05000338/LER-1981-057-03, /03L-0:on 810716,emergency Diesel Generator 1J Declared Inoperable.Caused by Small Fire Resulting from Oil Leak in Exhaust Manifold.Procedures Will Be Changed to Prevent Oil Accumulations in Exhaust

/03L-0:on 810716,emergency Diesel Generator 1J Declared Inoperable.Caused by Small Fire Resulting from Oil Leak in Exhaust Manifold.Procedures Will Be Changed to Prevent Oil Accumulations in Exhaust

ML20010C708
Person / Time
Site:	North Anna
Issue date:	08/14/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010C705	List: 05000338/LER-1981-057, Forwards LER 81-057/03L-0 05000338/LER-1981-057-03, /03L-0:on 810716,emergency Diesel Generator 1J Declared Inoperable.Caused by Small Fire Resulting from Oil Leak in Exhaust Manifold.Procedures Will Be Changed to Prevent Oil Accumulations in Exhaust
References
LER-81-057-03L, LER-81-57-3L, NUDOCS 8108200331
Download: ML20010C708 (4)

LER-1981-057, /03L-0:on 810716,emergency Diesel Generator 1J Declared Inoperable.Caused by Small Fire Resulting from Oil Leak in Exhaust Manifold.Procedures Will Be Changed to Prevent Oil Accumulations in Exhaust

Event date:
Report date:
3381981057R03 - NRC Website

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m U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR T7PE ALL REQUIRED INFORMATION)

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DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/ On July 16, 1981, with Unit I at 100 percent power, a small oil fire on IJ

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/ emergency diesel generator developed aad it was declared inoperable. This event /

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/ reportable pursuant to T.S. 6.9.1.9.b.

The action statement of the LCO (T.S.

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/ 3.8.1.1) was met. 1H emergency diesel generator and off-site power sources were

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/_ demonstrated operable.

IJ emergency diesel generator was returned to operable

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/, status on July 18, 1981. The public health and safety were not affected.

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SYSTEM

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VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE

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SEQUENTIAL OCCURRENCE REPORT REVISION LER/R0 EVENT YEAR REPORT NO.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP.

COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/ An oil leak in the exhaust manifold caused the fire. Oil accumulations above the/

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/ upper piston after stopping the engine drained to the exhaust manifold causing

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/ excess oil in exhaust manifold.

Leaking exhaust manifold gaskets allowed oil to /

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/ leak onto the engine.

Procedures will be changed to prevent oil accumlations in /

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/ the exhaust and gaskets will be replaced.

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FACILITY METHOD OF STATUS

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OPERATOR OBSERVATION

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NRC USE ONLY

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810:200331 810814*"E OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 PDR ADOCK O$000338 0

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'Northi Anna Power Station,' Jnit #1 -

Docket No.'.50-338'

Report No. LER 81-057/03L-0 Description of Event'

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Onj July 16,l1981,'with Unit I at 100 percent power, a small oil

' fire developed on.the exhaust manifold of the IJ es.ergency diesel generator.17 minutes.after it had been started for periodic testing.

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The.1J. emergency diesel generator was secured immediately and declared-inoperable..This event is reportable pursuant to.T.S.'6.9.1.9.b.

Probable Consequences of Occurrence

The operability of off-site power sour'ces and,1H emergency diesel.

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were demonstrated.every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> until the IJ> ersergency diesel generator was declared operable on July 18, 1981. The action statemeM of the LCO (T.S. 3.8.1.1) was met.

The public health and safety n ni not affected.

Cause of Event-Oil lickage from exhaust flange points _in the turbocharger regian caused a small oil fire. A representative from the Fairbanks Horse Engine Division of Colt' Industries was contracted to trouble shoot

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the problem. After examining the engine, he. stated-that excessive-oil accumulations in the exhaust was caused by' a failure to bar" the engine after shutdown.

The emergency diesel fs a 12 cylinder vertically opposed piston engine. During operation cooling ichrication oil flova through a 4

channel in the connecting rod to an area between the piston skirt and insert and out a hole in the insert. As the, piston moves from the inner dead center to the outer dead center position any. oil above the upper.

piston is thrown' eut into the upper crankcase compartment around' the upper ends of the cylinders.

This oil then drains either toward the blower or control end of the upper crankcase compartment and down to the oil pan. When the diesel'is stopped a substantial-amount of: oil accumulates above the upper pistons which stop near the inner dead center

. position..This oil eventually drains down the cylinder wall past the piston rings, into the combustion space, past the lower piston rings, into the exhaust ports, and into the~ exhaust manifolds. When the engine starts exhaust back pressure is initially high until the turbocharger turbine reaches terminal speed. The accumulated oil is forced out of any leaks in the exhaust manifold. To verify'that-the above condition was occurring, several therac. couples were removed. from

- the IJ diesel exhaust ports after it had been shutdown for 14 days. Oil was found.in the exhaust system. During the last run the diesel-had been loaded greater than 75 percent for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />;

- thus, any oil in the exhaust at that time would have vaporized and wg

- been exhausted.

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Immediate Corrective Action

An operator reported smoking oil on the exhaust manifold shortly i-before the fire broke out.

The Unit 2 SRO responded immediately.

Upon arriving in the IJ emergency diesel generator room moments after the initial report of smoke, the Unit 2 SRO found that a fire had developed. The diesel was stopped and the fire announced over the plant intercom system. Before the fire. brigade arrived, the Unit 2 SRO 5ad extinguished the fire with a portable dry chemical extinguisher.

The diesel was not damaged by the fire.

One-half hour after the fire the IJ diesel was started.

It ran normally in the loaded condition for five hours.

The diesel generator was returned to auto start, but was not declared operable until July 18, 1981, after a minor coolant leak (unrelated to the fire) was repaired.

Scheduled Corrective Action Procedures will bc changed to require cranking the engine over at least one full revolution 15 minutes after the engine has been stopped. This action will return any oil accumulated above the upper piston to the oil pan and prevent it from draining into the exhaust manifold.

During Unit shutdown of sufficient duration, leaking exhaust manifold gaskets will be replaced. Presently these leaks are minor and only a problem when oil accumulates in the exhaust manifold. With the actions taken to prevent exhaust manifold oil accumulation (see Actions to Prevent Recurrence) the present minor exhaust gasket leaks should not be a problem.

Actions Taken to Prevent Recurrence The same problem occurred on April 21, 1981 (LER 81-027/03L-0).

Two sources of_the exhaust manifold oil were suspect. One source could be prelubrication oil which can leak past the upper piston rings into the combustion region during the prelubrication oeriod (2 minutes at North Anna). The other source can be small amounts of lubrication oil normally found in exhaust gases. Normally oil from these sources would not be a problem rince they would be vaporized and exhausted to the atmosphere. When the diesels are run at light loads, exhaust flow and temperatures are substantially lower than during full lead operation. Exhaust temperatures and flows under light load conditions can be insufficient for complete vaporization and exhaust of oil from the two sources described above.

If many successive light load runs are made it is possible to accumulate oil in the exhsust manifold.

Based on the above analysis of the problem, operation practices were changed to load the diesels to at least 75 percent load for two hours whenever the diesel generators were started except when starts are expected every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. During operability checks conducted on a once every 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> schedule, the diesels are loaded -

to at least 75 percent load for two hours every other run.

Operation of the diesels as described above should prevent accumulations of oi,1 in the exhaust manifold due to the phenomenon described above.

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1 To ~ prevent oil accumulations above the ; upper pist'ons lfrom draining

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to the exhaust manifold after the engine has'been stopped, the. engine will be turned'over at least one complete. revolution 15 minutes.

'af ter the engine has-been stopped.

Turning the diesel engine over after it has been stopped and -

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i running the engine, loaded as described above should prevent recurrence.

l Oil leakage points will be cleaned of oil ' accumulations so any additional leakage can be detected and the success of the above corrective actions judged.

G_ene_ric Implications L.

Diesel en, tines similar in design to the emergency diesel engines used at No rth Anna can be expected to have similar problems. ;The

- problem may not' appear until the exhaust system gaskets start to age, have beer thermally tycled many times, and develop leaks.

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