ML20156A239
| ML20156A239 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-035-00 | |
| Download: ML20156A239 (4) | |
Text
B-141 PRECURSOR DESCRIPTION SHEET LER No.:
400/87-035 Event
Description:
Reactor trip and one of three AFW pumps fail Date of Event:
6/17/87 Plant:
Shearon Har-is 1 EVENT DESCRIPTION Sequence A reactor coolant pump tripped, which resulted in a reactor trip due to low flow in that reactor coolant loop.
During the plant response to the trip, the turbine-driven auxiliary feedwater (AFW) pump started and then tripped on overspeed.
The motor-driven AFW pumps started nor-mally.
The reactor trip was caused when a worker bumped a bus enclosure while moving a heavy load and power was lost to the reactor coolant pump.
The t~ibine-driven AFW pump tripped on overspeed due to an accumulation of water in the steam supply line.
Prior to This event, the moisture was being manually drained every 4 h.
Corrective Action A program was initiated to check and drain the steam supply lines once per hour.
If the lines drain more than 2-3 min, the frequency will be increased.
A plant modification is planned that will install drain traps on the steam supply lines to the turbine-driven AFW pump.
Plant/Event Data Systems Involved:
Auxiliary feedwater system Components and Failure Modes Involved:
Turbine-driven pump failed to run Component Unavailability Duration:
N/A Plant Operating Mode:
1 (100% power)
Discovery Method:
Operational event Reactor Age:
0.4 y Plant Type:
PWR Comments None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery Event Identifier:
400/87-035
C, B-142 Branches Impacted and Branch Nonrecovery Estimate AFW Base case TD AFWP trips after starting Plant Models Utilized PWR plant Class B Event Identifier:
400/87-035
B-143 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
400/87-035 Event
Description:
Reactor trip and 1 of 3 AFW pumps fails Event Date:
06/17/87 Plant:
Harris 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 1.0E+00 Probability CD CV TRANS Total TRANS Total 1.7E-06 1.7E-06 9.3E-06 9.3E-06 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 109 trans -rt
-AFW -porv.or.srv.chall ss.releas.term hpi 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 101 trans -rt
-AFW porv.or.srv.chall -porv.or.srv.reseat ss.releas
.term hpi 128 trans rt
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 101 trans -rt
-AFW porv.or.srv.chall -porv.or.srv.reseat ss.releas
.term hpi 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 AMW 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 End State CD CD CD CD CD CV CV CV CV ATWS End State CV CV CV CD CD CD CV Prob 7.6E-07
- 6. 9E-07 8.4E-08
- 7. 6E-08
- 7. 6E-08 6.2E-06 1.4E-06 1.3E-06
- 2. 6E-07 N Rec**
2.5E-02
- 3. OE-02
- 7. 4E-02 8.8E-02
- 3. OE-02
- 2. 9E-01
- 4. 9E-02 5.8E-02
- 2. 9E-01 3.4E-05 1.2E-01 Prob
- 2. 6E-07 6.2E-06 1.3E-06
- 6. 9E-07
- 7. 6E-08
- 7. 6E-08 1.4E-06 N Rec-*
2.9E-01 2.9E-01 5.8E-02
- 3. OE-02 8.8E-02 3.OE-02 4.9E-02 Event Identifier:
400/87-035
13-144 126 127 128 trans -rt AFW MFW hpi (f/b) -ss.depres's cond/mfw trans -rt AFW MFW hpi (f/b) ss.depress trans rt CD CD ATWS 7.6E.-07
?.5F.-02 8.4F-08
'7.4E-02 3.4E-05 1.2E-O1
- non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\pwr bnew.cmp c:\\asp\\newmodel\\ha--is.new c:\\asp\\newmodel\\pwr bnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABIIIITIES Branch System trans loop loca rt rt/loop emerg.power ep.rec AFW Branch Model:
1.OF.34ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
afw/emerg.power MFW Branch Model:
I.OF.1 Train 1 Cond Prob:
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 lpl/hpi lpr/-hpl.hpr lpr/hpi
- 4. 8E-04 4.6E-06 2.4E-06
- 2. 8E-04 0.OE+00
- 2. 9E-03 1.OE+00 3.8E-04 > 2.3E-03 2.OE-02 1.0E-01 5.OE-02 > Failed 2.8E-04 5.OE-02 2.OE-Ol > ].OE400 2.OE-01 > Unavailable 4.OE-02 3.OE-02 3.OE-02 1.5E-02 1.5E-03 1.5E-03 1.5E-04 1.OE-02 3.6E-02 1.OE400 1.5E-04 6.7E-01 1.5E-04 Non-Recov I.OE400 3.9E-01 4.3E-01 1.2E-01 I.OE400 8.OE-O1 1.7E-01 2.6E-01 3.4E-01 3.4E-01 I.OE+00 SI.E-02 1.OE+00 3.4E-01 8.4E-01 8.4E-01 1.0E+00 1.OE+00 1.OE+00 3.4E-01 3.4E-01 1.OE+00 1.OE+00 Opr Fall 1.OE-02 1.OE-03 4.OE-04 I.OE-02 branch model file
- forced Minarick 05-16-1989 06:53:16 Event ident I tIer:; 400/87-035