Mr. S. D. Ebneter Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta St., NW, Suite 2900 Atlanta,Ga. 30323 Mr. Victor Nerses U.S. Nuclear Regulatory Commission OfSce of Nuclear Reactor Regulation (14H25)

Washington, D.C. 20555 Mr. Robert E. Martin U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D.C. 20555 Mr. George F. Maxwell NRC Resident Inspector McGuire Nuclear Station Dayne Brown, Chief Division of Radiation Protection P. O. Box 27687 Raleigh, N. C.

27611-7687

4 U. S. Nuclear Regulatory Commission Page 3/3 bxc-E. Mac Geddie B. J. Dolan P. R. Herran G.A.Copp (EC050)

Z. L. Taylor (CN01RC)

E. Burchfield (ON0lRC)

R. J. Deese Dwin E. Caldwell W. R. Cross Kay L. Crane P.T.Vu John M. Washam I

i McGuire Nuclear Station I

Emergency Diesel Generator Turbocharger Failures Unit 2 Discretionary Enforcement - 6/28/95 Request Page 1/3 MNS Plan:

1/ Declare 1 A,1B, and 2A EDG's inoperable and enter TS 3.8.1.1, Action (f) and TS 3.7.1.2, Action (b) on both units.

2/ Shutdown Unit I as required by TS. This is required since no repairs are in progress for Unit I and the parts needed for repair are not available immediately.

3/ Begin a controlled shutdown on Unit 2 and pursue NOED in order to remain on-line until EDG 2B repairs are complete.

NOED Request:

1/ TS that will be violated:

a. TS 3.7.1.2 - Auxiliary Feedwater System In ACTION (b), extend the '.. 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.. ' requirement to be in IIOT STANDBY to 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

b. TS 3.8.1.1.f - Electrical Power Systems In ACTION (f), extend the '.. 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.. ' requirement to be in IIOT STANDBY to 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br />.

2/ The circumstances surrounding the situation..

EDG 2A and 2B have had turbocharger compressor blading failure in recent weeks. The vendor, ABB, has determined that the probable root cause is air flow holes which are machined into the compressor wall insert (stationary element). These holes serve a ' jet-assist' function and are not used at MNS, i.e. are dead-ended and appr. 2" deep. The presence of these holes appears to induce flutter on the compressor blading causing bladmg failure due to cycle fatigue. This is common to all four EDG l

turbochargers at MNS.

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4 McGuire Nuclear Station Emergency Diesel Generator Turbocharger Failures Unit 2 Discretionary Enforcement - 6/28/95 Request Page 2/3 3/ The safety basis for the request and safety significance:

• Maintenance of an onsite power supply for Unit 2 is in the best interests of nuclear safety. The Unit 2 generator represents an additional onsite power source powering all Unit 1 & 2 Auxiliary power system buses in the event ofloss of the transmission grid. Furthermore, the local grid is more reliable from a voltage stability standpoint with a large generator on line.

..!though there are several transmission lines connected to the McGuire 525 KV switchyard, the Unit 2 generator represents the source that is least likely to be lost in the event of a remote grid disturbance and thereby minimizing the possibility of a loss of offsite power at McGuire. See the attached PRA analysis which supports this conclusion.

• Shutting down both units puts an unnecessary burden on the control room operators in this situation.

• EDG 2B repairs are underway and will be complete by no later than app. midnight 6/29/95.

• After EDG 2B repairs are complete, the EDG 2A turbocharger repairs can proceed and will be done within its 72 hr TS requirement

• EDG 2A is available and will remain available until EDG 2B repairs are complete.

• EDG 2A has the original turbocharger rotor installed whose compressor blading are the original design and thus less susceptible to the failure mode.

4/ Potential hazards to the public safety...

Duke Power feels that the risk to the public will be reduced by Unit 2 remaining at power during the subject TS action statement extension considering: 1/ the increased consequence of potential LOOP events while in a shutdown mode, i.e loss of decay heat capability, et.al., and 2/ the reliable onsite power supply related to continued Unit 2 operation.

5/ Environmental impact statement No environmental impact is involved in this matter.

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McGuire Nuclear Station Emergency Diesel Generator Turbocharger Failures Unit 2 Discretionary Enforcement - 6/28/95 Request l

1 Page 3/3 6/ Proposed compensatory actions a/ Standby AC power (via SATA transformer) remains powered from Unit I switchyard.

b/ All discretionary work on safety-related components has been discontinued.

c/ All switchyard activity has been eliminated and gates locked.

d/ No onsite electrical power system work will be allowed during this period.

d/ EDG 2B repairs are proceeding on 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> basis.

c/ EDG 2A repairs will commence immediately upon declaring EDG 2B

operable, f/ SSF will remain operable during this period.

g/ Maintain EDG's I A,1B, and 2B available during the period of the extension until EDG 2B is declared operable.

7/ The justification for the duration of the noncompliance....

The requested extension of the action statements will provide a reliable power source onsite with Unit 2 in a stable condition while EDG 2B repairs are completed and TS retests completed. MNS feels that this action is in the best interest of nuclear safety, i.e. maintaining a Unit 2 onsite power supply during this period. After repairs to EDG 2B are complete, TS 3.8.1.1, Action (d) AOT of 72 will be the controlling action statement during the EDG 2A repairs.

8/ This matter has been reviewed by the MNS PORC which has approved this action.

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