ML20161A150
| ML20161A150 | |
| 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 1983-002-00 | |
| Download: ML20161A150 (5) | |
Text
B.36-1 B.36 LER No. 344/83-002 Event
Description:
Reactor Trip with Main Feedwater and Two Auxiliary Feedwater Pumps Unavailable Date of Event:
January 22, 1983 Plant:
Trojan B.36.1 Summary On January 22, 1983 a high-high steam generator level caused the main feedwater (MFW) pump to trip. The auxiliary feedwater (AFW) pumps auto started, but were manually shut down by the operator. The levels in two steam generators then decreased sufficiently to cause a reactor trip. The operator attempted to restart the AFW pumps, but was unsuccessful. Action was taken to reset the AFW pumps locally while the motor-driven nonengineered safety feature (ESF) AFW pump was started, which reestablished feedwater to the steam generators. Feedwater flow to the steam generators was lost for seven minutes. The conditional core damage probability estimated for this event is 9.7 x I10.
B.36.2 Event Description On January 22, 1983 with the unit at 4% power in mode 2, a high-high steam generator level caused the MFW pump to trip. The AFW pumps auto started, but the operator, assuming MFW was still operating, manually shut down the AFW pumps. The levels in steam generators B and C then decreased to the low-low level setpoint, which caused a reactor trip. Realizing that the MFW pump had tripped, the operator attempted to restart the AFW pumps. The diesel-driven pump would not start and the steam-driven pump started but tripped on overspeed. An operator was sent to reset the AFW pumps locally while the motor-driven non-ESF AFW pump was started, which re-established feedwater to all four steam generators. Feedwater flow to the steam generators was lost for seven minutes.
B.36.3 Additional Event-Related Information The diesel-driven AFW pump was secured before reaching full speed. This prevented restart from the control room. Both pumps were reset locally and restarted.
B.36.4 Modeling Assumptions This event was modeled as a transient with MFW and two AFW pumps unavailable. This was reflected in the analysis by setting train I of main feedwater (MFW) and trains I and 2 of AFW (the steam-and diesel-driven pumps) to unavailable. 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.
LER No. 344/83-002
B.36-2 B.36.5 Analysis Results The estimate of the conditional core damage probability (CCDP) resulting from this event is 9.7 x 10"'. The dominant core damage sequence, shown in Figure B.36. 1, involves a transient, successful reactor trip, failure of the AFW system, the unavailability of the MFW system, and failure of feed and bleed.
LER No. 344/83-002
B.36-3 00---
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Figure B.36.1 Dominant core damage sequence for LER 344/83-002 LER No. 344/83-002
B.36-4 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
344/83-002 Event
Description:
Reactor trip with MFW and two AFW pumps unavail.
Event Date:
1/22/83 Plant:
Trojan INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 1.OE+O0 Probability CD TRANS Total 9.7E-05 9.7E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 120 trans -rt AFW MFW feed.bleed 119 trans -rt AFW MFW -feed.bleed recov.sec.cool hpr
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 119 trans -rt AFW MFW -feed.bleed recov.sec.cool hpr 120 trans -rt AFW MFW feed.bleed
- 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 End State CD CD End State CD CD Prob 9.3E-05 3.OE-06 Prob 3.OE-06 9.3E-05 N Rec**
1.5E-01 1.5E-01 N Rec**
1.5E-01 1.5E-O1 No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch trans loop loca sgtr rt rt(loop)
System 1.6E-03 1.6E-05 2.4E- 06 1.6E-06 2.8E-04 O.OE+O0 Non-Recov 1.0E+O0 3.6E-01 5.4E-01 1.OE+0O I.OE-OI 1.OE+O0 Opr Fail LER No. 344/83-002
B.36-5 AFW Branch Model:
1.OF.3+ser Train 1 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 Branch Model:
1.OF.l+opr Train 1 Cond Prob:
porv.chall porv.chall/afw porv.chall/loop 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 sg.iso.and.rcs.cooldown rcs.cool.below.rhr prim.press.limited 3.3E-04 > 2.OE-02 5.OE-02 > Unavailable S.OE-02 > Unavailable 2.OE-02 2.8E-04 1.OE-01 > 2.OE-02 1.OE-01 > 2.0E-02 2.8E-03 > 1.OE+00 5.OE-02 > Unavailable 5.OE-02 > Unavailable 2.8E-04 2.OE-01 > 1.OE+00 2.OE-01 > Unavailable 4.OE-02 1.OE+00 1.OE+00 2.OE-02 2.0E-02 1,OE-01 1.OE-05 2.0E-02 0.0E+00 2.OE-01 3.4E-01 3.0E-03 2.2E-02 1.0E-03 4.OE-03 2.9E-03 2.3E-01 2.1E-01 9.9E-02 5.9E-01 6.1E-02 1.OE-02 3.OE-03 8.8E-03 4.5E-01
- 1.
OE+Q0 3.4E-01 3.4E-01 1.0E+00 1.0E+00 1.0E+00
- 1.
- 1.
OE+00
- 1.
OE+00 8.9E-01
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00 I
- E+00
- 1.
OE+00
- 1.
OE+00 8.9E-01
- 1.
OE+00
- 1.
OE+00 1.OQE+00
- 1.
OE+00 1.OE+00 1.OE-01 1.OE+00 1.OE+00 1.OE-03 1.OE-02
- 1.
OE -02 1.OE-03 1.OE-03
- 1.
OE- 03 1.OE-03
- 3.
OE-03 branch model file
- forced LER No. 344/83-002