ML20161A166
| ML20161A166 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-001-00 | |
| Download: ML20161A166 (3) | |
Text
B- 15 PRECURSOR DESCRIPTION SHEET LER No.: 251/87-001 Event
Description:
Reactor trip with one of three AFW trains unavailable Date of Event: 1/6/87 Plant: Turkey Point Units 3 and 4 EVENT DESCRIPTION Sequence While at 100% power during routine surveillance on power sensors, a failed sensor was placed in trip. Later, a spurious signal caused a second sensor to trip resulting in a reactor trip. The C AFW train was out for maintenance because it had tripped during testing earlier in the day. The A & B AFW trains responded as designed.
Corrective Action Repairs were made...
Plant/Event Data Systems Involved:
AFW Components and Failure Modes Involved::
Pump was unavailable Component Unavailability Duration: N/A Plant Operating Mode: 1 (100%)
Discovery Method: Testing Reactor Age: 14.2 and 13.4 y, respectively Plant Type: PWR Comments MFW believed lost due to SC level decrease to low-low set point.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient No recovery Branches Impacted and Branch Nonrecovery Estimate AFW One of three trains unavailable.
Station has three AFW trains for two units.
MFW Base case Plant Models Utilized PWR plant Class E Event Identifier: 251/87-001
B- 16 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 251/87-001 Event
Description:
Reactor trip with one of three AFW trains unavailable Event Date: 01/06/87 Plant: Turkey Point 3 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OE+O0 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 3.7E-06 Total 3.7E-06 CV TRANS 7.5E-06 Total 7.5E-06 ATWS TRANS 3.4E-05 Total 3.4E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 1.6E-06 3.1E-02 cond/mfw 126 trans -rt AFW MFW hpi(f/b) -ss.depress cond/mfw CD 1.6E-06 2.6E-02 121 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open as.depress CD 1.7E-07 9.2E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 1.7E-07 3.1E-02 127 trans -rt AFW MFW hpi(f/b) ss.depress CD 1.7E-07 7.7E-02 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress - CV 3.OE-06 6.1E-02 cond/mfw 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/mfw CV 3.OE-06 5.1E-02 109 trans -rt -AFW -porv.or.srv.chall ss.releas.term hpi CV 1.2E-06 2.9E-01 122 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw CV 3.3E-07 6.1E-02 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
109 trans -rt -AFW -porv.or.srv.chall ss.releas.term hpi CV 1.2E-06 2.9E-01 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress - CV 3.OE-06 6.1E-02 cond/mfw 120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 1.6E-06 3.1E-02 cond/mfw 121 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open ss.depress CD 1.7E-07 9.2E-02 122 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw CV 3.3E-07 6.1E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 1.7E-07 3.1E-02 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/mfw CV 3.OE-06 5.1E-02 126 trans -rt AFW MFW hpi(f/b) -ss.depress cond/mfw CD 1.6E-06 2.6E-02 127 trans -rt AFW MFW hpi(f/b) ss.depress CD 1.7E-07 7.7E-02 Event Identifier: 251/87-001
B- 17 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\newmodel\pwr_bnew.cmp BRANCH MODEL: c:\asp\newmodel\turkey.new PROBABILITY FILE: c:\asp\newmodel\pwr_bnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 4.BE-04 1.OE+00 loop 4.6E-06 3.9E-01 loca 2.4E-06 4.3E-01 rt 2.SE-04 1.2 E-01 rt/loop 0.OE+00 1 .0E+00 emerg .power 2. 9E-03 8.0E-01 ep.rec 1.0E+00 1.7E-01 AFW 1.5E-03 > 5.OE-03 2 .7E-01 Branch Model: l.OF.3 Train I Cond Prob: 5.0E-02 Train 2 Cond Prob: 1.OE-01 Train 3 Cond Prob: 3.OE-01 > Unavailable AFW/EMERG. POWER 1.5E-03 > 5.OE-03 2 .7E-01 Branch Model: 1.OF.3 Train 1 Cond Prob: 5.OE-02 Train 2 Cond Prob: 1.OE-01 Train 3 Cond Prob: 3.OE-01 > Unavailable MFW 1.9E-01 > 1.OE+00 3.4E-01 Branch Model: I.OF.I Train 1 Cond Prob: 1.9E-01 > Failed porv.or.srv.chall 4.OE-02 1.0E+00 porv.or. srv.reseat 2.OE-02 1 .1E-02 porv. or. srv.reseat/emerg.power 2.OE-02 1.OE+00 ss.releas.term 1.5E-02 3.4E-01 hpi 3.0E-04 B.4E-01 hpi (f/b) 3.OE-04 8.4E-01 1.OE-02 hpr/-hpi 1.5E-04 1 .OE+00 1.OE-03 porv. open 1.OE-02 1 .0E+00 4.OE-04 ss.depress 3.6E-02 1.0E+00 cond/mfw 1.0E+00 3.4E-01 1.OE-02 lpi/hpi 1.5E-04 3.4E-01 lpr/-hpi.hpr 6.1E-01 1.OE+00 lpr/hpi 1.5E-04 1.0E+00
- branch model file
- forced Minarick 05-16-1989 06:51:40 Event Identifier: 251/87-001