ML20099L251
| ML20099L251 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 09/06/1995 |
| From: | GEORGIA POWER CO. |
| To: | |
| References | |
| OLA-3-A-171J, NUDOCS 9512200229 | |
| Download: ML20099L251 (8) | |
Text
Co%g&T l;% Q ;,
,.ev-- TMf
]. j'] y$ ' }ld f C4 !)
s 7.
- l 7l,,d g
z L E R 1 -9 0,6 )'* I Ik'I.'i h.!
Isi-O ;f GPc EXHIBTT 11-1714
- 43
'f WIIB EX. c.10
,,r
- e V
- c. /
-i DOCKETED LOSS OF OFFSITE POWER LEADS TO SITE AREEY$MERGENCY USNRC
~ ~:
- v. ;;7 EVENT DATE: 3-20-90
. p'. i.'
% DCT 20 P3 :08 S.
'.~[5MS-. 00CKETING & SE 0FFICE OF SECRETARY ABSTRACT
%C On 3-20-90, Unit 1 was in a refueling oul5je.and Unit 2BRMsH the 3rs e,. support.l.1ver.of a fuel truck operating at 100% power.
At 0820 CST, fo7;'t he phase
C "
in the switchyard backed into insulator for the Unit 1 Reserve Auxiliary. Transformer (RAT) 1A.
The insulator and line fell;te,. ;,. v. -. 4,
. c a'u s'i n'g a phase to ground fault.
Both Unit 1 RAT 1A and Unit 2 RAT, 28 High Side and Low Side breakers
- tripped, causing a loss
'o f offsite power condition (LOSP).
Unit 1 Diesel Generator (DG) 1A and Unit 2 DG 28 started, but DG1A tripped, causing a" loss of residual heat removal (RHR) to the reactor core since the Unit 1 Train 8
RAT and DG were out of service for maintenance. A,S.ite' Area Emergency (SAE) was declared and the site Emergency Plan;'.was implemented.
The core heated up f rom 90 degrees F.to 1,36 de,grees F before the DG was emergency started at 0856 CST.and.RHR.,,was restored.
At 0915
I ' ' W. ~ ', _.
The direct cause of this series'of.
'even.ts, was a cognitive
(
personnel error.
The truck driver failed to.use proper backing procedures and hit a support, causing the phase.to ground fault and LOSP.
The most probable cause'of the DG1A trip was the intermittent actuation of the DG, Jacket watef temperature switches.
Corrective actions include strengthening policies for control of
6-
'4UCLEAR FICGUI ATOW COMMISSION Docket No. 50-424/425-OtW.
EXHIBITNO. G TC rr-rn 3 in the matter of Genrnia Power Co. et al Vnatie Units 1 & 2 O start g Applicant a w ramr O Othw_
5b s idonesed g) neceived a n.W n porter
\\
Das o9-co-U whness LMw 9512200229 950906 1
92 PROJECT 057604 PDR ADOCK 05000424 h
0 PDR
A.
REQUIREMENT FOR REPORT This event is reportable pers a) 10 CFR50.73 (a)(2)(iv), because an unplanned Engineered Saf ety Feature (ESF) actuation occurred when the ESF Actuation System Sequencer started, and b) Technical Specification 4.8.1.1.3, because a valid diesel generator failure occurred.
Additionally, this report serves as a summary of the Site Area Emergency event.
B.
UNIT STATUS AT TIME OF EVENT Unit 1 was in Mode 6 (Refueling) at 0% rated thermal power.
The reactor had been shutdown since 2-23-90 for a 45 day scheduled refueling outage.
The reactor core reload had been completed, the initial tensioning of the reactor vessel head studs was
- complete, and the outage team was awaiting permission from the control room to begin the final tensioning.
Reactor Coolant System (RCS) level was being maintained at mid-loop with the Train A
Residual Heat Removal (RHR) pump in service for decay heat removal.
The temperature of the RCS was being maintained at approximately 90 degrees F.
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 (DG18) was out of service for a required 36 month maintenance inspection.
The Train 8
Reserve Auxiliary Transformer (RAT) had been
(
removed from service for an oil change. The Train 8 Class 1E 4160 Volt switchgear, 18A03, was being powered from the Train A
RAT 1A through its alternate supply breaker.
All non-1E switchgear was being powered from the Unit Auxiliary Transformers (UAT) by backfeed from the switchyard.
All Steam Generator (S/G) nozzle dams had been removed, but only S/G's 1 and 4 had their primary manways secured.
Maintenance personnel were in the process of restoring the primary manways on S/G's 2 and 3.
RCS level was being maintained at mid-loop for valve repairs and the S/G manway restorations.
In addition, the pressurizer manway was removed to provide a RCS vent path.
C.
DESCRIPTION OF EVENT
- ,n 1
On March 20, 1990, at approximately 0817 CST, a truck driver amt4 d, security escort entered the protected area d"4 d g a fuel truck.
Although not a member of the plant operating staff, the driver was a Georgia Power Company employee belonging to a group under contract to perform various plant services.
t 2
92 PROJECT 057605 I
1Th7 driver, chockod'tha welding mach ne t hat was in the area and found.that
.it did not need fuel.
Ife returned to the fuel truck and was in the process of backing;out of-the area when he hit a
support-Lholding the phase "C"
insulator'for the RAT 1A.
The
' insulator and linegfellste-ths-scound, causing a phase to. ground fault, and the transformer tripped.
At 0820 CST, both Unit 1 RAT' 1 A and the Unit 2 RAT. 28 High Side and Low Side breakers tripped causing a loss of offsite-power condit1on (LOSP)-to'the Unit 1 Train A. Class 1E 4160 volt buss
- 1AA02, the Unit 2 Train 8 Class 1E buss 28A03, and the '480 volt busses supplied by 1AA02 and 28A03.
The Unit 1 Train 8' Class 1E 4160; volt buss 18A03 also lost power. since RAT 1A was feeding both Trains of Class 1E 4160 volt busses.
The. loss of power caused-the associated ESF Actuation System Sequencers to send a
start signal to one Unit 1.and one Unit 2 Diesel. Generators. DG1A i
and DG28 started and sequenced the loads to their respective t
busses.
Further description of the Unit 2 response to this event is provided. in LER 50-425/1990-002.
j!
One minute and twenty seconds after the DG1A engine started and
[
sequenced the-loads to the Class 1E bus,-
the engine tripped.
t This again caused an undervoltage (UV) condition to class 1E bus i
1AA02.
The UV signal is a maintained signal at the sequencer.
I
- However, since DG1A was coasting down from the
- trip, the i
shutdown logic did not~ allow the DG fuel racks or starting air
}
solenoids to open and start the engine.
This caused the engine starting logic to lockup,
.a condition that existed until the UV signal was reset.
For this. reason, D01A did notj re-start by-j
. ;~
h..lf after it tripped.
(,gjs.gg,)
After the trip, operators were dispatched to the engine control I
panel to investigate the cause of the trip.
According to the l
operators, several annunciators 'were lit.
Without fully evaluating the condition, the operators reset the annunciators.
During this time, a Shift Supervisor (SS) and a Plant Equipment Operator (PEO) went to the sequencer panel to determine if any problems were present on the 1A sequencer.
The SS quickly pushed the UV reset button, then reset the sequencer by deenergiring and energizing the power supply to the sequencer.
This caused the air solenoid to energire for another 5 seconds which caused the engine to start.
This happened 19 minutes af ter the DG tripped the,ffggg; time.
The engine started and the sequencer sequenced 2': 4. ;. - as designed.
After 1 minute and 10
- seconds, the Sid # breaker and the engine tripped a second time.
It did not automatically re-start due to the starting logic being blocked as described above.
By this time, operators, a maintenance foreman and the diesel generator vendor representative were in the DG room.
The initial report was that the Jacket water pressure trip was the cause of~the trip.
The maintenance foreman and vendor representative observed that the Jacket water pressure at the i
The trip set point is 6 PSIG and the alarm setpoint is 8 PSIG.
Also, the control room observed a lube
(
oil' sensor malfunction alarm.
1 I
3 92 PROJEGT 057606
Fiftscn minutsa ofter tha escond DG1 A trip, DG1A was started from the engine control panel using the emergency start breakglass button.
The engine started and loads were manually loaded.
When the DG is started in emergency mode, all the trips except four are bypassed.
- However, all alarms will be annunciated.
During the emergency run, no trip alarms were noticed by the personnel either at the control room or at the engine control panel.
The only alarms noted by the control room operator assigned for DG operation were lube oil pressure sensor malfunction and fuel oil level High/ Low alarm.
At 1040
DG1A supplied power to the 4160 volt buss 1AA02 until 1157 CST, at which time the 1AA02 buss was tied to RAT 18.
A Site Area Emergency was declared at 0840 CST, due to a loss of all of f-site and on-site AC power for more than 15 minutes.
The Emergency Director signed the notification form used to inform off-site government agencies of the emergency at 0848 CST and notifications began at 0857 CST.
Due to the loss of power, which rendered the primary Emergency Notification Network (ENN) inoperable, and some mis-communication, the initial notification was not received by all agencies until 0935 CST.
Subsequent notifications were made with~out difficulty.
The Emargency Director instructed persor.nel to complete various tasks for restoring containment and RCS integrity. All work was accomp' dished and maintenance personne" exited containment by 1050 CST.
3 The SAE was downgraded to an Alert Emergency at 0915 CST after restoration of core cooling and one train of electrical power. By 1200
- CST, plant conditions had stabilized with both trains of electrical power being supplied from off-site sources (RAT 18)
After discussions with the NRC and local government agencies, the emergency was terminated at 1247 CST and all agencies were notified by 1256 CST.
D.
CAUSE OF EVENT Direct Causes:
- 1) The direct cause of the loss of offsite class 1E AC power was the fuel truck hitting a pole supporting a 230kV line for RAT 1A.
- DG1A, to start and load the LOSP loads on bus 1AA02.
(
4 92 PRCklECT 057607 l
~
~ -.
b b
Root ~Ceuses t
j ~
1).The truck driver met all current site training and
. qualification requirements.
including holding a
Class 2
Georgia driver's license. EHowever, site safety rules, which h
require-a flagman for backing vehicles when viewing is
' i mpa i red, were violated.
4
.2) The ' root cause' for the failure of DG1A has not been j~'
conclusively dete mined. There is no record of the trips that were' annunciato after the first trip because the annunciators we.
reset before the condition was fully evaluated. Thereisco, the cause of the first trip can only be postulated, but it was most likely-the.same as that-which caused. the second trip.
The second trip occurred at the end of the timed sequence of the group 2 block logic.
This logic allows the DG to achieve operating conditions before the l
trips become active.
The block logic timed out and the trip
^
occurred at, about 70 seconds.
The annunciators observed at l
the-second trip included Jacket water high temperature along with other active trips.
In conducting an investigation, the trip conditions that were observed on the second DG trip on 3-20-90 could be duplicated by venting 2 out of 3
Jacket l
water temperature sensors, simulating a tripped condition.
.The simulation duplicated both the annunciators and the 70 sec.
trip time.
The most likely cause of the DG trips was intermittent actuation of Jacket water temperature switches.
i i
Following the 3-20-90
- event, all three Jacket water temperatura switches;4were bench tested.
Switch TS-19110 was
[
YEEund to Save e
setpoint of 197 degrees F,
which was approximately 6 degrees below its previous setting.
Switch TS-19111 was found to have a setpoint of 199 degrees F, which was approximately the same as the original setting.
Switch TS-19112 was found to have a setpoint of 186 degrees 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 to support diagnostic engine
?
tests and was reinstalled.
The switches were recalibrated with the manufacturer's assistance to ensure a
consistent calibration technique.
During the subsequent test run of the DG on 3-30-90, one of the switches (TS-19111) tripped and would not recet.
This appeared to ggp gan intermittent failure because it a
subsequently 1, reset.
This switch and the leaking switch (TS-19112) were replaced with new switches.
All subsequent testing was conducted with no additional problems, h%
SMt'.
et.
lV ftkp& A 2f5 ltfWT 4
I g p p )ECT O M O
J-
A teet of tha Jackot water system temperature transient during engine starts was conducted.
The purpose of this test was to determine the actual Jacket water temperature at the switch locations with the engine in a normal standby lineup, and then followed by a series of starts without air rolling the engine to replicate the starts of 3-20-90.
The test showed that Jacket water temperature at the switch location decreased from a
standby temperature of 163 degrees F
to approximately 156 degrees F and remained steady.
Numerous sensor calibrations (including Jacket water temperatures),
special pneumatic leak testing, and multiple engine starts and runs were performed under various have been started)9rshb~~!
conditions.
Since 3-20-90, DG1A and DG18 saucrel Ammrs-and no failures or problems have occurred it d C"'
during any of these starts.
In addition, an undervoltage start test without air roll was conducted on 4-6-90 and DG1A started and loaded properly.
Based on the above facts, it is concluded that the Jacket water high temperature switches were the most probable cause of both trips on 3-20-90.
4.
ANALYSIS OF EVENT d
The loss of offsite power to Class 1E buss 18A03 and the failure of DG1A to start and operate successfully, coupled with DG18 and
('
RAT 18 being out of service for maintenance, resulted in Unit 1 being without AC power to both Class 1E busses.
With both Class 1E busses deenergized, the RHR System could not perform its required safety function.
Based on a noted rate of rise in the pect t emperatu r e 4 A 1
- d---^--
maae""-'
c~a
- axit, rhnr w upi-. vrcr
tem. m h ns* = n=M %
the RCS water would not have 9 peen expected to begin boiling until approximately "F
_ 'cua :nd W minutes after the beginning of the event.
8" Restoration of RHR and closure of the containment equipment hatch were completed well within the estimated T.~r end 50 kminutes for the projected onset of boiling in the RCS.
A review of 1
information obtained from the Process and Effluent Radiation Monitoring System (PERMS) and grab sample analysis indicated all normal values.
-As a
result of this
- event, no increase in radioactive releases to either the containment or the environment occurred.
i Q
l c
(g e2 %s*& m& s fk 4 d%M nn..
6 92 PpCT 057609 J
l
Additional cystems woro 01ther available or could have been made available to ensure the continued safe operation of the plant:
- 1) The maintenance on RAT 16 was completed and the RAT was returned to service appecximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> into the event.
- 2) Offsite power was a va i la ble to non-1E equipment through the generator step-up transformers which were being used to "back-feed" the Unit Auxiliary Transformers
{
(UAT) and supply 'the non-1E busses. Provided that the phase to ground fault was cleared, Class 1E busses 1AA02 and 1BA03 could have been powered by feeding through non-1E bus 1NA01.
- 3) The Refueling Water Storage Tank could have been used to manually establish gravity feed to the RCS to maintain a
supply of cooling water to the reactor.
Consequently, neither plant safety nor the health and safety of the public was adversely affected by this event.
A more detailed assessment of this event and an assessment of potentially more severe circumstances will be performed and included in a
supplemental LER.
F. CORRECTIVE ACTIONS 1) a)A management policy on control and operation of vehicles has been established.
s.
b) Temporary barricades have been erected which directs authorization for control of switchyard traffic to the SS.
2) a)The Loss of Off-site Power (LOSP) diesel start and trip logic has.been modified so that an automatic " emergency" start will occur upon LOSP. Therefore, non-essential diesel engine trips are blocked upon LOSP.
The Unit 2 DG's will be modified by 4-30-90.
c,)dThe DG1A est frequency d d- 6h% hd W
once every 7
da in accordance with Taubnical Specification Table 4.
1.
This frequency will be continued until 7 consecutive lid tests are completed with no more than one va'.id failure in the last 20 valid tests.
Including the two valid failures of this event, there have been a total of four valid failures in 4fr valid tests of DG1 Ay af rf f-fp.7d, bj ) Operators d
are being trained prior to their next shift to l
ensure that they understand that an emergency reset will "i Y' M
]
override the high Jacket water temperature trip.
j 3)
Further corrective actions will be addressed in a
q~
supplemental LER.
g (nett4Y
) f'A e UR p,y 9p.ykt. A N 7 gl c
92 PROJECT 057610 s U ks nYY
i 3
i G.
ADDITIONAL INFORMATION i
1.
Failed Components:
Jacket Water High Temperature Switches manufactured by California Controls Company.
Model # A-3500-W3 2.
Previous Similar Events:
None
..'.p' '
l 3.
Energy Industry Ident,1fication System Code:
i l
Reactor Coolant Sy's" tem - A8 Residual Heat Removal System - 8P Diesel Generator,,;1.ube'. Oil System - LA Diesel Generator), Starting Air' System - LC Diesel Generatoc Cooling Water System - L8 Diesel Generatorf.' Power, Supply System - EK Safety Injection'Sy' stem - 8Q 13.8 kV Power System,- EA.
416 0 vol t non-1 E' p'istere system - EA 416 0 vol t,.'C1EdE' 1E"'fower system - EB
~
Chemical and VofusiinPChntr'o1 System - CB
'I Con t a i n me n t..B. u f fdT.n*g't.. NH 480 volt C. lass-Engineered Saf.e.'.1.Powe.r. System - ED
.t,,y,Fe.a..t..
Radiation Monitor ng Sy.ures Actuation System - JE n
- ' ~ 'f{f i,f.-. ' ',- I L stem' y
.i. I(
.u".?l* ?,,d Ny t ;
-.b. ; f,, i" S.'w'.,.
i
<-i
,,..s
.g..
g-f
. ggf..}j.%-
?.j.4.'.:
- i.y l[e;...
p;
.., i. -c
.,. ;.;..... d * [.
_ fy;...e e
~
i
}. -Q.
.' g
. '<,&.'.a e.. +..
%...e..
s
%g.y.y ;...
.e dy.u.'.f,'
.%.,[*-
.t i'-
g.;
.j;g...
-.-t.
y -
,2
.,p.2 g
- 1. <1 -
f.',. 6. ~ <.
- . w n,rq
. s r'.c-2. A
..ea. y.1
. sy?: -
.e-w:
.s 47-
. -A'.l. d.,:.,1 f.,.
- 'e M I<
. ;. s
.. ~., k,, n
'-yf%
,-. 3'
.f 6??
.y c,
.<; r...
p.r
)
Q.,g.m.
LCii(.c?'
' ^'
...s_.,
. v:y%
Q.t-w~
, ' ".. ] :.. -l%g.
. *9%':.
Eh 9..'
L
- } '
- t.*
92 PROJECT 057611
, 7 d *g.:,p.
a4
,n 7
,. tj*, qf, g
" ' 'T &.
sw.r,.. ; e m,.
-