ML20147A352
| ML20147A352 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-016 | |
| Download: ML20147A352 (5) | |
Text
PRECURSOR DESCRIPTION AND ANALYSIS LER No.:
259/85-016 Event
Description:
LOFW and RCIC Inoperability Date of Event:
January 16, 1985 Plant:
Browns Ferry 1 EVENT DESCRIPTION Sequence Unit 1 scrammed during normal operation because of low reactor water level while at 100% power.
The high-pressure steam to the reactor feed pump turbines isolated because of problems with the master level controller, resulting in a loss of feedwater to the reactor vessel.
The vessel level continued decreasing, becaus9 of the feedwater flow loss, past the isolation set point.
The primary containment isolation system functioned as designed, closing the MSIVs.
HPCI initiated and returned the water level to the high trip set point in '-6 min.
RCIC initiated but tripped immediately on mechanical and electrical overspeed and high turbine exhaust pressure.
Reactor pressure was maintained below the relief valve set point by manually opening 2 of the 13 safety relief valves after the MSIVs closed.
Corrective Action A cold solder joint in the master level controller was found to be the cause of loss of motive steam to the reactor feedpump turbines and subsequent loss of feedwater to the vessel.
The cold solder joint was resoldered, and no further problems have occurred.
Plant/Event Data Systems Involved:
MNW and RCIC Components and Failure Modes Involved:
MFW pump controllers -
failed in operation RCIC -
failed on demand Component Unavailability Duration:
NA Plant Operating Mode:
100% power Discovery Method:
Operational event Reactor Age:
11.6 years Plant Type:
BWR Event Identifier:
259/85-016 E-7 1
Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate Power conversion 1.0 Loss of feedwater and MSIV closure system (PGS) renders PCS unavailable MFW 1.0 Feedwater controller problem was not recoverable during the transient RCIC 0.12 Failure appeared recoverable but was not routine Plant Models Utilized BWR plant Class C Event Identifier:
259/85-016 E-7 2
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:
Event
Description:
Event Date:
Plant:
259/85-016 LOFW and RCIC Inoperability 6/16/85 Browns Ferry 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 1.00OE+00 Probability CV TRANS Total 2.711 E-06 2.71 IE-06 CD TRANS Total
- 9.
- 9.
- 2.
- 2.
034E-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
1.605E-06 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/F W.PCS -RHR(SDC)
End State:
CD Conditional Probability:
4.283E-05 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW/PCS.TRANS -HPCI RHR(SDC) RHR(SPCOOL)/-L PCI.RHR(SDC)
C.I.AND.V/RHR(SDC).RHR(SPCOOL)
End State: ATWS Conditional Probability:,
2.034E-05 Event Identifier:
259/B5-016 E-7 3
173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recovf*
102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FN
I.AND.VIRHR(SDC).RHR(SPCOOL) 103 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FN
/PCS.TRANS HPCI -RCIC/TRANS.OR.LOOP RHRfSDC) RHR(SPCOOL
C.I.AND.V/RHR(SDC).RHR(SPCOOL) 110 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS. -SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CR0 SRV.ADS 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FN IPCS.LOCA HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FWIPCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS -RHR(SDC) 138 TRANS SCRAM -SLC.OR.RODS PCSITRANS -SRY.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS CONDIFW.PCS -LPCS -RHR(
SDC) 155 TRANS SCRAM -SLC.OR.RODS 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.RODS CD CD CD CD CV CV CV CV 4.283E-05 f 1.126E-01 21.27GE-06 5.798E-02 1.517E-05 2.498E-03
- 3.
- 3.
245E-02 1.605E-06
- 4.141E-01'
- 8.
- 2.
133E-02 1.713E-07
- 1.
173E-01 B.B17E-08 6.045E-02 2.034E-05 f 2.IB1E-01 ATWS Idominant sequence for end state
- 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 in risk compared to a similar period without the existing failures.
MODEL:
DATA:
B: bwrctree. cmp B:bfprob.cep No Recovery Limit BRANCH FREQUENCIESIPROBABILITIES Branch TRANS LOOP LOCA SCRAM SLC. OR. RODS Event Identifier:
259/85-016 System
- 1.
- 1.
- 3.
- 4.
IOOE-04
- 1.
OOOE-02 Non-Recov 1.OOOE+00 3.400E-01
- 3.
400E-01 1.000E+00 1.000E+00 Opr Fail
- 4.
OOOE-02 E-74
PCS/TRANS Branch Model:
1.0F.1 Train 1 Cond Prob:
PCS/LOCA SRV. CHALL/TRANS. -SCRAM SRV.CHALL/TRANS.SCRAN SRV. CHALL/LOOP. -SCRAM SRV. CHALL (LOOP. SCRAM SRY. CLOSE EMERG. POWER FWiPCS. TRANS Branch Model:
1.0F.1 Train 1 Cond Prob:
FWIPCS. LCCA HPC I RCIC/TRANS.OR.LOOP Branch Model:
1.OF.1 Train 1 Cond Prob:
RCIC/LOCA CRD SRY. ADS COND/FW. PCS LPCS LPCI (RHR) ILPCS RHRSW/LPCS. LPCI.TRANS RHRSM/LPCS. LPCI.LOOP RHRSW/LPCS. LPCI.LOCA RHR (SDC)
RHR (SDC) I-LPCI RHR(SDC) /LPCI RHR (SPCOOL) /-LPCI.RHR(SDC)
C.
I.AND.V/RHR(SDC).RHR(SPCOOL) 1.700E-01 >'
1.OOOE+00 1.700E-01 2'1.OOOE+00 I.
000E+0O 1.000E+00 I.OOOE+Q0
- 1.
OOOE+00 1.000E+00
- 3.
630E-02 5.415E-04 4.600E-01 >1.000E+00 4.600E-01 >'
1.OOOE+00
- 1.
00OE +00
- 1.
OOOE-01 6.700E-02 )'
1.OOQE+00 6.700E-02 >'
Failed
- 1.
OOOE+00 I.
OOE -02
- 6.
700E -03 1.000E+00
- 3.
OOOE-03
- 4.
- 5.
OOOE-01
- 5.
OOOE-01
- 5.
OOOE-01
- 2.
- 2.
000E-02 1.OOOE+00
- 2.
- 5.
200E-01 1.'000E+00
- 1.
OOOE+00
- 1.
OOOE+00
- 1.
OOOE+00 1.000E+00
- 1.
OOOE+00
- 1.
OOOE+00
- 1.
OOOE+00 S.
IOOE-01 3.400E-01 )'
1.OOOE+00
- 3.
400E-01 5.700E-01 5.700E-01 >'
1.200E-01
- 1.
OOOE+00
- 1.
OO0E+00
- 1.
OOOE+00
- 3.
- 3.
- 3.
400E-01 1.000OE400
- 1.
OO0E+00
- 1.
OOOE+00
- 3.
- 3.
- 1.
OOOE+00 1.0OOOE+00
- 1.
OOOE+00
- 3.
- 4.
OOOE-02 4.000OE-02
- 4.
OOOE-02
- 4.
OOOE-02
- 4.
OOOE-02 1*1 forced Austin 08-13-1986 01:05:57 Event Identifier: 259/85-016 E-7 5