ML20092F793
| ML20092F793 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon, Vogtle  |
| Issue date: | 03/02/1989 |
| From: | Brown R GEORGIA POWER CO. |
| To: | |
| Shared Package | |
| ML20092F288 | List:
|
| References | |
| CON-IIT05-002-131D-90, CON-IIT5-2-131D-90, RTR-NUREG-1410 LO-LP-60990-02, LO-LP-60990-2, NUDOCS 9202190506 | |
| Download: ML20092F793 (10) | |
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LESSON FORMAT A.
Lecture with Visual Aids MATERIALS A.
Overhand Projector D.
Student Handout C.
Dry Erase Board and Markers EVALUATION A.
Written or oral exam in conjunction with othar lesson plana IV. REMARK 5 A.
This t.P satisfies the requirements of the commitments listad on the Ref erence Page of this LP.
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PURPOSE STATEMENT:
This case study is desig1ed to pt* ovide underett9 ding of th~e~~eWnTe T5T5TMg up sui l
during, and the corractihe actions associated with the loss of RFA cooling at i
Diadio Canyon.
Included.in tha case study are the act. ions taken at Plant Vogtle to reduce thJ possibility of a similar event occurring.
I b.
LI.S._T OF OBJECTIVES:
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1.
Describe briefly the initial conditions for operating with the RCS at utri-loop.
2.
List the instrumentation used to monitor RCS level khen operating at mid-loop.
i 3.
List thra ins'srumentation used to monitrr RCD temparature when operating at mid loop.
4.
Discuss the svents that led to the loss of RvW cooling at Diablo Canyon.
5.
Cescribe ths' actions that the operators took to nitig6te the loss of RHR coo!!ng.
6.
Describe the poss!ble crmequernces that could result from a loss of RHR cooling.
7 Describe actions taken to reduce the proaability of e similar event froa occurring at Plant Vogtle.
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LO-LP-60990-03-C s
REFERENCES:
1 NUREG 1269 LGBB 0F RHR SYSTEM 2.
IEN 07-23 LOSS OF DECAY HEAT REMCVAL DlRING LOW REACTOR COOLANT LGVEL OPERATION 3.
GENERIC LETTEN 87-12 LOSS OF RHR WHILE THE RCS IS PARTIALLY FILLED 4
PROCEDURER i
12000 REFUELING RECOVCRV i
12006 - UNIT C00LDOWN TO COLD BHU1DOWN 12007 - REFUELING ENTRY 13005 - REACTOR LOOLANT SYSTEM DRAINING-5.
GENERIC LETTER 88.017 NRC CONCERNB AND ACTION ON LOSS OF RHR 6.
GENERIC LETTER 87.012 VEEP RESPONSE TO GL-87-12 7.
BOE. 96.003 LOSSES OF RHR WITH REDUCED VESSEL WATER LEVEL AT e
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LO-LP-60990-01-C s
111. LESSON. OUTLINE:
NOTES INTRODUCTION i
A.
This case study eatorial covers a loss of residual heat removal during mid-loop operation nd the phenomena inf.luencing that bahavior at PG&E's Diablo Canyon Unit #2.
i 1.
37 additional events have occurred that are attributed to inadequate RCS water level.
2.
Coro damage or a release to the environment could have occurred.
1
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SUMMARY
A.
PGLE's Diablo Canyon linic #2 1.
Four loop Westinghouse 1119 MWe PWR - same as Vogtle 2.
Good initial operating history B.
Reactor ir. Mode 5 i
1.
7 days after shutdown for its first refueling outage l
2.
A loss of both RWt trains occurred for approximately 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> C.
Complications affacting the loss of RWt cooling 1.
Hemoval of the containment equipment hatch trolease path to the environment) 2.
RCH hot leg old-loop level operation 3.
Steam generator 'eanway removal in prn*;rcas during the event 4.
The reactor coolant heated froe 87". F to boiling '
i 5.
Steam nas vented from the RV head i
4.
Water spilled from the partially unsealed 86 manways 7.
Containment rJdiugas activity was observed to increase 4
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LO-LP-609GO-01-C r
i 111. LESSON.OQTLINE:
NOTES
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DETAILED EVENT DESCRIPTION A.
Initial Conditions i
1.
Mode 5 i
2.
The containment building equipment hatch was removed t
3.
The personnel airlock was open l
4.
Containment purge was in progress 5.
Removal of steam generator manways was in i
progress 6.
Local leak rate testing of containment penetrations was in progress 7.
The RHR pump 2-1 was operating through both RHR hwat exchangers, both trains were cross connected B.
The RCS was draiated down to the mid-loop level 9.
RV level was being monitored bya
- a. A tygon tube mancaster inside containment
- b. 2 electrical systems (a wide and narrow range) c.
Normal RVLIS was out of service 10.
The RV was vented to the pressucitor 11.
The 81 pumps circuit breakers were racked out 12.
RV level maintained bye u.
Sending excess rator to the RMST b.
Makeup from the RWST nV. EVENT INITIATION A.
A plant engineer opened a valve to perform a local leak rate test, creating a leak from the RCS B.
Loss of RHR cooling
- 1.. RHR pump began cavitating l.
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LO-LP 60090-01-C lil? LESSON O_UTLINE:
_ NOTES
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2.
Operator shutdown the running pump 3.
Operator started and then shutdowts the
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standby puir.p I
a.
It also cavitated 4.
RHR ccoling capability lost a.
No method of monitoring incore temperaturen b.
Validity of the temporary RV level i
indication suspecteci i) Operator dispatched to check local RV tygon tube indicaticn 5.
Operator attempted to verify RCS integrity 6.
Operators attempted to stop leak 7.
NOUE declared t
C.
Leak stopped af ter appronisately 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> by engineer 1.
Operators refilled the system from the RWT via a RHR pump
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FUNDAMENTAL CAUSES I.NO DISCUSSION TOPICS l
A.
RV level indication s,ystes problems B.
!sproperly seated valve C.
Operator awareness of evolutions 1.4 progrnes D.
Containment integrity problems j
E.
Mid-loop coeratioc.
F.
Instrumentation l
G.
Communications H.
Event Classification VI. POST-EVENT TECHNICAL AND ADMINISTRATIVE INVESTIGATIVE I
ACT!DNS TAKEN AT PLANY V0GTLE A.
Several procedure-related deficiencies were identified and corrected 6
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F to-te-6o,9o-oi-c I
111. LESSON OUTLINE:
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NOTES 0.
Hardware Changes Vlt.
PROBLEM UPDArdB A.
GL-80.o!4 Loss of Decay Heat Removal 1.
Significant new inf ormation has been generated since the Diablo Canyon event, April 10, 1987 a.
Sevarat previously unrecc;Jntred phe.3omena need to be addressed.
i 11 Some of these realistically can cause core uncovery or complete core voiding in less than half an hour (previously believed that 4 houre would be i
required),
- 2) New phenomena not previously understood l
a) Pressurtsstion (1) Caused by steam formation in utivented resetor vessel (2)
Inappropriate use of BG nozzle das can lead to core voiding within 15-20 minutes following loss of RHR
" (3) Cold leg opening can allow water to be ejected froe-vessel following loss of RHR until sufficient water is inet that steam is relievc4 by clearing the crossover pipes i
(4)
Pressure difference within RCS 1
may prevent water from reaching the RV (5) Rapid RCS-pressurization eay
. prever.t gravity f eed from tanks anticipated to be available (6) Rapid pressurization may cause inst.ruments to nelfunction or provide aisleading indications l
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LO-LP-60990-01-C Ill.
LESSON. OUTLINE:
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NOTES (7) Rapid pressurization may causs the RCS to respond in unanticipated ways (3)
Small RCB openings (vents and orains) say lead to instrument mu1 functions or unanticipated RCS responses I
(9) Large RCS pressure boundary openings (SG manway RCP seals, pressurizer manways) may lead to instrument malfunction or unanticipated RCS responses (10)
SG secondary side inventory and opening may influence RCS behavior i
b)
Vortening (1)
Small amount of a4r into RHR pump suction may lead to subtle changes that occur over a time of minutes to an hour or mora (2) Large amounts of air may cause immediate !ces of RHR (3i Vortexing-may occur at levels higher than anticipated (4) Vortexing may not be ref tweted by pump current and flow rate instrumente until it is suf ficiently severe to cause a loss of RHR (5) Vortexing may cause RCS level indication errors c)
B6 tube draining i
(1)_ frequently done by draining Draining SG U-tube in the RCS to point where vortexing could occur di RCS level differences B
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1.0-LP-60900-01-C Ill.
LESSON OUTLINE:
M NOT.ES (1)
Critical level parameters is in hot leg where RHR takes suction (2)
Laval instruments connected at other points j
(3) 8,evel difference exists between level indicator and hot leg RHR connection point teay be several inches difforonce) l e)
RHit system ef f ects (1)
Shifting from ons train to anothw may causa level changed due to differences in actual aire, retc.
(2)
Starting one systen uh!!n another is running can increase total flow thus increase vortexing (M
Oparator response to a loss of one RHR pump by starting the second pump may result in the loss of the second pump niso if started without co.'recting the cause of the loss of the first pump (4)
Stopping or storting RWt may cause RCS level changes due to partially filled system or air induction into the RHR system i
f)
Instrueentation (1)
Nay be in error by half a foot or more without detection of l
inaccuracies (2)
Flow dynamics, entrapped air, and pressurization may affect level indication individually or RV indicators simultaneously 9
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LO-LP-60990-01-C
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111. LESSON OUTLINN:
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(3) Many ncrmal instrtiesnts i
disconnected during RV head removat etc.
(4)
Remaining instruments may be inadequate B.
SOER 80.003 1.
This document addresses the following specific training concerns associated with this problem a.
Response te discrepancies in or loss of l
indicated level b.
Methods to determine decay heatup rates c.
Indications of pump cavitation and actions needed to restore core cooling flow d.
Response to a loss-of-core conting flow with no indication of core coolant temperature 2.
Review this SOER with the r, lass a.
A dotatted study of the SOER and associated concerns is covered in LO-LP-12101 and associated handouts and instructional units c
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