ML20147A478
| ML20147A478 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Regulatory Research |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-007-00 | |
| Download: ML20147A478 (3) | |
Text
B-179 PRECURSOR DESCRIPTION SHEET LER No.:
455/87-007 Event
==
Description:==
Trip with feedwater isolation and one AFW train unavailable Date of Event:
5/4/87 Plant:
Byron 2 EVENT DESCRIPTION Sequence Due to component failure, loss of an inverter deenergized instru-ment bus 211.
Because of RPS testing in progress, a high flux bistable had been tripped already, thus satisfying the two of four coincident trip logic.
As part of the normal posttrip sequence, the MFW was isolated as designed.
AFW responded, but the 2A motor pump failed to start because it drew control power from bus 211, which was deenergized.
Corrective Action The inverter was repaired.
Plant/Event Data Systems Involved:
Auxiliary feedwater Electrical Components and Failure Modes Involved:
Inverter and bus fail in operation AFW pump fails on demand Component Unavailability Duration:
N/A Plant Operating Mode:
1 (88%)
Discovery Method:
Operational event Reactor Age:
0.3 y Plant Type:
PWR Comments None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery Branches Impacted and Branch Nonrecovery Estimate AFW Base case One of three trains unavailable MFW Base case Plant Models Utilized PWR plant Class B Event Identifier:
455/87-007
B-180 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
455/87-007 Event
Description:
Trip with feedwater isolation and one AFW train unavailable Event Date:
05/04/87 Plant:
Byron 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 3.7E-05 Total 3.7E-05 CV TRANS 6.6E-05 Total 6.6E-05 ATWS TRANS 3.4E-05 Total 3.4E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
126 trans -rt AFW MFW hpi(f/b) -ss.depress cond/mfw CD 1.6E-05 2.SE-02 120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 1.5E-05 3.OE-02 cond/rmfw 127 trans -rt AFW MFW hpi(f/b) ss.depress CD 1.8E-06 7.4E-02 121 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open ss.depress CD 1.7E-06 8.8E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 1.7E-06 3.0E-02 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/msfw CV 3.0E-05 4.9E-02 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress -
CV 2.9E-05 5.BE-02 cond/mfw 109 trans -rt
-AFW
-porv.or.srv.chall ss.releas.term hpi CV 4.1E-06 2.BE-01 122 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw CV 3.2E-06 5.BE-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 4.1E-06 2.8E-01 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CV 2.9E-05 5.8E-02 cond/mfw 120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 1.5E-05 3.OE-02 cond/mfw 121 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open ss.depress CD 1.7E-06 8A.E-02 122 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw CV 3.2E-06 5.8E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 1.7E-06 3.0E-02 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/mfw CV 3.OE-05 4.9E-02 126 trans -rt AFW MFW hpi(f/b) -ss.depress cond/mfw CD 1.6E-05 2.5E-02 127 trans -rt AFW MFW hpi(f/b) ss.depress CD 1.8E-06 7.4E-02 Event Identifier:
455/87-007
B-181 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\pwrbnew.cmp c:\\asp\\newmodel\\byron.new c:\\asp\\newmodel\\pwrbnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System trans loop loca rt rt/loop emerg.power ep.rec AFW Branch Model:
l.OF.2+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Serial Component Prob:
afw/emerg.power MFW Branch Model:
l.OF.I Train 1 Cond 2rob:
porv.or.srv.chall 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 4.8E-04
- 4. 6E-06
- 2. 4E-06 2.SE-04 O.OE+00 2.9E-03 1.OE+00 1.3E-03 > 5.OE-02 2.OE-02 > Unavailable 5.0E-02 2.8E-04 5.OE-02 2.OE-01 > 1.OE+00 2.OE-01 > Unavailable 4.OE-02 2.OE-02 2.OE-02 l15E-02 l.OE-03 1.OE-03 1.5E-04 1.OE-02 3.6E-02 1.0E+00 1.5E-04 6.7E-01 1.5E-04 Non-Recov 1.OE+00 3.9E-01 4.3E-01 1.2E-O0 1.OE+00 8.OE-01 1.7E-01 2.6E-01 3.4E-01 3.4E-01 1.0E+00 1.lE-02 1.OE+00 3.4E-01 8.4E-01 8.4E-01 1.0E+00 1.0E+00 1.OE+00 3.4E-01 3.4E-01 1.0E+00 1.0E+00 Opr Fail 1.DE-02 I.OE-03 4.OE-04 1.OE-02 branch model file
- forced Minarick 05-16-1989 06:53:09 Event Identifier:
455/87-007