ML20094M487

Special Rept:On 920218,invalid Failure of Diesel Generator 1B Occurred During Operations Periodic Test & Diesel Generator Shutdown Due to High Jacket Water Temps.No Abnormal Indications Noted.Work Request Written

ML20094M487
Person / Time
Site:	Catawba
Issue date:	03/19/1992
From:	Tuckman M DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9204010011
Download: ML20094M487 (3)

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s- \\ l Duu twer evntun . us n<un Catau ba \udcar Genera! ion Department Vice Prnident (MA Com ord R+! 180.1)UlJ205 Olbre

, h>rk,5C X45 (SG1)Kil4426 fu DUKE POWER March 19,1992 U. S. Nuclear Regulatory Commission A1TN: Document Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 1 Docket No. 50-413 Special Report _

Invalid Failure of Diesel Genenttor IB l'ursuant 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 IB) invalid failure that occurred on February 18, 1992.

Very truly yours, c $ i f . . NhW-M. S. Tuckman CRUlBDGSR33.92 Attachment q xc: S. D. Ebneter Regional Adm',nistrator, Region 11 W. T. Orders Senior Resident Inspector

. R. E. Martin, ONRR I

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SPECIAL REPORT CATAWilA NUCLEAR STATION DIESEL GENERATOR lil INVAllD FAILURE DURING OPERADILITY TESTING OF ENGINE An invdid failure (start #973) of Diesel Generator (D/G) IB occurred on February 18, 1992 at 0022 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />. The invalid failure occurred Juring t)..: Operations Periodle Test (PT),

PT/1/A/4350/02A, D/G IB was on a monthly op rabils 'est schedule at the time of this invalid failure. There has been 0 valid failures in the past 20 valid starts and 0 valid failures in the past 100 valid starts for D/G 1B. D/G 1B remains on a monthly operability test schelate as a result of this failure. The D/G was unavailable for 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> ai-J 17 minutes as a result of this invalid failure.

The start, warm up and loading of D/G 1B during the performance of the operability PT were normal in all respects. Approximately 20 mitsutes into the full load run, the diewl generator shutdown due to high jacket water temperature. The operator no:cd that the hiEh Jacket water tempemture annunciator 11 ashed on, and then immediately off, before any operator action to acknowle: Ige the condition could be teken. The high temperature labe oil nnunciator also came on, but not unti' after the diesel generator had tripped.

Instrumentation and Electrical (I AE) personnel inspected and tested the pneumatic shutdown sensors in scarch of a possible fault that would have caused the engine to shutdon. The jacket water shutdown ser. sors were found :o operate as designed.

A work request was written to inspect the erankcase t.rea for any abnormal appearance or-indication of an over temperature condition.. The inspection found no abnormal appearances evident on the pistons, rods, liners, rod bearings or iaain ber. rings and no i

water leaks were observed.

Prior .o performing the Operations PT, performance t:cht.icians had equipment set up on

- the D/G in preparation for the D/G Engine Cooling Water / Nuclear Service Water (KD/RN) heat exchanger heat balance. The temperature tracking data from the heat balance test equipment was reviewed. The data indicated that, althou3h the thermostatic control valve had functioned, it old not start to open at the expected temperature. The late start allowed the temperature to spike and shutdown the diesel generator even though the system overall .

temperature had started trending down. This explained why the high temperature jacket wate. annunciatoi flashed on and then immediately cleated as reported by the operator.

A wo'rk request was written to disassemble mid inspect the thermostatic control valve.- The thermostatic control valve actuating assembly was removed intact from the valve body.

Discussions with AMOT, the valve manufacturer, pnxtuced a technique to exercise the -

whole assembly before further valve disassembly. The valve operated as specified by the manufacturer during this test.

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t The slide valve seat and o-ring sealing surfaces were examined and found to be srnooth, with 90 bruim or abraions. The o thig (cat surface felt tacky rather thari having its l normal slippery feel.

Next, the slide vahe o ring was examined. Previous inspections F this o-ring found it to be slippery. The last time the o-ring was examined it showed so.ne signs of wear and ,

minor aging but tac wear was not considered excessive. This inspection, the o-ring felt

, tacky, seemed soft, ar.d aging was readily apparent.

i System water cN ists records were checked to determine if any chemicals that might adversely affcet i , c ,ing were present. It was determined that the chemicals used, or mixed, in the system would not adversely effect the o-ring. Additional samplirg showed that no chlorides wtre present.

When the o-ring was replaced, it was discovered that the old o-ring was larger in diameter than the one replacing it. The o-ring is the only thing that the sliding sleeve comes in centact with, except for the seat at each end of its travel. The sleeve o-rings purpost is to prevent leakage around the valve sleeve. Leakage around the valve s!ceve would cause additional and possibly excess cooling.

li is believed that the slightly oversized o-ring, in conjunction with the tacky o ring surface, created increased dag forces that required additional _ capacity from the power element

, assembly to stait the valve moving. This was borne out in the data retrieved from the I temperature tracking system.

The failed o ring was sent to the Applied Science Center Metallurgy Lab to study the o-ring. This testing is not complete at this time. The reput findings will be availabb on request at a later time. >

The thermostatic control valve was reassembled with a new o ring, and the system was refilled with deminerahzed water, chemically treated, and brought back to the normal standby temperature. The D/G then successfully completed several test nms and then the l Operations PT. The temperatures were maintained automatically and satisfactorily by the thermostatic centrcl valve. The diesel generator was then declared operable.

Additional work requests were written to inspect and replace the thermostatic control valve slide o rings on DKis 2A,213, and 1 A at the eadiest opportunity.-

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