ML20043C323

LER 90-005-00:on 900427 & 29,computer Point FO-424A Discovered to Be Reading Lower than Control Board Indications.Caused by Intermittent Failure of Computer. Computer Input Card replaced.W/900529 Ltr

ML20043C323
Person / Time
Site:	Vogtle
Issue date:	05/27/1990
From:	Hairston W, Odom R GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-01700, ELV-1700, LER-90-005-02, LER-90-5-2, NUDOCS 9006050056
Download: ML20043C323 (5)

Text

. . . . . . -

l l'

• Cite n g., tN nwi ( t.mp,oi, 10 hs.dr r e twi.,e ,

Atlanta L .t, e p 4 ' t yi w..o, c .. 4 m . 1 m,. .

u , o y ua..... ,

de h im. it' r i ..r e.o l 'n > 4 3 g f'i M i ih r , h,i 'i l d if .r tr.ih. o LS b ' '..m:,..o....,'.o.

,y .. .

May 29, 1990 .

W G Hatraton. til

.. . ..m, o . , . m .. . , __

o ,o... -

.r. . # . " ELV-01700 0398 Docket No. 50-425

=

U. S. Nuclear Regulatory Commission A11N: Document control Desk -

Washington, D. C. 20555 Gentlemen:

V0G1LL ELECTRIC GENERAllNG PL ANT LICENSEE EVENT REPORT

~

COMPUTER POINT FAILURE RESULTS IN EXCEEDING -

))lE REACTOR PCWER LICENSE LIMil In accordance with 10 CFR 50.73, Georgia Power Company hereby submits the -r-enclosed report related to an event which was discovered on April 29, 1990.

Sincerely, i g

y . 4 _,

g (). /0 {<T n > ) 4 "

W. G. Hairston, 111 WGH,lll/NJS/gm

Enclosure:

LER 50-4?5/1990-005 xc: Georata Poxer Company ~

Mr. C. K. McCoy Mr. G. Bockhold, Jr.

Mr. R. M. Odom f Mr. P. D. Rushton NORMS U. S._NucI n r_h gulatorv_0_ommission Mr. S. D. Lbneter, Regional Administrator Mr. 1. A. Reed, Licensing Project Manager, NRR Mr. R. f. Aiello, Senior Resident inspector, Vogtle -

m M

1 lk gg y gh l '

IIbE $^4 { !l 14 i t l' it It[p t 14) , C t [n:

==

7622 -

WRC#sem 3e4 U s NUCLE A2 (Lt EULATORY COMMI&stON APPIOYtb OMS NO 3150o104 LICENSEE EVENT REPORT (LER) 8 ""a 's ' '8' "

DOCKET NuM9t h (2) # AGE 634 8 ACILfiv NAME ill V0GTLE ELECTRIC GENERATING PLANT - UNIT 2 o Is I o Io l o l4 1 25 1 ilo7l0 41 bMPUTERPOINTFAILURERESULTSINEXCEEDIETHEREACTORPOWERLICENSELIMIT tytNT DATEt6) Lipi Nuust m ist htPORT DATE 17e OTHER f ACILITits INVOLVED tel MONTH DAv v t. AR v t A88 f8 MON T H DA% D E A,t 8 AciLiTv hawas DOCRi f NUMeteust 0 15101010 1 I I

~ -

Ol4 2l7 9 0 9l0 0 l0l5 0 l0 d5 2l9 9l0 o isto t o io n I i n,,,,,,,,

tuis RtPont es susMirit0 PunsuaNT to Tut R8ouiREMENis ce io teR t ,cana m e, ,w e, rw ,,u ..,, oi:

" D'

• 1 to aozini to miei so ni.imb.i 73 ?une mi R n .imoi .o mi.im .o nisimi.i n m.i T g,=,,g,,_

"To',' 1 i 0,0 n .o. m H.) Ao mi,lm w ni.im.. i to ao6l alt 196eil 60.73 eH2it61 6 73teH2ilvesiltAl .kv6Al to ao6 sittilm) So.73teH2iteil 60.?31aH2Hedell8l to dalloitt He to.736all2H H 60.73te H2 Hal LICENstl CONTACT 9081 TMts Lim till ,

esAMt TE LEPHONE PiVM9tm Amt A CODI R. M. ODOM, NUCLEAR SAFETY AND COMPLIANCE 404i 8i 2,6, , 3 2,0[1 COMPLtit ONE LINE FOR E ACH COMPONENT f AILURE OfSCRittD IN THis REPORY tt31

" ' Q Cavat svsitu COMPON E NT M'%^C " QU" 'n'h' ' CAust systtM COMPONtNT "'"[g 'C ,D NPR X IDi ECB i i i D Wi l20 i N i i i i l l i i l l I I I I I I I i i i I suPPLIMENT AL REPORT E kPICTID (14 MONTH DAY VtAR

, 'E*ATPN ,"

q ,8, ,, ... ..n.. u nucue sm,ssioN oA n, 3 No l l l

..s , R A C, ,o,~, R, , . , , .,,,..~,..,,,,,..,.,,,.,,,,,,n.i l

On 4-29-90, at approximately 1530 CDT, Proteus computer point F0-424A (Steam Generator #2 feedwater flow) was discovered to be reading lower than control board indications. Since this computer point provides input to the computer calculated calorimetric power indication, F0-424A was promptly removed from the Proteus scan. This resulted in an. increase of indicated reactor power to 3411 megawatts thermal (i.e., the maximum power level specified in the Facility Operating License). The power range nuclear instrumentation channels were then adjusted accordingly.

While removal of computer point F0-424A only brought indicated reactor power up to 100% rated thermal power (RTP), a subsequent review of computer data indicated that actual reactor power had slightly exceeded 100% RTP beginning at approximately 2000 CDT on 4-27-90. It is estimated that reactor power averaged 100.5% RTP for a 15 hour1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> interval and a 25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> interval until discovery of the computer point failure terminated the event.

A computer input card for F0-424A was replaced and the computer point was verified to be indicating correctly. Corrective action to prevent recurrence includes tightening the cluster limit for acceptance of the feedwater flow input values as good data.

l l

l l

")Cy * *'* '**

e - ,

y.A u.. oco mowon co l ,

, 8 MPIRE$ 4/3092 Ws*'A,%'J"8Ein"o"'

• I?"U,' .#"'nY Mt.'AE LICENSEE EVENT REPORT (LER) '

TEXT CONTINUATION *?%",,'."4'.'F. *Z"oi,'J"?'.Mfe'O,'!2 l,".' Oc?M 0?",W " joe"#at .l OF MANAOLMENT AND.!M'.30.ic?"#.#M UDGET WA HINOTDN.DC 20603.

f AclVTV NA 8 411 DOC 9L61 NUndBER (2) ggg gygggg ggg pagg g33

(

VIA" ' ^

u[t'e ' Nefs a

'e'ECP UNIT 2 o p l o j o l o l4 l2 l 5 9l0 -

0l0 l5 -

Op 0l2 or 0 l4 TEXT ta musee mese as neouseet, use as aMar Mtc Fenn As.AW 1171 A. REQUIREMENT FOR REPORT This report is being submitted because the Vogtle Electric Ger> rating Plant.  !

Unit 2 Facility Operating License No. NPF-81, section 2.H. requires Georgia Power Company to report violations of the requirements contained in section i 2.C.- License condition 2.C.(1) stipulates that the reactor core power level shall not exceed 3411 megawatts thermal. The failure of a computer point caused the average core thermal power level to slightly exceed 3411 megawatts thermal for greater than an eight hour shift. In accordance with a previously developed Georgia Power Company pos'ition (reference LER 50-424/1987-069-01), this event is considered reportable.

B. UNIT STATUS AT TIME OF EVENT At the time of this event, Unit 2 was in Mode 1 (Power _0peration) at 100% of rated thermal power. Other than that described herein, there was no inoperable equipment which contributed to the occurrence of this event..

C. DESCRIPTION OF EVENT On 4-27-90, an intermittent failure of Proteus aputer point F0-424A (Steam '

Generator #2 feedwater flow) began to occur. Tus failure increased in frequency and gradually resulted in F0-424A reading an average of 200~

kilopounds/ hour (KBH) less than computer point F0-423A (also Steam Generator

1. 2 feedwater flow). Since these two computer points are averaged to provide an input value to the reactor thermal power computer point, U1118 (i e.,

computer calculated calorimetric power), this intermittent failure resulted 4 in feedwater flow being underestimated by an average-of 100 KBH. This in '

turn caused the Proteus computer to underestimate reactor power by an average of 0.7%.- Since reactor power is controlled based on the U1118 indication, this resulted in actual reactor power slightly exceeding 100%

rated thermal power beginning at approximately 2000 CDT on 4-27-90.

On 4-29-90, at approximately 1530 CDT, the overpower condition was terminated when computer point F0-424A was discovered to be reading lower than control board indications. Computer point F0-424A was promptly removed from the Proteus scan which resulted in an increase of indicated reactor power to 3411 megawatts thermal. Procedure 14030-2, " Power Range Calorimetric Channel Calibration," was performed and the power range nuclear instrumentation channels (NI's) were adjusted accordingly. A manual calorimetric was also performed per procedure 14030-2 which-validated the accuracy of the Ulll8 indication with the F0-424A input removed.

A subsequent review of computer data indicated that actual reactor power had -

reached a maximum of 100.6% of rated thermal power (3431 megawatts thermal) and had averaged approximately 100.5% for a 15 hour1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> interval and a 25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> interval during the overpower event.

NRC Penn 3 A (640

. uuuCu Anuou.,On Co.M. t.

ge,,,o.M, , , , , , , , , , , , , , ,  ;

• EXT 17.E8 4/30/92 f,Un'M#0."as"t",",0li',%O "

j',1' Cf7# ,%"d"'!

LICENSEE EVENT REPCRT (LER)

^

TEXT CONTINUATlON F.,""Rt,'O,",!

Mn AMEN'.M!'c'n,'Ml,*.'$$'N PAPtHWO Rt UCION t 60 $0 i OF MANAGEMENT AND DUDOET. WASHINGTON,DC 20603-F AC4lTY NAME tu DOCKl1 NURSLR 42) LtR NUM38R (.) PAGE (3) vtaa " = P. - "

'JJJ:

VEGP - UNIT 2 T6(T W more apose 4,ogiesel see asluitemet NRC Fem NBOJ lih o ls-l 0 l o o l4 l2 l 5 9l0 -

0l0l 5 -

0l0 q3 or 0l4 D. CAUSE OF EVENT l The direct cause of this event was the intermittent failure of computer point F0-424A. Although the cause for this failure could not be positively identified, a computer input card for F0-424A was replaced and trending of that point indicated _it to be operating correctly.

A contributing cause for this event is the cluster limit established for acceptance of the feedwater flow input values as good data. The present l cluster limit will cause a feedwater flow value to be rejected when it differs from a predetermined value by more than 250 KBH. The value for F0-424A did fall outside of the cluster . limit on several occasions; however, due to the intermittent nature of.the failure, F0-424A was typically not rejected as an input and therefore impacted the Proteus calculated calorimetric.

E. ANALYSIS OF EVENT The subsequent review of computer data demonstrated that none of the reactor trip limits were approached and the reactor safety limits shown in Technical Specification Figure 2.1-1 were not exceeded. Although the licensed power limit was slightly exceeded, this event did not result in the plant being in an unanalyzed condition. The plant was not operated above 102% of rated thermal power. Based on these considerations, there was no adverse effect-l on plant safety or public health and safety as a result of this event.

F. CORRECTIVE ACTIONS

1. The computer input card for F0-424A was replaced. I

2. The cluster limit for acceptance of tta feedwater flow input values to I the Proteus calculated calorimetric will be made tighter._ This modification is expected to be complete by 7-1-90.

G. ADDITIONAL INFORMATION

1. Failed Components Identification F0-424A Computer Analej Input Card Westinghouse QAW Card, located in Proteus Input / Output Cabinet.

l

- NIC Poem 3 A (649)

.. . j

. F9AM,3864 U.S. KUCLE AX kt1ULAihY COMMtGBtON 4 (KPtHES 4/30/92 LICENSEE EVENT REPORT (LER) ISnUA,' o'J'?8'",'C4",oa '5%MIT%cf7.V .To"N."n'r, '*

TEXT CONTINUATION ^

• ,fo'"n'",1,* "l'M%"d 'YN'."!PC'"^'!JP

, u '"' OEf"fA 0?"t^,'a".'Ji"n't'#N"^i=iC?"df##:0?ili OF MANAGEMENT AND DVDOET, WASHINGTON.DC 20603

)

f ACILITY NAast HI DOCKti NUtdStR (2) ggg gygggg ggg pggg gg, vtan .

sagejaatp .y ma]isYo q a VEGP - UNIT 2 0 l51010 l0 l4 l 2l5 9l 0 -

0l0l 5 -

0l0 0l4 or 0l4 TSxT run a w ww-awsoun

2. Previous Similar Events A somewhat similar event occurred for Unit 2 on 6-15-89'(reference LER  !

when a slight overpower condition was suspected to have 50-425/1989-022) occurred before discovery of a feedwater flow input-error to the Proteus ,

computer. However, the root cause for the feedwater flow input error in j the prior event was different since it involved improper venting of  !

sensing lines.

I

3. Energy Industry Identification System Codes 3

Reactor Core - AC Feedwater - SJ Plant Computer - ID-i 1

NIC Foren 304A (649)