ML17261B074

LER 90-007-00:on 900510,reactor Trip Occurred from Steam Generator a Low Level Coincident W/Feed Flow/Steam Flow Mismatch.Caused by Shorting of Two High Gain Ac Amplifier Transistors.Plant Stablized in Hot shutdown.W/900611 Ltr

ML17261B074
Person / Time
Site:	Ginna
Issue date:	06/11/1990
From:	Backus W, Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-007, LER-90-7, NUDOCS 9006220036
Download: ML17261B074 (9)

Text

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ACCESSION NBR:9006220036 DOC.DATE: 90/06/11 NOTARIZED: NO DOCKET ¹ FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION BACKUSFW.H. Rochester Gas 6 Electric Corp.

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

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-007-00:on 900510,inadvertent closure of A steam generator regulating valve causes reactor trip.

W/9 DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

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

NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). 05000244 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ZD CODE/NAME LTTR ENCL PD1-3 LA 1 1 PD1-3 PD 1 1 JOHNSONiA 1 INTERNAL: ACNW 2 AEOD/DOA 1 1 AEOD/DSP/TPAB AEOD/ROAB/DSP 2 2 DEDRO 1 NRR/DET/ECMB 9H 1 NRR/DET/EMEB9H3 1 NRR/DLPQ/LHFBll 1 NRR/DLPQ/LPEB10 1 NRR/DOEA/OEABll 1 1 NRR/DR"P/PRPBll 2 NRR/DST/SELB SD 1 1 NRR/DST/SICB 7E 1 PLBSD1 1 1 NRR/DST/SRXB SE 1 EG FIL 02 1 1 RES/DSZR/EIB 1 R rILE Ol 1 EXTERNAL: EGGG STUARTFV.A L ST LOBBY WARD 1 LPDR NRC PDR 1 1 NSZC MAYSFG NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 69o9sy g.g g 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!

rULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 34 ENCL 34

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$ TA1C ROCHESTER GAS AND ELECTRIC CORPORATION ~ ee EAST AVENUE, ROCHESTER, N.Y. 14649-0001 TCLI,PwOSf ARcA cool: 7IB 546 2700 June 11, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Subject:

LER 90-007, Inadvertent Closure of "A" Steam Generator Main Feedwater Regulating Valve Due To Controller Malfunction Causes A Reactor Trip On Low Steam Generator Level.

R. E. Ginna Nuclear Power Plant Docket No. 50-244 In accordance with 10CFR50.73, License Event Report System, Item (a)(2)(iv), which requires a 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 License Event Report, LER 90-007, is hereby submitted.

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

Very truly yours, Division Manager Nuclear Production XC: U. S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 xco Ginna USNRC Senior Resident Inspector

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'LVSMI$ $ (ON OATI II II Ytl IIC trr, C<<o>>rr>> CXtCCCCO SVSICISSIOrr OATCI NO IAITAAOTIL>>vl N lo44 Moc>>, I A. roororor>>>>rt Al>>oo rrotrrrooco rrto<<rrrrro oooo( (ill On May 10, 1990, at 0219 EDST, with the reactor at approximately 884 full power, a reactor trip occurred from "A" Steam Generator (S/G) Low Level coincident with "A" S/G Feed Flow/Steam Flow mismatch.

The two reactor trip breakers opened as required and all shutdown and control rods inserted as designed.

The reactor trip was due to a malfunctioning "A" S/G Main Feedwater Regulating Valve Control System.

The underlying cause of the malfunctioning "A" S/G main feedwater regulating valve control system was attributed to the shorting of two high gain AC amplifier transistors in the flow controller, due to the transistor cans touching each other.

Immediate corrective action was to stabilize the plant in hot shutdown.

Subsequent action was to physically separate the two transistor cans so that they could not touch each other.

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NIIC Sasm ESSA U,S, NUCLEAII NEOULATONY COMMISSION (9451 c LICENSEE EVENT REPORT ILER) TEXT CONTINUATION A991IOYEO OMS NO 5150WI04 EIIPIIIES 'SISI IS5 FACILITY NAME 111 COCKET NUMSEA LTI LEN NUMSEII (EI SAOE 1$ 1 SEOUCNTI*L 1EVOION NUM ~ 8 NUM CA R.E. Ginna Nuclear Power Plant o s o o o 2 4 4 9 0 0 0 7 00 02 OF 0 7 TEXT lllmen tOeCe e needed. uM NANNNMIIYITC ferw JSK4'll IITI I. PRE-EVENT PLANT CONDITIONS Unit startup was in progress per operating procedure 0-1.2 (Plant From Hot, Shutdown to Full Load) from the annual refueling and maintenance outage. Reactor power was approx-imately 88% full power. Plant operators were swapping All Volatile Treatment (AVT) full flow demineralizer beds on the secondary plant. The AVT full flow demineralizer bed swapping routinely places a moderate transient on the condensate and feedwater system.

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

0 May 10, 1990, 0219 EDST: Event date and time 0 May 10, 1990, 0219 EDST: Event discovery date and time 0 May 10, 1990, 0219 EDST: Control Room Operators verify both reactor trip breakers open and all control and shutdown rods inserted.

0 May 10, 1990, 0253 EDST: Plant stabilized at Hot Shutdown1 B. EVENT:

On May 10, 1990, at 0219 EDST, with the reactor at approximately 88% full power, a reactor trip occurred due to low level in the "A" Steam Generator (i.e.,

Steam Generator level < 30%) coincident with Steam -

Flow-Feed Flow (SF/FF) mismatch (i;e., Steam Flow 0.8E6 ibm/hr more than feedwater flow) .

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NIIC Saem 888A U.S, NUCLEAIl AECULATOIIYCOMMISSION 19481 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION I ASSROVEO OM8 NO 9150&IOS E)ePIAES.'8/Sl/89 SACILITV NAME III OOCKET NUMEEA IEI LEII NUMEEII IEI ~ AOE 181 SSQUSNTtAL ASVI5104 4@M SA NUM '1 A R.E. Ginna Nuclear Power Plant 2 4 4 9 0 000 3 or- 0 7 TEIL litware sPSCe N nyusnd. v>> oaeOonV INC ~~ 91 (ITI o s o o o 0 0 7 The Control Room Operators performed the applicable actions of Emergency Operating Procedures, E-0 (Reactor Trip Or Safety Injection) and ES-0.1 (Reactor Trip Response), and stabilized the plant. Both reactor trip breakers opened as required and all control and shutdown rods were verified inserted.

The Control Room Operators notified higher supervision and the Nuclear Regulatory Commission (NRC) of the Reactor Protection System activation from the >>A>> Steam Generator (S/G) Low Level coincident with SF/FF mismatch.

C. INOPERABLE STRUCTURES s COMPONENTS g 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.

F. OPERATOR ACTION:

After the reactor trip, the Control Room Operators performed the actions of Emergency Operating Procedures, E-0 (Reactor Trip Or Safety Injection) and ES-O.l (Reactor Trip Response), and stabilized the plant.

G. SAFETY SYSTEM RESPONSES:

None.

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)945 I V.S. NUCLEAR REOULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ASOROVEO OME NO I 5150&IOI E)/SIRES '9/51/85 SACILITY NAME III OOCKE1 NUMEER Ql LER NUMEER ISI SAOE ISI 1 SOU 1 HSING L o 5 v IS IO //

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R.E. Ginna Nuclear Power Plant ZEXT /)f mO/O SAOCO R /OSVVO//. vOO O/NOSOOM H)IC //O//O/ ~'O) Ill) o so o o 2 4490 0 0 7 000 4 DF 07 III. CAUSE OF EVENT A. IMMEDIATE CAUSE:

The reactor trip occurred due to "A" S/G Low Level 30% coincident with "A" S/G SF/FF mismatch > O.SE6 ibm/hr.

B. INTERMEDIATE CAUSE:

The "A" S/G Low Level coincident with "A" S/G SF/FF mismatch was due to the "A" S/G main feedwater regulating valve closing due to a controller malfunction.

C. ROOT CAUSE:

The underlying cause of the event was the FC-466A flow controller malfunction. This Foxboro model 62H controller's current signal output failed low, which was attributed to the metal cans of transistors Q3 and Q4 momentarily touching together. The collector of the transistor is electrically connected to the can for power and heat dissipation. The design of the circuit board positions these transistors in close proximity, on plastic stands. If disturbed'uring maintenance, the transistor can pivot on the collector, emitter and base leads land allow the metal cans 'to become close enough to touch. FC-466A has had maintenance done internally in the past, including capacitor and relay replacement and necessary resoldering. Vibration of the relay room during the swapping of the demineralizer beds could have provided the necessary force to cause the transistors to touch. Failure of the output current immediately causes the feedwater valve to close.

Subsequent to this failure, FC-466A exhibited a similar failure mode on June 9, 1990. This subsequent failure also caused closure of the "A" S/G main feedwater regulating'alve, and resulted in a reactor trip. This event will be reported as LER 90-010.

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NRC form ESSA 19451 II,S. NUCLEAR RECULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION /

ASSROVEO OMI NO 5150MIOr EXPIRES '9191/S5 SACILITY NAME <<I OOCKET NUMEER Lll LER NI/IAEER I ~ I SAOE 191 Sf CMC rr T EAL fNgrr 5 VISION fR HQI ~ f R R.E. Ginna Nuclear Power Plant o s o o o 2 4 4 90 00 7 00 05 pF 07 TExT llfweve Nearer R srRrrrrL MrS rrMsrrMr HRc ArrrR ~'rl ITI I

IV. I ANALYS S OF EVENT This event is reportable in accordance with 10CFR50.73, License 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 <<A<< S/G Low Level coincident with <<A<< S/G SF/FF mismatch reactor trip was an automatic actuation of the RPS.

An assessment was per formed considering both the sa fety consequences and implications of this event with the following results and conclusions:'here were no operational or safety consequences and implica.-

tions attributed to the <<A<< S/G Low Level coincident with

<<A<< S/G SF/FF mismatch reactor trip because:

o The two reactor trip breakers opened as required.

o All control and shutdown rods inserted as designed.

o The plant was stabilized in Hot Shutdown.

This transient was compared to the Loss of Normal Feedwater Flow Transient described in the Ginna Updated Final Safety Analysis Report .(UFSAR). None of the assumptions of the UFSAR were violated during this event.

The response of the plant to this transient is bounded by the results of the UFSAR analysis. The analysis of this transient showed that the plant responded as expected to the Loss of Feedwater to the <<A S/G.

During the entire event, the <<A<< and <<B<< S/Gs were always available as a heat sink due to sufficient auxiliary feedwater flow to both S/Gs and adequate steam release from both S/Gs.

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

'eiC rORM SSS A i9491

HRC Form 444A 0 U 4 NUCLEAR REOULATORY COMMISSIOH (945 I LICENSEE EVENT REPORT ILER) TEXT CONTINUATION r APPROVEO OM4 1IO 5150WIOf ERPIRESVSISI145 FACILITY NAME III OOCRET IIUMEER Ill LER RUMEER IEI ~ AOE ISI Sf OVS HT1AL REVISIOR 4VV fo VVV SR TEXT IIImom fpofo e 1oovred. ooo ~

R.E. Ginna Nuclear Power Plant HRC Porno ~ LU I ITI o s o ohio 2 44 9 0 0 0 7 00 06 DF 07 V. CORRECTIVE ACTION A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

o The Instrument and Control (I&C) Department did extensive troubleshooting on the "A" S/G Feedwater Control System and determined the apparent cause of the control malfunction. The "A" S/G Feedwater Control System was repaired and tested satisfac-torily and returned to service.

0 The high gains AC amplifier transistors Q3 and Q4 were physically separated to their original design position, which prevented them from being able to touch again.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

0 The similar controller on the "B" S/G (FC-476A) was inspected, and verified that transistors Q3 and Q4 were separated, The. spare Foxboro model 62H controllers were inspected and verified that transistors Q3 and Q4 were separated.

0 The industry will be notified via Nuclear Network, describing this failure.

Procedures used for rework and inspection of these controllers will be changed by the end of August, 1990, to include concerns for maintaining component separation.

Foxboro model 62H series controllers will be identified and will be inspected prior to the end of the 1991 Outage, to ensure there is proper separation of these transistors.

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NRC Form SSSA ITS I U.S. NUCLEAR REOULA'TORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION J AFFROYEO OMS rrO IISOWISe ENFIRE S 'SINAI rSS FACILITY NAME III COCKET NUMSER ISI LER NUMSER ISI ~ AOE ISI YSAA $ (QUCNTrAL REVISION Nvoeeo ~ rQM eo R.E. Ginna Nuclear Power Plant TEXT Ire more eoece re eerreerF, rree erooooner ArreC fcerrr SISSSYI o s o o o 2 4 4 90 00 7 0 0 0 70F 0 7 IITI VI. ADDITIONAL INFORMATION A. FAILED COMPONENTS:

The failed component was the "A" S/G main feedwater regulating valve controller FC-466A. This controller was manufactured by Foxboro Company. The controllers Model Number is 62H-4E and Serial Number is 2208968.

B. PREVIOUS LER'S 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, LERs85-006, 85-019,88-003, and 88-005 were similar events with different root causes.

C. SPECIAL COMMENTS:

Subsequent to this failure, FC-466A exhibited a similar failure mode on June 9, 1990. This subsequent failure also caused closure of the "A" S/G main feedwater regulatixg valve, and resulted in a reactor event will be:reported as LER 90-010.

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