ML17262A322

LER 90-018-00:on 901220,dropped Control Rod/Turbine Runback Occurred During Rod Control Exercises.Caused by Degraded Power Bridge Thyristor Suppression Filter Capacitors. Capacitors replaced.W/910121 Ltr

ML17262A322
Person / Time
Site:	Ginna
Issue date:	01/21/1991
From:	Backus W, Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-018, LER-90-18, NUDOCS 9101290229
Download: ML17262A322 (14)

Text

ACCELERATED DISpPBUTION DEMONS'TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9101290229 DOC.DATE: 91/01/21 NOTARIZED: NO DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION BACKUS,W.H. 'ochester Gas & Electric Corp.

MECREDY,R.C. Rochester Gas & Electric Corp.

RECIP.NAME RECIPIENT AFFILIATION R

SUBJECT:

LER 90-018-00:on 901220,dropped control rod/turbine runback occurred during rod control exercises. Caused by degraded power bridge thyristor supporession filter capacitors.

Capacitors replaced.W/910121 ltr.

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

l SIZE:

NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). . 05000244 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL, PD1-3 LA 1 1 PD1-3 PD 1 1 JOHNSON,A 1 1 INTERNAL ACNW 2 2 AEOD/DOA 1 1 AEOD/DS P/TPAB 1 1 AEOD/ROAB/DS P 2 2 NRR/DET/ECMB 9H 1 .1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST SELB 8D 1 1 NRR/DST/SICB 7E 1 1 NRR DS RE FILE SR'D 02 1

1 1

1 NRR/DST/SRXB 8E RES/DSIR/EIB 1

1 1

1 RGN1 I.LE~0'1 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1 1

/V'u D p~y vi f2(C S

D D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

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

"RPZF Pi7ifi8",>VI "0'"'"'!'""'Ir"""(I (J<v~!P)v lilkz!"iivv ROCHESTER GAS AND ELECTRIC CORPORATION ~ 89 EAST AVENUE, ROCHESTER N.K 14649-0001 ROBERT C MECREDY TELEPHONE Vice Prestdent AREA cOOE 71ts 546 2700 Ctnne etucteei Production January 21, 1991 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

LER 90-018, Dropped Control Rod During Rod Control Exercises Causes Automatic Actuation of RPS (i.e.

Turbine Runback)

R.E. Ginna Nuclear Power Plant Docket No. 50-244 In accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(iv), which required s report of, "any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS)", the attached Licensee Event Report LER 90-018 is hereby submitted.

This event has in no way affected the public's health and safety.

Ve truly yours, Robert C. Me redy xco U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Ginna USNRC Senior Resident Inspector 9i01290229 95000244 PDR @DOCK o PDR S

J NAC oorN Ssl ISAtl UA NUCLIAA AIOVLATOA+ COW~

AJOAOVI0 OOOI INL $ 144 0 I 0 V LICENSEE EVENT REPORT (LERI IXSIAII IJSIJSS fAcIuTY NAJJI Ill OOCXIT NVOOSIA Ql R.E. Ginna NUclear Power Plant 0" 6 0 0 0 SOo08 111 LI IOJ Drop Control Rod Durin Rod Control Exercise Causes Automatic Actuation of RPS III i.e. Tur LIANVUIIAltl OATS 1lf01T OATt Ifl OTNI1 f ACIurlllINVOLVIOItl

'VINf UOIITU OAY TIAA, TtAA otovlvtrAL Aovvovr UONTN OAY rtAA JACILITYNAUIS OOCXIT NVIJSIAISI

~ rVUOtl ~ ArUo o A 0 6 0 0 0 2 0 9 0 9 0 0 1 8 0 0 0 1 2 1 9 1 0 6 0 4 0 TNII 1lfOAT II WSUITTIO fVANJANTT 0 TNI AIOUI A IUINTS Of IS Cf 1 $ : ICfooo orv or ovro or VU NrorrUSJ Illl Oft AATINO IJOOt I~ I t I.ootlrl SS.ASS 4I It.f$4IQIINI fAfI rol fONI1 St.Alt 4 I III I~ ISMIol11l ~ S.f $ 4IQllrl fit 1 lol LtvlL 0 $ 4 ANlolllI Itl ~ IMNIQI I.f$ 4IQllool 4 I IIIINI '4AIQ

~ S.f $ 41QI II

~

IID$4)QIITNNW OTNIA JSANXV AI Aorooor

~ oroUorrf Jo forL JJAC

$ SIAJ I~

$ 4AMNIIIIINI ~ I.f$ 41Q llxl ~ O.f $ 4IQIIUSIISI

$ 4.oll41 llllrl ~ 4.$ $ 4IQIIVO SS.TSNIQI41 LICINtllCONTACT fOA TNIS LtA lltl TILtfUONI NVUIIA Wesley H. Backus AAIACOOI Technical Assistant to the Operations Manager COJJfLITI ONI LINC fOA IACN COOJJONINT fAJLUAI OISC1I ~ IO IN TNII Alf01T IIII 315 24-44 Srtftil COUJONINT UANVfAC tfOATAILI t STSflU COUJONINT UANUfAC lfOATAIL CAVSI TVAIA TO NJAOI CAUS I

TVA 1 TO NJAOS B J G A P W1 20 Y SVffLtNINTALAIJO1T IXflCTIOIIOI UONTN CAY T tAA IxfICTIO WIUIIIION OATS Il II Tll IIJ roe. JNofrrN CXfCCTCO SVCJJISSION OATCJ NO oscTAAcf JLrrvr 4 JJJO Nore. I A. roororrrvrrrf ATNorr rrrvrroooro IrprenrNo frrrr lilt On December 20, 1990 at 1321 EST, with the reactor at, approximately 22% full power; a turbine runback occurred due to a dropped control rod.

The Control Room operators performed the appropriate actions of Abnormal Procedures AP-TURB.2 (Automatic Turbine Runback) and AP-RCC.2 (RCC/RPI Malfunction) to stabilize the plant. The Control Room operators manually tripped the turbine to prevent reverse power to the generator. Subsequently the xeactor was taken subcritical, to accomodate anticipated corrective maintenance The Main Steam Isolation Valves were then cloyed to limit a plant cooldown.

'ctivities.

r The underlying cause of the event was attributed to degraded power bridge thyristor suppression filter capacitoxs in the circuit supplying power to the stationaxy, movable and lift coils of the affected control rod.

Corrective action was to replace the degraded capacitors in the power cabinet supplying power to the affected rod.

N1C fore  %

ISASI

KIIC fOrAt SSOA U.S. NUCLEAII IIEOULATOIIYCOMMISSION AffAOVEO OMS rKO SISO&IOI ISOSI UCENSEE EVENT REPORT (LER) TEXT CONTINUATION EXfIREE. SISI ISS fACILITYNAME III OOCXET NUMOEII ISI LEII NUMOEII ISI ~ AOE ISI YSAA SSOUSHTIAL IIS V IS IO It NOMIC II M A NIJM R.E. Ginna Nuclear Power Plant 0 5 0 0 0 OF TEXT IITANIIYNMAfN teyvtWf. tNf AINeenar Antt ~ S I IITI 2 4 4 9 0 0 1 8

'RE-EVENT PLANT CONDITIONS The reactor was at approximately 224 with the turbine generator on the line, producing approximately 80 megawatts.

The following activities were in progress:

o Plant startup was continuing from the reactor trip of 12/11/90 (LER 90-013) and subsequent reactor trip of 12/12/90 (LER 90-016).

o The Instrument and Control (I&C) Department was in the process of troubleshooting a control problem with the Control Bank "D" Control Rods. (When manually stepping Bank "D" Control Rods out to control Reactor Coolant System (RCS) temperature, that the Bank "D" Control Rods stepped out to 128 it was observed steps, then stepped in 3 steps (with the rod control switch still held in the out position)). As part of this troubleshooting effort, the IGC Department requested that Periodic Test procedure PT-1 (Rod Control System) be performed.

II DESCRIPTION OP EVENT A. DATES AND APPROXIMATE TIMES OP MAJOR OCCURRENCES:

o December 20, 1990, 1321 EST: Event date and time.

o December 20, 1990, 1321 EST: Discovery date and time.

o December 20, 1990, 1321 EST: Control Room operators perform the appropriate actions of Abnormal Procedures AP-TURB.2 (Automatic Turbine Runback) and AP-RCC.2 (RCC/RPI Malfunction) to stabilize the plant.

o December 20, 1990, 1323 EST: Turbine tripped manually.

itAC SOIIM SSSA

~ ~

0 NIIC fetet 55EA V.E. NVCLEAII 1EOULATOIIY COMMISSION (545 l LICENSEE EVENT REPORT {LER) TEXT CONTINUATION AffAOVEOOME NO 5ISOWIOS hatt 5/SI/55

'EXPIAE5.

fACILITYNAME III COCKET NVMEEII IEI LEII NUMOEII Ill ~ AOE ISI SSOU ~ NTIAL ASvtSION tt Vtt A ~ t A R.E. Ginna Nuclear Power Plant 0 5 0 0 0 2 4 9 0 018 0 003 oF0 8 TExT Alm<<e N>>t>> te teetteee. we etAse<<>>t Hlsc f<<ttt HECATO IITI December 20, 1990, 1338 EST: Control Room operators close both Main Steam Isolation Valves (MSIVs) to terminate a RCS cooldown.

0 December 20, 1990, 1344 EST: Shutdown and control rods were fully inserted manually, and both reactor trip breakers were opened.

0 December 20, 1990, 1345 EST: Plant stabilized in hot shutdown.

B. EVENT:

On December 20, 1990, at 1321 EST, with the reactor at approximately 22~ full power, a dropped control rod/turbine runback occurred. Control Bank "C" Control Rod J-10 dropped approximately thirty-eight (38) steps into the core during the performance of PT-1. The turbine runback reduced generator load from approximately 80 megawatts to approximately 15 megawatts.

The Control Room operators performed the appropriate actions of AP-TURB.2 (Automatic Turbine Runback) and AP-RCC.2 (RCC/RPI Malfunction) to stabilize the plant. Subsequently', at 1323 EST, the turbine was tripped manually to prevent reverse power to the generator. The Control Room operators then performed the appropriate actions of AP-TURB.1 (Turbine Trip Without Rx Trip Required).

At 1329 EST, with the reactor at approximately 64 full power and the "A" Main Feedwater Pump running feeding both Steam Generators (S/G) through the Main Feedwater Regulating Bypass valves, the 'IAII Main Feedwater Pump tripped on feed pump seal water low differential pressure. The motor driven auxiliary feedwater pumps started automatically (as designed) and reactor power was reduced to approximately 34 full power to ensure that required feedwater flow was within the capacity of the auxiliary feedwater pumps.

NRC far~ 555A US. NUCLEAR REOULA'TORY COMMI55ION N4J I L'iCENSEE EVENT REPORT (LER) TEXT CONTINUATiON /

AftROVEO OME NO 5150&104 E)lfIREE 5/5II55 fACILITYNAME 111 DOCKET NUMEER 151 LER NUMEER 151 fAOE IJI vEAR 5 ~ QU5NTIAL AEVOIOH NUM 1 NUM EA R.E. Ginna Nuclear Power Plant 24 490 018 0 04 TEXT IF ~ <<ece N ~. v<<O4SeeW'VRC f<<R 4%i 5I IITI o s o o o 0 pF Due to the low power condition and to support trouble-shooting activities, the Shift Supervisor conserva-tively ordered the control and shutdown rods to be inserted into the core, in accordance with normal operating procedures.

Subsequently at 1338 EST the MSIVs were closed to limit the RCS cooldown. The reactor trip breakers were opened at 1344 EST and the plant was stabilized in hot shutdown.

C INOPERABLE STRUCTURES f COMPONENTS f OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None.

D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None.

E. METHOD OF DISCOVERY:

The event was immediately apparent due to alarms and indications in the Control Room.

OPERATOR ACTION.

Subsequent to the turbine runback, the Control Room operators performed the appropriate actions of,AP-TURB.2 and AP-RCC.2 to stabilize the plant. The turbine was manually tripped to prevent reverse power to the generator. The Control Room operators then performed the appropriate actions of AP-TURB.1 and subsequently, when the main feedwater pump tripped, assured auxiliary feedwater flow to S/G, took the reactor subcritical by inserting. all control and shutdown rods, and opened-the reactor trip breakers.

The plant was then stabilized 'in hot shutdown.

SAFETY SYSTEM RESPONSES:

None.

NAC fORM 555A

N1C farm $ AAA U4. NVCLEA1 1EOULATOAY COMMITEION

($ 4$ I I.'ICENSEE EVENT REPORT {LER) TEXT CONTINUATION 1 Aff<<OVEO OMS NO $ I$0&10i Ehf IAES;SI$ I 4$

fACILITYNAME Ill OCCAM ET NUMIEII Ill LEII NUMOEII III 1AOE 1$ I YTA1 $ $ QVCHTIAL htV IS KIN HVM 1 V R.E. Ginna Nuclear Power Plant o s o o o 24 4 9 0 0 1 8 0 0 0 5 OF 0 8

'tEXT Iftmme <<MCe <<noded. vM <<AHknM NIIC fehh ~<<I Iltl, III. CAUSE OF EVE2FZ A. IMMEDIATE CAUSE:

The automatic turbine runback was'aused by dropped Control Rod Z-10.

B. INTERMEDIATE CAUSE:

The cause for dropped Control Rod J-10 is attributed to a noisy incoming power supply to Control Rod J-,

10's stationary and movable gripper coils.

The noisy incoming power supply is attributed to degraded thyristor capacitors in the power bridge circuit for the stationary, movable and A review of Westinghouse Technical Bulletin (NSD-TB-lift coils.

74-16), was performed, and the power bridge circuitry was analyzed, supporting this conclusion.

C. ROOT CAUSE:

The underlying cause of the degraded thyristor capacitors is attributed to decreased service life due to elevated operating temperatures for the capacitors.

IV. ANALYSIS OF EVENT The event is reportable in accordance with 10 CFR 50.73, Licensee Event ,Report System, item (a)(2)(iv), which requires reporting of,, "any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF) including the, Reactor Protection System (RPS)", in that the automatic turbine runback from .

the dropped rod was an automatic actuation of the RPS.

An assessment was performed considering both the safety consequences and implications of this event with the following results and conclusions:

NAC 1 01M $$ 4A

<<AC Serm $ eeA V.S <<VCLEAII AEOVLATOIIYCOMMITNOII (94) I L'ICENSEE EVENT REPORT (LER) TEXT CONTINUATION AOOIIOVEO OME <<0 $ I $ 0&104 E)COIAES $ /$ 1/$ $

SACILITY NAME III OOCXET IIVMEEII ITI LEII HVINEII IEI JAOC IEI

$ OQVO<<TIAL oovrlor gVM 1 M OA R.E. Ginna Nuclear Power Plant o s o o o 24 490 0 1 8 0 0 6 OF 0 8 TExT IlI'ore <<roo r teevoaf, vm oooeonsl HlIC Amt ~'ol I ITl o Power was reduced automatically to compensate for the negative reactivity. of the dropped rod.

o All reactor control and protection systems performed as designed thus limiting the overall effects of the transient.

The transient was compared to the dropped rod event evaluated in Section 15 of the Ginna Updated Final Safety Analysis (UFSAR). No assumptions specified in Chapter 15 of the UFSAR were violated during this event.

Based on the above, it can be concluded that the public's health and safety was assured at all times.

V. CORRECTIVE ACTION A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

0 The control problem with the undesired stepping of Bank "D" control rods was caused by previously installed test equipment. This equipment was removed and the rod control system was tested and verified to be operating properly.

0 The electricians measured the resistance of control rod J-10's stationary, movable and coils, and verified the resistance was correct lift for hot shutdown conditions. Meggering verified no grounds existed.

0 The ISC Department checked coil polarity and verified there were no blown fuses. These activities confirmed that conditions which normally cause dropped rods, within the industry, did not exist for this event.

<<AC OOIIM $ OOA

I'll NRC Eor>> EEEA L'ICENSEE EVENT REPORT (LERI TEXT CONTINUATION US. NUCLEAR REOULATORY COMMIEEION Al'1ROVEO OME NO lIE0-OI04 ERtlREE, E/EI4$

SACILITY NAME III OOCXET NUMEER Ill LER NUMEER IEI ~ AOE IEI SEQUENTIAL HVM I1 Ii 'IV>>ION M IA TEXT IJF @are N>>ce>> ~~

R.E. Ginna Nuclear Power Plant wt NRC Ann ~ E I IITI o s o o o 244 90 018 0 0 7 oF 0 8 0 To correct'he cause of dropped rod J-10, the I&C Department replaced the power bridge thyristor suppression filter capacitors in the 'circuit supplying power to the stationary, movable and lift coils of Control Rod J-10.

B. ACTION TAKEN OR PLANNED TO PREVENT RECUEGUBTCE:

As the underlying cause of the event was attributed to premature aging of the thyristor capacitors, the following actions are being planned:

o All power bridge thyristor capacitors, in Power Cabinet 1 AC were replaced. (Control Rod J-10 is powered from this cabinet).

0 All power bridge thyristor capacitors in the other power cabinets (feeding the stationary, movable and lift coils of all control rods) will be replaced during the next annual outage.

0 The need to set up a program for the periodic replacement of these thyristor capacitors, based on their time in service, will be evaluated.

VI. ADDITIONAL INFORMATION A. FAILED COMPONENTS:

The thyristor capacitors involved were purchased from Westinghouse Electric Corporation, 'part number 2383A34H01 (capacitor, .5 ufd, 660 VAC). These capacitors had been previously installed as a sub-component of Field Change Kit, drawing No. 2379A94.

8 1 C 1 0 1 M EEEA

<OAl

HHC Sons SSSA U.S. HUCLSAII 1SOULATOHY COMMISSIOH 104S I L'ICENSEE EVENT REPORT ILER) TEXT CONTINUATION AttlIOVSO /

OMS HO SISOWIOO SHtIASS 'SISIISS SACILITY HAMS 111 OOCXSY HUMSSH ISI LSII HUMSSII ISI ~ AOS 'IS)

SSQUSHTIAL n n SSVISIQH vSA II nvM II R.E. Ginna Nuclear Power Plant 0 5 0 0 0 2 4 9 0 oF0 8 raxr IIS IIHoo <<oco <<<<oooo'oo <<Asoosor Hllc Sons ~ S1 I m B. 'REVIOUS LERs ON SIMILAR EVENTS:

A similar LER event historical search was conducted with -the following results: No documentation of similar LER events with the same root cause at Ginna Station could be identified. However, LER 89-008 was a similar event, with no known root cause.

C. SPECIAL COMMENTS:

None.

H1 C t 0 II M SSS A lOA'll

11