ML18008A032

LER 89-011-00:on 890915,manual Reactor Trip Initiated When Control Rods Failed to Insert in Automatic or Manual in Response to Sudden Turbine Power Decrease.Caused by Inadequate Field installation.W/891012 Ltr

ML18008A032
Person / Time
Site:	Turkey Point
Issue date:	10/12/1989
From:	Harris K, Dawn Powell FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-89-374, LER-89-011-01, LER-89-11-1, NUDOCS 8910190123
Download: ML18008A032 (9)

Text

gccP~RATED DIPBUTION DKMONSTR~Y 'YSIZM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8910190123 DOC.DATE: 89/10/12 NOTARIZED: NO DOCKET FACIL:50-251 Turkey Point Plant, Unit'4, Florida Power and Light C 05000251 AUTH. NAME AUTHOR AFFILIATION POWELL,D.R. Florida Power & Light Co.

HARRIS,K.N. Florida Power & Light Co.

'RECIP.NAME RECIPIENT AFFILIATION SUWECT: LER auto stop oil line break.'/8 89-011-00:on 890915,turbine stop valve closure due to SIZE:

ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL

'1 ID CODE/NAME LTTR ENCL PD2-2 LA 1 PD2-2 PD 1 1 EDISON,G 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 DEDRO 1 1 NRR/DEST/ESB 8D 1' 1 NRR/DEST/ICSB 7 NRR/DEST/MTB 9H 1

1 1

1 NRR/DEST/MEB NRR/DEST/PSB 9H 8D 1

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. 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/PEB 10 1 1 NRR/DOEA/EAB 11 1 1 N REP RPB 10 2 2 NUDOCS-ABSTRACT 1 1 REG 02 1 1 RES/DSIR/EIB 1 '1 C82 FILE 01 1 1 EXTERNAL EG&G WILLIAMS~ S 4 4 L ST LOBBY WARD 1 1 LPDR NSIC MAYS,G NUDOCS FULL TXT 1

1 1

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"1 NRC PDR NSIC MURPHY,G.A 1, 1 1 1

NOXE TO ALL 'KIDS" RECIPIENIS'IZASE HELP US TO REDKZ HASTE! CGg~ 'IHE DXGNEÃZ CONGEAL DESK RDCN Pl-37 (EZI'. 20079) K) ELQQBAXR YOUR NAME FKR DIPHGEPZICRi LISTS BDR DOCUMEHIS YOU DQiN~T NEZDt FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38

P. O. Box 3088, Florida City, FL 33034 I 89-374 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn:, Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 4 Docket No. 50-251 Reportablc Event: 89-11 Date of Event: September 15, 1989 Turbine Stop Valve Closure Due to Auto Stop Oil Leak Resulted In a Manual Reactor Tri And A Manual Safet In'ection The attached Licensee Event Report is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Very truly yours, i9 /,mar~.g K. ! Harris - Vice Prcsidcnt Tur ey Point Plant Nuclear KNH/JEC/VAK/DRP/DWH Attachment CC: Stcv,art D; Ebnctcr, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant

NAC Ports 555 (9021 VA. NIICLKAAAEOVLATORY COMMISSION APPAOVEO OMS NO. 21500)OC LICENSEE EVENT REPORT {LER) EXPIRES: 5/21( 55 PACILITY NAME (11 DOCKET NUMSEA (21 PA Turke Point Unit 4 0 5 0 0. 02 511oFO 6 Turbine Stop Valve Closure ue o u o op Line Leak Resulted In A Manual Reactor Trip And A 11anual Safety Injection EVENT DATE IS) LER NVMSER (5) RKPOA'Z DATE (71 OZHCA FACILITIES INVOLVED IS)

MONTH DAY YEAR YEAR 5 5 0 V 5 N 7 I A I. (I;":.

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MODE IS) S02(5) 20.505(c) 50.7241(2)(N I 72.71( ~ I

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LICCNSEE CONTACT POR THIS LKA (12)

NAME TELEPHONE NUMSER AREA CODE David R. Powell, Regulation and Compliance Supervisor 3 5246 -655 COMPLETE ONK LINE POA EACH COMPONCNT PAILUAK DCSCAI ~ CD IN THIS REPORT ()21 CAUS'E SYSTEM COMPOHEHT MAHUPAC. MANUPAC. EPORTASL TUNER CAUSE SYSTEM COMPOHEHT

x@gc<@>re$ TUNER TO NPROS W ELD X 999 N B C B' S U07 5 Y' A A I MOD H015 D J FS A60 9 Y SUPPLEMENTAL ACPOAZ EXPECTED (lcl MONTH OAY YEAR EXPECTED SUSMISSION DAZE 115)

YES (tt yet, compiete EXI'ECTED $ (IESIISSION OATEI X AssTAAcT (Limit to Ic00 Ipecet.'i.e., eppes ~ imetsty tatters Iihpie specs typerrrrttsh tiheet 115)

At 0426, on September 15, 1989, with Unit 4 operating at 100 percent power, a manual reactor trip was initiated. A High Pressure (HP) tur-bine stop valve Auto Stop Oil line weld leak identified at 0045 led to closure of 'the stop valve. When the control rods failed to insert in automatic or manual in response to the sudden turbine po~er decrease, as called for by a T-AVE/T-REF mismatch signal, a manual reactor trip was initiated. A failure of the 4C Steam Generator feedwater control valve to close during a subsequent Feedwater Isolation (slow closure) signal resulted in overfeed of the Steam Generator and "shrink" of the Reactor Coolant System inventory. A manual Safety Infection signal was initi-ated by procedure because pressurizer level dropped below 12 percent.

The Auto Stop Oil line weld failure was,due to inadequate field install-ation and fatigue failure. The failure of the control rods to drive in automatically was due to an inadequacy in the refueling Preventive Main-tenance program. The Automatic Rod Control Speed Signal output summator seas out of calibration. The feedwater control valve failure to close is due to an inadequate procedure used during a recent modification. The thermal transient experienced did not affect the structural integrity of Reactor Coolant System components'arious corrective actions have been/

will be performed.

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Turkey Point Unit 4 51 89 01 00 02 oF0 6 W ~~ 6 terAe4 IRf eAAArel fffC Arm ~'W IITI 2 1 Descri tion of the Event At 0045, on September 15, 1989, the Nuclear Turb'ine Operator (NTO) notified the Plant Supervisor - Nuclear (PSN) of oil leakage in the vicinity of the left High Pressure (HP) turbine stop valve (4-10-010) guarded oil line. After removing the inspection cover, a 0.5 to I.J) gallon per minute (gpm) leak was identified on an Auto Stop Oil line weld (EIIS:TG, Component:WELD) for the left HP turbine stop valve. The oil leak-was not considered by the PSN to pose an immediate

. threat to unit operation. A Reactor Control Operator (RCO) was assigned to per-form hourly inspections of the leaking weld and Auto Stop Oil pressure for signs of increased 'leakage. Operations and maintenance personnel di,scussed options for repair of the cracked weld.

At 0426, orI September 15, 1989, with Unit 4 in Mode 1 operating at 100 percent power, the left turbine stop valve failed closed. The reduction in steam flow to the main turbine caused the steam generators to experience an increase in pressure and a decrease in level (shrink). The large power mismatch '(Reactor Power greater than Turbine Power) led to an increase in the average Reactor Cool-ant System temperature (T-AVE) and an expansion of the Reactor Coolant System fluid (swell), causing the pressurizer level to increase. At the setpoint of 75 percent pressurizer level, the 4C charging pump (EIIS:CB, Component:P) received a signal for low speed operatton. The 4C charging pump tripped following receipt of this signal.

Due to an increase in T-AVE and a decrease in the Reactor Coolant System refer-ence temperature (T-REF) (setpoint of 5 degrees F deviation between T-AVE and T-REF), control rods began "stepping in" automattcally. The Nuclear Watch Eng-ineer (NWE) noted that the control rods (EIIS:AA, Component:ROD) stopped auto-matically driving in after moving four steps. The RCO tried unsuccessfully to drive the control rods in manual. The Assistant Plant Supervisor Nuclear (APSN) noted T-AVE increasing and the main st'earn code safety valves had opened.

The APSN ordered a manual reactor trip.

At 0427, a manual reactor trip was initiated from the Control Room co'nsole by opening the Reactor Trip Breakers and Unit 4 entered Emergency Operating Pro-cedure 4-EOP-E-O, "Reactor Trip or Safety Injection." The manual reactor trip resulted in an automatic turbine trip and, with a low T-AVE (less than the 554 degrees F setpoint), an automatic Feedwater Isolatton (slow closure) signal which causes closure of the main feedwateT control valves within 20 seconds.

The Balance Of Plant (BOP) operator noted dual position indication on feedw'ater control valve FCV-498 (EIIS:SJ, Component:FCV) and increasing level in Steam Generator 4C. The BOP operator placed FCV-498 control in manual and attempted to close the valve.

Failure of FCV-498 to close within 20 seconds resulted in overfeed of Steam Generator 4c and a decrease in T-AvE. This led to a-.decrease (shrink) in press-urizer level. The RCO started charging pumps 4A and 4C to compensate for the decrease in pressurizer level, however, the level could not be maintained. When

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The cause of the control rod drive mechanisms failure to automatically or man-ually drive in is due to an inadequacy in the refueling Preventive Maintenance program. The Automatic Rod Control Speed signal output summator. to the Rod Con trol Logic Cabinet was found to be out of specification. The maximum expected voltage should be 9.'5 Vdc and it was found to be 10.14 Vdc. This high voltage caused the Rod Control System pulser/oscillator to call for rod speed which was faster than the sy'tem capability. A Logic Cabinet Urgent Failure Alarm halted rod motion as designed. FPL believes the Automatic Rod Contrpl module setpoint drifted over time. These components 'are normally calibrated during refueling outages. During the last refueling outage for Unit 4, a decision was made not to perform the calibrations. A Preventive Maintenance task for periodic cali-bration check's on the Automatic Rod Control Speed Signal output summator does not exist.

The cause of the 4C Steam Generator feedwater control valve FCV-4-498 failure to close within 20 seconds of receiving a Feedwater Isolation signal is due to an inadequate procedure. Foreign material was found in solenoid valve SV-4-4988 which prevented it from totally "switching states" (i.e., all three ports were open at the same time). The foreign material consisted of metal.lic particles (magnetic and non-magnetic) and thread sealant. FPL believes this material entered the solenoid valve during Plant Change/Modification (PC/M)88-241 per-formed during the recent Unit 4 refueling outage. Failure to establish adequate system cleanliness controls led to the introduction of foreign materials. The ASCO solenoid val,ves on feedwater control valves FCV-4-478 and FCV-4-488 were found to be free of debris which 'would prevent proper solenoid valve operation.

The cause of the condenser air ejector radiation monitor spiking is due to design.

During plant transients, where elevated main steam pressure causes moisture carry--

over through the steam jet air ejectors, slight impacts may occur on the thin wall of the beta/gamma Geiger-Meuller.tube. The result is momentary spiking with a re-turn to normal readings.

The cause of the EDG A lube oil low pressure switch hose leak is due to aging,and vibration induced rubbing and chafing from contact with the EDG control cabinet cover plate.

Anal s is of the Event Operator actions in response to the identified equipment problems wer e .appro-priate and resulted in a safe shutdown of the unit. These actions were in accordance with approved plant procedures.

The Reactor Coolant System thermal transient experienced during this event has been evaluated by Westinghouse. The thermal transient has been determined to be similar co the design basis reactor trip from full power event.

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~ lI 0 5 0 0 0 P 5 1 8 9 0 1,1 00 05 of 0 H refvPPX HITC Arrrr II0 Corrective Actions

1) The insert between the metering valve and the Auto Stop Oil line for the Unit 4 left HP turbine stop valve was replaced. This same section of Auto.

Stop Oil line for the right HP turbine stop valve was visually inspected.

The readily accessiblw welds were found to have acceptably spaced welds.

2) A visuals inspection of the readily accessible welds in "the same section of-Auto Stop Oil lines to the Unit 3 left and right HP tuibine stop valves will be performed by November 1, 1989.

3) Viuration on the Auto Stop Oil lines to both Unit 4 HP turbine stop valves will be observed and measured during unit restart. Appropriate corrective actions will be implemented as necessary.

4) The 4C charging pump lube oil pressure switch was replaced with the same type switch. Loctite thread sealant was applied to the adjustment set screw for each of the Unit 3 and Unit 4 charging pump lube oil pressure switches.

5) Plant Changes/Modi f i cat i ons PC/M 89-388 (Uni t 3) and PC/M 89-473 (Uni t 4) were issued to replace the charging pump lube oil pressure switches with a different switch type which is more appropriate for this application and to remount the replacement switches to a'location of lower vibration. Imple-mentation of these PC/Ms should be complete prior to restart from the next refueling outage for each unit.

8) The Unit 3 and Unit 4 Automatic Rod Control Speed signal output summators were recalibrated.

7) A Preventive Maintenance task for periodically performing a calibration check on the Automatic Rod Control Speed signal output summator for Unit 3 and Unit 4 is being developed and will be issued'by December 1, 1989 for canceling refueling outage activities will be reviewed

')

The mechanism and revised appropriately prior to the next scheduled refueling outage.

9) The 4C Steam Generator feedwater control valve solenoid valve (SV-4-4988) was replaced with the same type solenoid valve. The ASCO solenoid .valves for Steam Generator feedwater control valves FCV-4-478 and FCV-4-488 were blown down, disassembled, and inspected. The solenoid valves were found to be free of debris which would hinder proper operation.

10) Cleanliness requirements for Instrument Air System tubing to instrumenta-tion will be developed and incorporated into Backfit Construction Admin-istrative Site Procedure ASP-24, "System Cleanliness," by December 1, 1989.

11) The background activity level after the condenser air ejector radiation monitor spike was verified to be the same as the background level before the spike. A response check of the radiation monitor was performed with satisfactory results.

12) The EDG A lube oil 'low pressure switch hose was repa,ired. The remaining hoses on EDG A and hoses on EDG 8 were visually inspected. No o'ther hose leaks were identified.

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HITC Ann ~l 1 (171 o s o o o 0 1 1 0 OF0 6 i3) Preventive Maintenance tasks for replacing rubber hoses in the EDG engine panels every 5 years were created January 27, 1989. Initial performance of these PM tasks will occur during the next scheduled diesel outages of sufficient duration.

Additional Information No similar Licensee Event Reports Wave been identified.

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