ML20149K377
| ML20149K377 | |
| Person / Time | |
|---|---|
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 366-85-030 | |
| Download: ML20149K377 (5) | |
Text
PRECURSOR DESCRIPTION AND ANALYSIS LER No.: 366/85-030 Event
Description:
LOFW and RCIC Trip Date of Event: November 5, 1985 Plant: Hatch 2 EVENT DESCRIPTION Sequence At -.2157 h the plant was in steady state operation at 2422 MW(t) ('-99%
power) when a reactor scram occurred. Following the scram, reactor water level dropped, resulting in ESF actuations (groups 2 and 5 primary containment isolation valves isolated, standby gas treatment system initiated, HPCI initiated, and control room vents switched to Mode II).
The scram occurred because the 2B condensate booster pump tripped on low oil pressure (the 2A condensate booster pump was already out of service for preventive maintenance and repair of an oil leak on the oil system three-way valve) . At full power two of the three condensate booster pumps are required to maintain operation. As a result of the equipment failure, both feed pumps tripped, causing a reactor scram on low reactor water level. RCIC initially started and then tripped on overspeed because of a failed component. Vessel water level dropped to -68 in.
(96.5 in. above the fuel).
The low oil pressure on 2B condensate booster pump was evaluated as being caused by a stuck suction (foot) valve on the main oil pump.
Corrective Action The suction (foot) valve, strainer, and the oil sump were cleaned, related oil filters were changed, and the 2B condensate booster pump was returned to service. The 2A and C condensate booster pumps were also inspected.
Plant/Event Data Systems Involved:
Condensate, feedwater, and RCIC Components and Failure Modes Involved:
Condensate booster pumps - failed in operation RCIC - failed on demand Event Identifier: 366/85-030 E-227
Component Unavailability Duration: NA Plant Operating Mode: (99% power)
Discovery Method: Operational event Reactor Age: 6.9 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 PCs 1.0 Two of three booster pumps unavailable RCIC 1.0 Required repairs MFW 0.34 Possible recovery locally at equipment and using third booster pump Plant Models Utilized BWR plant Class C Event Identifier: 366/85-030 E-228
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number., 3~6I85-030 Event
Description:
LOFW and RCIC Trip Event Date., 11/5/85 Plant- Hatch 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.O0OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS
,End State/Initiator Probability CV TRANS 7. 201E-06 Total 7.201E-06 CD TRANS 1.152E-04 Total 1.152E-04 ATWS TRANS 2.034E-05 Total 2.034E-05 DOMINANT SEQUENCES End State: CV Conditional Probability: 4.592E-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. 4.341E-05 110 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CRD SR V.ADS End State: AIMS Conditional Probability: 2.034E-05 Event Identifier: 366185-030 E-229
173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-Recov*l 101 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS. -SCRAM -SRV.CLOSE -FN CD 3.026E-05 7.630E-02
/PCS.TRANS RHR(SDC) RHR(SPCOOL)/-LPCI.RHR(SDC) C.I.AND.
V/RHR(SDCI .RHR(SPCOOL) 102 TRANS -SCRAM PCS/TRANS SRV.CHALLITRANS. -SCRAM -SRV.CLOSE FW CD 1.470E-05 3.828E-02
/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 FN CD 4.341E-05
- 7.076E-03
/PCS.TRANS HPCI RCIC/TRANSOR.LOOP CRD SRV.ADS 119 TRANS -SCRAM PCSI'TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW CD 2.42?E-05 3.-745E-02
/PCS.LOCA HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS CV 4.592E-06
- 1.1773E-01 HPCI RCIC/TRANS.OR.LOOP -SRV.AOS -COND/FW.PCS -RHR(SDC) 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS CV 2.363E-06, 6.045E-02 HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FW.PCS -LPCS -RHR(
S3DC) 173 TRANS SCRAM SLC.OR.ROOS ATWS 2.034E-05
- 2.1G1E-01
- dominant sequence for end state IInon-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.iEmp DATA: b:hatchpro.~:mp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.142E-03 1.O0OE+00 LOOP 1.305E-05 3.400E-01 LOCA 3.250E-06 3.400E-01 SCRAM 4.IOOE-04 1.OOOE+00 SLC. OR. RODS 1.OOOE-02 1.OOOE+00 4.OOOE-02 PCS/ TRANS 1.700E-01 > 1.000E+00 1.O00E+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 1.700E-01 ) Failed PCS/LOCA 1.OOOE+00 1.OOOE+00 Event Identifier: 366/85-030 E-2 30
SRV. CHALL/TRANS. -SCRAM 1.000E+00 1.0OOOE+00 SRV. CHALLITRANS. SCRAM 1.OOOE+00 L.OGOE+00 SRV.CHALL/LOOP. -SCRAM 1.OOOE+00 1.OOOE+00 SRV. CHALL/LOOP. SCRAM 1.000OE+00 1.OOOE+00 SRV. CLOSE 2.700E-02 1.OOOE+00 EMERG. POWER 5.415E-04 5.IOOE-01 FW/IPCS. TRANS 4.600E-01 > 1.000E+00 3.400E-01 Branch Model: l.OF.1 Train 1 Cond Prob: 4.600E-01 > Failed FNIPCS. LCCA 1.000E+00 3.400E-01 HPC I 1.000E-01 5.700E-01 RCIC/TRANS. OR. LOOP 6.700E-02 > 1.000E+00 5.700E-01 > l.0OOE+00 Branch Model: 1.0F.1 Train I Cond Prob: 6.700E-02 > Failed RCIC/LOCA 1.O0OE+00 1.OOOE+00 CRD 1.OOOE -02 I..ONE+00 4.OODE-02 SRY. ADS 6.700E-03 1.OOOE+0O 4.OOOE-02 COND/FW. PCS 1.00 0E+00 3.400E-01 LPCS 3.OOOE-03 3.400E-01 LPCI (RHR) ILPCS 4. 000E-04 3.400E-01 RHRSW/LPCS. LPCI .TRANS 5.OOOE-01 1.OOOE+00 4.OOOE-02 RHRSN/LPCS. LPCI.LOOP 5.OOOE-01 1.OOOE+00 4.OOOE-02 RHRSW/LPCS.LPCI .LOCA 5.OOOE-01 1.OOOE+00 4.OOGE-02 RHR(SDC) 2.039E -02 3.400E-01 RHR (SDC) /-LPCI 2.000E -02 3.400E-01 RHR(SDC) /LPCI 1.OOOE+00 1.OOOE+00 RHR (SPCOOL) /-LPCI .RHR (SDC) 2.OOOE-02 1.OOOE+00 RHR(SPCOOL) /LPCI.RHR(SDC) 5.200E-01 1.OOOE+00 C.I.AND.V/RHR(SDC) .RHR(SPCOOL) 1.OOOE+00 3. 40DE-01 ill forced Austin 08-13-1986 06: 18:58 Event Identifier: 366/B5-030 E-231