05000424/LER-1993-004

LER 93-004-00:on 930410,ESFAS Sequencer Operation Initiated During Testing.Caused by Design Flaw in Circuit Card. Affected Cards in Both Train a & Train B Sequencers modified.W/930503 Ltr

ML20056C210
Person / Time
Site:	Vogtle
Issue date:	05/03/1993
From:	Mccoy C, Sheibani M GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-05421, ELV-5421, LER-93-004, LER-93-4, NUDOCS 9305110097
Download: ML20056C210 (4)

LER-2093-004,

Event date:
Report date:
4242093004R00 - NRC Website

text

Geo g>a Power Company

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C.K facCoy Georgia Power vce Prese;unt NucW Yogite Pictect I?IF SCWM*n UllCIHC Sf;IO71 May 3, 1993 ELV-05421 Docket No. 50-424 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT LICENSEE EVENT REPORT ENGINEERED SAFETY FEATURE ACTUATION SYSTEM SEOUENCER OPERATION IS INITIATED DURING TESTING In accordance with the requirements of 10 CFR 50.73, Georgia Power Company submits the enclosed report related to an event which occurred on April 10,1993.

Sincerely, of '

C. K. McCoy CKM/NJS

Enclosure:

LER 50-424/1993-004 xc: Georcia Power Company Mr. W. B. Shipman Mr. M. Sheibani NORMS U. S. Nuclear Reculatory Commission Mr. S. D. Ebneter, Regional Administrator Mr. D. S. Hood, Licensing Project Manager, NRR Mr. B. R. Bonser, Senior Resident Inspector, Vogtle 070000 9305110097 930503 '

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M IT hAML (1) Daau hsMbtR gj nu rs) l V0GTLE ELECIRIC CENERATDC PLA!TI - INIT 1 05000424 I lDrl3 -

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DEINEERED SAFEIY FEARRE ACIUATION SYSTDi SEQUENCER OPERATION IS INITIATED DURING TESTI!C T AT DAi; (5) LER huMBER (6) kEP0RI DATE (7)' OTHER FACILITIES IhkOLbED (8) i GTn DAY VEAR TEAR SEQ huh REW N0hTH DAY VEAR FALILIIV hAMES DOCLET huMBER(5) 05000 i 04 10 93 93 004 00 05 03 93 05000 i OPERATING THI5 MRT 15 M M MN M M WRM5 W M UR U1) f QODE (9) 6 ^ 50.73(a)(2)(iv) '

20.402(b) 20.405(c) 73.71(b)

POUER -

20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) .i LEVEL 0 20.405(a)(1)(ii) 20.405(a)(1)(iii)

[ 50.36(c)(2) _

50.73(a)(2)(vit) _

OTHER (Specify in

_ _ 50.73(a)(2)(1) _ 50.73(a)(2)(viii)(A) Abstract below) 20.405(a)(1)(iv) -

50.73(a)(2)(ii) -

50.73(a)(2)(v111)(B) f 20.405(a)(1)(v) 50.73(a)(2)(111) 50.73(a)(2)(x)

LICEh5E E C0hT ACT FOR THIS LER (11)  ;

NAME TELEPn0hE huMbER f

4REA LODE MD!DI SHEIBANI, NUCIIAR SAFE 1Y AND COMPLIANCE 706 826-3209 COMFLETE OhE LIhE FOR EACH FAILORE DESCRIEED IN THIS kEP0kT (13)

CAUSE SYSTEN COMPONENT gP0RT CAUSE SYSTEN COMP 0hEhe MAhUFAC- R PD T l N(hhUFAC-ER pRDS TU ER SUFFLEMEhTAL REPDRI EXPECTED (14c MONIn DAY VEAR ,

SUBMISSION '

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Ab5 TRACT (16) ,

On April 10, 1993, personnel were testing the Train A engineered safety features .

actuation system (ESFAS) sequencer. New circuit cards had been installed as a followup corrective action to LER 50-424/1992-002. During the test, the  !

sequencer caused the Train A 4160 volt bus to open the normal incoming feeder breaker (causing a loss of power to the bus), shed its loads, and initiat.e the undervoltage loading sequence. Components actuated as designed, and operators  :

in the control room responded by stopping equipment started by this engineered  ;

safety feature actuation.

The cause of this event was a design flaw in a circuit card not affected by the  !

card replacements. Investigation found that a protective filter allowed a small j portion of a test signal to pass. This small portion of the test signal }

initiated the load shed. However, it was shown that this condition existed only during testing with a specific circuit board configuration and would not have j

~

affected sequencer operation during normal use. The affected circuit cards in both the Train A and Train B sequencers were modified to shorten the initiating I test pulse. Both cards were reinstalled, and testing was completed successfully. >

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g g rm m u.a. xxww awaum um>>m uggegpm 3 3 LICENSEE EVENT REPORT - (LER) -l TEXT CONTINUATION :l FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (5) PAGE (3) l YEAR SEQ huh REW i

05000424 93 004 00 2 0F 3 90GIII ELECIRIC GINERATING PIANT - UNIT 1 i T Lu I A. REQUIREMENT FOR REPORT .l This report is required per 10 CFR 50.73 (a)(2)(iv) because an unplanned  ;

engineered safety features (ESF) actuation occurred when the ESF actuation 'l system sequencer initiated an undervoltage loading sequence during testing. j B. UNIT STATUS AT TIME OF EVENT t

At the time of this event Unit I was operating in Mode 6 (refueling) at  !

O percent of rated thermal power. Other than that described herein, there l was no inoperable equipment that contributed to the occurrence of this event, j i

C. DESCRIPTION OF EVENT t l

On April 10, 1993, personnel were testing the Train A engineered safety j features actuation system (ESFAS) sequencer. New circuit cards had been [

installed as a followup corrective action to LER 50-424/1992-002. During the j test, the sequencer caused the Train A 4160-volt bus to open the normal incoming feeder breaker (causing a loss of power to the bus), shed its loads,  ;

and initiate the undervoltage loading sequence. . Components actuated as  ;

designed, and operators in the control room responded by stopping equipment started by this ESF actuation. ,

i D. CAUSE OF EVENT

{

The cause of this event was a design flaw in a circuit card not affected by  !

the card replacements. Investigation found that a protective filter allowed  ;

a small portion of a test signal to pass. This small portion of the test signal initiated the load shed. However, it was shown that this condition existed only during testing with a specific circuit board configuration and  ;

would not have affected sequencer operation during normal use.

}

E. ANALYSIS OF EVENT l

When the ESFAS sequencer sensed a loss of voltage on the primary bus, it i commenced operation, starting the emergency diesel generator to energize the  !

bus and loading'the necessary equipment,-as designed. Plant operators responded to shut down.this equipment, and there was no detrimental impact on  ;

unit operations. Based on this' consideration, there was no adverse effect on  ;

plant safety or on the health and safety of the public as a result of this  !

event. i l

F. CORRECTIVE ACTIONS-

1. The affected circuit card'in both the Train A and Train B sequencers.was  :

modified to shorten the initiating test pulse. Both cards were i reinstalled, and testing was. completed successfully.  !

2. Other cards of this type will be modified and installed in the Unit 2 sequencers during the Fall 1993 refueling outage. j i

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. .i 15 0 m U.5. IlhA,LLAR HLUdLAlWK1 wmlbblUN APFAUV W M ND 31 W-DID4 (6 . ,' EXPIRES: 4/30/92 LICENSEE-EVENT REPORT (LER) ,

't TEXT CONTINUATION '  !

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rACILITV NAME (1) DOCKET NUMBER (2) LER NUMBER (5) PAGE (3)  !

TEAR SEQ hum REV

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l V0GIII ELECIRIC GENERATING FURI - INIT 1 05000424- 93 004 00 3 0F 3- -[

ItxI l G. ADDITIONAL'INFORMATION f

1. Failed Components None  :

2. Previous Similar Events l

.None

3. Energy Industry Identification System Code l Engineered Safety Features Actuation System - JE I

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