ML20042F473

LER 90-012-00:on 900401,ESF Actuations Occurred Due to Electrical Protection Assembly Breakers Trip.Caused by Voltage Regulator Failure.Replacement Voltage Regulator Card Installed in MG 1C71-S001B.W/900501 Ltr

ML20042F473
Person / Time
Site:	River Bend
Issue date:	05/01/1990
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-012, LER-90-12, RBG-32764, NUDOCS 9005080366
Download: ML20042F473 (4)

Text

- _ _ . . . .

+

GULF ' STATES UTELETIES COnfP21NY Alvte f4ND S TATION POST CWitCE BOX 220 57 FRANCISVILU. LOO 15iAN A ?v775 ARE A CODE boo 635 6004 - 346 8661 May- 1 , 1990 ';

RBG- 32764 .

File Nos. G9.5, G9.25.1.3 i

i U.S. Nuclear Regulatory Commission 1

. Document Control Desk Washington, D.C. .20555 j

Gentlemen: 1 River Bend Station'- Unit 1 Docket No. 50-458 k Please find enclosed Licensee Event Report No.90-012 for River Bend Station - Unit 1. This . report is--being' submitted-- -

pursuant to 10CFR50.73.

Sincerely, V

H.' 0de l' f W.Manager-0versight:

River-Bend Nuclear Group TFP/PDG/RGW/ 0JB/pg cc: U.S. Naclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector ,

P.O. Box 1051.

St. Trancisv111e, LA 70775 l INP0 Records Center 1100 Circle 75 Parkway Atlanta.-SA 30339-3064

^

Obbk $O0$0hs PDC  ! -- .

~

s

\:_

NaC p.m kJ U 8 NUCLE A4 s toukatud? ConsmessioN

'

• MPa!vt0 OMS NO 31tikCies LICENSEE EVENT REPORT (LER) t * * * "W F ACILITY haut HI DOCKlf NVeeSER 12l FAGe .L RIVER BEND STATION o 15 I o l o I o l 4l 5l E 1 loFl0 l3

'* Engineered Safety Feature Actuations Due to Trippina of Electrical Protection Assenbly Breakers Caused by Failure of a Voltane Reculator in the Motor Generator Set EVENT Daf t Ill LER NUMtt R 16) RtPORT DAf t 171 OTHER P ACILITitS INv0LvtD tel w0%7* OAv vtaa vtAR .$, ih' 4 fy*,$

"8 MONfM Dav vtAR 8 AC#Lef v hauts DOcat f Nuveters, 01510101ol t l

~ ~

0 l4 0 l1 9 'O 9 l0 0 l1 l 2 0l 0 0l5 0l1 9l0 0 # 5l0 t 0 ioi i I o,, , , , ,,,a twis atPosit is sueuertto evasuANt to twt aboviatutNts or 10 Cam i ,ca.ca . ., .* e ra n< u...asi 01:

MODE Ill } 20 402tti 20 408tel

] to 73teH2Hivl 73 tilti tn 20 406teH1Hd 50 36tell11 90 73teH2His 73.714e6 0 06 1I 01 0 80 asi.Huw a *Hai a 73ian:Hai g,w,8 a <la, ;7,;allp;<',,

20 405teH11Ini) to.73teH2Hil 90 73teH2HudH1Al J6dAJ 20 406teH1 Heel SolSteH2 Hill 90.73teH2HedilISI 2J 44MieH1 Het 50.736eH2Hdst to.73teH2Hel LICtesSEE CONT ACT FOR TMit Ltm ital NAug TattpuoNE Nyusta Anta COOL L. A. England, Director-Nuclear Licensing 51014 318111-l413l415 CouPLatt ONE LING Pon IACH ConspoestNT F AILust otacmistD IN fnis RI*on? H3i CowpoNENt m -

CAust 8vsftv COM*0NENT

• • )Nl'C' "' #0".*

oN *b C AUSS Sv 87tM WpgNC pomfggt p

B JCi i 9 90i Gi0i 8:0 Y i , i , i i i l l i l l l 1 l' l l l 1 1 I SUPPLEMENT AL REPORT EXPECTSD H4) l MONTa Dav vtAR

'T

-l vts ,,,, . ,1,rerso rv,wss,oM ca ri, 3 No l l l Ant. ACT ,L.- ,. , a u., . .....,,,,,,r..~,.....e,o.i At approximately 2017 on 04/01/90, with the unit at 100 percent power (0perctional Condition 1), a loss of the Division II reactor protection system (RPS) bus occurred due to the trip of the output breaker of the motor-generator (MG) set IC71-S001B. This caused the tripping of electrical protection assembly (EPA) breakers 1C71*S003B and IC71*S0030 and the expected Division II half scram and half isolation with the automatic start of the applicable engineered safety feature (ESF) systems. The bus was re-energized from the alternate l power source. All isolations, half scrams and ESF actuations were I

reset. This report is submitted pursuant to 10CFR50,73(a)(2)(iv) to l document the actuation of ESF systems.

The voltage regulator and the over voltage relay printed circuit cards were replaced in the generator section of the MG set. The MG was successfully tested and was released for service.

During the event, all systems functioned per their design. The L alternate source of power was used to restore the systems to their i

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

L 1

$1J"'"

1 LICENSEE EVENT REPORT (LER) TEXT CONTINUAT13N g i g no mo-eio.

ne ut, ni oocm av=.ea m u num. . m uim 3 viaa "W;P -

"'#.?:  !

RIVER BEND STATION 0 l51010 l014l 5l 8 01 2 0F 013 91 0 --

011 l 2 -

Ol0

.n . . . .= ~. . m ,nn BEP981EQ_CQBQ11108 At approximately 2017 on 04/01/90 with the plant at 100 percent power (Operational Condition 1), _ a loss of power occurred to the Division II )

RPS (*JC*) bus (*BU*). The loss of the RPS bus caused a half scram ,

signal, automatic initiation of the associated trains of the standby 'l gas treatment (SBGT) system (*BH*) and fuel- building charcoal ,

ventilation systems (*VG*), and the isolation of various  !

balance-of-plant (B0P) containment isolation valves. This report is  !

submitted pursuant to 10CFR50.73(a)(2)(iv) to document the actuation 1 of ESF systems._ j i

Operations immediately took action to restore power to the bus from 1 the alternate power supply. The half. scram and all isolations were j reset.and systems restored to their normal configurations.

I!VESTIGATIO!

(

Immediate investigation found that the output breaker (*BKR*) of MG IC71-S001B (*MG*) and. EPA breakers 1071*S003B and 1071*S0030 (*BKR*)

had tripped..

breakers EPA breakers 1071*S003B and IC71*S003D are the- two EPA installed between the RPS bus normal power supply MG set and j

i the RPS bus itself. Two other EPA breakers are also installed between the alternate bus power supply and the RPS bus. Alternate power is  !

supplied from a divisional motor control center through-a power- line  !

conditioning . transformer. There.are a total of eight EPA breakers in 4 use at River Bend Station, two_on each of the normal and _ alternate l 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 condition to ensure that i power to the RPS bus is maintained within the . equipment design t requirements. The RPS bus was being supplied from the normal power supply at the time of the event..

A review of previously submitted LERs revealed thret which reported ESF actuations due to EPA breaker trips or failures. LER 85-006 reported an RPS actuation due to an EPA breaker tripping. LER 86-024 and later revisions reported two cases of EPA breaker trips.- The first case resulted in a loss of shutdown cooling and actuation of containment isolation valves. The second case reported Division II 3' isolations, actuation of the SBGT, 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 previous cases, the integrated circuit, (IC) logics were implicated as the root cause of the EPA breaker failures.

t i

.g.. ~ .o udi ...+.a. .i i

• IIRC term MSA

~

e U S NUCLE &a C 30U4LTDav COnausgston '

LICENSEE EVENT REPORT (LER) TEXT C3NTINUATl3N ue:ovie oue no sino.eio. l swines s w a -

9Atiktiv haast tis 00CE51 Nunsesa tan gga nyespen is, pa04 tai VI'" ,waha -

IwaI*

RIVER BEND STATION 0 l5 l0 lo l0 l4 l5l9 Ol ll 2 0F sex,mm 91 0 - -

010 t:. I 3

. 013 e a .ana,auneo smanam

_C_O_R_R_E_C_TIVE__A_C_T.I.O._N

_ i While troubleshooting MG IC71-S001B, heavy discoloration was observed i on the printed circuit: cards for the voltage regulator (*90*) (VR) and i the overvoltage trip . delay. This appeared to be a result of overheating of resistors located-on the cards. A replacement VR card was installed in MG .1071-S0018. This r.eplacement card is of a different design that is resistant ~to overheating failures. The VR l'

was calibrated'and MG~1071-S001B was successfully tested and returned to service, j

l i

SAFETY ASSESSMENT l During the event, all systems functioned per their-design. The alternate sourcr of power was used to restore the systems to_ their  !

normal configurations. Therefore, there was no significant it,pret 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*).

i I

i 4

,~, g o ~ ~ .u.a.o .. .. .k.s

1. m