ML18153B322

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LER 93-004-00:on 930823,reactor Tripped Due to Turbine - Generator Trip.Caused by Loss of Field Relay.Reactor Trip Breakers Verified Open & Control Rods Verified Inserted Into core.W/930920 Ltr
ML18153B322
Person / Time
Site: Surry Dominion icon.png
Issue date: 09/20/1993
From: Kansler M
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
93-606, LER-93-004-02, LER-93-4-2, NUDOCS 9309280047
Download: ML18153B322 (8)
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Text

ACCEL:ERA'"~D DOCUMEN'"f DIS'"fRIBU'"flON SYS1,EM REGUL~RY INFORMATION DISTRIBUTI~SYSTEM {RIDS)

ACCESSION NBR:9309280047 DOC.DATE: 93/09/20 NOTARIZED: NO DOCKET#

FACIL:50-281 Surry Power Station, Unit 2-, Virginia Electric & Powe 05000281 AUTH.NAM~ . AUTHOR AFFILIATION KANSLER,M.R. Virginia Power (Virginia Electric & Power Co.)

RECIP.NAME RECIPIENT AFFILIATION R

SUBJECT:

LER 93-004-00:on 930823,reactor tripped due to turbine -

generator trip.Caused by loss of field relay.Reactor trip breakers verified open & control rods verified inserted into D core.W/930920 ltr.

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

I NOTES:lcy NMSS/SCDB/PM. 05000281 A

RECIPIENT COPIES RECIPIENT COPIES D

ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 BUCKLEY,B 1 1 D INTERNAL: ACRS 2 2 AEOD/DOA 1 1 s AEOD/D!,P /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 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 R,!G~~ - 02 1 1 RES/DSIR/EIB 1 1 RGf*J2=FILE 01 1 1 EXTERNAL: EG&G BRYCE,J.H 2 2 L ST LOBBY WARD 1 1 R NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 I NOTES: 1 1 D

J s

I A

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEA.SE HELP US TO REDUCE WASTE! CONTACI' THE DOCUMENT CONTROL DESJ-:,

s ROOM Pl-37 (EXT. 504-2065) TO ELIMINATE YOUR NAME_FIWM DISTRiI3l:TION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

10CFR50.73 Vn-ginia Electiic and Power Company Sorey P~wer S1ati.on P.O.Box:315 Surry, Vn-ginia 23883 September 20, 1993 U.S. Nuclear Regulatory Commission Serial No.: 93-606 Document Control Desk SPS:JDK Washington, D. C. 20555 Docket No.: 50-281 License No.: DPR-37

Dear Sirs:

Pursuant to Surry Power Station Technical Specifications, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to Surry Power Station Unit 2.

BEPQRTNUMBER 50-28V93-004-00 This report has been reviewed by the Station Nuclear Safety and Operating Committee and will be forwarded to the Management Safety Review Committee for its review.

Very truly yours,

~

1/

Enclosure cc: Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 '

M. W. Brimch NRC Senior Resident Inspector Surry Power Station

0. r t,~..,

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9309280~)4 7 930920 PDR ADOCK 05000281 5 PDR

J NRC FORM 366 . U.S. NUCLEAR REGULATORY COMMISSION AP.PROVED BY 0MB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LIC.ENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH {MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF (See reverse _for required number of digits/characters for each block) MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

Surry Power Station, Unit 2 05000 - 281 1 OF 6 I TITLE (4)

Unit 2 Turbine-Generator Trip Via the Loss of Field Relay

~~a EVENT DATE 151 LEA NUMBER (6 REPORT NUMBER (7) OTHER FACILITIES INVOLVED (8)

FACILITY NAME DOCKET NUMBER SEQUENTIAL REVISION MONTH DAY YEAR MONTH DAY YEAR NUMBER NUMBER 05000 FACILITY NAME DOCKET NUMBER 08 23 93 93 -- 004 -- 00 09 20 93 05000 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more (111 MODE (9)

N 20.402(b) 20.405(c) ) 50.73(a)(2)(iv) 73.71 (b)

POWER

  • 20.405(a)(1 )(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71 (c)

LEVEL (10) 97.5 20.405(a)(1 )(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a) (1) (iii) 50.73(a)(2)(viii)(A) (Specify in Abstract X 50.73(a)(2)(i) b)

      • tL ): 5*** . below and in Text, NRC

)********* ::-:\?

,:::****.:.:.::--/

*iti**ili
!!ll!Il!!!
I 20.405(a) (1) (iv) 20.405(a)(1)(v) 50.73(a)(2)(ii) 50.73(a)(2)(iii) 50.73(a)(2)(viii)(B) 50.73(a)(2)(x)

Form 366A)

LICENSEE CONTACT FOR THIS LEA (121 NAME TELEPHONE NUMBER (Include Area Code)

M. R.

  • Kansle:r, Station Manager (804) 357-3184 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

REPORTABLE REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER TO NPRDS TO NPRDS

'7 L\.. TL PSD Wl20 Yes 1111111 -

11 11 1i1:J 11 !!:!!ij:lillill!l!l1 1!i!l:i!!l!IIIl!l!

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR I YES (If yes, complete EXPECTED SUBMISSION DATE) X NO SUBMISSION DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) {16)

At 0519 hours0.00601 days <br />0.144 hours <br />8.581349e-4 weeks <br />1.974795e-4 months <br /> on August 23, 1993, with Unit 1 at 100% power and Unit 2 at 97.5%

pow,ar, the Unit 2 reactor tripped due to a turbine - generator trip. Control room operators promptly initiated the appropriate emergency operating procedures. The reactor was plac1:K:t in a stable, Hot Shutdown condition. The turbine-generator trip was caused by a loss of excitation field for the main generator due to a component failure in the voltage regulator (VA). During troubleshooting of the VA, a failed phase shifter card was discovered and replaced. As an additional precaution, two other cards were replaced alof"l{J with the fuses between the field breaker and the firing cirruit drawer. Following the trip, .a fire watch notified the Shift Supervisor that sliding Fire Door 18 had shut. As a result, he could not complete his fire watch rounds of the Unit 1 Emergency Switchgear .

Aoorn (ESGR) at 0523 hours0.00605 days <br />0.145 hours <br />8.647487e-4 weeks <br />1.990015e-4 months <br />, in accordance with Technical Specification 3.21. This fire door separates Unit 1 and 2 ESGRs. Following stabilization of Unit 2, an operator was dispa.tched and the sliding fire door was opened and relatched.

During this event the health and safety of the public were not affected. This event is being reported pursuant to 10 CFR 50.73(a)(2)(iv) and 10 CFA 50.73(a)(2)(i)(b).

NRC FORM 366 (5*92)

... I

e NRC FORM 366A *u.s. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104 (5-92) EXPIRES _5/31/95

  • I ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB IT14), U.S. NUCLEAR TEXT CONTINUATION REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Surry Powe~ Station, Unit 2 05000 -281 2 OF 6 93 004 00 TEXT {II more space is required, use oo'dWona/ copies of NRC Form 356'\) (17)

1.0 DESCRIPTION

OF THE EVENT At 11245 on August 21, 1993, the control room operators received a Unit 2 main generator low voltage alarm. Concurrently, 30 MWe swings were not,~d on the generator output megawatt chart recorder. An operator was dispatched to locally monitor the excitation switchgear cabinet [EIIS-TL~

SWGR]. Electrical Maintenance and the System Operator (SO) were noti'fied. The SO informed the Unit's Senior Reactor Operator (SRO) that there were no known system disturbances on the 500 KV circuit that could be causing the transient. At that time, exciter voltage and amperage were varying from approximately 1O to 70 volts/amps from a nominal 60 volts/amps. The permanent magnet generator [EIIS-TL-PMG]

(PMG) supply voltage was also observed to be oscillating. The Unit 2 main generator VR [EIIS-TL-RG] was subsequently placed on base adjuster control (manual control) and no further al~rms or megawatt swings were observed. A check by the electricians for blown fuses in the exciter diode wheel revealed no problems. On August 22, 1993, with the VR's auto regulator off and with excitation being controlled by the base ~

adjuster only, no fluctuations in the main generator or PMG output were noted.

At 0217 hours0.00251 days <br />0.0603 hours <br />3.587963e-4 weeks <br />8.25685e-5 months <br /> on August 23, 1993, main generator reactive power (measured in MVARS) and Virginia Power system voltage were obse,rved fluctuating. Virginia Power system voltage had changed from 500 KV to 530 KV and main generator [EIIS-TB] MVARS from -35 (in) to

+200 (out).' Using the base adjuster, the reactor operator adjusted main gene!rator output to reduce the generator excitation field thereby restoring voltage to 22 KV.

At Ofi19 hours on August 23, 1993, with Unit 1 at 100% power and Unit 2 at 97.5% power, the Unit 2 reactor tripped due to a turbine - generator trip

[EIIS-'TA-TRB]. The turbine - generator trip was caused by a generator differential lockout relay (86G relay) actuation caused by actuation of the loss of field relay (KLF relay). Actuation of the KLF relay picks up the lockout relay 86G which trips the exciter field breaker (41 breaker), the generator output breakers, the Station service normal supply breakers, the main stop valves, and the main turbine.

  • NRG FORM 366A (5*92)

e NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB n14}, U.S. NUCLEAR

. TEXT CONTINUATION REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) lER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION YEAR  ;

NUMBER NUMBER Surry Power Station, Unit 2 05000-281 3 OF 6 93 - 004 - 00 TEXT //1 more space is required, use additional copies of NRC Form 356A) (17)

Control room operators promptly initiated the appropriate emergency operating procedures. The reactor trip breakers [EIIS-JC-BKR] were verified open and control rods [EIIS-JD-ROD] were verified inserted into the core. The Auxiliary Feedwater Pumps [EIIS-BA-P] started as designed on Lo-Lo Steam Generator Level signal. The Anticipated Trar1sient Without Scram Mitigation System Actuation Circuitry (AMSAC) armied and initiated as designed. Decay heat was removed by the main steam dump valves [Ells.:ss-PCV] to the main condenser. The Individual Rod Position Indicator (IRPI) M-1 O rod bottom light was slow in illuminating. Minimum Reactor Coolant System (RCS) [EIIS-AB]

temperature during the transient was approximately 530°F. A shutdown marnin calculation verified that the shutdown margin was acceptable at 53oc'F.

After the trip, a fire watch notified the Shift Supervisor that sliding Fire Door 18 had shut. As a result, he could not complete his fire watch rounds of the Unit 1 ESGR at 0523 hours0.00605 days <br />0.145 hours <br />8.647487e-4 weeks <br />1.990015e-4 months <br />, in accordance with Technical Specification 3.21. This fire door separates Unit 1 and 2 ESGRs.

Following stabilization of the Unit, an operator was dispatched to open and relatch the sliding fire door. Fire Door 18 was opened at 0615~

In accordance with 10CFR50. 72(b)(2)(ii), a 4-hour Non-Emergency report to the NRC operations center was made at 0908 hours0.0105 days <br />0.252 hours <br />0.0015 weeks <br />3.45494e-4 months <br /> due to the Reactor Protection System (RPS) actuation. Additionally, a State Department of Emergency Services (DES) Non-Emergency notification was made at 091 O hours.

This *event is being reported pursuant to 10 CFR 50.73(a)(2)(iv) and 10 CFR 50.73(a)(2)(i)(b).

2.0 SAFl:TV CONSEQUENCES AND IMPLICATIONS Upon receipt of the reactor trip, RPS actuation functioned as designed and a.II control rods inserted into the core. Station operating personnel promptly* placed the plant in a stable, Hot Shutdown condition in accordance with the proper procedures ... The. shutdown margin of reactivity was calculated and found to be satisfactory. Unit, ESGR fire NRC FORM 366A (5-92)

U.S. NUCLEAR REGULATORY COMMISSION e APPROVED BY 0MB NO. 3150-0104 NRC FORM 366A (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR TEXT CONTINUATION REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT {3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION

. YEAR NUMBER NUMBER Surry Power Station, Unit 2 05000 -281 4 OF 6 93 - 004 00 TEXT (II more space is required, use ar.lditiono/ copies of NRC Form 365A) (17)

  • detection and fire suppression systems were available and operable.

After stabilizing the unit at Hot Shutdown, operators promptly relatched Fire Door 18 and the continuous fire watch coverage was resumed. The health and safety of the public were not affected by this event.

3.0 kl~USE Th19 reactor tripped due to a turbine - generator trip. The troubleshooting and root cause investigation for the trip determined that the turbine -

generator trip was caused by an intermittent failure of a phase shifter card in the firing circuit of the main generator's voltage regulator. - The phase shi:fter card output regulates the excitation field of the generator. A low output from the phase shifter card results in a continuous gate signal to the thyristor circuits which provide current for the main generator excitation field. This continuous gate signal to the thyristors increases the current sent to the exciter field. The increased current overexcites the generator and results in a high generator output voltage.

Thei phase shifter card intermittent low output caused the Unit 2 voltage anal reactive power fluctuations, and the power increase experienced whi1le in VA base adjuster operation at 0217 hours0.00251 days <br />0.0603 hours <br />3.587963e-4 weeks <br />8.25685e-5 months <br /> on August 23, 1993.

The* actions taken by the operator to correct the overexcited condition took the base adjuster close to its lower limit by reducing main generator excitation. At 0519 hours0.00601 days <br />0.144 hours <br />8.581349e-4 weeks <br />1.974795e-4 months <br /> on August 23, 1993, with the base adjuster close to the lower limit, the phase shifter card returned to its normal output value. (The intermittent problem cleared.) This resulted in less current to the exciter field causing the exciter field to decay to the loss of field setpoint actuating the KLF relay.

4.0 IMMEDIATE CORRECTIVE ACTION(S)

Following the reactor. trip at 05f9_hours on August 23, 1993, control room ope1*ators initiated the appropriate emergency operating procedures.

The reactor trip breakers were verified open and control rods were verified inserted into the core.

The Shift Technical Advisor monitored the critical safety function status trees to ensure that plant parameters remained within safe bounds.

NRC FORM 366A (5*92/

e e NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104 (5-92) EXPIRES 5/31 /95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICEN!,EE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION

. AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR TEXT CONTINUATION REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503, FACILITY NAME (1) DOCKET NUMBER (2) lER NUMBER (8) PAGE (3)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Surry Power Station, Unit 2 05000 - 281 5 OF 6 93 - 004 - 00 TEXT /II more space is required, use additional copies of NRC Form 3664) (17)

After the trip, a fire watch notified the Shift Supervisor that sliding Fire Door 18 had shut. As a result, he could not complete his fire watch rounds of the Unit 1 ESGR at 0523 hours0.00605 days <br />0.145 hours <br />8.647487e-4 weeks <br />1.990015e-4 months <br />, in accordance with Technical Specification 3.21. This fire door separates Unit 1 and 2 ESGRs.

Folloiwirig stabilization of the Unit, an operator was dispatched to open and 1relatch the sliding fire door. This fire door closes by activation of the halol'l system, the smoke detector alarm, or. the manual release pushbutton. The halon system had not discharged nor were the smoke detectors in alarm. The door closure was spurious. Fire Door 18 was opened at 0615, and the fire watch coverage in the Unit 1 ESGR was re-established.

A root cause investigation of this trip was initiated including plans for troubleshooting of the main generator VR by the vendor.

5.0 ADDIITIONAL CORRECTIVE ACTION(S)

Troubleshooting of the Unit 2 main generator voltage regulator by the vendor between August 23, 1993 and August 25, 1993 discovered a

  • failed phase shifter card in the firing circuit. The phase shifter card was replaced. As an additional precaution, the excitation dampening and volta~1e error cards were replaced along with the fuses between the field breaker and the firing circuit drawer.

The ll~PI M-10 rod bottom light was slow in illuminating. This condition has been observed during previous Unit 2 trips from "at power"

.conditions. The Nuclear Steam Supply System vendor was recently reque:sted to re-evaluate this condition and confirmed that the condition is an indication.problem. The cause of the problem is associated with the permeiability (magnetic properties) of either the control rod M-1 O pressure housing *or its control rod driveline. Control rod M-10 has been evaluated as oporable based _on control rod drop testing.

NRC FORM 366A (5*92)

NRC FORM 366A e U.S. NUCLEAR REGULATORY COMMISSION e APPROVED BY 0MB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLlECTION REQUEST: 50.0 HRS. FORWARD

  • LICENSEE EVENT REPORT {LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR TEXT CONTINUATION REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF.

MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Surry Power Station, Unit 1 05000 - 281 6 OF 6 93 - 004 00 TEXT /// more space is required, use aclditiona/ copies of NRC Form 356A) (17)

  • 6.0 AC:TIONS TO PREVENT RECURRENCE A review* of voltage regulator* performance will be undertaken to determine whether any additional actions are required to enhance reliability. In addition, Engineering is investigating spurious closure of Fine Door 18. Appropriate corrective measures identified by the inviestigation will be implemented. Engineering is also investigating if effoctive actions can be undertaken to correct the control rod M-1 O IRPI indication problem.

7.0 $.!MILAR EVENTS LEF.~ 2-89-009-00, "Turbine Trip/Reactor Trip Due to 86 BU Trip Caused by Spurious Actuation of KD-41 Relay" 8.0 MANUFACTURER/MODEL NUMBER Phase Shifter Card Manufacturer Westinghouse Model S588C625G03 NRC FORM 366A (5*92)

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