Text

Final ASP Analysis - Wolf Creek 1 (LER 482-85-041)
	ML20161A175
Person / Time
Site:	Wolf Creek
Issue date:	06/09/2020
From:	Christopher Hunter; NRC/RES/DRA/PRB
To:	;
	Littlejohn J (301) 415-0428
References
	LER 1985-041-00
	Download: ML20161A175 (5)
	v • d • e

PRECURSOR DESCRIPTION AND ANALYSIS LER No.:

482/85-041 Event

Description:

Startup LOFW and AFW Pump Trip Date of Event:

June 9, 1985 Plant:

Wolf Creek 1 EVENT DESCRIPTION Sequence on June 9, 1985, and June 13, 1985, events that were initiated by trips of MFW pump A occurred.

on June 9, 1985, an AFW actuation and SC blowdown and sample isolation occurred when MFW pump A tripped during a start attempt. MFW pump B was not operating because its discharge valve was under repair.

At the time of the event, the plant was in Mode 2, startup, with a reactor power level of ~-2%, and feedwater was being supplied by the motor-driven AFW pumps.

on June 13, 1985, the main turbine generator was being loaded, but it was shut down at 0345 h CDT and at 15% power because of a turbine vibration condition.

Plant response to the tubine trip was normal.

Following the trip, reactor power level was being slowly decreased and was at '-9% when the operating MFW pump A tripped.

AFW flow to the SGs was immediately established by manual actuation of the motor-driven AFW pumps, and reactor power was rapidly reduced by driving in the control rods.

As SG water levels continued to decrease, the TD AEW pump was manually started to provide additional feedwater flow, but it tripped on overspeed when the operator opened the trip/throttle valve before opening the steam supply valve.

At 0400 h CDT with reactor power at ~-1%, SG "B* water level reached the low-low level trip set point, and a reactor trip, AFW actuation signal, and SG blowdown and sample isolation signal were automatically ini-tiated.

The reactor trip, coupled with a low RCS average temperature (Tavg) of 5600 F, initiated a feedwater isolation signal.

The MSIVs were manually closed to prevent excessive RCS/SG cooldown.

MSIV "A" failed to close initially and was fast closed on a manual actuation.

Corrective Action Recovery procedures were implemented; the pump problems were not determined.

Event Identifier:

482/85-041 E-311

Plant/Event Data Systems Involved:

MFW, AFW, and MSIVs Components and Failure Moides Involved:

MEW pump -

failed in operation twice 1 AFW pump plus 1 MSIV -

failed in second event Component Unavailability Duration:

NA Plant Operating Mode:

2 (2% power)

Discovery Method:

Operational event Reactor Age:

0.3 year Plant Type:

PWR Comments Two events:

second event is modeled here; first is an uncomplicated LOFW modeled as a nonspecific reactor trip transient for PWR plant Class B.

MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate MFW 0.12 Cause of trip could not be identified, but later pump tests had acceptable results Third AFW train Base case Plant Models Utilized PWR plant Class B Event Identifier:

482/85-041 E-312

CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:

Event

Description:

Event Date:

Plant:

482/85-041 Startup LOFW and AFW Pump Trip 6/9/85 Wolf Creek I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV TRANS Total

1.

OOOE+00 Probability B.

592E-06 B.

592E-06 CD TRANS Total ATWS TRANS Total DOMINANT SEQUENCES End State: CV Conditional Probability:

.109 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI End State: CD Conditional Probability:

126 TRANS -RT AFW MFW HPI(F/BI -SS.DEPRESS COND/MFW End State:

ATWS Conditional Probability:

128 TRANS RT

4.

217E-06

4.

217E-06

3.

OOOE-05

3.

OOOE-05

2.

544E-06

1.

255E-06

3.

OOOE-05 Event Identifier: 482/85-041 E-313

SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recovf' 101 TRANS -RT -AFW PORV.OR.SRV.CHALL -PORV.OR.SRV.RESEAT SS.RELE AS.TERII HPI 102 TRANS -RT -AFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HPI HP RI-HP] -SOS.DEPRESS -LPRI-HPI.HPR 103)

TRANS -RI -AFW PORV.OR.SRY.CHALL PORV.OR.SRV.RESEAT -HPI HP RI-HP] -SS.DEPRESS LPRI1-HPI.HPR 104 TRANS -RT -AFN PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HP] HP RI-HPI SS.DEPRESS 109 TRANS -RT -AFN -PORV.OR.SRY.CHALL SS.RELEAS.TERM HP]

119 TRANS -RT AFW MFW -HPI(FiB) -HPRI-HPI PORV.OPEN -SDS.DEPRESS

-COND/MFW 120 TRANS -RT AFN MFW

-HPI(FIB) -HPR/-HPI PORV.OPEN -SS.DEPRESS COND/MFW 122 TRANS -RT AFW MFW

-HPI(FIB) HPR/-HPI -SS.DEPRESS -COND/MFW 123) TRANS -RT AFW MFW -HPI(FIB) HPR/-HPI -SS.DEPRESS COND/MFW 124 TRANS -RI AFW MFN -HPI(F/8)

HPRI-HPI SS.OEPRESS 125 TRANS -RT AFW MFW HPI(F/B) -SS.DEPRESS -COND/MFW 126 TRANS -RT AFW NFW HP](F/BI -SS.DEPRESS COND/MFW 127 TRANS -RI AFW 1MFW HPI(FIB) SS.DEPREKS 128 TRANS RT CV CV Co CD CV CV CD 1.059E-07

1.

766E-01 5.288E-07 2.964E-03 1.074E-06 21.964E-03

5.

984E-08

2.

964E-03 2.544E-06