ML20082C402

Special Rept 91-005-00:on 910619,EDG a Tripped on Turbocharger Lube Oil Low Pressure During Performance of Operating Procedure 903-068.Procedure Changed to Require Lubrication of Turbocharger

ML20082C402
Person / Time
Site:	Waterford
Issue date:	07/15/1991
From:	Packer D ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
91-005-00, 91-5, W3B5-91-0211, W3B5-91-211, NUDOCS 9107190081
Download: ML20082C402 (4)

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Operations W305 91 0211 A4.05 QA July 15, 1991 U.S. Nuclear Regulatory Commission ATTENTION:

Document Control Desk Washington, D.C.

20555

SUBJECT:

Waterford 3 SES Docket No. 50 382 License No. NPf-38 Reporting of Special Report Gentlemen:

Attached is Special Report Number SR 91-005-00 for Waterford Steam Electric Station Unit 3.

This Special Report is submitted per 10CfR50.36(c)(2) and Technical Specifications 4.8.1.1.3 and 6.9.2.

Very truly.yours,

(,

D.F. Packer General Manager Plant Operations DfP/DDW/jrr Attachment cc:

Messrs. R.D. Martin G.L. Florreich J.T. Wheelock - INPO Records Center E.L. Blake D.L. Wigginton R.S. Reynolds NRC Resident Inspectors Office

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Special Report 91 005 00 Invalid failure of Emergency Diesel Cenerator

'A' due to a spurious turbocharger lube oil low pressure trip.

1NTRODUCT10N At 1017 on June 19, 1991 Emergency Diesel Generator (EDG)

'A' tripped on tutbocharger lube oil low pressure during the performance of Operating procedure (Op) 903 068, "EDG Operability Test Verification." EDG

'A' was restarted and Op.903 068 was satisfactorily completed.

This event is classified as an invalid failure and is reported in accordance with Technical Specification'(TS) 4.8.1.1.3.

The-root cause of this event is a slow i

turbocharger lube oil system response time that, due to a restrictive pressure j

tolerance between the turbocharger lube oil low pressure trip set point at,J the turbocharger lube oil pressure regulator band, causes spurioua turbocharger lube oil trips.

NARRATIVE At 1017, EDG 'A' was started to perform OP.903 068 EDG

'A' tripped soon aftor being started.

The plant Monitoring computer showed that the EDO.

tripped on turbocharger lube oil low pressure.

Since norinal oil pressures were present, the EDG was restarted and Op-903 068 wan completed during this' second attempt.

The root cause of this event is the slow build up of turbocharger lube oil at the shutdown sensor location. To prevent recurrence of these spurious trips, l_

two_ actions will be taken.

First, as reported in Special Report 91 004 00, i

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the turbocharger lube oil low pressure trip set point will be reduced.

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- Reducir.g the set point will conpensate for the slow system pressure increase

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at the shutdown sensor location. The vendor has provided written Suidance to lower the turbocharger lube oil low pressure trip set point to 3.0 pst and the System Engineer has generated set point document change request 91 014.

The set point will be changed during the next EDG outage.

The second action to prevent spurious turbocharger lube oil low pressure trips is to ensure that the oil line between the turbocharger bearing and the shutdown sensor is purged of air.

During shutdown, this line will drain to the turbocharger bearings through the oil / air separctors to the oil sump.

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to the bearings tapa off between the oil supply and the shutdown sensor.

l Because of this physical arrangement, an air pocket can form betwee he oil supply and the shutdown sensor when the oil in the line drains to the bearings during shutdown.

During EDG startup. when oil is supplied, this air pocket slows the build up of pressure at the oil sensor.

Since the oil line is filled from the previous start attempt and has not yet drained to the sump, second start attempts-of the EDG have always been successful when the initini trip was due to a low turbocharger lube oil trip.

To prevent the system sluggishness caused by air in the oil line, the normal

. EDG start up procedure. Emergency Diesel Generator, OP 009 002, will be changed to require lubrication of the turbocharger before a normal EDG start.

Lubricating the' turbocharger ~ shortly before an EDG start will-fill the oil line to the-shutdown sensor and enhance system response time since pressure at

- the shutdown sensor will increase quickly.

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This failure is classified as an invalid failure since, in the emergency mode, the turbocharger low lube oil trip is bypassed. There have been two valid failures of EDG

'A' and one valid failure of EDG

'B' at Waterford 3 since the operatitig license was issued.

The current surveillance test interval is at least once per 31 days, which is in conformance with the schedule of Regulatory Position C.2.d.

The EDG would have performed as designed in the emergency mode; therefore, this event was not a threat to the health and safety of the general public, PIANT CONTACT W.R. Brian, Plant Engineering Superintendent,-504/464 3127