ML20156A138
| ML20156A138 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1986-027-00 | |
| Download: ML20156A138 (5) | |
Text
LER No.:
Event
Description:
Date of Event:
Plant:
PRECURSOR DESCRIPTION SHEET 293/86-027 LOOP occurs due to winter storm November 19, 1986 Pilgrim 1 EVENT DESCRIPTION Sequence While the reactor was shut down for refueling, an arcing of the high-voltage lines due to locally heavy ice and snow occurred at 0819 h during a severe winter storm.
A loss of offsite power occurred when both transmission lines tripped off due to near-simultaneously detected faults.
All safety systems responded as designed.
Offsite power was restored at 1015 h when the two lines were reenergized.
By 1128 h the switchyard was restored to service.
Corrective Action An inspection revealed no damage to any system.
Plant/Event Data Systems Involved:
Electrical Components and Failure Modes Involved:
Offsite power -
failed in operation Component Unavailability Duration:
NA Plant Operating Mode:
6 (0% power)
Discovery Method:
Operational Reactor Age:
14.4 years Plant Type:
BWR Comments Given the circumstances, this event could have occurred at full power and is analyzed on this basis.
Event Identifier:
293/86-027 D-87
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP 0.12 Backup power source available Branches Impacted and Branch Nonrecovery Estimate None Plant Models Utilized BWR plant Class C Event Identifier:
293/86-027 D-88
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
293/86-027 Event
Description:
LOOP Due to Winter Storm Event Date:
11/19/86 Plant:
Pilgrim I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 1.2E-01 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV LOOP 3.3E-08 Total 3.3E-08 CD LOOP 7.7E-06 Total 7.7E-06 ATWS LOOP 2.2E-06 Total 2.2E-06 DOMINANT SEQUENCES End State:
CV Conditional Probability:
3.2E-08 226 LOOP -EMERG.POWER SCRAM -SLC.OR.RODS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -LPCS,-RHR(SDC)
End State:
CD Conditional Probability:
5.6E-06 201 LOOP -EMERG.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM -SRV.CLOSE -HPCI RHR(SDC)
RHR(SPCOOL)/-
C.I.AND.V/RHR(SDC).RHR(SPCOOL)
End State:
ATWS Conditional Probability:
2.1E-06 Event Identifier: 293/86-027 D,-89
240 LOOP -EMERG.POWER SCRAM SLC.OR.ROOS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
201 LOOP -EMERS.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM -SRV.CLOSE -HP CI RHR(SDC)
C.I.AND.V/RHR(SD C).RHR(SPCOOL) 208 LOOP -EMERG.POWER
-SCRAM SRV.CHALL/LOOP.-SCRAM -SRV.CLOSE HP CI RCIC/TRANS.OR.LOOP CRD SRV.ADS 215 LOOP -EMERG.POWER
-SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CLOSE HP CI RCIC/LOCA SRV.ADS 226 LOOP -EMERG.POWER SCRAM -SLC.OR.RODS HPCI RCIC/TRANS.OR.LOO P -SRV.ADS -LPCS -RHR(SDC) 240 LOOP -EMERG.POWER SCRAM SLC.OR.RODS 243 LOOP EMERG.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM -SRV.CLOSE HP CI RCIC/TRANS.OR.LOOP 250 LOOP EMERG.POWER SCRAM CD CD CD CV 5.6E-06
- 1.4E-02 2.1E-07 4.2E-02 1.4E-06 6.OE-02 3.2E-08
- 5.8E-02 2.IE-06
- dominant sequence for end state
- non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\aspknewmodel\\bwrctree.cmp c:\\asp\\newmodel\\pilgrim.txt c:\\asp\\newmodel\\bwrcc.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS LOOP Branch Model:
INITOR Initiator Freq:
LOCA SCRAM SLC.OR.RODS PCS/TRANS PCS/LOCA SRV.CHALL/TRANS.-SCRAM SRV.CHALL/TRANS.SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CHALL/LOOP.SCRAM SRV.CLOSE EMERG.POWER Event Identifier: 293/86-027 8.6E-04 1.7E-05 > 1.7E-05 1.7E-05 3.3E-06 3.5E-04 1.OE-02 I.7E-01 1.OE+00 I.OE+00 1.0E+00 I.OE+00 1.OE+00 1.3E-02 2.9E-03 1.OE+00 3.2E-01 > 1.2E-01 5.OE-01 1.0E+00 1.0E+00 1.0E+00 1.0E+00 1.0E+00 1.0E+O0 1.0E+00 1.0E+00 1.0E+00 8.OE-01 4.OE-02 D-90
FW/PCS.TRANS FW/PCS.LOCA HPCI RCIC/TkANS.OR.LOOP RCIC/LOCA CRD SRV.ADS COND/FW.PCS LPCS LPCI(RHR)/LPCS RHRSW/LPCS.LPCI.TRANS RHRSW/LPCS.LPCI.LOOP RHRSW/LPCS.LPCi.LOCA RNR (SDC)
RHR (SDC)/-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 12:08:17 Event Identifier: 293/86-027 2
.9E-01 4.E-02 2
.9E-02 6
.OE-02 1.OE+00 1
.OE-02 3.71-03 1
.0OE+00 3
.0E-03 1.0E-03 5.OE-01 S.0E-01 5.0E-01
- 2.
1E-02 2
.OE-02 1.OE+00 2
.OE-02 5.2E-01 1
.0E+00 3.4E-0 I M.E-01 7.6E-01 7.OE-01 I.OE+00 1
.OE+00 7.1E-01 3.E-01 3
.E-01
.7.1E-01 I.OE+00 1
.0E+00 1
.0E+00 M.E-01 3
.E-01 1
.0E+00 I.OE+00 1
.OE+00 3
.E-01 4.OE-02 4.0E-02 4.0E-02 4.0E-02 4.0E-02 D-91