ML20156A123
| ML20156A123 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1986-003-00 | |
| Download: ML20156A123 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
277/86-003 Event
Description:
DG trip in test causes scram Date of Event:
January 24, 1986 Plant:
Peach Bottom 2 EVENT DESCRIPTION Sequence Before the event, the DG E-2 was in service supplying the E-22 and E-23 emergency buses in preparation for a loss of power test on Unit 3.
At 0612 h, DG E-2 automatically tripped, thereby removing all power to the E-22 and E-23 buses.
Loss of bus E-22 caused MSIVs AO-2-2-86B and AO-2-2-86D to close inadvertently (their solenoids deenergized).
The redundant dc solenoids were later found failed.
Closure of these valves resulted in a high core-flux condition, which was sufficient to initiate a full reactor scram.
Immediately following the scram, reactor water level decreased to -32 in.
Group II and III isolations occurred properly at the 0-in. water level.
The speeds of all three reactor feed pumps automatically increased to recover reactor water level.
At +45 in.
the reactor feed pumps and the main turbine received trip signals indicating high reactor water level.
The feed pumps and main turbine tripped properly.
Both reactor recirculation pumps tripped properly during the 13.2-kV bus fast transfer.
At 0634 h reactor feed pump C was reset from the high-water-level trip and placed in service to control reactor water level.
Both recirculation pumps were returned to service by 0645 h.
Additionally, Group II and III outboard isolations occurred on Unit 3 as a. result of this event.
Corrective Action A review of the most recently completed surveillance test indicated that all MSIV ac and dc coils had satisfactory operating currents when tested 2 d before the event.
The dc solenoids were replaced on Janu-ary 25.
Plant/Event Data Systems Involved:
Emergency power, main steam isolation, and MFW Event Identifier:
277/86-003 D-52
Components and Failure Modes Involved:
DG -
failed in test MSIVs -
failed closed during operation Component Unavailability Duration:
NA Plant Operating Mode:
1 (95% power)
Discovery Method:
Testing Reactor Age:
12.3 years Plant Type:
BWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient, Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate MFW 0.04 Recoverable from control room (tripped off on high head after scram)
Emergency power Base case DG train E-2 is unavailable system RHR/shutdown Base case One train unavailable because of loss cooling buses RHR/SDC Base case One train unavailable because of loss buses RHR service Base case One train unavailable because of loss water buses SLC/rod insert Base case One train unavailable because of loss buses LPCS Base case One train unavailable because of loss buses Plant Models Utilized BWR plant Class C Event Identifier:
277/86-003 D-53
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 277/86-003 Event
Description:
Diesel Generator Trip Test Causes Scram Event Date:
1/24/86 Plant:
Peach Bottom 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator I.OE+00 Probability CV TRANS Total 9.OE-08 9.OE-08 CD TRANS Total B. IE-05
CV Conditional Probability:
5.2E-08 155 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS -C OND/FW.PCS -RHR(SDC)
End State:
CD Conditional Probability:
6.4E-05 101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE -FW/PCS.TRANS RHR(SDC)
C.I.AND.V/RHR(SDC).RHR(SPCOOL)
Event Identifier: 277/86-003 D-54
End State:
ATWS Conditional Probability:
1.7E-05 173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE -FW
C.I.AND.
V/RHR(SDC).RHR(SPCOOL) 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW
C.
I.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.TRANS 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 -COND/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 CV CV CV 6.4E-05 *
.IE-O1 2.6E-06 4.6E-03 1.1E-05 1A.7E-01 6.8E-09 1.3E-02 3.5E-09 6.6E-03 5.2E-08
- 1.6E-01 2.7E-08 8.OE-02 1.7E-05
- 1.0E+00 CV ATWS
- dominant sequence for end state
- non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodelI\\bwrctree.cmp c:\\asp\\newmodel\\peach.txt c:\\asp\\newmodel\\bwr-c.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS LOOP LOCA SCRAM SLC.OR.RODS PCS/TRANS Branch Model:
1.OF.1 Train I Cond.Prob:
PCS/LOCA Event Identifier: 277/86-003 8.6E-04 1.7E-05 3
.3E-06 3.5E-04 I.OE-02 1.7E-01 > 1'.OE+00 1.0E+00 3.2E-01 5.OE-01 1.OE+00 1.0E+00 1.0E+00 1.OE+00 4.0E-02 I.7E-01 1.OE+00
> Unavailable D-55
SRV.CHALL/TRANS.-SCRAM SRV.CHALL/TRANS.SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CHALLILOOP.SCRAM SRV.CLOSE EMERG.POWER FW/PCS.TRANS Branch Model:
INOF.I Train I Cond Prob:
FW/PCS.LOCA HPCI RCIC/TRANS.OR.LOOP RCIC/LOCA CRD Branch Model:
1.OF.1+opr Train I Cond Prob:
SRV.ADS COND/FW.PCS LPCS I.OE+00 I.OE+O0 I.OE+O0 I.OE+00 3.6E-02 2.7E-05 4.6E-01 > 1.OE+00 4.6E-01 > Unavailable I.OE+00 2.9E-02 6.0E-02 I.OE+0Q I.OE-02 > 1.OE+00 1.0E-02 > Unavailable 3.7E-03 I.OE+00 3.OE-03 > 3.OE-02 3.OE-02 1,0E-01 > Unavailable 1.0E-03 > I.OE-02 I.E-02 I.OE-0l > Unavailable 5.OE-01 5.0E-01 5.OE-01 2.1E-02 > 3.OE-02 1.OE+00 I
.0E+00 1
.0E+00 1
.0E+00 1
.0E+00 B.OE-01 3.4E-01 > 4.OE-02 3.4E-01 7.OE-01 7
.OE-01 I
.0E+00 1
.OE+00 7.1E-01 3.4E-01 3.4E-01 4
.0E-02 4
.OE-02 Branch Model:
Train I Cond Train 2 Cond LPCI(RHR)/LPCS 1.OF.2 Prob:
Prob:
7.IE-0I Branch Model:
1.OF.2 Train I Cond Prob:
Train 2 Cond Prob:
RHRSW/LPCS.LPCI.TRANS RHRSW/LPCS.LPCI.LOOP RHRSW/LPCS.LPCI.LOCA RHR(SDC)
Branch Model:
1.OF.2+ser Train I Cond Prob:
Train 2 Cond Prob:
Serial Component Prob:
RHR(SOC)/-LPCI RHR(SDC)/LPCI RHR(SPCOOL)/-LPCI.RHR(SDC)
C.I.AND.V/RHR(SDC).RHR(SPCOOL)
- branch model file
- forced Minarick 02-24-1988 12:06:26 Event Identifier: 277186-003 I.OE+00 I.OE+00 I
.OE+00 3.4E-01 4.0E-02 4.OE-02 4.OE-02 I.OE-02 I.OE-01 2.0E-02 2.OE-02 I.OE+00 2.0E-02 5.2E-01 I.OE+00
> Unavailable 3.4E-0I I.OE+00 1.OE+00 1.OE+00 3.4E-01 D-56