ML20147A479
| ML20147A479 | |
| 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 1987-019-00 | |
| Download: ML20147A479 (4) | |
Text
B-182 PRECURSOR DESCRIPTION SHEET LER No.:
455/87-019 Event
Description:
Trip with loss of offsite power Date of Event:
10/02/87 Plant:
Byron 2 EVENT DESCRIPTION Sequence Operators lost control of feedwater during reactor startup, and a reactor trip occurred at 13% power.
A main feedwater regulating valve allowed excessive "leak-by," and the excess water caused high level in a
As part of the trip re covery it was necessary to realign the ring bus.
During the realignment, an equipment operator opened the wrong transformer disconnect and caused a loss of offsite power.
The diesel generators automatically started and the safe shut-down loads sequenced on to the diesel generators.
The labeling on the disconnects was not consistent with the nomenclature used to identify the disconnect and contributed to the equipment operator error.
Offsite power was restored -5 h later.
Corrective Action The equipment operator was disciplined.
The main feedwater regulating valve was repaired.
Plant/Event Data Systems Involved:
Main feedwater Offsite power Components and Failure Modes Involved:
MFW regulating valve leaked in operation Operator opens wrong breaker in operation Component Unavailability Duration:
N/A Plant Operating Mode:
1 (13% power)
Discovery Method:
Operational event Reactor Age:
0.7 y Plant Type:
PWR Comments None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP 0.34 Recoverable locally Event Identifier:
455/87-019
B-183 Branches Impacted and Branch Nonrecovery Estimate None Plant Models Utilized PWR plant Class B Event Identifier:
455/87-019
B-184 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
455/87-019 Event
Description:
Trip with loss of offsite power Event Date:
10/02/87 Plant:
Byron 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 3.4E-01 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD LOOP 1.5E-04 Total 1.5E-04 CV LOOP 4.7E-06 Total 4.7E-06 ATWS LOOP 0.OE+00 Total 0.OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
217 LOOP -rt/loop emerg.power ep.rec CD 1.3E-04 4.6E-02 216 LOOP -rt/loop emerg.power -ep.rec afw/emerg.power CD I.IE-05 7.7E-02 215 LOOP -rt/loop emerg.power -ep.rec -afw/emerg.power -porv.or.srv CV 3.1E-06 7.6E-02
.chall ss.releas.term 209 LOOP -rt/loop
-emerg.power -afw -porv.or.srv.chall ss.releas.te CV 1.4E-06 9.7E-02 rm hpi 213 LOOP -rt/loop emerg.power -ep.rec -afw/emerg.power porv.or.srv CV 1.3E-07 7.6E-02
.chall -porv.or.srv.reseat/emerg.power ss.releas.term non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
209 LOOP -rt/loop
-emerg.power -afw -porv.or.srv.chall ss.releas.te CV 1.4E-06 9.7E-02 rm hpi 213 LOOP -rt/loop emerg.power -ep.rec -afw/emerg.power porv.or.srv CV 1.3E-07 7.6E-02
.chall -porv.or.srv.reseat/emerg.power ss.releas.term 215 LOOP -rt/loop emerg.power -ep.rec -afw/emerg.power -porv.or.srv CV 3.1E-06 7.6E-02
.chall ss.releas.term 216 LOOP -rt/loop emerg.power -ep.rec afw/emerg.power CD I.IE-05 7.7E-02 217 LOOP -rt/loop emerg.power ep.rec CD 1.3E-04 4.6E-02
- non-recovery credit for edited case SEQUENCE MODEL:
c:\\asp\\newmodel\\pwrbnew.cmp BRANCH MODEL:
c:\\asp\\newmodel\\byron.new PROBABILITY FILE:
c:\\asp\\newmodel\\pwrbnew.pro Event Identifier:
455/87-019
B-185 No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 4.8E-04 1.OE+00 LOOP 4.6E-06 > 4.6E-06 3.9E-01 > 3.4E-01 Branch Model:
INITOR Initiator Freq:
4.6E-06 loca 2.4E-06 4.3E-01 rt 2.8E-04 1.2E-01 rt/loop O.OE+00 l.OE+00 emerg.power 2.9E-03 8.OE-01 ep.rec l.OE+00 1.7E-Ol afw 1.3E-03 2.6E-01 afw/emerg.power 5.OE-02 3.4E-01 mfw 2.OE-01 3.4E-01 porv.or.srv.chall 4.OE-02 1.OE+00 porv.or.srv.reseat 2.OE-02 1.lE-02 porv.or.srv.reseat/emerg.power 2.OE-02 1.0E+00 ss.releas.term 1.5E-02 3.4E-01 hpi 1.OE-03 8.4E-01 hpi(f/b) 1.0E-03 8.4E-01 l.0E-02 hpr/-hpi 1.5E-04 1.0E+00 1.0E-03 porv.open l.OE-02 1.0E+00 4.0E-04 ss.depress 3.6E-02 1.OE+00 cond/mfw 1.OE+00 3.4E-01 1.0E-02 lpi/hpi 1.5E-04 3.4E-01 lpr/-hpi.hpr 6.7E-01 1.OE+00 lpr/hpi 1.5E-04 1.OE+00 branch model file forced Minarick 05-16-1989 07:03:22 Event Identifier:
455/87-019