ML20099L239

Applicant Exhibit A-171F,consisting of LER 1-90-6 Re Loss of Offsite Power Leads to Site Area Emergency,

ML20099L239
Person / Time
Site:	Vogtle
Issue date:	09/06/1995
From:	GEORGIA POWER CO.
To:
References
OLA-3-A-171F, NUDOCS 9512200210
Download: ML20099L239 (9)

Text

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LOSS OF OFFSITE POWEg LEADS TO SITE AREA EMERaycb 20 P3:08

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EVENT DATE:

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3-20-90.,~.

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F OF SEC?E'AR

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TRACT

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9-20-90, Unitj.fw wperating at 100% powe., as,,ih a r ueling outa e and Unit 2

was 4

r At 0820 ST, the dei r of a fuel truck in the s witchya rdi. 'bick'ed,fnto support 52 f t.; f 'C' has forthejUn.1 1

insuletor insulator' e6d 14,n,,t.1' Reserve Auxiliary Transformer (RAT) je'f'elT to'the ground, causing a phase to The y

ground fault.!? Botflih4~IRAT 1A and Unit 2 RAT 28 Hhide and Low Side b'r'e'ah t7ippad';'; Eausing a less of offsite power condition (LOSPK,"ET.'te ::;r;,u, Of r: 1 On:r: tere 30'C a

a ta-t"_

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?i t M ;;:f, causing a loss of residual heati removal: (RH

'thefeaictor core since the Unit 1 Train B

RAT; and D0"'were o

.4eFvios for maintenance.

A Site Area I

. implemented. ','Th's[was. ' isFed 'ind the siteEmergency Plan was Emergency (SAE) eaied"Qfi:o 136 degrees F before the 00

~

core i

was emergency]siar ',do' wagrg

. N o'en1 Alert ter onsite power was et'0858 CST'and RH restored.

At 0915 CST, l.the SAE was restored.

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I The direct cause series of evente W e cognitive per s ennel erro frijifdt 1ver failed to use proper backing l

pror sdur es t, th ? C[end ' hit a support, causing the phase l

ta geo.nd f ault"aTdil08P.g. Ths inost probable eause of the / D01 A

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l trip the~ 1'HtA7iiTEtent actuati,on of the Do

.lacket/.w.ater l

temper urs swite

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i Corrective actions-e stre'ngthening policies for control of j

vehicles,. extensi've 't'e~st.ing'of_. the D0 and replacement of suspect A$

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ewitches.

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.,1 f0CIIAR REGULATORY COMMISSION y

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~,,y Docket No. 50-424/425-OLA-3 EXHtBITNO. 6 E IT-Of r

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.f. in the maner of Georola Powse Co. et al Voatie Units t & 2 l(-

) Ostatf [3 Applicant O irdenomr O Otar

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Og identmed g ReceCved O N >cied Nporter 3D

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A. REQUIREMENT FOR REPORT gg This event is reportable peri a) 10 CF

0. rTa (2)(iv), because an unplanned Engineered Safety Feature (ESP) actuation occurred i

when the ESP Actuation System Sequence started, and b) Technical Specification 4.8.1.1.3, because a

diesel generator failure occurred. Additionally, this report a summary of the site Area Emergency event.

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$c/W.s 4J k.. UNIT STATUS AT TIME OF EVEN pjat

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Unit 1 was in Mode 8 (Kefu g) at 0 ed thermal power.

The reactor had bee s utidow" 2-for a 45 day scheduled re-fueling outage, h

eactor ore reload had been completed, the initial possummeo-tensiong he rea vessel head studs was

complete, and the outage team wasl ow ting permission from the control room to begin the final oning.

Reactor Coolant System (RCS) level was being maintained at mid-loop -C""

m with Train A Residual Heat Removal (RHR) pump in service for deca heae removal. 7Jr.Rse temperatur was being maintained at opp oximately 90 degress F.

0f VL-AC.S fQ 1

Due to the refueling outage maintenance activities in

progress, some equipment was out of service and several systems were in abnormal configurations.

The Train 8 Diesel Generator (DG15) was out of service for a required 36 month maintenanc inspection.

The Train B

Reserve Auxiliary Transformer (RAT 18) ad been

_ removad from service for an oil change.

'EEE3iitTh ein 8 Class

/

1E 4160 Volt switchgear.,7 was being powered from the Train A RAT l

1Alffbrough its alternate supply breaker.

A11)f6n-1E switchgear was being powered f rom the Unit Auxiliary Transformer $(UAT).

All (S/0)

removed, but only had the/ozzleffams had been Steam Oferator i

S/O's y1 and ir primary manways secured.

Maintenance personn gelare Qn the process of restoring the primary manways on i

S/G's

...! and $ r.

RCS level was being maintained at mid-loop for M v6 :ve repairs and the S/0 manway restorations.

In addition, j

the pressurizer manway was removed to provide a RCS vant path.

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_he' meF ncy Re ponfo F c111d (Ep) r,4mppergwaf~

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t cov in re iab[e h$ tor %al Mta go the MF J

sit,es d ing thi av t.

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DESCRIPTION OF EVENT l

on Merch 20, 1990, at approximately 0817 CST, a truck driver and i

secursty escort entered the protected area driving a fuel truck.

rAl gh no a me bor of he pla t opor tio a e af,

he de er Q

e a

ear a Po er omp ny emp oyes 10 ing o

oup de on re t

perf rm ar us p1 t ser ce.

Te 1

r's ti M-we e

ual ir om essors and w di ma 1

e taged ro d v

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y-t it for he ute e on U it 1.

H had a

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est thee w

ks.

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2 92 PROJECT 057638

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"; checked the welding d-was in the eres [; "and machine tha t Found that it did not need

, fuel.

He returned to the fuel truel w s in the process of backing when he hit a support holding 1 C'

s insyjetor for4Jw RAT 1A.

The insulator and line fell to t e ground., seusing l

a phase to ground fault, and the transformer tripped.,.,

,, ht 0920 CST, both RAT 1A and the Unit 2 RAT $1 Hh e

an Low j

41de breakers tripped causing a loss f offs to power c

ition l

• i(LOSP) to the Unit 1 Train A Cla 416 c1% gu's 1AA02,

i the Unit 2

Tr9 n & Cla s 1E gu 2BA0 and the 40 volt 1

busses supplieM 1AA nd 28A03.

The Unit 1 Train 8 Class 1E 4160 volt bueF( 15A03 elso lost power since RAT 1 A was feeding both Trains of Class 1E 4160 volt busses.

The loss of power caused the associated ESF Actuation System Sequencers to send a I

start signal to Unit 1 and Unit 2 Diesel Generators.

D01A and DG2B started and sequenced the loads to their respective busses.

Further description of the Unit event is d-r ^L:favj&

d in LER 50-425/1990-002.

ye gg. (, g I

one minute and twenty seconds efter the D01A engine started nd l

sequenced the loads to the Class 1E bus, the engine trip ed.

l This again caused an undeOoltage (UV) condition to slass 1 bus 1AA02.

The estdeemesse+ UV signal is a saintained signal a the i

sequencer.. t^'i ___..: + W e=eees&-r d'-

=*7 ' Ord./[,

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ince t

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D01 A was coasting down from the trip, the shutdown logic d d not ellow the 00 fusi racks or starting air solenoids to open and start the engine.

This caused the engine starting logic to loc I

l up, a

condition that existed until the UV signal was resete. emf i

- A, i lea.'

For this reason, DG1A did not re-start by itself after it tripped.

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t After the trip, operators were dispatcho to the engine control panel to investigate the cause of the tri.

According to the j

j ope ra tors,

seversi ennunciators were lit.

Without fully evaluating the condition, the operators eset the annunciators,

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j 1;amba-aosweeedy During this time, a ShAft Supervisor (SS) and 4

' Plant Equipment operator (PEO) went to the sequencer panel to j c(r. k o rits f > "

r if any problems were present onu1A sequencer.

The 88 quickly pushed the UV reset button, then reset the sequencer by deoe.o rgiring and energiring the power supply to the sequencer.

1 This caused 'h:

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dase the air solenoid to energire for another 5 seconds which

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saused the engine to start.

This happened 19 minutes af ter the j

D0 tripped the first ties.

The engine started end the sequencer eequenced the loads as designed.

Af ter 1 minute end 10 seconds, the breaker and the engine tripped a second ties. 9Mt did not 4

j trastert huuNt due to the starting 1o01o being blocked,es described l

ebove.

this time, operators, a maintenance foreman and the j

l diesel g erator vendor representative were in the DG room.

The initial report was that the Jacket, water pressure trip i

wf

• r weee the cause of the trip.

The maintenance d

q 92 PROJECT 057639

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'forcm:n cnd vondor rcprosontotive obsorv0d that tha jackot catcr prosauro at tha gaugo was about 12-13 PSIG.

Th3 trip tot point is 6 pSIG and the e1erm satpoint is O PSIO.

Also, the control room observed a lube oil sensor malfunction alarm.

Fif teen minutes af ter the second DGI A trip, DG1A was started from the engine control panel using the emergency start treakglass button.

The engine started and loads were manually 1 dad.

When the DG is started in emergency mode, all the trips capt four are bypassed.

However, all alarms will be annunctated.

During the emergency run, no trip alarms were noticed by the personnel either et the control room or at the engine control panel.

The only alarms noted by the control room operator assigned for DG Wam were lube oil pressure sensor malfunction and fuel oil level High/ Low alarm.

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- 4 Site Area Emergency was declared at 0840 CST, due to a loss of all off-site end on-site AC power for more than 15 minutes.

The Emergency D, rector signed the notification form used to inform oft Osite government agencies of the emergency at 0848 CST and notifications began at 0057 CST.

Due to the loss of powery and i

eome mis-communication, the initial notification was not rece ived by all agencies until 0935 CST.

Subsequent notifications were made without difficulty.

which nstden/Ne n,nc fs waone Ab//A kA k W Wl hV%df-The Emsegency 1rache insTruc ed personnel to complete va$1ous tasks for restoring containment and RCS integrity. All work was l

eccomplished and maintenance personnel exited containment by l

1050 CST. a/;eyin/prafien af cut co*//D s4a!w Min d f )

i ekcuiu/pr wW 3

l The SAE was downgraded to an Alert Emergency a[0915 CS. By 1200 l

CST, plant conditions had stabilized withe 7

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tirect:r dadtieted

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c..com.ni g

y tr:iS5 tS-dd ?CUSO terThetieri GI-the 0.?:rgerOy.

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vesed -d o th:.1 Age::mera wa. rs.wl.d ith :11 g,e r u d.

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emerwensy

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• e -dne+++. g,The emergency was 1247 CST andYagencies werepotified by 1256 CST. g terminated at kNW OWH/MJ LJiH Me AMC ad /scelgnmimf quictQ y

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CAUSE OF EVENT M Direct Causes g

i e direct cause of the lose of of to class 1E AC power h{

j was the fuel truck hitting a polo supporting a 430kV line f or RAT 1A, w H : h-::.1.ae H M e 1er O f e##-3* m y,

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g,h The direct cause of the loss of ogito class 1E power ki was the f ailure of the operable DQ,

DG1A, to start nd load the 4g g

6 92 PR061ECT 057640

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92 PROJECT 057641 i

LOSP loodo en bua 1 AA02.

M Root Causes

[

e truck driver met all current site training and qualific'ation requirements, including holding a

Class 2

Georgia driver's license.

However.

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site safety rule

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"h when viewing is tog a f1agman for backing, vehicles paire were violated.

c pfy JueguafAe wude,:r wac gf(a,si:no e M a7//h 2,

he root cause for the failure o

D01A conclusively determined. There is no een were annunciated af ter the first tri ocord of the trips that 3 A trip can e -ic. only be postulated,7he cause of the first

/

but rmost 'likely 4=ee N

y gg

_ the.same m:t

- ; ;; es#the second trip.

The second trip case. d -

occurred at ene end of the timed sequence of the the DG to er-cgroupp:: a44/cu.

block logve.

This logic ;r-operating conditions before the tr1ps become active.

The gg block logic timed out and the trip occurred at about 70 seconds.

The annunciators observed at the second trip included Jacket water high temperature along with other active trips.

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re-a.f trip.

In conducting erl

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tions that were. observed on the second 00 trip o

O essentially

00:td i{

venting 2 out of 3dtemperatur

sensors, simulating a trippedby gg.g{

i condition.

The ra: rec.^.ier. d p11cated both the I

annunciatore and the 70 sec, tr' pt lee.

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,)Followingtadttd* W$ter -

1 t-J4skstw&hmenhw-l t-the 3-20-90 eve lnt, all thraelswitches were bench l

N tested.

Switch TS-19110 was found to have a satpoint of 197 i

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degress F,

which 9

was approximately 6 degrees below ite previous setting.

Switch TS-19111 was found to have a

i setpoint of 109 degrees F, which was approximately the as the original setting.

Switch TS-19112 was found to have a same f

setpoint of 186 degrams F which was approximately 17 degrees F below the previous setting and was re-adjusted.

Switch TS-19112 also had a small leak which was judged to be acceptable j

to support diagnostic engine tests and was reinstalled.

j%

switches were recalibrated with the manufacturer's assistance The Q.

to ensure a consistent calibration technique.

I During the subsequent test run of the D0 on 3-30-90, one of the switches (TS-19111) tripped and would not reset.

This a ppeared to be an intermittent failure because it S

aubsequently reset.

This switch and the leaking switch p\\.

(TS-19112) were replaced with new switches.

All testing was conducted with no additional problems,; subsequent

)(

A test of the Jacket water system temperature transient o

during engine starts was conducted.

The purpose of this test i

was to determine the actus1 Jacket water tamparature at t he 5

92 PROJECT 057642 i

4

4

.i owitch locations with the ongino in o noraal standby lineup,

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and then followed by a series of starts without air j

the engine to replicate the starts of 3-20-90.

The test i

rolling showed that Jacket water temperature at the switch location decreased from a

standby temperature of 163 degrees F

to approximate 1y 156 degrees F and remained steady.,

Numerous sensor calibrations (including Afsyket water i

temperatures),

special pneumatic leak testing, M undend multiple i

4 engine starts and runs were performed r

various conditions.

Since 3-20-50, 001A and D018 have been started 4

j.

r' several times and no failures or problems have occurr'ed during any of these starts.

In addition, an undervoltage start test without air roll was conducted on 4-6-90 and 001A started and ioaded proper 1y.

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Based on the above facts, it is concluded that the Jacket high temperature switches were the most probable cause water j

of both trips on 3-20-90.

4.

ANALYS!8 DF EVENT fhG The loss of offsite power to 9dar Class IE bus 18A03 and/ fa11ure I

of 001 A to start and operate successfully, coupled with 001B and RAT 18 being ou of service for maintenance, resulted in Unit 1 being without power to both Class 1E busses.

Wi g bo less if 1E busses de energized, the O__ : d. _ " "::t *.L

. 1 CRH System oculd not perform its required safet'y function.

Based on a noted rete of rise in the RCS temperature of 16 degrees F, measured at the core exit thermocouples over a fif teen minute period, the RCS water would not have been expected to begin boiling until approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 50 minutes after the beginning of the

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and clos e

i of the containment equipment hatch were completed e44mw-i

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$: h well within the estimated 1

hour 50

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m_inuteep $242, iv the projected onset of boiling in the RCS.

A i

review of information obtained from the Process and Effluent Radiation Monitoring System (PERMS) and greb sample analysis 1

indicated all normal values.

As a result of this

event, no

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increase in radioactive releases to either the i

l containment or the environment occurred.

Additional systems were either eve 11eble or could have been made available to ensure the continued safe operation of the plants i

f, he maintenance RAT 18 was completed and the RAT 8415 returned to service,onapproximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> into the event.

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92 PROJECT 057643 6

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fMvided Hnf y444. pd4se hj(Nnp{$rv/

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ffo1to pawor wso ovo11ablo to f(on-1E e u1pment through the generator step-up transformers wh h

were being used to "back-feed

• the Unit Aux 111 ry Transformers 4

(UAT) and supply the fon-1E busses.

Class 1E busses 1AA02 and 16A03 could have been powered by feeding j

i through/f'on-1E bus 1NA01.

i c) The Refueling Water Storage Tank could have beEn used to

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i manually establish gravity feed P : ;.'

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to the RCS to maintain a

s supply of cooling

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"* water to the reactor.

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Consequently, neither plant safety nor the health and safety of the public was adversely affected by this event.

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F. CORRECTIVE ACTIONS A

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dr er ice re u re e ts 11 b ch n ed

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eurmn y

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Sensitive and uln rabi areas ins de the the protected will be evaluated by 7-1-90 and appropriate barriers erecced area or controls established.

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din / mise.

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g a Loss of of f71te Power (LOSP) diesel start and trip logic has been ur upon LOSP. ThenO% Y #f'tNANdlMYJmodified so that an auto l

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G operating procedures will be revise to

.inc1 specific instructions for restarts following a D

trip during LOSR by f ghpera; tor

~-1^.

7-/-fd guidance on recording per inent alarms and indications is being developed in order to assist in investigations of future plant events and will be in place by p1-90.

b

$' he DG1A test frequency will ba increased to once every 7 days in accordance with Technical Specification Table 4.8-1.

This frequency will be continued until 7 consecutive valid tests i

l are completed red ;..d one W valid failures h...

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in the last 20 valid tests.

Including thest two valid failures t

ce have been a total of four valid failures in 88 l

valid t sto f DG1A.

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92 PROECT 057644 7

4

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O. ADDITIONAL INFORMATION

1. Failed Components:

Jacket Water High Temperature Switches manufactured by California Controle Company.

Model # A-3500-W3 5,-

2. Previous Similar Events:

Nons

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3

.4.

4I 4-

3. Ensegy Industry Identification System Code:

4 i

Reactor Coolant System - AD xs_s-.~

y -

Residual Heat Removal System - BP Diesel Generator Lubs 011 System - LA Diesel Generator Starting Air System - LC Diesel Generator Cooling Water System - LB Diesel Generator Power Supply System - EK Safety InJoction System - SQ 13.8 kV Power System - EA 4160 volt non-1E power system - EA 4160 volt' Class 1E power system - EG chemical and Volume control System - CB Containment Mu11 ding - NH 480 volt class 1E Power System - ED Engineered Safety Features Actuation System - JE

=R 12.-M **;e Syst::

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3 L'u: 12:r 2_.;-i;. -;. ".ing Wet _

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0; -

Radiation Monitoring System - IL f

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92 PROJECT 057645

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