ML20161A155
| ML20161A155 | |
| 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 1987-037-00 | |
| Download: ML20161A155 (3) | |
Text
B-88 PRECURSOR DESCRIPTION SHEET LER No.:
344/87-037 Event
Description:
Reactor trip and one AFW pump fails to start Date of Event:
12/6/87 Plant:
Trojan EVENT DESCRIPTION Sequence At 1010 h, a microswitch in a load decrease button in the electro-hydraulic control system failed due to normal aging.
A turbine runback occurred.
The reactor was manually tripped.
Main feedwater was run back but remained available.
The TD AFW pump failed to auto-start due to a loose electrical connection in the auto-start circuitry in control panel C-05.,
The TD AFW pump was successfully started manually from the control room.
The loose connection was a result of prior, unspecified, maintenance activities in 1985.
The pump had started in all subsequent tests until this time.
Corrective Action The loose connection was tightened.
Plant/Event Data Systems Involved:
Auxiliary feedwater Components and Failure Modes Involved:
Turbine EHC system -
microswitch failure AFW pump fails on demand Component Unavailability Duration:
N/A Plant Operating Mode:
1 (100%)
Discovery Method:
Operational event Reactor Age:
12.0 y Plant Type:
PWR Comments None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient Base case nonrecovery Branches Impacted and Branch Nonrecovery Estimate AFW Base case One of two trains fails to start Plant Models Utilized PWR plant Class C Event Identifier:
344/87-037
B-89 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
344/87-037 Event
Description:
Reactor trip and one AFW pump fails to start Event Date:
12/06/87 Plant:
Trojan INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator
- 1. OE+00 Probability CD CV TRANS Total TRANS Total
- 4. BE-05 4.8E-05 8.5E-05 8.5E-05 3.4E-05 3.4E-05 ATWS TRANS Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 126 trans -rt AFW mfw hpi(f/b) -ss.depress cond/mfw 120 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 127 trans -rt AFW mfw hpi(f/b) ss.depress 121 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open ss.depress 123 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress cond/mfw 125 trans -rt AFW mfw hpi(f/b) -ss.depress -cond/mfw 119 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 122 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw 109 trans -rt
-AFW -porv.or.srv.chall ss.releas.term hpi 128 trans rt
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 109 trans -rt
-AFW -porv.or.srv.chall ss.releas.term hpi 119 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 120 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 121 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open ss.depress 122 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw 123 trans -rt AFW mfw -hpl(f/b) hpr/-hpi -ss.depress cond/mfw 125 trans -rt AFW mfw hpi(f/b) -ss.depress -cond/mfw 126 trans -rt AFW mfw hpi(f/b) -ss.depress cond/mfw 127 trans -rt AFW mfw hpi(f/b) ss.depress End State CD CD CD CD CD CV CV CV CV ATWS End State CV CV CD CD CV CD CV CD CD Prob
- 2. IE-05
- 2. OE-05 2.3E-06 2.2E-06 2.2E-06 3.9E-05 3.7E-05
- 4. 1E-06
- 4. OE-06
- 3. 4E-05 Prob
- 4. OE-06 3.7E-05
- 2. OE-05 2.2E-06 4.1E-06 2.2E-06
- 3. 9E-05
- 2. 1E-05 2.3E-06 N Rec-*
- 3. 3E-02
- 3. 9E-02 9.7E-02 1.2E-01
- 3. 9E-02 6.4E-02
- 7. 6E-02
- 7. 6E-02 2.8E-01 1.2E-01 N Rec**
2.8E-01
- 7. 6E-02
- 3. 9E-02 1.2E-01 7.6E-02
- 3. 9E-02 6.4E-02 3.3E-02 9.7E-02 Event Identifier:
344/87-037
B-90 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\pwr_bnew.cmp c:\\asp\\newmodel\\trojan.new c:\\asp\\newmodel\\pwr_bnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System trans loop loca rt rt/loop emerg.power ep.rec AFW Branch Model:
Train 1 Cond Train 2 Cond AFW/EMERG.POWER Branch Model:
Train 1 Cond Train 2 Cond mfw porv.or.srv.chall 1.OF.2 Prob:
Prob:
1.OF.2 Prob:
Prob:
4.8E-04
- 4. 6E-06 2.4E-06 2.8E-04 0.OE+00 2.9E-03 1.OE+00 2.5E-03 > 5.OE-02 5.OE-02 5.OE-02 > Failed 2.5E-03 > 5.OE-02 5.0E-02 5.0E-02 > Failed 1.OE+O0 4.0E-02 2.0E-02 2.0E-02 1.5E-02 1.0E-03 1.OE-03 1.5E-04 1.0E-02 3.6E-02 1.OE+00 1.5E-04 6.7E-01 1.5E-04 Non-Recov 1.OE+00 3.9E-01 4.3E-01 1.2E-OI 1.OE+00 8.OE-01 1.7E-01 3.4E-01 3.4E-01 3.4E-01 1.0E+O0 1.IE-02 1.0E+O0 3.4E-01 8.4E-01 8.4E-01 1.0E+00 1.OE+00 1.OE+O0 3.4E-01 3.4E-01 1.OE+O0 1.OE+00 Opr Fail porv.or.srv.reseat porv.or.srv.reseat/emerg.power ss. releas.term hpi hpi(f/b) hpr/-hpi porv.open ss.depress cond/mfw lpi/hpi lpr/-hpi.hpr lpr/hpi branch'model file forced Minarick 05-16-1989 06:55:04 1.OE-02 1.OE-03 4.OE-04 1.OE-02 Event Identifier:
344/87-037