ML20149K357
| ML20149K357 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-011-00 | |
| Download: ML20149K357 (5) | |
Text
B-66 PRECURSOR DESCRIPTION SHEET LER No.: 321/87-011 Event
Description:
Loss of feedwater and RCIC trip Date of Event: 7/23/87 Plant: Hatch 1 EVENT DESCRIPTION Sequence While the plant was at 100% power, vital AC electrical power was lost due to failure of the vital AC inverter (b:; ieved caused by high internal temperature compounded by dust in the inverter). The electri-cal failure caused reactor feedwater pump runback on loss of control power and isolation of the reactor water cleanup system. Subsequent reactor water level reduction occurred as the feedwater flow attenu-ated. A reactor scram automatically initiated when the reactor protec-tion system setpoint was reached on vessel low water level. As the vessel water level continued to decrease, automatic initiation occurred for the primary containment isolation, the standby gas treatment system, the high-pressure. coolant injection system, and the reactor core isola-tion cooling system. Through RCIC initiated, it tripped on overspeed due to failed diodes in the power supply for the electric governor magnetic pickup module, caused by a bent internal pin, which resulted in a higher than normal current in the diodes.
Reactor water level was temporarily stabilized by HPCI. Three minutes after the AC inverter failed, operations personnel transferred the vital AC to an alternate electrical source. Operators then restarted a feedwater pump and initiated and began reactor water level recovery. Six minutes after vital AC power failure, both HPCI and the feedwater pump tripped on high reactor water level At this point, the control rod drive pump was used to maintain the reactor level. During the event, reactor pressure was controlled by the main turbine bypass valves, and by the steam flow to HPCI and the feedwater pump turbines.
Corrective Action Immediate corrective action was to reset the PCIS valve group isolations and reset the scram signal. Long-term corrective action was taken to repair or replace the failed inverter, provide cooling to the inverter, and replace the failed RCIC module.
Plant/Event Data Systems Involved:
Vital AC power RCIC Main feedwater Event Identifier: 321/87-011
B-67 Components and Failure Modes Involved:
AC inverter - failed due to high ambient temperature RCIC - tripped due to component failures Component Unavailability Duration: N/A Plant Operating Mode: 1 (100% power)
Discovery Method: Operational event Reactor Age: 12.9 y Plant Type: BWR Comments None.
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery assumed possible Branches Impacted and Branch Nonrecovery Estimate PCS 1.0 Unavailable MFW Base case nonrecovery RCIC 1.0 No recovery assumed possible Plant Models Utilized BWR plant Class C Event Identifier: 321/87-011
B-68 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 321/87-011 Event
Description:
Loss of feedwater and RCIC trip Event Date: 07/23/87 Plant: Hatch 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1. OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 7.7E-06 Total 7.7E-06 CV TRANS 1. 6E-05 Total 1.6E-05 ATWS TRANS 7.OE-o6 Total 7. OE-06 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
145 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close fw/p CD 3.2E-06 1.7E-01 cs.loca hpci srv.ads 102 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CD 1.7E-06 7. 6E-02 CS.TRANS rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v rhrsw (c.i.and.v) 125 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CD 1.7E-06 1.7E-01 CS.TRANS hpci RCIC crd srv.ads 105 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CD 8.7E-07 3.9E-02 CS.TRANS -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v rhrsw(c.i.and.v) 103 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CD I.1E-07 2.2E-01 CS.TRANS rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) c.i.and.v 101 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CV 8.4E-06 1.9E-01 CS.TRANS rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v -rhrsw (c.i.and.v) 104 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CV 4.3E-06 9.9E-02 CS.TRANS -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v
-rhrsw(c.i.and.v) 913 trans scram -slc.or.rods PCS/TRANS -srv.close FW/PCS.TRANS h CV 1. 5E-06 1. 6E-01 pci RCIC -srv.ads -cond/fw.pcs -rhr(sdc) 917 trans scram -slc.or.rods PCS/TRANS -srv.close FW/PCS.TRANS h CV 7. 6E-07 8.0E-02 pci RCIC -srv.ads cond/fw.pcs -lpcs -rhr(sdc) 126 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close -fw/p CV 3. 2E-07 1. 9E-01 cs.loca rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v -rhrsw(
c.i.and.v) 963 trans scram slc.or.rods ATWS 7.OE-06 1.0E+00
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Event Identifier: 321/87-011
B-69 Sequence End State Prob N Rec**
101 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P Cv 8.4E-06 1.9E-01 CS.TRANS rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v -rhrsw (c.i.and.v) 102 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CD 1.7E-06 7.6E-02 CS.TRANS rhr(sdc) rhr(spcool)/-ipci.rhr(sdc) -c.i.and.v rhrsw (c.i.and.v) 103 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CD 1.1E-07 2.2E-01 CS.TRANS rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) c.i.and.v 104 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P Cv 4.3E-06 9.9E-02 CS.TRANS -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v
-rhrsw(c.i.and.v) 105 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CD 8.?E-07 3.9E-02 CS.TRANS -hpci rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v rhrsw(c.i.and.v) 125 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CD 1.7E-06 1.7E-01 CS.TRANS hpci RCIC crd srv.ads 126 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close -fw/p Cv 3.2E-07 1.9E-01 cs.loca rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.and.v -rhrsw(
c.i.and.v) 145 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close fw/p CD 3.2E-06 1.7E-01 cs.loca hpci srv.ads 913 trans scram -slc.or.rods PCS/TRANS -srv.close FW/PCS.TRANS h Cv 1.5E-06 1.6E-01 pci RCIC -srv.ads -cond/fw.pcs -rhr(sdc) 917 trans scram -slc.or.rods PCS/TRANS -srv.close FW/PCS.TRANS h Cv 7.6E-07 8.OE-02 pci RCIC -srv.ads cond/fw.pcs -lpcs -rhr(sdc) 963 trans scram slc.or.rods ATWS 7.OE-06 1.0E+00
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\newmodel\bwrcnew.cmp BRANCH MODEL: c:\asp\newmodel\hatch.new PROBABILITY FILE: c:\asp\newmodel\bwrcnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 8.6E-04 1.0E+00 loop 1.7E-05 3.2E-01 loca 3.3E-06 5.0E-01 scram 3.5E-04 1.OE+00 slc.or.rods 1.0E-02 1.0E+00 1.OE-02 PCS/TRANS 1.7E-01 > 1.0E+00 1.0E+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 1.7E-01 > Unavailable srv.chall/trans.-scram 1.0E+00 1.0E+00 srv.chall/loop.-scram 1.OE+00 1.0E+00 srv.close 3.6E-02 1.0E+00 emerg.power 5.4E-04 8.0E-01 ep.rec 1.0E+00 1.7E-01 FW/PCS.TRANS 4.6E-01 > 1.OE+00 3.4E-01 Branch Model: 1.OF.1 Train 1 Cond Prob: 4.6E-01 > Unavailable fw/pcs.loca 1.OE+00 3.4E-01 hpci 2.9E-02 7 .0E-01 RCIC 6.0E-02 > 1.0E+O0 7.OE-01 > 1.0E+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 6.OE-02 > Failed crd 1.OE-02 1.OE+00 1.0E-02 srv.ads 3.7E-03 7.1E-01 1.OE-02 cond/fw.pcs 1.OE+00 3.4E-01 1.OE-03 lpcs 3.OE-03 3.4E-01 lpci(rhr)/lpcs 1.OE-03 7.1E-01 rhr(sdc) 2.1E-02 3.4E-01 1.0E-03 rhr(sdc)/-ipci 2.OE-02 3.4E-01 1.OE-03 rhr(sdc)/ipci 1.OE+00 1.0E+00 1.OE-03 rhr(spcool)/-ipci.rhr(sdc) 2.OE-03 1.OE+00 rhr(spcool)/lpci.rhr(sdc) 5.2E-01 1.0E+00 Event Identifier: 321/87-011
B-70 c.i.and.v 1.OE-03 I.OE+0O0 .0E-02 rhrsw 2.OE-02 3.4E-01 2.OE-03 rhrsw(c.i.and.v) S.OE-01 3.4E-01
- branch model file
- forced Minarick 05-16-1989 07:00:01 Event Identiffei: 321/87-011