ML17342B102

LER 87-034-00:on 871229,manual Reactor Trip from Approx 70% Reactor Power Occurred,Caused by Stuck Contacts on Overspeed Controller 20% Underpower Relay.Contacts Freed & Cleaned. Inputs to Relay Satisfactorily calibr.W/880128 Ltr

ML17342B102
Person / Time
Site:	Turkey Point
Issue date:	01/28/1988
From:	Hart R, Woody C FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
L-88-46, LER-87-034, LER-87-34, NUDOCS 8802020288
Download: ML17342B102 (6)

Text

REGULA Y INFORMATION DISTRIBUTIO lYSTEM (RIDS)

ACCESSION NBR: 8802020288 DOC. DATE: 88/01/28 'OTARIZED: NO DOCKET I FACIL 50 250 Turkey Point Plant> Unit 3. Florida Poeer and Light C 05000250 AUTH. NAME AUTHOR AFFILIATION HART> R. D. Florida Power h Light Co.

WOODY> C. O. Florida Poeer 4 Light Co.

RECIP. NAME RECIPIENT AFFILIATION

SUBJECT:

LER 87-034-00: on 871229 manual reactor trip from approx 70/

reactor poeer occurred> Caused by stuck contacts on overspeed controller 20/ underpoeer relay. Contacts %reed fk cleaned.

Inputs to relay satisfactorily ca 1 ibr. W/880128 1 tr.

DISTRIBUTION .CODE: IE22D COPIES RECEIVED: LTR Q ENCL I SIZE; TITLE: 50. 73 Licensee Event Report (LER>> Incident Rpt> etc.

NOTES:

REC I P IENT COP I ES REC IP IENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 McDQNALD> D 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAD 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 1 DEDRO 1 NRR/DEST/ADS 1 0 NRR/DEST/CEB 1 1 NRR/DEST/ELB 1 1 NRR/DEST/ICSB 1 1 NRR/DEST/MEB 1 1 NRR/DEST/MTB 1 1 NRR/DEST/PSB 1 1 NRR/DEST/RSB 1 1 NRR/DEST/SGB 1 1 NRR/DLPG/HFB 1 1 NRR/DLPG/GAB 1 1 NRR/DOEA/EAB 1 1 NRR/DREP/RAB 1 1 NRR/DREP/RPB 2 2 NRR/D /SIB 1 1 NRR/PMAS/ ILRB 1 1 RE 02 1 1 RES TELFORD. J 1 1 R /DE/EIB 1 1 RES/DRPS DIR 1 1 RGN2 FILE 01 1 1 EXTERNAL: EGSG GROH> M 5 5 FORD BLDG HOY> A 1 1 H ST LOBBY WARD 1 LPDR 1 NRC PDR 1 NSIC HARRIS> J 1 1 NSIC MAYS> G 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 4b ENCL 45

NRC Foim 358 (9.83) t LICENSEE EVENT REPORT {LER) t U.S. NUCLEAR RECULATORY COMMISSION APPROVED OMB NO, $ )504104 EXPIRESI'Sl$ 1(88 PA PACILITY NAME III DOCKET NUMBER (2l 0 5 0 0 0 1 OF

'"""'1anual Reactor Trip From 70% Reactor Power Due to Loss of Turbine EVEN'7 DATE IS) LER NUMBER (5) REPORT DATE ITI OTHER FACILITIES INVOLVED (SI YEAR SEOMENTIAL HR REYIEION MONTH OAY YEAR FACILITY NAMES DOCKET HUMBERISI MONTH DAY YEAR Fy NUMEER NUMEER N/A 0 5 0 0 0 1 2 2 9 87 87 034 0 0 0.1 28 88 N/A 0 5 0 0 0 THIS REPORT IS SUBMITTED PURSUANT T 0 tHE REDUIREMENTB of 10 cFR III fchrc>> onr ormoie of the fodow ndl I(1 OPERATINO MODE (EI 20.402(4 I 10AOB)cl 50.7$ (e I (2 I I(c I 73.7((II)

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LICENSEE CONTACT FOR THIS LER 112I NAME TELEPHONE NUMBER AREA CODE COMPLETE ONE LINE fOR EACH COMPONENT FAILURE DESCRI ~ ED IN TH(S REPOR'T l)3)

CAUSE SYSTEM COMPONENT MAHUFAC EPORTABLE 34g4~ ~n'(g CAUSE SYSTEM COMPONENT MANUFAC. EPORTABLE TURER TO IiIPRDS TURER TO HPRDS Ic~@P>p)Jg@gp"..';:

R Y SUPPLEMENTAL REPORT EXPECTED (14( MONTH DAY YEAR EXPECTED SUBMISSION DATE (15)

YE 5 (/I yet, complete dxpdcTED $ (fdetlssloly DA ydf NO ABETRACT (Limit to trod iorcrt, l 8, roolocimetrty fifteen tine/eroecr tyorwn'ttrn linNI (18)

On December 29, 1987, Unit 3 experienced a reactor trip from approximately 70% reactor power. The reactor control operator (RCO) began a load increase on unit 3 from 50% power to 75% power at a ramp rate of approximately 3% per hour. Various secondary alarms came in for turbine overspeed protection, and for generator anti~otoring trip.

The RCO immediately noticed that the turbine generator electrical load had dropped to approximately 24 megawatts (MW) electrical and the load limit on the turbine generator was indicating approximately 1 pound per square inch (psi) with no appreciable decrease in reactor Nuclear (PSN) authorized power. At this time the Plant Supervisor a manual reactor trip which was completed by the RCO. The reactor trip occurred as designed and the plant was stabilized in mode 3 (hot standby).

An event response team (ERT) was formed to review this event to assist in determining the root cause and corrective actions. The root cause for the loss of turbine load was stuck contacts on the overspeed controller 20% underpower relay. The relay contacts were freed and cleaned. The inputs to the relay were satisfactorily calibrated. Upon completion of the post trip review and appropriate maintenance, the unit was returned to service on December 31, 1987 8802020288 880128 PDR ADDCK 05000250 g ggZ S PDR 'RC I/(

Folm 358 (9 8$ )

U.S. NUCLEAR REGULATORY COMMISSION NRC form 388A (983)

LICENSEE )aNT REPORT ILER) TE)(T CONTINUEN APPROVEO OMS NO.

EKPIRESI 8/31/88 3150&)04 OOCKET NUMBER (21 I.ER NUMBER (d) PAGE 131 PACILITY NAME (ll YEAR 5 8 OI/8 N T I A L o'.ro REVISION NUM EA Nl/M EA P int Unit 3 o s o o o 250 87 0 3 4 00 02 OF 0 3 Tm(T (8'ANoo <<<<oo << /ododord MM eAI5nsl /YRC frnn ~3/ (IT) rvONTL

<<ember 29, 1987, at 1438, Unit 3 experienced a reactor trip from approxi.mately 70% reactor power. At 0615 the reactor control operator began a load increase for "nit 3 from 50% power to 75% power at a ramp rate of approximately 3% per hour. At 14381 various secondary alarms came in for turbine overspeed protection (EIIS:IT),

and for generator anti-motoring trip. The RCO immediately noticed that the turbine generator (EIIS:TA) electrical load had dropped to approximately 24 megawatts (MW) electrical and the load limit on the turbine generator was indicating approximately 1 pound per square inch (psi) with no appreciable decrease in reactor power. At this time the Plant Supervisor'- Nuclear (PSN) authorized a manual reactor trip whi,ch was completed by the RCO. The reactor trip occurred as designed and the plant was stabilized in mode 3 (hot standby). An event response team (ERT) was formed to review this event to assist in determining the root cause and corrective actions.

CAUSE OP EVENT:

An investigation found the overspeed protection controller (OPC) 20X underpower relay (237/G3) failed with its contacts stuck. The OPC is a device which senses a sudden loss in load and closes the control valves and intercept valves before the turbine speed rises. The OPC uses the low pressure turbine steam pressure, PS-3639, and a power sensing relay connected to a potential and current transformer on the main generator. The controller receives a signal from both of these and compares them to determine if any potential overspeed condition exists. With the low pressure turbine steam pressure above 50X and an electrical load of less than 20% the controller will supply a protective signal which opens solenoid valve SV 20 OPC to dump control oil (EIIS:TG), thereby closing the intercept and control valves, preventing the turbine from overspeeding.

Therefore, when power increased above 50X steam flow on PS-3639, the stuck contacts on 237/G3 actuated turbine overspeed protection and dumped control oil.

This caused electrical load to decrease to approximately 24 MW electric. In anticipation of a generator trip and subsequent turbine/reactor trip, a manual reactor trip was performed.

ANALYSIS OP EVENT:

A post trip review was performed to assess the proper operation of the safety related equipment. The post trip review established that the transient behavior of pertinent plant parameters for the reactor coolant system (RCS) and steam generators (SG) responded as expected for a transient of this kind.

Specifically, the RCS pressures and temperatures were determined to have followed an expected pattern based on the conditions leading up to the transient. Other than the manual reactor trip, there were no manual or automatic reactor protection system or engineered safety features actuations.

The shift technical advisor (STA) performed a.critical safety function (CSF) status tree evaluation which indicated the parameters were within NAC POAM 3SSA oU.S GPO;1988 0 82o 538/A55 (94)3)

NRC Form 388A U S NUCLEAR REGULATORY COMMISSION 1983)

LICENSEE+NT REPORT ILERI TEXT CONTINVON API'ROVED OMS NO. 3150-0104 EXPIRES: 8/31/88 fACILITYNAME (11 POCKET NUMSER l21 LER NUMSER ISI PAGE 131 YEAR rEX~'EQVENTIAL

'o'PA NVM ER grf REvrSIQN NVMIER Turke Point Unit 3 0 5 0 0 0 P 5 0 87 0 34 0 3 OF TSET /8'awe <<Mce <</PEaSed, voo a%sr/Oor/////IC forIR 38SAS/ (131 specifications . Based on the above, the health and safety of the public were not affected .

CORRECTIVE ACTIONS:

1) An event response team was formed to review the event to assist in evaluating the root cause and providing corrective actions .

2) The contacts for relay 237/G3 were freed by hand and cleaned'hen the inputs to the relay were satisfactorily calibrated in accordance with preventative maintenance procedure 3-PMR-089.1, Turbine Overspeed Power Relay 237/G3 Calibration.

3) The similar relay on Unit 4 will be inspected and cleaned during the next outage of sufficient duration.

4) PS-3639 was inspected and calibrated in accordance with preventative maintenance procedure 3-PMI-089.3, Turbine Overspeed Protection System Instrumentation Channel P-3-3639 Calibration. No problems were found and no adjustments were made.

5) General operating procedures (GOPs) 3(4)-GOP-301, Hot Standby to Power Operation, were revised to require that the turbine overspeed protection amber 20%

Load light is out when reactor power is above 45%.

6) Upon completion of the post trip review and scheduled maintenance activities, the unit was placed back on the line at 1049 on December 31, 1987.

ADDITIONAL DETAILS:

The turbine governor manufacturer is Westinghouse, serial number 13-A-2893.

Similar occurrences: LERs 250-86-039, 250-87-009 and 250<<87-010 discuss reactor trips due to loss of turbine load. However, the root cause for those LERs is different from this occurrence .

NRC FORM SSSA o U.S.GPO;1988 0 82A 538/A55 I983 I

P. O. 14000, JUNO BEACH, F L 33408 0420 NNUARL 2 8 1988 L-88-46 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 3 Docket No. 50-250 Reportable Event: 87-34 Date of Event: December 29, 1987 Manual Reactor Trip From 704 Reactor Power Due to Loss of Turbine Generator Electrical Load The attached Licensee Event Report (LER) is being submitted pursuant. to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Very truly yours,

0. Woody ecutive Vice President COW/SDF/gp Attachment cc: Dr. J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant SDF/026. LER an FPL Group company