ML20149K399

Final ASP Analysis - LaSalle 1 (LER 373-85-017)

ML20149K399
Person / Time
Site:	LaSalle
Issue date:	05/28/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1985-017-00
Download: ML20149K399 (5)

Text

PRECURSOR DESCRIPTION AND ANALYSIS LER No.:

373/85-017 Event

Description:

LOFW and RCIC Trip Date of Event:

February 8, 1985 Plant:

LaSalle 1 EVENT DESCRIPTION Sequence At 1018 h with Unit 1 at 75% power, the reactor scrammed on low reactor vessel level.

An operator error during maintenance on an instrument valve caused a low feedwater pump suction pressure signal that tripped the 1A and 1B turbine-driven reactor feedwater (TDRFP) pumps.

An unsuccessful attempt was made to restart the 1A TDRFP.

The motor-driven feed pump was out of service for maintenance.

When vessel level reached '-12.5 in.,

the reactor scrammed (10:18:45), and the recirculation pumps shifted to low speed.

When the vessel level reached about -50 in. (1.0:18:48), the HPCs system initiated, the recirculation pumps tripped as required, and the No. 3 DG started.

The RCIC system also initiated but tripped because of overspeed.

The MSIVs closed, and other isolations occurred.

ADS valve E opened twice to relieve vessel pressure at 1125 psig.

Its nominal set point was 1175 psig.

Vessel level dropped to approximately -60 in. before it was restored to normal.

ROTC was reset and restarted at 10:21:29.

Corrective Action The primary cause of the unit scram was placing a jumper in the feed-water pump NPSH trip circuit that did not serve its intended function.

The jumper was installed utilizing a revision of the print that did not reflect the present system configuration.

The circuit had been modified (Mod No. 1-1-82-293), during the September 1984 outage, and the drawing change request had not yet been processed.

Plant/Event Data Systems Involved:

MFW, recirculation pumps, ROTC, MSIVs and ADS., HPCS Components and Failure Modes Involved:

MFW -

instrument maintenance error caused trips, of MFW pumps ADS valve -

opened twice at incorrect pressure RCIC -

failed on demand EventIdentifier:

373/85-017 E-242

Component Unavailability Duration:

NA Plant Operating Mode:

1 (75% power)

Discovery Method:

Operational event Reactor Age:

3.2 years Plant Type:

BWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate PCs5 1.0 No recovery of PCS under given circum-stances RCIC 0.12 Manual recovery from control room Feedwater 0.34 Possible but difficult MFW recovery locally at pumps Plant Models Utilized BWR plant Class C Event Identifier:

373/85-017 E-2 43

CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:

Event

Description:

Event Date:

Plant:

373/85-017 LOFW and RCIC Trip 2/8/85 LaSalle 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator

1.

OOOE+00 Probability CV TRANS Total

1.

305E-07

1. 305E-07 CD TRANS Total

5.

325E-05

5.

325E-05 ATWS TRANS Total 2.034E-05

2. 034E-05 DOMINANT SEQUENCES End State: CV Conditional Probability:

6.510E-OB 134 TRANS SCRAM -SLC.OR.RODS PCSITRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCICITRANS.OR.LOOP -SRV.ADS -CONDIF W.PCS -RHR(SDC)

End State: CD Conditional Probability:

3.O9BE-05 101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE -FM/PCS.TRANS RHiR(SDC)

RHR(SPCOOL)/-LPCI.RH R(SDC) C.

I.AND.VIRHR(SDC).RHR(SPCOOL)

End State: ATWS Conditional Probability:

2.034E-05 Event Identifier: 373/85-017 E-244

173)

TRANS SCRAM SLC.aR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recov*"

101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SOCRAM -SRV.CLOSE -FW

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

V/RHR (SDC).RHR (SPCOOL) 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FN

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

I.AND.V/RHR(SDC).RHR(SPCOOL)

II1 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE 4FW

/PCS.LOCA 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

/PCS.LOCA HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCSITRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS -RHR(SDC) 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FN.PCS -LPCS -RHR(

SDC) 155 TRANS SCRAM -SLC.DR.RGDS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS -COND/FW.PCS -RHR(SDC) 159 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS COND/FW.PCS -LPCS -RHR(SDC) 173 TRANS SCRAM SLC.OR.RDDS CD CD CD CD CV Cv CV CV J.09BE-05

• 7.630E-02 1.585E-05 33913E-02 1.16b7E-06 7.6b30E-02 3.895E-06

1.

936E-02 6.510E-08

• 8.398E-03 3..331E-OB 4.306E -03

2.

043E-O8

6.

998E-02 1.046E-08 3.589E-02 2.034E-05 *2.IBIE-01 ATWS Idominant sequence for end state Ifnon-recovery credi-t for edited case Note:

Conditional probability values are differential values which reflect the added risk due to observed failures.

Parenthetical values indicate a reduction in risk compared to a similar period without the existing failures.

MODEL:

DATA:

b:bwrctree.cmp b: laslprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch TRANS LOOP LOCA SCRAM System

1.

142E-03

1.

305E-05

3.

250E -06

4.

IOOE-04 Non-Recov 1.000E+00

3.

400E-01

3.

400E-01

1.

OOOE+00 Opr FailI Event Identifier: 373/85-017 E-245

SLC. OR. RODS PCS/TRANS Branch Model:

1.OF.1 Train I Cond Prob:

PCSILOCA SRV.CHALL/TRANO. -SCRAM SRV.CHALL/TRANS. SCRAM SRV.CHALL/LOOP. -SCRAM SRV. CHALL/LODP. SCRAM SRV. CLOSE EMERG. POWER FW/PCS. TRANS Branch Model:

1.OF.1 Train I Cond Prob:

FW/PCS. LOCA HPCI RCIC/TRANS. OR.LOOP Branch Model:

I.0F.1 Train 1 Cond Prob:

RCIC/LOCA CR0 SRV. ADS COND/FW.PCS LPCS LPCI (RHR) /LPCS RHRSW/LPCS. LPCI.TRANS RHRSW/LPCS. LPCI.LOOP RHRSW/LPCS. LPCI.LCA R

HR (S DC RHR(SDC) /-LPCI RHR (SDC) /LPCI RHR (SPCOOLI I-LPCI.RHR (SDC)

RHR(SPCOOL) /LPCI.RHR(SDC)

C.

I.AND.V4/RHR(SDC).RHR(SPCOOL)

1.

OOOE-02 1.700E-01 1

.OOOE+00 1.700E-01 >Failed

1.

OOOE+00

1.

OOOE+00

1.

OOOE+00

1.

OOOE+00

1.

OOOE+00

3.

630E-02

2.

850E-03 4.600E-01 > 1.OOOE+00 4.600E-01 > Failed 1.OOOE+00 2,.

OOOE-02 6.700E-02 >f 1.00OE+00 6.700E-01' > Failed

1. O0E+ 00 1.OOOE-02

6.

700E-03 1.000E+00

2.

OOOE-02

6.

OOOE-04 I.

O0OE+00 I.

OOOE+00

1.

O0OE+00

2.

1OBE-02 2.000OE-02

1.

OO0E+00

2.

OOOE-02

5.

200E-01 I.

OOOE+00

1.

OOOE+00

1.

OOOE+00

4. OOOE-02

1.

OOOE+00

1.

OOOE+O0

1.

O0OE+00

1.

OO0E+00

1.

OOOE+00

1.

OOOE+00

5.

100OE-01I

3.

400E-01

31.

400E-01

3. 400E-01 5.700E-01 > 1.200E-01

1.

OOOE+00

1.

OOOE+00 I.

OOOE+00

3. 400E-01

3. 400E-01

3. 400E-01

1.

OOOE+00

1.

OOOE+00

1.

OOOE+0O

3.

400E-01

3.

400E-01

1.

OOOE+00

1.

OOOE+O0

1.

OOOE+00

3.

400E-01

4. OOOE-02

4.

OOOE-02 4** forced Austin 08-13-1986 06: 34:54 Event Identifier:

373/85-017 E-246