ML20086A611
| ML20086A611 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 05/17/1995 |
| From: | Hairston W GEORGIA POWER CO. |
| To: | |
| References | |
| OLA-3-I-MOSBA55, NUDOCS 9507030309 | |
| Download: ML20086A611 (9) | |
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April 19, 1990 v.h f' : "' "
0FFICE OF SECRETARY ELV-01545 30 00CKETING & SERVICE 0342
. $3 BRANCli j?'!.
49 Docket No. 50-424 TR U. S. Nuclear Regulatory Comission Document Control Desk 2
ATTN:
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Washington, D. C.
20555
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~ Gentlemen:
I I V0GTLE ELECTRIC GENERATING PLANT LICENSEE EVENT REPORT 4
LOSS OF OFFSITE POWER LEADS TO SITE AREA EME i
I In accordance with 10 CFR 50.73, Georgia Power Company hereby s t
i 20, 1990.
enclosed report related to an event which occurred on March j
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Sincerely, O )i J..$ bAi W. G. Hairston, III WGH,Ill/NJS/gm
Enclosure:
LER 50-424/1990-006 xc: Georcia Power Comoany Mr. C. K. McCoy Mr. G. Bockhold, Jr.
Mr. R. M. Odom Mr.. P. D. Rushton NORMS U. S. Nuclear Reculatory Comission Mr. S. D. Ebneter, Regional Administrator Mr. T. A. Reed, Licensing Project Manager, NRR Mr. R. F. Aiello, Senior Resident Inspector Vogtle NUCLEAR REGULATORYCOMMIS$10N DR DO O O 0424 O
PDR Co-nu.eL4-3 Docket No. ## - "5<4 4 -3 Official Exh. No. M+ 6f i
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On 3-20-90, Unit I was in a refueling outage and Unit 2 was operating at 100%
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At 0820 CST, the driver of a fuel truck in the switchyard backed into a support for the phase 'C" insulator for the Unit 1 Reserve AuxiliaryThe in power.
Transformer (RAT) 1A.Both Unit 1 RAT 1A and Unit 2 RAT 2B High Side and Low S f ault.
Unit I Diesel tripped, causing a loss of offsite power condition (LOSP).
Generator (DG) 1A and Unit 2 DG2B started, but DG A Site Area Emergency (SAE) was DG were out of service for maintenance.
The Reactor Coolant declared and the site Emergency Plan was implemented.
System heated up to 136 degrees F from 90 degree F before the DG was em l
The initial notifications were not started at 0856 CST and RHR was restored.
made within the required 15 minutes due to the loss of power to the Emergency i
At 0915 CST, the SAE was downgraded to an Alert Notification Network (ENN).
after onsite power was restored.
The The direct cause of this series of events was a cognitive personnel error.
truck driver failed to use proper backing procedures and hit a support, causin the phase to ground fault and LOSP. The most probable cause of the DGIA was the intennittent actuation of the DG jacket water temperature switches.
Corrective actions include strengthening policies for con improvements in the ENN system.
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REQUIREMENT FOR REPORT a) 10 CFR 50.73 (a)(2)(iv), because an i
unplanned Engineered Safety Feature (ESF) actuation occurre This event is reportable per:
,i Actuation System Sequencer started, and b) Technical Specification Additionally, 4.8.1.1.3, because a valid diesel generator failure gs 1
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UNIT STATUS AT TIME OF EVENT m.v?
The reactor had
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Unit I was in Mode 6 (Refueling) at 0% rated thermal power.
The been shut down since 2-23-90 for a 45 day scheduled refueling outage reactor core reload had been completed, the in d%
&"1 Reactor permission from the control room to begin the final tensioning.
f Coolant System (RCS) level was being maintained at mid-loop The
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fi temperature of the RCS was being maintained at approximately j
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Due to the refueling outage maintenance activities in progress, some equipment was out of service and several systems we b
The Train B Reserve Auxiliary configurations.
a required 36 month maintenance inspection.
i Transformer (RAT IB) had been removed from se l
All non-lE switchgear 1
Train A RAT 1A through its alternate supply breaker.
was being powered from the Unit Auxiliary Transformers (UAT) b l
All Steam Generator (S/G) nozzle dams had been from the switchyard. removed, but only S/G's 1 and 4 had their primary Maintenance personnel were in the process of restoring the primary m RCS level was being mainta1ned at mid-loop for valve
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in addition, the pressurizer on S/G's 2 and 3.
repairs and the S/G manway restorations, j
manway was removed to provide an RCS vent path.
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C.
DESCRIPTION OF EVENT at approximately 0817 CST, a truck driver with a se On March 20, 1990, escort entered the protected area in a fuel truck.
l the plant operating staff, the driver was a Georgia Power Compa The
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belonging to a service group used to perform various plant services.
driver checked the welding machine that was in the a i
i did not need fuel.
backing out of the area when he hit a support holding the p insulator for RAT 1A.
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fault, and the transformer breakers tripped.
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~ ~ m u.m r Exhibit 6,page fid At 0820 CST, botn Unit 1 RAT 1A and the Unit 2 RAT 28 High Side and L Ef]
i to the sy breakers tripnd causing a loss of offsite power condition (LOSP) lass IE Unit 1 Train A Class IE 4160 volt Bus 1AA02, the Unit 2 Train B C
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j The Unit I Bus 2BA03, and the 480 volt busses supplied by 1AA02 and 2BA03.
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U~ f Train 8 Class IE 4160 volt bus IBA03 also lost power since RAT 1A wasThe feeding both Trains of Class 1E 4160 volt busses.
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the associated ESF Actuation System Sequencers to send a start signal t l
DGIA and DG2B started and i
one Unit I and one Unit 2 Diesel Generators.
Further description of the j
t sequenced the loads to their respective busses. 50-425/1990-002.
Unit 2 response to this event is provided in LER l
j One minute and twenty seconds after DGIA started and sequenced the lo This again caused an undervoltage l
the Class IE bus, the engine tripped.
The UV signal is a maintained signal j
(UV) condition to class IE bus 1AA02.However, since DGIA was coasting d shutdown logic did not allow the DG fuel racks or starting air solenoids to at the sequencer.
j This properly caused the engine starting logic l
open and start the engine.
For to lock up, a condition that existed until the UV signal was reset.
i this reason, DGIA did not automatically re-start after it tripped.
l After the trip, operators were dispatched to the engine control panel to According to the operator, several l
investigate the cause of the trip.The operator briefly reviewed several instrum j
annunciators were lit.
In order to restore emergency read-outs and detected no immediate problem.
l power, the operator reset the annunciators without delaying to evaluat record the annunciators that were present. During this time, a Shift i
Supervisor (SS) and a Plant Equipment Operator (PEO) went to the sequenc The SS panel to determine if any problems were present on l
j energizing the power supply to the sequencer. solenoid to energiz The engine This happened 19 minutes after the DG tripped the first time.
After started and the sequencer sequenced the available loads as designed.
I minute and 10 seconds, the breaker and the engin By this time, operators, a maintenance foreman and the The initial described above.
diesel generator vendor representative were in the DG room.
i report was that the jacket water pressure trip was the cause of the trip.
l This report was discounted because the maintenance foreman and vendor l
representative observed that the jacket water pressure at the
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about 32-13 PSIG.
Also, the control room observed a lube oil sensor malfunction alarm.
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Fifteen minutes after the second DGIA trip, DGIA was started from the e The engine l
$q control panel using the emergency start breakglass button.When the DG is s started and loads were manually loaded.
However, all alarms
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fg a emergency mode, all the trips except four are bypassed.Durin 1
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by the personnel either at the control room or at the engine contro g
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The only alarms noted by the control room operator assigned for DG C'
b were lube oil pressure sensor malfunction and fuel oil level high/ low v
neither of which would have tripped the diesel.
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i At 1040 CST, RAT 1B was energized to supply power to 4160 volt bus l
i DGIA supplied power to 4160 volt bus lAA02 until 1157 CST, at whic lC p
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1AA02 was tied to RAT 18.
l A Site Are: Emergency was declared at 0840 CST, due to a loss of all gi The Emergency offsf te and onsite AC power for more than 15 minutes.
Director signed the notification form used to infom offsite government The shift clerk attempted to agencies of the emergency at 0848 CST. initiate offsite notific The shift clerk then went to but found it inoperable due to loss of power.the back-up ENN Due to the loss of power, which rendered the primary Emergency Notification Network (ENN) inoperable, and some mis-comunication, the 0857 CST.
O initial notification was not received by all agencies until 0935 CST.
The Emergency Director instructed personnel to complete various task All work was accomplished and restoring containment and RCS integrity.
maintenance personnel exited containment by 1050 CST.
The SAE was downgraded to an Alert Emergency at 0915 CST after res By 1200 CST, plant of core cooling and one train of electrical power.
conditions had stabilized with both trains of electrical power beingAfte supplied from an offsite source (RAT 1B).and local governme all agencies were notified by 1256 CST.
D.
CAUSE OF EVENT Direct Cause:
The direct cause of the loss of offsite Class 1E AC power was the fue This was a truck hitting a pole supporting a 230kV line for RAT 1A.
1.
There were cognitive personnel error on the part of the truck driv contributed to this personnel error.
The direct cause of the loss of onsite Class IE AC power was the failur l
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of the operable DG, DGIA, to start and load the LOSP loads on buss O,i IAA02.
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., nn The direct cause of the failure of the primary ENN system in theThe primar p
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=r control room was the loss of electrical power to Unit 1.
ENN in the control room is powered from Unit 1 Class IE AC power.
Therefore, when Unit 1 lost Class 1E AC electrical power, the primaryb I
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(k ENN in the control room did not work.
y.2 Root Cause:
f The truck driver met all current site training and qualification requirements, including holding a Class 2 Georgia driver's license.
1.
'Sf M.l However, site safety rules, which require a flagman for backing O_
vehicles when viewing is impaired, were violated.
a The root cause for the failure of DGIA has not been con 2.
after the first trip because the annunciators were reset before determined.
condition was fully evaluated.
can only be postulated, but it was most likely the same as that which The second trip occurred at the end of the caused the second trip.
This logic allows the DG to timed sequence of the group 2 block logic.
The block achieve operating conditions before the trips become active.
O The logic timed out and the trip occurred at about 70 seco In conducting an investigation, temperature along with other trips.the trip conditions that were could be duplicated by venting 2 out of 3 Jacket water temperatureTh sensors, simulating a tripped condition.
The most likely cause both the annunciators and the 70 sec. trip time.
4 of the DG trips was interinittent actuation of the jacket water
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temperature switches.
Following the 3-20-90 event, all three jacket water te l
Switch TS-19110 was found to have a setpoint of 197 degrees F, which l
Switch was approximately 6 degrees below its previous setting.
l TS-19111 was found to have a setpoint of 199 degrees F, which was Switch TS-19112 was approximately the same as the original setting.found to ha Switch degrees F below the previous setting and was re-adjusted.
i TS-19112 also had a small leak which was judged to be acceptable to The switches were support diagnostic engine tests and was reinstalled.rec calibration technique.
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During the subsequent test run of the DC on 3-30-90, one of theThis ap m
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switches (T5-19111) lure because it subsequently mechanically reset.
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All subsequent testing was conducted with no additional U)
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problems.
l A test of the jacket water system temperature transient during engine]
The purpose of this test was to determine the l
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actual jacket water temperature at the switch locations with the enginej
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s.g in a normal standby lineup, and then followed by a series of starts i
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The without air rolling the engine to replicate the starts of 3-20-90.
I-test showed that jacket water temperature at the switch location o
T' decreased from a standby temperature of 163 degrees F to approxima J
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156 degrees F and remained steady.
Numerous sensor calibrations (including jacket water temperatures),
special pneumatic leak testing, and multiple engine starts and runsA were performed under various conditions.
control systems of both engines have been subjected I
started at least 18 times each and no failures or problems have test program.
In addition, an undervoltage occurred during any of these starts. start test without air roll wa 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.
E.
ANALYSIS OF EVENT The loss of offsite power to Class IE bus IBA03 and the failure of DGIA to start and operate successfully, coupled with DGIS and RAT IB being out o service for maintenance, resulted in Unit I being without AC power to both With both Class IE busses deenergized, the RHR System Based on a noted rate of Class IE busses.
could not perform its required safety function.
rise in the RCS temperature of 46 degrees F in 36 minutues, the RCS water would not have been expected to begin boiling untti approximately I ho 36 minutes after the beginning of the event.
Restoration of RHR and closure of the containment equipment hatch were j
completed well within the estimated I hour and 36 minutes for the p A review of information obtained from the onset of boiling in the RCS.
and grab sample Process and Effluent Radiation Monitoring System (PERMS)is event, no As a result of th i
analysis indicated all normal values. increase in radioactive relea Ol:
i environment occurred.
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Additiona'l systems were either available or could have been made available
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to ensure the continued safe operation of the plant:
.j Mi The maintenance on RAT IB was completed and the RAT was returned to
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service approximately 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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.s Offsite power was available to non-1E equipment through the generator oQ 2.
step-up transformers which were being used to "back-feed" the Unit I
Provided Auxiliary Transformers (UAT) and supply the non-IE busses.
SL that the phase to ground fault was cleared, Class IE busses IAA02 and 1,
IBA03 could have been powered by feeding through non-IE bus INA01.
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The Refueling Water Storage Tank could have been used to manually 3.
i 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 A more detailed assessment of this was adversely affected by this event.
O event and an assessment of the event had it occurred under more severe circumstances will be performed and included in a supplemental LER.
F.
CORRECTIVE ACTIONS A management policy on control and operation of vehicles has been 1.
established.
Temporary barricades have been erected with signs which direct 2.
authorization for control of switchyard traffic to the SS.
The Loss of Offsite Power (LOSP) diesel start and trip logic has been 3.
modified on Unit I so that an automatic ' emergency" start will occur i
upon LOSP. Therefore, non-essential diesel engine trips are blocked upon LOSP. The Unit 2 DG's will be modified by 4-30-90.
The DG1A test frequency was increased to three times per week until 4.
4-20-90 when the test frequency will be changed to once every 7 days in accordance with Technical Specification Table 4.8-1.
This frequency will be continued untti 7 consecutive valid tests are completed with no 2
more than one valid failure in the last 20 valid tes~ts.
Including the two valid failures of this event, there have been a total of four valid
.t failures in 69 valid tests of DGIA as of 1157 CST cn 3-20-90.
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@ Fmm. guns e aussunt aus asemer mulC Are mW 1178 erature switches have been replaced. In addition, ThedefectiveDGtembeconductedatWyleLaboratoriestoinvestigatethe g
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a test program will reliability of this type of temperature switch under various conditions.
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A back-up ENN system powered from the AT&T system, which previously
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existed and was operational for South Carolina agencies, has beenInstructi co extended to include Georgia local and state agencies.
l been given to Emergency Directors and Comunicators concerning use of j
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I 4-Further corrective actions will be addressed in a supplemental LER.
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ADDITIONAL INFORMATION I
1.
Failed Components:
Jacket Water High Temperature Switches manufactured by California i
il Controls Company.
Model fA-3500-W3 j
i, 2.
Previous Similar Events:
i None Energy Industry Identification System Code:
3.
Reactor Coolant System - AB kesidual Heat Removal System - B Diesel Generator Lube Oil System - LA l
Diesel Generator Starting Air System - LC Diesel Generator Cooling Water System - LB Diesel Generator Power Supply System - EK l
Safety Injection System - BQ 13.8 kV Power System - EA j
1460 volt non-lE power system - EA 1460 volt Class IE power system - EB Chemical and Volume Centrol System - CB Containment Building - NH 480 volt Class IE Power System - ED Engineered Safety Features Actuation System - JE Radiation Monitoring System - IL l
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