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 1.0E+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 1.7E-06 Total 1.7E-06 CV TRANS 9.3E-06 Total 9.3E-06 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 7.6E-07 2.5E-02 120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 6. 9E-07 3. OE-02 cond/mfw 127 trans -rt AFW MFW hpi(f/b) ss.depress CD 8.4E-08 7. 4E-02 121 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open ss.depress CD 7. 6E-08 8.8E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 7. 6E-08 3. OE-02 109 trans -rt -AFW -porv.or.srv.chall ss.releas.term hpi CV 6.2E-06 2. 9E-01 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/mfw CV 1.4E-06 4. 9E-02 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress - CV 1.3E-06 5.8E-02 cond/mfw 101 trans -rt -AFW porv.or.srv.chall -porv.or.srv.reseat ss.releas CV 2. 6E-07 2. 9E-01
.term hpi 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-*
101 trans -rt -AFW porv.or.srv.chall -porv.or.srv.reseat ss.releas CV 2. 6E-07 2.9E-01
.term hpi 109 trans -rt -AFW -porv.or.srv.chall ss.releas.term hpi CV 6.2E-06 2.9E-01 119 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress - CV 1.3E-06 5.8E-02 cond/mfw 120 trans -rt AFW MFW -hpi(f/b) -hpr/-hpi porv.open -ss.depress CD 6. 9E-07 3. OE-02 cond/mfw 121 trans -rt AMW MFW -hpi(f/b) -hpr/-hpi porv.open ss.depress CD 7. 6E-08 8.8E-02 123 trans -rt AFW MFW -hpi(f/b) hpr/-hpi -ss.depress cond/mfw CD 7. 6E-08 3.OE-02 125 trans -rt AFW MFW hpi(f/b) -ss.depress -cond/mfw CV 1.4E-06 4.9E-02 Event Identifier: 400/87-035
13-144 126 trans -rt AFW MFW hpi (f/b) -ss.depres's cond/mfw CD 7.6E.-07 ?.5F.-02 127 trans -rt AFW MFW hpi (f/b) ss.depress CD 8.4F-08 '7.4E-02 128 trans rt ATWS 3.4E-05 1.2E-O1
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\newmodel\pwr bnew.cmp BRANCH MODEL: c:\asp\newmodel\ha--is.new PROBABILITY FILE: c:\asp\newmodel\pwr bnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABIIIITIES Branch System Non-Recov Opr Fall trans 4. 8E-04 I .OE400 loop 4.6E-06 3.9E-01 loca 2.4E-06 4.3E-01 rt 2. 8E-04 1.2E-01 rt/loop 0.OE+00 I .OE400 emerg.power 2. 9E-03 8.OE-O1 ep.rec 1.OE+00 1.7E-01 AFW 3.8E-04 > 2.3E-03 2.6E-01 Branch Model: 1.OF.34ser Train 1 Cond Prob: 2.OE-02 Train 2 Cond Prob: 1.0E-01 Train 3 Cond Prob: 5.OE-02 > Failed Serial Component Prob: 2.8E-04 afw/emerg.power 5.OE-02 3.4E-01 MFW 2.OE-Ol > ].OE400 3.4E-01 Branch Model: I.OF.1 Train 1 Cond Prob: 2.OE-01 > Unavailable porv.or.srv.chall 4.OE-02 I.OE+00 porv.or.srv.reseat 3.OE-02 SI.E-02 porv.or.srv.reseat/emerg.power 3.OE-02 1.OE+00 ss.releas.term 1.5E-02 3.4E-01 hpi 1.5E-03 8.4E-01 hpi(f/b) 1.5E-03 8.4E-01 1.OE-02 hpr/-hpi 1.5E-04 1.0E+00 1.OE-03 porv.open 1.OE-02 1 .OE+00 4 .OE-04 ss.depress 3.6E-02 1.OE+00 cond/mfw 1.OE400 3.4E-01 I .OE-02 lpl/hpi 1.5E-04 3.4E-01 lpr/-hpl.hpr 6.7E-01 1.OE+00 lpr/hpi 1.5E-04 1.OE+00
- branch model file
- forced Minarick 05-16-1989 06:53:16 Event ident I tIer:; 400/87-035