ML17352A101

LER 93-002-00:on 930622,RT Occurred Due to Manual Turbine Trip.Installed Guard Preventing Inadvertent Operation of Auxiliary Governor Trip lever.W/930722 Ltr

ML17352A101
Person / Time
Site:	Turkey Point
Issue date:	07/22/1993
From:	Knorr J, Plunkett T FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-93-166, LER-93-002-03, LER-93-2-3, NUDOCS 9307270061
Download: ML17352A101 (10)

Text

ACCELERATED DOCVMENT DISTKCBUTION SYSTEM REGULAQIY INFORMATION DISTRIBUTI SYSTEM (RIDE)

ACCESSION NBR:9307270061 DOC.DATE: 93/07/22 NOTARIZED: NO DOCKET FAClLq50-251 Turkey Point Plant, Unit 4, Florida Power and Light C 05000251 AUTH.::AME AUTHOR AFFILIATION KNORR,J.E. Florida Power & Light Co.

PLUNKETT,T.F. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 93-002-00:on 930622,RT occurred due to manual turbine trip. Installed guard preventing inadvertent operation of auxiliary governor trip lever.W/930722 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 RAGHAVANFL 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 NRR/DRSS/PRPB 2 2

~DS SPLB 1 1 NRR/DSSA/SRXB 1 1 REG FIL 02 1 1 RES/DSIR/EIB .1 1 G FILE 01 1 1 EXTERNAL 'G&G BRYCE F J H ~ 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYFG.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTEI CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 30 ENCL 30

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0. Box 029100, Miami, FL, 33102-9100 APL L-93-166 10 CFR 50.73 JUL 2g]ggg U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 4 Docket No. 50-251 Reportable Event: 93-002-00 Reactor Tri Due to Manual Turbine Tri The attached Licensee Event Report 251/93-002-00 is being provided in accordance with 10 CFR 50.73 (a) (2) (iv) .

If there are any questions, please contact us.

Very truly yours,

>~

pgj)Plunkett T. F'.

Vice President Turkey Point Nuclear TFP/JEK/3k enclosure cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC Ross C. Butcher, Senior Resident Inspector, USNRC, Turkey cate Plant Point 9307270061 PDR

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930722

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LICEN E EVENT REPO (LER)

DOCKET NUMBER (2) PACE (3)

PACILITY NAME (1)

TURKEY POINT UNIT 4 05000251 1 " 3 TITLE (4) REACTOR TRIP DUE TO MANUAL TURBINE TRIP EVENT DATE (5) LER NUMBER(6) RPT DATE (7) OTHER PACILITIES INVOLVED (8)

MON DAY YR YR SEQ 4 Rt MON DAY PACILITY NAMES DOCKET 4 (S) 06 22 93 93'02 00 07 22 93 OPERATING MODE (9) 10 CFR 50.73 a 2 iv POWER LEVEL (10) 33%

LICENSEE CONTACT FOR THIS LER (12)

J. E. Knorr, Regulation and Compliance Specialist TELEPHONE NUMBER 305-246-6757 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAU SYSTEM COMPONENT MANUPACTURER NPRDS7 CAUSE SYSTEM MANUPACTURER NPRDS2 COMPONENT SE TG 94 W120 SUPPLEMENTAL REPORT EXPECTED (14) NO Z YES 0'XPECTED SUBMISSION DATE (15)

MONTH DAY (1f yes, cmaplete EXPECTED SUBMISSION DATE)

ABSTRACT (16)

On the morning of June 22, 1993, Turkey Poi.'nt Unit 4 was at 100% power and conducting a turbine trip test on the main turbine in accordance with procedures and procedural requirements. At the successful completion of the turbine trip test, the plant operators were unable to relatch the turbine trip. Turkey Point Unit was reduced in power with the intent of taking the turbine off line to 4

trouble shoot and repair, if necessary, the turbine trip latching, mechanism.,

At 1231 Eastern Daylight Time (EDT), with reactor power having been reduced to approximately 33% power, loss of turbine control oil pressure resulted in a turbine anti-motoring trip followed by a generator lockout. Based on the turbine anti-motoring indication .and the generator lockout, plant operators manually .tripped the turbine. A reactor trip at 1232 EDT resulted from the manual turbine trip. The NRC was notified in accordance with 10 CFR 50.72 (b) (2) (ii) June 22I 1993( at 1315 EDT.

Extensive investigations of probable cause for the turbine anti-motoring trip and generator lockout were completed. The investigations concluded that the cause was an inadvertent operation of the auxiliary governor .trip lever by personnel restoring the turbine controls to normal after the turbine trip test. The unrelated inability to relatch the turbine trips was caused by incorrect clearances in the overspeed trip block between the trip relay and the relay bushing, and between the relay cup valve and the relay cover plate. These clearances were corrected and Unit 4 was returned to service on June 26, 1993.

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LICENSEE VENT REPORT (LER) TEXT CONTINUATION r

FACILITY NAME DOCKET NUMBER LER NUMBE PAGE NO.

TURKEY POINT UNIT 4 05000251 93-002-00 2 QF 3 I. DESCRIPTION OF THE EVENT On the morning of June 22, 1993, Turkey Point Unit 4 was at 100% power and conducting a turbine trip test on the main turbine in accordance with operations surveillance procedure 4-0SP-200.3, Secondary Plant Periodic Tests. At the successful completion of the'urbine trip test, the plant operators were unable to relatch the turbine trip. Turkey Point Unit 4 was reduced in power with the intent of taking the turbine off line to trouble shoot and repair, if necessary, the turbine latching mechanism. Prior to the load reduction, discussions were held with operations personnel to alert them of actions to be taken (such as initiating manual trips) if any unexpected events were to occur during the load reduction. Direct communications were established between the turbine front standard and the control room for use during the load reduction. At 1231 Eastern Daylight Time (EDT), with reactor power reduced to approximately 33% power, loss of turbine control oil pressure resulted in a turbine anti-motoring trip followed by a generator lockout. Based on the turbine anti-motoring indication and the generator lockout, plant operators manually tripped the turbine. A reactor trip at 1232 EDT resulted from the manual turbine trip. An Event Response Team was established to investigate the root cause of the trip.

II. CAUSE OF THE EVENT The release of the turbine trip test lever by the operator after receipt of the turbine anti-motoring trip indication resulted in the manual turbine trip and the subsequent reactor trip. After extensive troubleshooting of the turbine trip block, the overspeed trip block and the control oil system, no mechanical reason for the turbine valve closure could be found. The investigation results led to the conclusion that the cause of the original turbine anti-motor signal was the inadvertent tripping of the auxiliary governor trip lever. While holding the lever on the overspeed trip block in the test position during the power reduction, the operator, who was wearing a heavy fire coat for personnel protection, may have caught the coat on the auxiliary governor trip lever causing the turbine anti-motoring indication.

A contributing cause to the turbine tri;p/reactor trip was the inability to relatch the turbine trip. After troubleshooting and testing the overspeed trip block and turbine trip block, a dimensional setup error in the overspeed trip relay plunger was discovered. The inability to relatch the turbine trips was caused by incorrect clearances in the overspeed trip block between the trip relay and the relay, bushing, and between the relay cup valve and the relay cover plate. The dimension between the relay cup valve end surface and the relay plunger shoulder must be identical to the dimension between the end plate and the lip on the relay bushing. If these dimensions are inexact, the pressure in the oil system will not permit relatching the turbine trip.

III. ANALYSIS OF THE EVENT During the testing of the turbine trips, the test lever allows the testing to proceed without a turbine trip occurring. If the test =lever

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LICENSEE gjPNT REPORT (LER) TEXT~ONTINUATION' FACILITY NAME DOCKET 'NUMBER LER NUMBER PAGE NO.

TURKEY POINT UNIT 4 05000251 93-002-00 3 QF 3 had been returned to its normal operation position without relatching the turbine trip, an actual turbine trip would have occurred. When the turbine anti-motoring signal occurred, the test lever was released and a turbine trip and, subsequently, a reactor trip occurred. The anti-motoring signal apparently occurred when the auxiliary governor trip lever was inadvertently actuated and control oil pressure was lost.

All systems responded as designed to the trip signal.

A turbine trip is an event analyzed in the Turkey Point Units 3 and 4 Updated Final Safety Analysis Report (UFSAR). The UFSAR discusses the expected plant response to a complete loss of generator load. The UFSAR analysis assumes a complete loss of load without a subsequent reactor trip and shows the adequacy of theevent pressure relieving devices and that a reactor trip occurred as no core damage results. In this designed. Therefore, the .UFSAR analysis bounds the turbine trip and reactor trip which occurred in this case.

This event was reported in accordance with 10 CFR 50.73 (a) (2) (iv), due to an actuation of the Reactor Protection System.

IV. CORRECTIVE ACTIONS

1. A guard preventing the inadvertent operation of the auxiliary governor trip lever was installed.

2. The critical dimensions on the relay plunger of the overspeed trip relay were restored and the relay was tested successfully. Unit 4 was returned to service on June 26, 1993.

V. ADDITIONAL INFORMATION No other events of this type are known to have occurred at Turkey Point.

The overspeed trip device manufacture and model details are as follows:

Westinghouse Electric Corporation

.Overspeed Trip Valve Print No. 676J811 System and component identification described in this report:

SYSTEM OR COMPONENT EIIS CODE IEEE 803a/83 Main Turbine TA TRB Turbine Trip Block TG 94 Overspeed Trip Block TG 94 Reheat Valves SB FCV Intercept Valves TA FCV Generator Breakers EL BKR

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