ML20161A151
| ML20161A151 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1983-012-00 | |
| Download: ML20161A151 (5) | |
Text
B.37-1 B.37 LER Number 344/83-012 Event
Description:
Auxiliary Feedwater Pump Tripped Following Reactor Trip Date of Event:
August 20, 1983 Plant:
Trojan B.37.1 Summary After a reactor trip occurred on August 20, 1983, the diesel-driven auxiliary feedwater (AFW) pump auto started but tripped due to overspeed. Several attempts to restart the purrip were unsuccessful. The other AFW pumps operated as required. The event was analyzed as an AFW pump failure in conjunction with the reactor trip. The conditional core damage probability (CCDP) estimated for this event is 3.0 x 10'.
B.37.2 Event Description On August 20, 1983 a reactor trip occurred at 100% power due to a spurious main turbine high vibration signal. The diesel-driven auxiliary feedwater pump auto started but tripped due to overspeed. Several attempts to restart the pump in automatic mode failed. The steam-driven AFW pump and non-ESF motor-driven AFW pump supplied flow as required.
B.37.3 Additional Event-Related Information The apparent cause of the diesel AFW pump overspeed was procedural deficiencies for restoration of the pump following annual maintenance combined with human error. Following the failure, the diesel engine controls were adjusted and the engine was tested successfully.
B.37.4 Modeling Assumptions The event was modeled as an AFW pump failure in conjunction with a reactor trip. Train 1 of AFW, representing the diesel-driven pump, was failed. The potential for common cause failure exists, even when a component is failed. Therefore, the conditional probability of a common cause failure was included in the analysis for those components that failed as part of the event. Since success of AFW given an anticipated transient without scram (ATWS) requires that both of the auto-start AFW pumps operate, this branch (AFW/ATWS) was assumed to be failed.
B.37.5 Analysis Results The conditional core damage probability estimated for this event is 3.0 x 10i. The dominant accident sequence, shown in Figure B.37. 1, consists of the transient followed by a failure to trip the reactor, successful limiting of reactor coolant system pressure (<3200 psi), and failure of AFW for ATWS mitigation.
LER No. 344/83-012
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- 2cc, Figure B.37.1 Dominant core damage sequence for LER 344/83-012 LER No. 344/83-012
B.37-3 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
344/83-012 Event
Description:
Diesel AFW pump trip after reactor trip Event Date:
8/20/83 Plant:
Trojan INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OE+O0 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 3.OE-05 Total 3.OE-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
508 trans rt -prim.press.limited AFW/ATWS CD 2.8E-05 1.0E-01 120 trans -rt AFW mfw feed.bleed CD 1.2E-06 1.5E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
120 trans -rt AFW mfw feed.bleed CD 1.2E-06 1.5E-01 508 trans rt -prim.press.limited AFW/ATWS CD 2.8E-05 i.0E-OI
- non-recovery credit for edited case SEQUENCE MODEL:
c:\\asp\\models\\pwrb8283.cmp BRANCH MODEL:
c:\\asp\\models\\trojan.82 PROBABILITY FILE:
c:\\asp\\models\\pwr8283.pro No Recovery Limit LER No. 344/83-012
B.37-4 BRANCH FREQUENCIES/PROBABILITIES Branch trans loop loca sgtr rt rt(loop)
AFW Branch Model:
l.OF.3+ser Train I Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
AFW/ATWS Branch Model:
1.OF.1 Train 1 Cond Prob:
AFW/EP Branch Model:
1.OF.2+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Serial Component Prob:
mfw porv.chall porv.chall/afw porv.chall/loop porv.chall/sbo porv.reseat porv.reseat/ep srv.reseat(atws) hpi feed.bleed emrg.boration recov.sec.cool recov.sec.cool/offsite.pwr rcs.cooldown rhr rhr.and.hpr hpr ep seal.loca offsite.pwr.rec/-ep.and.-afw offsite.pwr.rec/-ep.and.afw offsite.pwr.rec/seal.loca offsite.pwr.rec/-seal.loca System 1.6E-03 1.6E-05 2.4E-06 1.6E-06 2.8E-04 O.OE+00 3.3E-04 > 1.3E-03 5.0E-02 > Unavailable 5.0E-02 2.OE-02 2.BE-04 I.OE-OI > 1.OE+O0 IOE-OI > Failed 2.8E-03 > 5.0E-02 5.OE-02 > Unavailable 5.0E-02 2.8E-04 2.OE-O1 4.OE-02 1.OE+O0 1.0E-OI 1.OE+O0 2.0E-02 2.0E-02 1.OE-01 1.OE-05 2.0E-02 O.OE+00 2.0E-01 3.4E-01 3.OE-03 2.2E-02 1.OE-03 4.OE-03 2.9E-03 2.3E-01 2.1E-O1 9.9E-02 5.9E-01 6.1E-02 Non-Recov 1.0E+O0 3.6E-01 5.4E-01 1.OE+00 I.OE-01 1.OE+00 4.5E-01 1.0E+00 3.4E-01 Opr Fail 3.4E-01 1.0E+00
- 1.
OE+00 1.0 E+00
- 1.
OE+00 1.1E-02
- 1.
OE+00
- 1.
OE+00 B.
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00
- 7.
OE -02
- 1.
OE+00
- 1.
OE+00 8.9E-01
- 1.
OE+00
- 1.
OE+00 1.0OE+00
- 1.
OE+00
- 1.
OE+00 1.OE-03 1.OE-02 1.OE-02 1.OE-03 1.OE-03 1.0E-03 1.OE-03 LER No. 344/83-012
B.37-5 sg.iso.and.rcs.cooldown 1.0E-02 1.OE-01 rcs.cool.below.rhr 3.OE-03 1.OE+O0 3.0E-03 prim.press.limited 8.8E-03 1.OE+O0
- branch model file
- forced LER No. 344/83-012