ML20149K400
| ML20149K400 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-045-00 | |
| Download: ML20149K400 (6) | |
Text
PRECURSOR DESCRIPTION AND ANALYSIS LER No.: 373/85-045 Event
Description:
Loss of Circulating Water and Nonsafety Service Water Due to Expansion Joint Failure Date of Event: May 31, 1985 Plant: LaSalle 1 EVENT DESCRIPTION Sequence Flooding caused by failure of the LB circulating water pump discharge valve expansion joint rendered the circulating water pumps and plant SW pumps unavailable. Before the leak was discovered, the 1B pump tripped off (1822 h). At 1825 h standby pump IC was started after several attempts. Pump LA was not affected yet. When the leak (2000 gal/mmn) was first discovered at 1829 h, a load drop was initiated. At 1945 h and 65% power, the unit was manually scrammed in anticipation of loss of the circulating water system.
.Cold shutdown of the reactor was initiated with a combination of RCIC and the SRVs. Use of the SRVs caused high temperatures in the drywell and suppression pool. Total loss of SW had occurred by 2045 h, placing operation of the plant instrument air, RBCCW, TBCCW, the plant computer; the drywell pneumatics compressor (necessary for operation of the SRVs),
and primary containment air coolers at risk. The plant computer was finally shut down. The RRR steam condensing mode was considered inoperable because of the degraded condition of plant instrument air.
The RWCU isolated because of cycling of the SRVs. Water in the pump house reached 675,000 gal.
Fire protection water was cross-tied to the RBCCW to cool the drywell pneumatics compressor to maintain operability of the SRVs for cooldown. The unit reached cold shutdown at 1027 h the next day.
Corrective Action See LER for repair and restoration of circulating water and service pump equipment. The LB pump valve was repaired.
Plant/Event Data Systems Involved:
SW, circulating water, RHR, instrument air, RBCCW, TBCCW, and plant computer Event Identifier: 373/85-045 E-2 47
Components and Failure Modes Involved: I The systems listed below were rendered unavailable during operation by flooding caused by the failed circulating water discharge valve.
SW System TBCCW heat exchangers RBCCW heat exchangers TG all heat exchangers and other TG systems Fuel pooi heat exchangers Auxiliary, service, and radwaste air conditioning systems Containment coolers Fire system Circulating water screen wash Other minor systems RB CCW RCP cooling CR13 feed pumps RWCU heat exchangers Other minor systems TBCCW TG electrohydraulic control cooling Condenser vacuum coolers MFW, condensate, and condensate booster pump coolers Station air compressors other minor systems Component Unavailability Duration: NA Plant Operating Mode: 64% power Discovery Method: During operation Reactor Age: 2.86 years Plant Type: BWR Comments None Event Identifier: 373/85-045 E-248
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate PCs 1.0 Circulating water lost; cannot dump heat to the condenser MFW 1.0 Cooling lost to feedwater, condensate, and condensate booster pumps Condensate pumps 1.0 Cooling water lost to pumps CRD cooling 1.0 Cooling water lost to pumps Plant Models Utilized BWR plant Class C Event Identifier: 373/85-045 E-2 49
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number: 373/85-045 Event
Description:
Loss Of Circ and Non-Safety Serv Water Due to Exp Jnt Fail Event Date: 5/31/85 Plant. LaSalle I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.000E+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV TRANS 1.8647E-07 Total 1.B47E-07 CD TRANS 7. IPLE-05 Total 7. 1B2E-05 ATWS TRANS 2.034E-05 Total 2.034E-05 DOMINANT SEQUENCES End State: CV Conditional Probability: 9.170E-00 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/F W.PCS -LPCS -RHR(SDC)
End State: CD Conditional Probability: 4.662E-05 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW/PCS.TRANS -HPCI RHR(SDC) RHR(SPCODL)/-L PCI.RHRfSDC) C.I.AND.V/RHR(SDC).RHRtSPCOOL)
End State: ATWS Conditional Probability: 2.034E-05 Event Identifier: 373/B5-045 E-2 50
173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recovit 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRY.CLOSE FW CD 4.662E-05 I 1.15IE-01
/PCS.TRANS -HPCI RHR(SDC) RHR(SPCOOL)/-LPCI.RHR(SDC) C.
I.AND.V/RHR(SDC) .RHR(SPCOOL) 110 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW CD 1.162E-05 2.996E-02
/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP. CR0 SRV.ADS 112 TRANS -SCRAM PCSITRANS SRV.CHALL/TRANS.-SCRAM SRVCLOSE FN CD 1.756E-06 1.151E-01
/PCS.LOCA -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 1.146E-05 5.693E-02
/PCS.LOCA HPCI RCIC/L0CA SRV.ADS 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS CV 9.170E-08 I 1.770E-01 HPCI RCIC/TRANS.0R.LDOP -SRV.ADS COND/FW.PCS -LPCS -RHR(
SDC) 159 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA CV 9.044E-08 3.104E-01 HPCI RCIC/LOCA -SRV.ADS COND/FW.PCS -LPCS -RHR(SDC) 173 TRANS SCRAM SLC.OR.RODS AIWS 2.034E-05 I 2.IBIE-01 I dominant sequence for end state Itnon-recovery credit for edited case Note:
Conditional probability values are differential values which reflect the added risk due to observed failures.
Parenthetical values indicate a reduction inrisk compared to a similar period without the existing failures.
MODEL: b:bwrctree.cmp DATA: b-laslprob~cmp No Recovery Limit BRANCH FREgUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.142E-03 I. 000E+00 LOOP 1.305E-05 3.400E-01 LOCA 3.250E-06 3.400E-01 SCRAM 4.IOOE-04 l.000E+00 SLC. OR. RODS 1.000E-02 1.000E+00 4.OOOE-02 PC S/TRANS 1.700E-01 > l.00(iE+00 I. 000E+00 Branch Model: 1I.OF.1 Train 1 Cond Prob: 1.700E-01 > Failed PCS/LOCA 1.000E+00 1.000E+00 Event Identifier: 373/B5-045 E-251
SRV. CHALL/TRANS. -SCRAM 1.ODOE+00 1.DOOE+00 SRV. CHALL/TRANS. SCRAM 1.000OE+0C' 1.OOOE+00 SRV.CHALLILOOP.-SCRAM 1.000OE+00 1.OOOE+00 SAV. CHALL/LGOP.SCRAM 1.000E+00 1.000 E+00 SRV. CLOSE 3.630E-02 1.OOOE+00 EMERG. POWER 2.850E-03 5.IOOE-01 FWIPCS. TRANS 4.600E-01 ) l.O0OE+00 3.400E-01 > 1.00OE+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 4.600E-01 ) Unavailable FW/PCS.LOCA I.OOOE400 ) 1.000E+00 3.400E-01 ) I.000E+00 Branch Model: 1.0F.1 Train I Cond Prob: 1.000E+00 HPCI 2.000E-02 3.400E-01 RCIC/TRANS. OR. LOOP 6.700E-02 5.700E-01 RCICILOCA 1.000E+00 1.OOOE+00 CRD 1.000E-02 > 1.000E+00 1.000 E+00 4.OOOE-02 Branch Model: 1.OF.1+opr Train I Cond Prob. 1.000E-02 )Unavailable SRV. ADS 6.700E-03 1.000OE+00 4.OOOE -02 COND/FW. PCS 1.OOOE+00 > .000E+00 3.400E-01 > 1.OOOE+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 1.000E+00 LPCS 2.000E-02 3.400E-01 LPCI (RHR) /LPCS 6.OOOE-04 3.400E-01 RHRSW/LPCS. LPCI. TRANS 1.OOOE+00 1.O0OE+00 RHRSW/LPCS.LPCI .LOOP I.OOOE+00 1.000E+00 RHRSWILPCS. LPCI .LOCA 1.000E+00 1.OOOE+00 RHR(SDC) 2.IOBE-02 3.400E-01 RHR(SDC) i-LPCI 2.000E-02 3.400E-01 RHR(SDC) /LPCI 1.000E+00 1.O0OE+00 RHR(SPCOOL) I-LPCI. RHR(SDC) 2.OOOE-02 1.OOOE+00 RHR(SPCOOL) ILPCI.RHR(SDC) 5.200E-01 1.OOOE+00 C,1.AND.VfRHR(SDC) .RHR(SPCOOL) 1.000E+00 3.400E-01 113 forced JD HARRIS 10-03-1986 10:21:3 Event Identifier: 373/B5-045 E-252