ML20042G800

LER 90-015-00:on 900409,loss of Div II Reactor Protection Sys Bus Occurred Due to Trip of Electrical Protection Assembly.Another Trip Also Occurred on 900415.Caused by Faulty Integrated Circuit logics.W/900509 Ltr

ML20042G800
Person / Time
Site:	River Bend
Issue date:	05/09/1990
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-015, LER-90-15, RBG-32813, NUDOCS 9005160110
Download: ML20042G800 (4)

Text

-

I, GULF STATES UTILITXES COMPANY n.m u m.*non e,sr m oa w o n se irmnsmo mou.u um Afst A CODI %Da 0/5 (O%t 345 FM1 Mey 9 , 1990 RBG- 32813 File Nos. G9.5, G9.25.1.3 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:

River Bend Station - Unit 1 Docket No. 50-458 Please find enclosed Licensee Event Report No.90-015 for River Bend Station-- Unit 1. This repor,t is being submitted pursuant to 10CFR50.73.

Sincerely, f

i {}

" V i

W. H. dell Manager-Oversight River Bend Nuclear Group TFP/LAE/PDG/RGWfDCH/0JB/pg cc: U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive. Suite 1000 Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, LA 70775 INPO Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064 900536011o poogo9 ((12 .

{DR ADOCK 0500043s PDC

//

w _

,- M.ac

.s> ,..a aus vs wucLaa atovutonv c0esMiesi0=

LPPaovt) Owt 8u0 Ste641st

, UCEZ8EE EVENT REPORT (LER) 6:'*t s s '8' a s

sacsLity Nawl m DOCElf NuMete :: rear x RIVER DEND STATION 0 I610101014 l5 18 1 lorl0 l3

'" ESP Actuations on Loss of Power to the Division II RPS Bus Caused by the Failure of a Trin Coil of the TPA Breaker.

tvtNT DATE fll Lt A huMtth s6i htPORT DAf f til OtMta f ACILl?its souv0LvtD ISi MO% t es DA* vl88 *tAA lh a L "'gd$ MONtw Det v t AP.~ .Aci6ett% Awes DOCat t Nuvst m.s>

015101010 t i 1

~ ~

0 l4 0l9 9 0 9l0 0l1l5 0l 0 0l 5 0l9 9l0 0 1 6:01 00 ! l l

,,,,,,,,,, t.us .4,0at is sueMitn o eu.sve f t0 t t .LouietMi=n ce io cia e ,e..,. . ., ... .,,a. "..v mi "UDI

• 1 20 4021D1 20 4061sl 60 ni.ntne.i 73 Filti

] _

g n ot. wino .o mi.im u ni.nen.i nm.i 0 06 01219 m ==innw so mi.nz w ni.nsn. i ovata,s= < -Aa,, ,

so aainn m .o ni.uana

.o n,.nen..nai

~~~

"u'",'"

n . n n .. .. ni.n n., .o n,.n n..n.,

IJ 40H.i1111 1 $673i.n2;ted to ns.n2ns t LICIN$tt CONiect son twis Lim 03:

NAVE TELEPMONE NUMDIR Amt & COC't L. A. England, Director - Nuclear Licensing 5 l0 14 31811 l- 14 11 1415 COMPLitt ONI (60 #0a I ACM COMPONENT f Astunt DiaCaseto em twas atront nas Y'

Cav58 avltiv COMPONENT C "I,' ",('j,d CAvst tvstiv cov80NENT WA C a OptA e pp B ED t lB;K;R G082 i Y , , i i , , , -

1 I I I I I I I I I I I I I sue,ttMm AL af ront o teno n., e&v

,, ,,, l MO.o. vtA.

D vis ,,, v.. 'diMC

..,,,. u ectro svowss,0N 0, rs, 3 No A e s t A C t e, ,, e m ,.. , . .. . .-, , ,,,, . -,, . . ,,,,.,,,,,. . n e i At approximately 0559 on April 9, 1990 with the unit at 29 percent power (operational Condition 1) and with the reactor protection system (RPS) bus being powered by the alternate source, a loss of the Division II RPS bus occurred due to the trip of electrical protection '

assembly EPA breaker IC71*S003H. This resulted in the expected Division II talf scram and Division II isolation with the automatic start of the applicable engineered safety features (ESP) systems.

This report is submitted pursuant to 10CFR50.73 (a) (2) (iv) to document these ESF actuations. The RPS bus was re-energized from the normal power source and all isolations, half scrams, and ESF actuations were I

reset. The surveillance test procedure (STP) was successfully performed and the EPA breaker was returned to service.

Another trip of the same breaker occurred on April 15, 1990. This time however, no ESP actuaticns resulted because the RPS bus was i powered from the normal power supply. This second trip was due to i

failure of the trip coil of the EPA breaker. The failed component was replaced and the EPA breaker was returned to service.

l l

l During the events, all systems functioned per their design and were restored to their normal configurations by operations personnel.

l Therefore, there was no significant impact on the health and safety of l the public as a result of this event.

l c r e,,,, m l

WRC pero m u t asuCLl&R ht,Ubitpay Comeusgeger

[ UCENSEE EVENT REPORT (LER) TEXT C NTINUAT;;N ***aovio owe =o u o-e+

n.. . . . .

Fachaft osaast ne pocas,op.seg, m ,

n s* " t %.  %*s:

RIVER BEND STATION o plojojol41518 910 --

Ol i E -

O l0 Ol2 0' 0 13

,we n . - we , mm nn REPORTED CONDITION At approximately 0559 on April 9, 1990 with the unit at 29 percent power (Operational Condition 1) and with the RPS bus powered by the alternate source, power was lost to the Division II RPS (*JE*)

bus (*BU*). GSU's investigation revealed that EPA breaker (

• BKR* )

IC71*S003H had tripped. This resulted in a Division II half-scram and the following ESP actuationst

. A Division II containment isolation (*JM*)

. Train B of the standby gas treatment (SBGT) (*BH*) and annulus mixing (*BH*) systems automatically started

. Train B of the fuel building filtration system (*VG*)

automatically started

. Train B of the containment atmosphere and Icakage monitoring (CMS) system (*IK*) automatically started This report is submitted pursuant to 10CFR50.73 (a) (2) (iv) to document '

these ESP actuations.

Power was restored to the RPS bus from the normal power source. The half scram and all isolations were reset and the systems were returned to their normal configurations.

INVESTIGATION Immediate investigation found that EPA Breaker IC71*S003H had tripped.

This EPA breaker is located closest to the RPS bus. It was the only breaker to trip. Two EPA breakers are installed between the alternate power supply and the RPS bus. Alternate power is supplied from a divisional motor control center (*MCC*) through a power line conditioning trans f ormer (*XFMR* ) . There are a total of eight EPA breakers in use at River Bend Station, two on each of the normal and alternate power supplies on each of the two RPS buses. The EPA breakers monitor power supply voltage and frequency and, after a time delay, trip on an overvoltage, undervoltage or underfrequency conditions to ensure that power to the RPS bus is maintained within the equipment design requirements. The RPS bus was being supplied from the alternate power supply at the time of the event. Trouble shooting and testing was performed but did not identify any problems.

The surveillance test procedure (STP) was successfully performed and the EPA breaker was returned to service.

! As the trouble shooting continued on April 15, 1990, EPA breaker l

1C71*S003H tripped again. At that time, however, the RPS bus was not i on the alternate source but was being powered by the normal source.

l Therefore, there were no ESF actuations, half scrams and/or a,g,* oaw =a .o e o.o ions o n. sie di l

l l

E l one . 3 v =vetime.vuton, co==.mios.

, UCENSEE EVENT REPORT (LER) TEXT CCNTINUATION <*aovie ous =o am-o*

txpings are

,actuTV einest m Docali =vesten tai ten wouMa iti '600 @

.... stu;t- 6,f RIVER BEND STATION o p j o lo j o l al 51 R 4C --

O ll l 5 --

01 0 01 3 0' ol?

viu - . we m. nm isolations. The trouble shooting process did however, reveal that the trip coil of the EPA breaker had failed and is considered the root cause for both tr1ps. The EPA breaker was replaced, the STP was successfully performed and the EPA breaker was returned to service.

A review of previously submitted LERs revealed no prior event where trip coil failure was a root cause. There were four reported ESP actuations due to EPA breaker trips or failures including LER 85-006 which reported an RPS actuation due to a tripped EPA breaker. LER 86-024 and later revisions reported two cases of EPA breaker trips.

The first case resulted in a loss of *hutdown cooling and actuation of containment isolation valves. The second case reported Division II isolations, actuation of the standby gas treatment, annulus mixing and fuel building ventilation systems. LER 87-033 also reported two cases of EPA breaker trips. Both cases resulted in a loss of the RPS B bus while the unit was in cold shutdown, resulting in the appropriate isolations and actuations. In each of these cases, the integrated circuit (IC) logics were implicated as the root cause of the EPA breaker trips. LER 90-012 also reported ESP actuations due to the tripping of an EPA breaker. The corrective action in that case was to replace the voltage regulator in the motor generator set.

CORRECTIVE ACTION Following the EPA breaker trip on 04/09/90, no problems were found with the EPA breaker and it was returned te service. Ilowever, on 04/15/90, the same EPA breaker tripped and it was discovered that the trip coil of the EPA breaker had failed. The EPA breaker was replaced, successfully tested and returned to service.

SAFETY ASSESSMENT During the event, all systems functioned per their design and were restored to their normal configurations by Operations personnel.

Therefore, there was no significant impact on the health and safety of the public as a result of this event.

NOTE: Energy Industry Identification System Codes are identified in the text as (*XX*).

g,'oa = => .v s o.o iese o-o. en .ii