ML20147A349
| ML20147A349 | |
| 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 1984-027-00 | |
| Download: ML20147A349 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.: 259/84-027 Event
Description:
Inadvertent Relief Valve Opening with Subsequent Trip Date of Event: June 27, 1984 Plant: Browns Ferry 1 EVENT DESCRIPTION Sequence During normal unit startup following a short unit outage, while approaching 1% power with -400-psig reactor pressure, a main steam RV began to unseat. It continued to leak, causing the torus temperature to approach Technical Specifications' limits, and the unit was manually scrammed at 350 psig. The RV subsequently reseated at 100 psig.
Corrective Action The valve was replaced and the unit restarted. The RV was tested at Wyle Laboratories, and it performed normally. It was then disassem-bled, and all internal parts were found to be normal. No reason, either electrical or mechanical, could be found to explain the premature valve actuation.
Plant/Event Data Systems Involved:
Main steam Components and Failure Modes Involved:
RV inadvertently opened Component Unavailability Duration: NA Plant OperAting Mode: 2 (1% power)
Discovery Method: Operational event Reactor Age: 10.9 years Plant Type: BWR Comments It has been assumed that the RV's spurious opening could have occurred while the plant was at power.
Event Identifier: 259/84-027 D-4 6
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Small-break LOCA 0.1 To account for likelihood of occurring at power and likelihood that relief would have been sufficient to require LOCA mitigation Branches Impacted and Branch Nonrecovery Estimate None Plant Models Utilized BWR plant Class C Event Identifier: 259/84-027 D-4 7
CONDITIONAL CORE DAMIAGE PROBABILITY CALCULATIONS Event Identifier: 259/84-027 Event
Description:
Inadvertant Relief Valve Opening with Subsequent Trip Event Date: 6/27/84 Plant: Browns Ferry 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOCA I.OE-0l SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV LOCA 7.'/E-07 Total 7.2E-07 CD LOCA 9.5E-05 Total 9.5E-05 ATWS LOCA 2.OE-06 Total 2.OE-06 DOMINANT SEQUENCES End State: CV Conditional Probability: 4.7E-07 314 LOCA SCRAM -SLC .OR .RODS PCS/LOCA FW/PCS .LOCA HPCI -SRV .ADS -COND/FW .PCS -RHR (SDC)
End State: CD Conditional Probability- 9.OE-05 310 LOCA -SCRAM PCS/LOCA FW/PCS .LOCA HPCI RCIC/LOCA SRV .ADS End State: ATWS Conditional Probability: 2.OE-06 Event Identifier: 259/84-027 1)-48
332 LOCA SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES SequenceEnd State Prob N Rec*I 302 LOCA -SCRAM PCS/LOCA -FW/PCS .LOCA RHR (SDC) RHR (SPCOOL) /-LPC CD 3.1E-06 7.6E-03 I .RHR(SDC) C.I .AND.YIRHiR(SDC) .RHR(SPCOOL) 310 LOCA -SCRAM PCS/LOCA FW/PCS.LOCA HPCI RCIC/LOCA SRV.ADS CD 9.OE-05
- 1.3E-02
-COND/FW.PCS -RHR(SDC) 318 LOCA SCRAM -SLC.OR.RODS PCS/LOCA FW/PCS.LOCA HPCI -SRV.ADS CV 2.4E-07 6.6E-03 COND/FW .PCS -LPCS -RHR (SDC) 332 LOCA SCRAM SLC.OR.RODS ATWS 2.OE-06
- 1.DE-01
- dominant sequence for end state
- 4 non-recovery credit for edited case MODEL: b:\bwrctree .cmp DATA: b:\bf prab .cmp No Recovery Limit BRANCH FREUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.IE-03 1.0E+00 LOOP 1.3E-0.5 3.4E-01 LOCA 3.3E-06 > 3.3E-06 3.4E-01 > 1.OE'-01 Branch Model: INITOR Initiator Freq: 3.3E-06 SCRAM 4. 1E-04 1.0E+00 SLC.OR.RODS 1.OE-02 1.0E+00 4.E-02 PCS/TRANS 1.7E-01 1.0E+00 PCS/LOCA 1.0E+00 1.0E+00 SRV .CHALL/TRANS .-SCRAM 1.0E+00 1.0E+00 SRV .CHALL/TRANS .SCRAM' 1.OE+00 1.0E+00 SRV .CHALL/LOOP`.-SCRAM 1.0E+00 1.0E+00 SRV .CHALL/LOOP .SCRAI¶ 1.0E+00 1.OE+00 SRV .CLOSE 3.6E-02 1.OE+00 EMERS .POWER 5.4E-04 5.11E-01 FW/PCS .TRANS 4.6E-01 3.4E-01 FN/PCS .LOCA 1.0E+00 3.4E-01 HPCI 1.OE-01 5.7E-01 RCIC/TRANS .OR .LOOP 6.7E-02 5.7E-01 RCIC/LOCA 1.OE+00 1.OE+00 CRD 1.OE-02 1.0E+00 4.E-02 SRV .ADS 6 .7E-03 1.0E+00 U.E-02 Event Identifier: 259/84-027 D-4 9
COND/FW.PCS 1.OE+00 3 .E-01 LPCS 3.OE-03 M.E-O1 LPCI (RR) /LPCS 4 OE-04 3 .E-O1 RNRSW/LPCS.LPCI .TRANS 5.OE-O1 1.OE+OO 4 OE-02 RHRSW/LPCS.LPCI .LOaP 5.OE-01 I .OE+OO 4 OE-02 RHRSW/LPCS .LPCI .LOCA 5.OE-O1 1.OE+OO 4.OE-02 RHR(SDC) 2.OE-02 3 .E-01 RHffSDE) I-LPCI 2.OE-02 3.E-O1 RHR(SDC) /LPCI 1.OE+00 I .OE+OO RHR (SPCOOL) /-LPCI .Rf (SDC) 2.OE-02 I .OE+OO RH(SPCOOL)/LPC1 .RHR(SDC) 5.2E-01 I .OE+OO C.I .AND.V/RHR(SDC) .RHR(SPCOOL) 1.OE+OO M.E-01
- 4* forced tiinarick 04-41-1987 13:,51:40 Event Identifier: 259/84-027 D- 50