ML20149K401

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Final ASP Analysis - LaSalle 2 (LER 374-84-017)
ML20149K401
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 05/28/2020
From: Christopher Hunter
NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1984-017-00, LER 1984-018-00
Download: ML20149K401 (5)
v • d • e


Text

PRECURSOR DESCRIPTION SHEET LER No.: 374/84-017, -018 Event

Description:

LOFW While Shutting Down and HPCS Fails in Test Within +15 d of LOFW Date of Event: May 3 and 17, 1984 Plant: LaSalle 2 EVENT DESCRIPTION Sequence On May 3, 1984, while the reactor was at 10% power and shutting down, it was scrammed manually following failure to restart the motor-driven FW pump. The pump had tripped due to a clogged strainer follow-ing a valving. error. The tu'rbine-driven FW pumps had been valved out due to the shutdown in progress. .On May 17, with the reactor at 30%

power, the HPCS system failed in testing when the HPCS pump breaker failed to close and start the pump. Faulty position switch contacts were found, and certain breaker/switch components had not been in-stalled. Due to the nature of these events, HPCS may have been unavail-able during the May 3 LOFW.

Corrective Action The motor-driven FW pump was repaired and steps were taken to pre-vent a similar valving error from recurring. The breaker position switch that caused the HPCS breaker failure was replaced. In addition, all of the Division III 4160-V switchgear were inspected and cleaned before being returned to service.

Plant/Event Data Systems Involved:

MEW, HPCS Components and Failure Modes Involved:

Motor-driven FW pump - tripped due to operator error HPCS pump - failed to start on demand (breaker failure)

Component Unavailability Duration: NA Plant Operating Mode: 10%, 30% power Discovery Method: See sequence description Reactor Age: 0.2 year Plant Type: BWR Event Identifier: 374/84-017, -018 Dý-212

Comment s None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate PGs 1.0 Failed due to LOFW Main feed- 0.34 Motor-driven train was not recover-water able; possible recovery through use of turbine-driven feed pump HPCS 0.34 Potential recovery at breaker Plant Models Utilized BWR plant Class C Event Identifier: 374/84-017, -018 D-213

CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Evenit Identifier: 374/84-017 Event

Description:

LOFW 'While Shutting Dawn and HPCS Fails inTest (4/-15 days)

Event Date: 5/3/84 Plant: LaSalle 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.0E+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV TRANS 4.1E-06 Total 4. 1E-06 CD TRANS 3.8E-04 Total 3.BE-04 ATWS TRANS 2 .OE-05 Total 2.OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability: 1.7E-06 155 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS -COND/FW.PCS

-RHR(SDC)

End State: CD Conditional Probability- 3.2E-04 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA SRV.ADS End State: ATWS Conditional Probability: 2.OE-05 Event Identifier: 374/84-017 D-2 14

173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**

101 TRANS -SCRAM PGS/TRANS SRV .DHALL/TRANS .-SCRAM -SRV .CLOSE -FW CO 3.OE-05 7.6E-02

/PCS.TRANS RHR(SDC). RHR(SPCOOL)/-LPCI.RHR(SDC) C.i .AND.

W/RHR (SDC) .RHR (SPCOOL) 102 TRANS -SCRAM PCS/TRANS SRY .CHALL/TRANS .-SCRAM -SRV .CLOSE FW CD 1.OE-05 2.6E-02

/PCS.TRANS -HPCI RHR(SDC) RHR(SPCOOL)/-LPCI.RHR(SDC) C.

I.AND.V/RHR(SDC) .RHR(SPCOOL) 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW CD 3.2E-04

  • 1.2E-01

/PCS.LOCA HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS CV 1.OE-06 4.3E-02 HPCI RCIC/TRANS .OR .LQOP -SRV .ADS -COND/FW.PCS -RHR(SDC) 138 TRANS SCRAM -SLC .OR .RODS PCS/TRANS -SRV .CLOSE FW/F125. TRANS Cv 5.2E-07 2.2E-02 HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FW.PCS -LPCS -RHR(

SDC) 155 TRANS SCRAM -SLC .OR .RODS PCS/TRANS SRV .CLOSE FN/PCS .LOCA CV 1.7E-06

  • 1.0E+00
  • dominant sequence for end state
    • non-recovery credit for edited case MODEL: b:\bwrctree .cmp DATA:- b: \1asl prob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.1E-03 1.0E+00 LOOP 1.3E-05 3.4E-01 LOCA 3.3E-06 3.4E-01 SCRAM 4.1E-04 1.0E+00 SLC .OR.RODS 1.OE-02 1.0E+00 4.OE-02 PCS/TRANS 1.7E-01 > 1.OE+00 1.OE+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 1.7E-01 > Failed PCS/LOCA I.OE+00 1.0E+00 SRV.CHALL/TRANS .-SCRAM 1.0E+00 1.0E+00 SRV .CHALL/TRANS .SCRAM 1.0E+00 1.OE+00 Event Identifier: 374/84-017 1)-2 15

SRY .CHLLILOOP .-SCRAMi I.0E+00 1.OE+00 SRV .CHALL/LOOP .SCRAM I OE+00 1.OE400 SRY .CLOSE 6.OE-02 I.OE+00 EMERG .POER 2.9E-03 5.1E-01 FW/PCS.TRANS 4.6E-01 > 1.OE+0O 3.4E-01 Branch Model: 1.0F.1 Train 1 Cond Prob: 4.6E-01 > Failed FW/PCS .LOCA 1.OE+00 3.4E-01 HPCI 2.OE-02 > 1.OE+00 3.4E-01 Branch Model: 1.OF.1 Train I Cond Prob: 2.OE-02 > Failed RCIC/TRANS IR.LOOP 6.7E-02 5.7E-01 RCIC/LOCA 1.OE+00 1.OE+00 CRD 1.0E-02 1.OE+00 .E-0*22 4.

SRV.ADS 6.7E-03 1.0E+00 4.OE-02 COND/FW .PCS 1.OE+00 3A.E-01 LPCS 2.OE-02 3A.E-01 LPC.I(RHR) /LPPS 6.OE-04 3.4E-01 RHRSW/LPCS .LPCI .TRANS 1.0E+00 1.OE+00 RHRSW/LPCS.LPCI .LOOP 1.OE+00 1.0E+O0 RHiRSW/LPCS .LPCI SLOCA 1.OE+00 1.OE+00 RHR (SDC) 4.1E-02 3A.E-01 RHR (SDC) /-LPCI 2.OE-02 3.4E-01 RHR (SDC) /LPCI I.OE+00 1.OE+00 RHR(SPCOOL) /-LPCI .RHR(SDC) 2.OE-02 1.OE+00 RHR(SPCOOL)/LPCI .RHR(SDC) 5.2E-01 I.OE+00 C.I .AND.V/RHR(SDC) .RHR(SPCOOL) 1.OE+00 3.4E-01

    • forced Minarick 04-12-1987 12:02:46 Event Identifier: 374/84-017 D- 216
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