ML20147A494
| ML20147A494 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Regulatory Research |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-043-00 | |
| Download: ML20147A494 (5) | |
Text
PRECURSOR DESCRIPTION AND ANALYSIS LER No.: 413/85-043 Event Identifier: LOFW and Secondary-Side Relief Problems Date of Event: June 22, 1985 Plant: Catawba 1 EVENT DESCRIPTION Sequence At 0104 h manual reactor shutdown was initiated following an automatic trip of MFW pump turbine 1B due to a loss of condenser vacuum. The three pressurizer PORVs opened and closed twice before the manual scram.
The loss of condenser vacuum was caused by an operator's opening a drain valve associated with MFW pump turbine 1A, which was in the process of being returned to service after a lengthy repair period. The operator had received instructions from his supervisor to reposition certain valves to support filling and warming of the nonoperating MFW pump. The AFW pumps started on low-level demand. The condenser dump valves opened as intended. A PORV on SGs "A" and "B" failed to open on demand. Two other SG PORVs and one SC SRV did open and close on demand.
Corrective Action The B MFW pump was restarted. PORV set points were recalibrated.
Procedures were revised.
Plant/Event Data Systems Involved:
MFW and secondary-side relief Components and Failure Modes Involved:
MFW pump - trippped off in operation Two SC PORVs - failed to open on demand Component Unavailability -thiration: NA Plant Operating Mode: 1 (64% power)
Discovery Method: Operational event Reactor Age: 0.5 year Plant Type: PWR Comments See LER 413/85-041 on June 13, 1985, for a similar event Event Identifier: 413/85-043 E-2 96
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate MFW 0.34 Recoverable but difficult to recover immediately because of the loss of vacuum Steam-side 0.34 Two SG PORVs only recoverable locally depressurization if at all, but condenser dump valves were available Plant Models Utilized PWR plant Class F Event Identifier: 413/85-043 E-297
CONDITIONAL CORE DAMIAGE CALCULATIONS LER Number: 413/I85-043 Event Description- LOFW and Secondary Side Relief Problems Event Date: 6/22/85 Plant: Catawba I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OO0E+00 SEQUENCE CONDITIONAL PROBABILITY SUMPS End State/'Initiator Probability CV TRANS 6.871 E-06 Total 6.871E-06 CD TRANS 6.b9BE-06 Total 6.698E-06 ATWS TRANS 3.OOOE-05 Total 3.OOOE-05 DOMINANT SEQUENCES End State: CV Conditional Probability: 5.45E-06 109 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI End State: CD Conditional Probability: 1.289E-06 127 TRANS -RT AFW IIFWHPI(F/BI SS.DEPRESS End State: ATWS Conditional Probability: 3.OOOE-05 128 TRANS RT Event Identifier: 413/85-043 E,-298
SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recov*#
101 TRAN -RT -AFW PORV.OR.SRV.CHALL -PORV.OR.SRV.RESEAT SS.RELE 1.059E-07 1.765E-01 AS.TERM HP]
102 TRANS -RT -AFN PORV.OR.SRY.CHALL PORY.GR.SRV.RESEAT -HPI HP Cv 5.433E-071 1.956E-03)
R/-HPI -SS.DEPRESS -LPR/-HPI.HPR 103 TRANS -RT -AFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HP] HP CD 1.103E-06 1.956E-03 R/-HPI -SS.DEPRESS LPR/-HPI.HPR 104 TRANS -RT -AFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HPI HP ED 8.482E-07 1.008E-03 R/-HPI SS.DEPRESS 109 TRANS -RT -AFN -PORV.OR.SRV.CHALL SS.RELEAS.TERM HP! CV 2.545E-06
-COND/MFW 120 TRANS -RT AFW MFW -HPI(F/B) -HPR/-HPI PORV.OPEN -SS.DEPRESS CD 1.932E-07 1.897E-02 COND/MFW 121 TRANS -RT AFN MFN -HPI(F/B) -HPR/-HPI PORV.OPEN SS.DEPRESS CD .2.927E-07 2.874E-01' 122 TRANS -RT AFW tIFW -HPI (F/B) HPR/-HPI -SS.DEPRESS -COND/MFW CV 1.62BE-06 2.275E-07)
TRANS -RT AFW NFW -HPI(F/B) HPR/-HPI -SS.DEPRESS CONDiMFW CD 8. 389E-07 1.172E-03 124 TRANS -RT AFW MFW -HPI(F/B) HPR/-HPI SS.DEPRESS CD 1.271IE-06 1.776E-03 125 TRANS -RT AFW MFW HPI(F/B) -SS. DEPRESS -COND/MFW CV 1.652E-06 1.826E-03 TRANS -RT AFW MFW HPI(F/B) -SS.DEPRESS COND/MFW CD 8.509E-07 9.406E-04 127 TRANS -RT AFN MFW HPI(F/B) SS. DEPRESS CD 1.289E-06 I 1.425E-03 128 TRANS RT ATWS 3OOOE-05 I 1.200E-01
- dominant sequence for end state m*non-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.
/
I, MODEL: b:pwrbtree.cmp DATA: b: catawpro. cup No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.030E -03 I.OOOE+00 LOOP 2.280E-05 3.400E-01 LOCA 4.170E-06 3.400E-01 RT 2.500E-0; 1.200E-01 RT/LOOP 0.OOOE+00 1.00OE+00 EME RB.POWER 2.850E-03 5.100E-01 Event Identifier: 413/85-043 E-299
AFW/EMERG. POWER 5'.OOOE-02 3.400E-01 PIFW 2.OOOE-01 )1.0O0E+00 3.400E-01 Branch Model: l.0F.1 Train I Cond Prob: 2.OOOE-O1 >Failed PORt/. R.SPV. HALL 4.OOOE-02 1.000E+00 PORY. OR. SRV. RESEAT 3J.OOE-02 5.000OE-02 PORY. OR. SRV. RESEAT/EMERG. POWER 3.OOOE-02 5.OOOE-02
- 55. RELEAS. TERN 1.5C10E-02 3.400E-01 SS. RELEAO. TERM/-MFW 1.500E-02 3.4OOE-01 HP I 1.000OE-03 5.200E-01 HPI (F/B) 1.000OE-03 5.200E-01 4.OOOE-02 HPR/-HPI 3.OOOE-03 5.600E-01 4.OOOE-02 PORY. OPEN 1.000OE-02 1.OOOE+0O SS. DEPRESS 3.600E-OL' 1.0OOE+00 l.OOOE+00 3.400E-01 Branch Model: 1.0F1K Train I Cond Prob: 3.600E-02 )Failed COND/MFW 1.OOOE+00 3.400E-01 LPI /HPI 1.OOOE-03 3.400E-01 LPR/-HPI.HPR 6.700E-01 1.OOOE+0O LPR/HPI 1.OOOE-03 1.000E+00
- forced Austin 08-13-1986 17: 52:01 Event Identifier: 413/B5-043 E,-300