ML20149K343
| ML20149K343 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-030-00 | |
| Download: ML20149K343 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
416/84-030 Event
Description:
LOFW, Trip, and RCIC Failure Date of Event:
May 25, 1984 Plant:
Grand Gulf 1 EVENT DESCRIPTION Sequence At -.091.5 h during startup, a reactor scram occurred at low water level number 3, 11 in. above instrument zero.
The low level was due to a trip of the condensate pump, condensate booster pump, and feedwater pump and the inability to start ROTC manually to restore level.
Maintenance personnel had previously begun to investigate the cause of a dual indication on valve N19F504, the condensate minimum-flow con--
trol valve.
The cause was determined to be a high-voltage output on the controller, which was then adjusted.
As the technician touched the positioner arm linkage to check for tightness, a noise was heard inside the positioner, and the valve moved to full open.
A later investigation revealed a broken linkage and a bent valve stem positioner bracket, which occurred at an unknown time.
With the valve full open, a path bypassing the booster pumps was created to the condenser.
The running condensate and condensate booster pump and feedwater pump tripped immediately on low suction at 0910 h.
The reactor was operating at -4% thermal power, 540'F, and 920 psig.
Operators attempted to restart the condensate system, but the condensate pumps again tripped.
The reactor water level began to decrease from 38 in. above instrument zero.
Operators tried twice to start RCIC man-ually, but both times the RCIC turbine tripped. When initially started, RCIC operated properly and momentarily stabilized water level at -~27 in.
before tripping on overspeed.
It was reset and again tripped on over-speed.
The turbine evidently oversped on initial startup, but the trip valve did not close instantaneously, which allowed RCIC to operate for a short time.
A reactor scram occurred on a low level 3 signal at 0915 h. By 0927 h all main steam inboard isolation valves were manually closed by hand switch.
RCIC was restarted and began feeding the vessel at 0928 h with the vessel level at 10 in. below instrument zero.
The normal RCIC automatic initiation is at 41.6 in. below instrument zero at which time HPCS, which was available, would also start.
By 0934 h the condensate system was made available by isolating the recirculation flow path.
RCTC was then secured with the water level at -37 in. above instrument zero.
Event Identifier:
416/84-030 D-256
Corrective Action The N19F504 valve positioner arm was replaced, and the valve was restored to service by 1640 h the same day. A modification was made to the RCIC turbine governor valve to restrict it from full opening and causing a turbine overspeed trip.
The turbine trip valve was lubricated and retested satisfactorily.
Startup recommenced at 0420 h on May 26.
Plant/Event Data Systems Involved:
Condensate and RCIC Components and failure Modes Involved:
Condensate system -
failed in operation RCIC -
failed on demand Component Unavailability Duration: NA Plant Operating Mode:
2 (4% startup)
Discovery Method:
Operational event Reactor Age:
1.7 years Plant Type:
BWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate MFW RU~IC 0.34 No recovery assumed possible (MSIVs closed)
Recoverable locally at turbine con-t ro ls Plant Models Utilized BWR plant Class C Event Identifier:
4 16/84-030 D-257
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 416184-030 Event
Description:
LOFW and RCIC Failure Event Date:
5/25/84 Plant:
Grand Gulf 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator I OE+00 Probability CV TRANS Total
.OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
1.8E-07 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS
-COND/FW.PCS;
-RHR (SDC)
End State: CD Conditional Probability:
3.OE-05 101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE -FW/PCS.TRANS RHR(SDC) RHR(SPCO1OL)/
-LPCI.RHR(SDC) C.I.AND.V/RHR(SDC).RHR(SPCOOL)
Event Identifier: 41h/84-030 D-258
End State: ATWS EndStae: TWSConditional Probability:
2.0E-05 173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
101 TRANS -SCRAM PCS/TRANS SRY.CHALL/TRANS.-SCRAM -SRV.CLOSE -FW
/PCS.TRANS RHR(SDC) RHR(SPCOOL)/-LPCL.RHR(SDC) C.I.AND.
V/RHR,(SDC).RHR (SPCOOL) 102 TRANS -SCRAM PCS/TRANS SRV.CH4ALL /TRANS. -SCRAM -SRV.CLOSE FW
/PCS.TRANS -HPCI RHR(SDC) RHR(SPCOOL)/-LPCI.RHR(SDC) C.
I.AND.V/RHR(SDC).RHR(SPCOOL) 110 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CRD SRV.ADS III TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE -FW
RHR(SPCOOL)/-LPCI.RHR(SDC) C.I.AND.V
/RHR(SDC).RHR(SPCOOL) 112 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW
C.1
.AND.V/RHR(SDC).RHR(SPCOOL) 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW
/PCS.LOCA HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS STRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS -RHR(SDC) 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FW.PCS -LPCS -RHR(
SDC) 155 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS -CONO/FW.PCS -RHR(SDC) 159 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS COND/FW.PCS -LPCS -RHR(SDC) 173 TRANS SCRAM SLC.OR.RODS CD CD CD CD CD CD CV CV CV Cv 3.OE-05
- 7.6E-02 1.5E-05 3.9E-02 1.7E-06~
3.9E-02 2.1E-06 7.6E-02 1.1E-06 3.9E-02 7.1E-06 1.2E-01 1
.8E-07
- 2.6E-02 9.IE-08 1.3E-02 3.7E-08 7.6E-02 1.9E-08 3.9E-02 2.OE-05 *
.OE+00 ATWS
- dominant sequence for end state
- non-recovery credit for edited case MODEL:
DATA:-
b
- \\bwrctree.cmp b:\\gulfprob.cmp No Recovery Limit BRANCH FREGUENCIES/PROBABIL IT JES Branch TRANS LOOP System 1.1E-03 1.3E-05 Non-Recov I.OE+00 3.4E-01 Opr Fail Event Identifier: 416/84-030 D-259
LOCA SCRAM SLC.OR.RODS PCS/ TRANS Branch Model:
1.0F.1 Train I Cond Prob:
PCS/LOCA SRV.CHALL/TRANS.-SCRAM SRV.CHALL/TRANS.SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CHALL/L0OP.SCRAM SRV.CLOSE EMERS.POER FW/PCS.STRANS Branch Model: 1.0F.1 Train I Cond Prob:
FW/PCS SLOCA HPCI RCIC/TRANS.fR.LOOP Branch Model:
1.OF.1 Train 1 Cond Prob:
RCIC/LOCA CRD BRY ADS COND/FW.PCS LPCS LPCI (RHR) /LPCS RHRSW/LPCS.LPCI.STRANS RHRSW/LPCS.LPCI.LOOP RHRSW/LPCS.LPCI SLOCA RHR (SDC)
R4R (SDC) /-LPCI RHR(SDC) /LPCI RHR (SPCOOL) I-LPCI SRHR (SDC)
C.I.AND.V/RHR(SDC) SRHR(SPCOOL) 3.3E-06
- 4. 1E-04 1.OE-02 1.7E-01 > 1.OE+0O 1.7E-01 > Unavailable 1
.OE+0O I
.OE+OO 1
.OE+OO 1
.OE+OO 1
.OE+OO 6.6E-02 2.9E-03 4.6E-01 > 1.OE+OO 4.6E-01 > Failed I
.OE+OO 2.OE-02 6.7E-02 > 1.OE+0O 6.7E-02 > Failed 1.OE+OO 1.OE-02 6.7E-03 I
.OE+OO 2.OE-02 6.OE-04 1
.OE+OO I.OE+00 1.OE400 2.1E-02 2.OE-02 1.OE+00 2.OE-02 5.2-01 1.OE+O0 3.4E-01 1
.OE+00 1
.OE+00 I
.OE+00 1.OE+00 I.OE+00 1.OE+O0 1.OE+00 I.
OE+0O 1
.OE+00 5.IE-01 3.4E-01 3.4E-01 3.4E-01 5.7E-01 > 3.4E-01 1.OE+00 1.OE+00 1.OE+00 M.E-01 3.4E-01 3.4E-01 1
.OE+00 1
.OE+00 1
.OE+00 3.4E-01 3.4E-01 1
50E+00 1
.OE+O0 I
.OE+00 3.4E-01 4.OE-02 4.OE-02 4.OE-02 forced Minarick 04-12-1987 12:52:55 Event Identifier: 416/84-030 D-260