ML20156A266
| ML20156A266 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-003-00 | |
| Download: ML20156A266 (3) | |
Text
B-126 PRECURSOR DESCRIPTION SHEET LER No.:
387/87-003 Event
Description:
Both diesel generators are unavailable Date of Event:
1/27/87 Plant:
Susquehanna 1 EVENT DESCRIPTION Sequence Diesel generator (DG)
B was removed from service for maintenance.
The DC A trip alarm occurred and the local panel would not respond to an alarm test.
Both DGs were out of service for 8 h.
Corrective Action Repairs were made.
Plant/Event Data Systems Involved:
Emergency power Components and Failure Modes Involved:
Diesel generators and controls are unavailable Component Unavailability Duration:
8 h Plant Operating Mode:
1 (100%)
Discovery Method:
Operational event Reactor Age:
4.3 y Plant Type:
BWR Comments None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated LOOP Base case nonrecovery Branches Impacted and Branch Nonrecovery Estimate EPS No recovery assumed possible (limited information provided in LER)
Plant Models Utilized BWR plant Class C Event Identifier:
387/87-003
B-127 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
387/87-003 Event
Description:
Both diesel generators are unavailable Event Date:
01/27/87 Plant:
Susquehanna 1 UNAVAILABILITY, DURATION= 8 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 4.4E-05 Probability CD CV LOOP Total LOOP Total 7.5E-06 7.5E-06 2.5E-10 2.5E-10 ATWS LOOP Total 1.5E-08 1.5E-06 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 274 loop EMERG.POWER -scram ep.rec 256 loop EMERG.POWER -scram -ep.rec srv.chall/loop.-scram -srv.clo se -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v
-rhrsw (c.i.and.v) 263 loop EMERG.POWER -scram -ep.rec srv.chall/loop.-scram srv.clo se -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v
-rhrsw (c.i.and.v) 828 loop -EMERG.POWER scram -sic.or.rods srv.close hpci -srv.ads
-lpcs -rhr(sdc) 221 loop -EMERG.POWER
-scram srv.chall/loop.-scram srv.close -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-ci.and.v-rhrsw(c.i.and.v 202 loop -EMERG.POWER
-scram srv.chall/loop.-scram -srv.close -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v rhrsw(c.i.and.v 201 loop -EMERG.POWER
-scram srv.chall/loop.-scram -srv.close -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v
-rhrsw(c.i.and.v 841 loop EMERG.POWER scram
- non-reCovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 201 loop -EMERG.POWER
-scram srv.chall/loop.-scram -srv.close -hpci rhr(sdc) rhr(spcool)/-ipci.rhr(sdc)
-c.i.and.v
-rhrsw(c.i.and.v 202 loop -EMERG.POWER
-scram srv.chall/loop.-scram -srv.close -hpci End State CD CV Prob 7.4E-06 4.4E-10 N Rec**
5.4E-02 7.8E-02 CV CV CV CV CV 3.1E-11 7.8E-02 2.OE-Il
( 3.7E-11 )
1.1E-01 4.7E-02 ATWS End State CV CV 1.1E-10 1.8E-02 5.3E-10 4:7E-02 1.5E-08, 3.2E-01 Prob N Rec**
( 5.3E-10 )
4.7E-02
( 1.lE-10 )
1.8E-02 Event Identifier:
387/87-003
B-128 rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v rhrsw(c.i.and.v 221 loop -EMERG.POWER
-scram srv.chall/loop.-scram srv.close -hpci CV rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.i.and.v
-rhrsw(c.i.and.v 828 loop -EMERG.POWER scram -slc.or.rods srv.close hpci -srv.ads CV
-ipcs -rhr(sdc) 256 loop EMERG.POWER -scram -ep.rec srv.chall/loop.-scram -srv.clo CV se -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)
-c.L.and.v -rhrsw (c.i.and.v) 263 loop EMERG.POWER -scram -ep.rec srv.chall/loop.-scram srv.clo CV se -hpci rhr(sdc) rhr(spcool)/-ipci.rhr(sdc)
-c.i.and.v
-rhrsw (c.i.and.v) 274 loop EMERG.POWER -scram ep.rec CD 841 loop EMERG.POWER scram ATWS
( 3.7E-1I 1
4.7E-02 2.OE-Il 1
I.1E-01 4.4E-10 7.8E-02 3.lE-ll 7.8E-02 7.4E-06 5.4E-02 1.5E-08 3.2E-01
- non-recovery credit for edited case Note:
For unavailabilities, conditional probability values are differential values which reflect the added risk due to failures associated with an event.
Parenthetical values indicate a reduction in risk compared to a similar period without the existing failures.
SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\bwrcnew.cmp c:\\asp\\newmodel\\susquhan.new c:\\asp\\newmodel\\bwr-cnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch trans loop loca scram slc.or.rods pcs/trans srv.chall/trans
.- scram srv.chall/loop. -scram srv.close EMERG.POWER Branch Model:
2.OF.4 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Train 4 Cond Prob:
ep. rec fw/pcs.trans fw/pcs.loca hpci rcic crd srv.ads cond/fw.pcs lpcs lpci (rhr)/lpcs rhr (sdc) rhr (sdc)/-lpci rhr (sdc)/lpci rhr (spcool)/-lpci.rhr (sdc) rhr (spcool)/lpci.rhr (sdc) c.i.and.v rhrsw rhrsw(c.i.and.v)
System Non-Recov Opr Fail 8.6E-04
- 1. 7E-05 3.3E-06 3.5E-04 1.0E-02 1.7E-01 1.0E+00 1.0E+00
- 6. 6E-02 2.1E-03 > 1.OE+00 **
5.0E-02 > Unavailable 5.7E-02 > Unavailable 1.9E-01 5.0E-02 1.0E+00 4.6E-01 1.0E+00 2.9E-02 6.0E-02 1.OE-02 3.7E-03 1.0E+00 3.OE-03 1.0E-03 2.1E-02 2.0E-02 1.OE+00 2.OE-03 5.2E-01 1.0E-03 2.0E-02 5.OE-01 1.OE+00 3.2E-01 5.0E-01 1.0E+00 1.OE+00 1.OE+00 1.0E+00 1.OE+00 1.0E+00 B.OE-01 > 1.0E+00 1.7E-01 3.4E-01 3.4E-01 7.0E-01 7.0E-01 1.OE+00 7.1E-OI 3.4E-01 3.4E-01 7.1E-01 3.4E-01 3.4E-01 1.0E+00 1.OE+00 1.0E+00 1.0E+00 3.4E-01 3.4E-01 1.0E-02 1.0E-02 1.OE-02 1.0E-03 1.OE-03 1.0E-03 1.0E-03 1.0E-02 2.OE-03 branch model file forced Minarick 05-16-1989 Event Identifier:
387/87-003