ML20147A476

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Final ASP Analysis - Brunswick 2 (LER 324-87-004)
ML20147A476
Person / Time
Site: Brunswick 
Issue date: 05/26/2020
From: Christopher Hunter
Office of Nuclear Regulatory Research
To:
Littlejohn J (301) 415-0428
References
LER 1987-004-00
Download: ML20147A476 (5)
v • d • e


Text

B-75 PRECURSOR DESCRIPTION SHEET LER No.:

324/87-004 Event

Description:

HPCI unavailability during trip recovery Date of Event:

3/11/87 Plant:

Brunswick 2 EVENT DESCRIPTION Sequence While the plant was at 100% power, uninterruptable AC electrical power was lost during operational troubleshooting because of operator error.

The electrical failure caused reactor feedwater pump runback on loss of control power.

Subsequent reactor water level reduction occurred as the feedwater flow attenuated.

Reactor scram,

RCIC, and HPCI were initiated when the reactor vessel low level set point was reached.

Initially, HPCI performed as required, filling the vessel at a rate of 4250 gal/min.

As the vessel level began to go high, flow con-trol was used to reduce the rate to 3000 gal/min.

The HPCI turbine tripped when the vessel reached the high level set point.

Feedwater backflow occurred with the reduction in pump discharge pressure via the HPCI injection valve, then through a common valve from the condensate storage tank into the CST.

Flashing was heard in the CST.

As soon at the HPCI injection valve fully closed from the HPCI trip

signal, the backflow was terminated.

While returning the HPCI system to a standby state, the operator noticed that the power to the HPCI pump discharge valve was tripped.

The valve motor was later found damaged (thermally bound as a

result of the reverse flow condition) and could rot be manually opened.

HPCI would have been unavailable if required for injection later in the transient.

HPCI was declared inoperable.

Corrective Action The motor of the failed discharge valve was replaced, and the HPCI system was investigated for backflow damage.

Procedures were estab-lished to require supervision on UPS transfer functions.

Plant/Event Data Systems Involved:

Main feedwater High-pressure coolant injection Components and Failure Modes Involved:

Feedwater -

loss of flow after control power loss HPCI -

failed after feedwater backflow Component Unavailability Duration:

N/A Plant Operating Mode:

1 (100% power)

Discovery Method:

Operational event Reactor Age:

10.4 y Plant Type:

BWR Event Identifier:

324/87-004

B-76 Comments For the purpose of this analysis, it has been assumed that the likelihood of requiring HPCI after the high level trip was 0.1.

MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery assumed possible Branches Impacted and Branch Nonrecovery Estimate HPCI 0.1 Assumed likelihood of requiring HPCI following high level trip PCS 1.0 Unavailable MFW Base case Assumed unavailable but recoverable due to HPCI, RCIC demand Plant Models Utilized BWR plant Class C Event Identifier:

324/87-004

B-77 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:

324/87-004 Event

Description:

HPCI unavailable during trip recovery Event Date:

03/11/87 Plant:

Brunswick 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENt PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 1.0E+O0 Probability CD CV TRANS Total TRANS Total 1.9E-05 1.9E-05

1. 4E-05 1.4E-05 7.0E-06 7.0E-06 ATWS TRANS Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)

Sequence 145 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close fw/p cs.loca HPCI srv.ads 102 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CS.TRANS rhr(sdc) rhr(spcool)/-ipci.rhr(sdc)

-c.i.and.v rhrsw (c.i.and.v) 105 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CS.TRANS -HPCI rhr(sdc) rhr(spcool)/-ipci.rhr(sdc)

-c.i.and.v rhrsw(c.i.and.v) 101 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P 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 CS.TRANS -HPCI rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)

-c.i.and.v

-rhrsw(c.i.and.v) 107 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CS.TRANS HPCI -rcic rhr(sdc) rhr(spcool)/-lpci.rhr(sdc)

-c.i.

and.v -rhrsw(c.i.and.v) 126 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close -fw/p cs.loca 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

PCI rcic -srv.ads -cond/fw.pcs -rhr(sdc) 941 trans scram -slc.or.rods PCS/TRANS srv.close fw/pcs.loca HP CI -srv.ads -cond/fw.pcs -rhr(sdc)

End State CD CD Prob

1. 6E-05 1.7E-06 N Rec**
2. 4E-02 7.6E-02 CD CV CV CV CV CV CV 8.OE-07 3.5E-02 8.4E-06 1.9E-01 3.9E-06 9.0E-02 4.2E-07 9.9E-03 3.2E-07 1.9E-01 3.0E-07 1.6E-02 2.7E-07 2.2E-02 7.0E-06 1.0E+00 963 trans scram slc.or.rods
    • non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)

ATWS Event' Identifier:

324/87-004

B-78 Sequence 101 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P CS.TRANS rhr(sdc) rhr(spcool)/-Ipci.rhr(sdc) -c.i.and.v -rhrsw (c.i.and.v) 102 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close -FW/P 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 CS.TRANS -HPCI rhr(sdc) rhr(spcool)/-Ipci.rhr(sdc) -c.i.and.v

-rhrsw(c.i.and.v) 105 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CS.TRANS -HPCI rhr(sdc) rhr(spcool)/-Ipci.rhr(sdc) -c.i.and.v rhrsw(c.i.and.v) 107 trans -scram PCS/TRANS srv.chall/trans.-scram -srv.close FW/P CS.TRANS HPCI -rcic rhr(sdc) rhr(spcool)/-lpci.rhr(sdc) -c.i.

and.v -rhrsw(c.i.and.v) 126 trans -scram PCS/TRANS srv.chall/trans.-scram srv.close -fw/p 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 cs.loca NPCI srv.ads 913 trans. scram -slc.or.rods PCS/TRANS -srv.close FW/PCS.TRANS H

PCI rcic -srv.ads -cond/fw.pcs -rhr(sdc) 941 trans scram -slc.or.rods PCS/TRANS srv.close fw/pcs.loca HP CI -srv.ads -cond/fw.pcs -rhr(sdc) 963 trans scram slc.or.rods End State Prob N Rec*

Cv CD Cv CD Cv Cv CD Cv Cv 8.4E-06 1.9E-01 1.7E-06 7.6E-02 3.9E-06 9.OE-02 8.OE-07 3.5E-02 4.2E-07 9.9E-03 3.2E-07 1.9E-01 1.6E-05 2.4E-02 3.OE-07 1.6E-02 2.7E-07 2.2E-02 7.OE-06 1.0E+00 ATWS

    • non-recovery credit for edited case SEQUENCE MODEL:

BRANCH MODEL:

PROBABILITY FILE:

c:\\asp\\newmodel\\bwr_cnew.cmp c:\\asp\\newmodel\\brunswck.new c:\\asp\\newmodel\\bwr_cnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch trans loop loca scram slc.or.rods PCS/TRANS Branch Model:

I.OF.1 Train 1 Cond Prob:

srv.chall/trans.-scram srv.chall/loop.-scram srv.close emerg.power ep.rec FW/PCS.TRANS Branch Model:

1.OF.1 Train 1 Cond Prob:

fw/pcs.loca HPCI Branch Model:

I.OF.I Train 1 Cond Prob:

rcic crd srv.ads cond/fw.pcs lpcs ipci(rhr)/lpcs rhr(sdc) rhr(sdc)/-Ipci rhr(sdc)/lpci rhr(spcool)/-lpci.rhr(sdc) rhr(spcool)/lpci.rhr(sdc) c.l.and.v rhrsw Event Identifier:

324/87-004 System Non-Recov Opr Fail 8.6E-04 1.7E-05 3.3E-06 3.5E-04 1.OE-02 1.7E-01 > 1.OE+00 1.7E-01 > Unavailable I.OE+00 1.OE+00 3.6E-02 2.9E-03 1.OE+00 4.6E-01 > 1.OE+00 4.6E-01 > Unavailable 1.0E+00 2.9E-02 > 1.OE+00 2.9E-02 > Failed 6.OE-02 1.OE-02 3.7E-03 1.OE+00 3.OE-03 1.OE-03 2.1E-02 2.OE-02 1.OE+00 2.OE-03 5.2E-01 1.OE-03 2.OE-02 1.OE+00 3.2E-01 5.OE-01 1.OE+00 1.OE+00 1.OE+00 1.OE+00 1.0E+00 1.OE+00 8.OE-01 1.7E-01 3.4E-01 3.4E-01 7.OE-01 > 1.OE-01 7.OE-01 I.OE+00 7.1E-01 3.4E-01 3.4E-01 7.1E-01 3.4E-01 3.4E-01 1.OE+00 1.OE+00 1.OE+00 1.OE+00 3.4E-01 1.OE-02 I.OE-02 I.OE-02 I.OE-03 I.OE-03 1.OE-03 1.0E-03 1.OE-02 2.OE-03

B-79 rhrsw(c.i.and.v) 5.OE-01 3.4E-01 branch model file forced Minarick 05-16-1989 07:00:11 Event Identifier:

324/87-004

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