ML20045H983

LER 93-004-00:on 930628,steam Flow/Feed Flow Mismatch Alarm Received for SGs 2,3 & 4,resulting in Manual Reactor Trip.Caused by Failure of Main Feedwater Regulating Valve 2 Tracking/Driver Card.Card replaced.W/930716 Ltr

ML20045H983
Person / Time
Site:	Vogtle
Issue date:	07/16/1993
From:	Mccoy C, Sheibani M GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LCV-0073, LCV-73, LER-93-004-03, LER-93-4-3, NUDOCS 9307220219
Download: ML20045H983 (4)

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• 1 i ' Georgsa Power Company i ' 40 inverness Center Parkway Post Offce Box 1295 . I

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, . Birmingham, Alabama 35201 - '

Teiephone 205 B77 7122

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, c. x. uccoy - Georgia Power .  ;

Vce President, Nuclear Vog:\e Project I the southern electrc sptern July 16,L 1993:

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LCV-0073 q t

a Docket No. 50-425 l l

U. S. Nuclear Regulatory Commission ATTN: Document Control Desk.

Washington, D. C. - 20555. j; Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT I LICENSEE EVENT REPORT-- .

MANUAL REACTOR TRIP DUE TO MAIN -

EEEDWATER REGULATING VALVE FAILING CLOSED  !

In accordance with the requirements of 10 CFR 50.73, Georgia Power Company submits the  :

enclosed report related to an event which occurred on June 28,1993.-

Sincerely, C. K. McCoy' j CKM/NJS . l

Enclosure:

LER 50-425/1993-004 xc: Georgia Power Company : q Mr. J. B. Beasley 1 Mr. M. Sheibani NORMS U. S. Nuclear Regulatory Commission Mr. S. D. Ebneter, Regional Administrator-Mr. D. S. Hood, Licensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident Inspector, Vogtle; i

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U.S. NULLLAR RLbulAiUKT LUPfilbbiUR Anxu D 50-0104 .

, LICENOEE EVENT REPORT (LER)

FACilllY NAML (1) UULKti NUMbtR (2) FEhF fil V0GTIL ELECIRIC GENERATING PIANT - UNIT 2 05000425 1 0Fl3 TITLE (4) l MANUAL REAC11R 1 RIP DUE TO MAIN FEEDWATER REGUIATING VALVE FAIIlNG CIDSED EVENT DATE (5) LER huMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQ hum REV M0hTH DAY YEAR FACILITY NAMES DOCKET NUMBER (5) 05000 06 28 93 93 004 00 07 16 93 05000 )

OPERATING S RMRWH M 10 UR (1U MODE (9) 1 20.402(b) 20.405(c) ^ 50.73(a)(2)(iv) 73.71(b)

POVER - 20.405(a)(1)(1) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

LEVEL 99 20.405(a)(1)(it) 50.36(c)(2) 50.73(a)!2)(vii) [OTHER(Specifyin 20.405(a)(1)(111) 50.73(a)(2)(1) _

50.73(a)(2)(viii)(A) Abstract below)

""'" 20.405(a)(1)(tv) ~""

50.73(a)(2)(11) ""~

50.73(a)(2)(vill)(B) 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LICEtSEE C0hTACT FOR THIS LER (IL)

NAME TELEPH0hE huMBER AREA CODE MEHDI SHEIBANI, NUCIFAR SAFETY AND COMPLIANCE 706 826-3209 COMPLETE OhE LIhE FOR EACH FAILURE DESCRIBED IN THIS REPOLT (13)

CAUSE SYSTEN COMPONENT NANUFAC- R P0R CAUSE SYSTEM COMPONENT MANUFAC- P0 i TU p TU B SJ CPOS W120 Y B IG JC W120 Y SUPPLEMEhlhL REPORT EXFECIED (14, M0hTH DAY YEAR SUBMIS$10N

] YES(If yes complete EXPECTED SUBMISSION DATE)  % NO DATE (15)

AB5 TRACT (16)

On June 28, 1993, at 0456 EDT, Unit 2 was operating normally when a steam flow / feed flow mismatch alarm was received for steam generators (SC) 2, 3, and

4. Operators observed SG 2 feedwater flow at approximately zero, narrow range (NR) level instrumentation trending down to approximately 45 percent, and main feedwater regulating valve (MFRV) 2 closed. All main feedwater isolation valves (MFIV) and bypass feedwater isolation valves (BFIV) were verified open. With SG water level dropping at a fast rate, the unit shift supervisor (USS) directed the reactor operator (RO) to manually trip the reactor at 0457 EDT. Appropriate procedural steps were implemented to return SG levels'to normal and place the unit in a stable condition.

1 Troubleshooting determined that the cause of this event was the failure of the MFRV 2 tracking / driver card. This card supplies the control signal for MFRV valve position. The card failure caused the valve demand signal to fail low, and MFRV 2 closed, resulting in reduced feed flow to SG 2. The failed circuit card was replaced and will undergo failure analysis.

u.s. nuatAR uuMARM Wm1WUN D0 3 0104 g rm m a Ar LICENSEE EVENT REPORT (LER)

. TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (5) Pt.GE (3)

YEAR SEQ hum REV I WXTr1E EIICIRIC GENERATING PLANI - UNIT 2 05000425 93 004 00 2 0F 3 TEXT A. REQUIREMENT FOR REPORT This report is required per 10 CFR 50.73 (a)(2)(iv) because an unplanned actuation of the reactor protection system (RPS) occurred.

B. UNIT STATUS AT TIME OF EVENT At the time of this event, Unit 2 was operating in Mode 1 (power operation) l at 99 percent of rated thermal power. Other than that described herein, there was no inoperable equipment that contributed to the occurrence of this event.

C. DESCRIPTION OF EVENT P

On June 28, 1993, at 0456 EDT,' Unit 2 was operating normally when a steam flow / feed flow mismatch alarm was received for steam generators (SC) 2, 3, and 4. Operators observed SG 2 feedwater flow at approximately zero, narrow l range (NR) level instrumentation trending down to approximately 45 percent, and main feedwater regulating valve (MFRV) 2 closed. All main feedwater isolation valves (MFIV) and bypass feedwater isolation valves (BFIV) were verified open. With SG water level dropping at a fast rate, the unit shift supervisor (USS) directed the reactor operator (RO) to manually trip the reactor at 0457 EDT. Appropriate procedural steps were implemented to return SG 1evels to normal and place the unit in a stable condition. Both neutron source range detectors were energized as required, but channel N32 malfunctioned and did not indicate onscale. Channel N32 was removed from service for troubleshooting. The motor driven auxiliary feedwater (AW) pumps were used to maintain SG water levels in Mode 3 (hot standby).

D. CAUSE OF EVENT Troubleshooting determined that the cause of this event was the failure of the MFRV 2 tracking / driver card. This card supplies the control signal for MFRV valve position. The card failure caused the valve demand signal to fail low, and MFRV 2 closed, resulting in reduced feedwater flow to SG 2.

An investigation of the malfunction of source range channel N32 revealed a failure of the channel's pulse driver circuit card which caused the indicator to fail downscale.

E. ANALYSIS OF EVENT i During this event, the reactor was manually tripped and the A W pumps actuated as designed to provide feedwater to the SGs, ensuring unit safety during this transient. Manually tripping the reactor reduced the challenges that an automatic trip would have placed on plant safety systems and provided a more controlled approach to placing the unit in a stable condition. Based on these considerations, there was no adverse effect on plant safety or the health and safety of the public as a result of this event.

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LICENSEE EVENT REPORT - (LER)

,- TEXT CONTINUATION  !

FACILITY NAME (i) DOCKET NUMBER (2)- LER NUMBER (5) PAGE (3) l YEAR 5EQ NUM REV

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V0GTLE EECIRIC CENIRATING PIANT - UNIT 2 05000425 93 004 00 3 0F 3 TEu  ;

F. CORRECTIVE ACTIONS l The failed circuit card for the MFRV position controller was replaced. A {

failure analysis will be performed on the failed circuit' card, and any further corrective actions will be based on the results of the analysis.

The pulse driver circuit card for source range channel N32 was replaced, and the channel was returned to service.

C. ADDITIONAL INFORMATION

1. Failed components

• Tracking / driver circuit card manufactured by Hagen  ;

Controls / Westinghouse.

Part No. 2838A45G01 Pulse Driver Card manufactured by Westinghouse Part No. 3378C23G01

2. Previous Similar Events  :

None .

3. Energy Industry Identification System Code Main Feedwater System - SJ Auxiliary Feedwater System - BA Nuclear Instrumentation System - IG l

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