ML20156A267
| ML20156A267 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-006-00 | |
| Download: ML20156A267 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
388/84-006, -008 Event
Description:
Trip and LOEW with "B" LPCI Train Unavailable Date of Event:
May 27, 1984 Plant:
Susquehanna 2 EVENT DESCRIPTION Sequence At 0530 h, on May 27, 1984, shutdown of the reactor commenced from low-power testing due to the inoperability of the "B" Loop of the LPCI system, which had occurred 7 d earlier.
The shutdown was being accomr-plished by inserting control rods individually into the reactor's core by utilizing the rod pull sheet until all of the control rods were at the full-in position.
Shutdown proceeded normally until at 0605 h, when it was observed that TBV 1 would not close below the 18% open position.
Shutdown of the Unit 2 reactor was halted, and control rods in Group 5 were pulled sequentially to maintain reactor pressure with the TBV 1 controlling at a position slightly greater than 18%.
Instrumentation and Control and Mechanical Maintenance personnel were sent to investigate the valve's failure to close.
These investiga-tions determined that TBV 1 could not be closed below 18%.
It was then determined that the best means available for shutting 'down the reactor would be with an reactor protection system manual scram.
At 1346 h, the Unit 2 reactor was manually scrammed,' and at RV pressure of 700 psig all inboard MSIVs were closed, thus isolating the TBV.
Subsequent investigations of the EHC pressure control and TBV con-trol logic indicated that all control functions.were operating normally.
Investigation of TBV 1 revealed that a chipping hammer was wedged be-tween the valve seat and the valve disk, preventing TBV 1 from fully closing.
Although a sizeable portion of the handle and the head of the hammer itself remained intact, a spring portion, "small in comparison to the overall dimensions of the hammer, is believed to have been severed from the handle.
This severed portion would most likely be deposited in the TBS's sparger into the main condenser, posing no threat to compo-nents in other parts of the system.
Corrective Action Disassembly of TBV 1 showed small dents on the disk and the seat of the valve.
The valve's seat was machined to remove the dents, the disk was replaced due to the difficulties in removing the old disk, and the valve was returned to service.
Event Identifier:
388/84-006, -008 D-2 28
A review of unit work documents indicates TBV system was one of the last systems worked on prior to startup for preoperational testing.
Based on this review and the fact that system flushes are performed as part of the Preoperational'Test Program, it is concluded that the occur-rence of this loose tool in the unit's piping is an isolated event..
Plant/Event Data Systems Involved:
LPCI, TEXT Components and Failure Modes Involved:
LPCI injection valve -
failed during operation TBV -
stuck open in operation Component Unavailability Duration:
NA Plant Operating Mode:
2 (2% power)
Discovery Method:
Operational event Reactor Age:
0.1 year 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 MFW LPCI 1.0 1.0 Unavailable because of MSIV closure Unavailable because of MSIV closure Base case Base case Degraded; one train failed Degraded; one train failed RHR (SDC)
Plant Models Utilized BWR plant Class C Event Identifier:
388/84-006, -008 D-2 29
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
388/84-006 Event
Description:
Trip and LOFW With "B" LPCI Train Unavailable Event Date:
5/27/84 Plant:
Susquehanna 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV TRANS Total 1.IE-06 1
.1E-06 CD TRANS Total 3.3E-04 3
.3E-04 ATWS TRANS Total 2.OE-05 2.OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
4.9E-07 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.AEIS
End State:
CD Conditional Probability:
2.4E-04 102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW/PCS.TRANS -HPCI RHR (SDC)
RHR (SPCOOL
)/-LPCI.RHR(SDC) C.I.AND.V/RHR(SDC).RHR(SPCOOL)
Event Identifier: 388/84-006 D-230
End State: ATWS EndStae: TWSConditional Probability:
2.OE-05 173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
102 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAH -SRV.CLOSE FW
C.
I.AND.,V/RHR(SDC).RHR(SPCOOL) 103 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI -RCIC/TRANS.OR.LOOP RHR(SDC)
RHR(SPCOOL
C.I.AND.V/RHR(SDC).RHR(SPCOOL-)
11I TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE -FW
C.I.AND.V
/RHR(SDC).RHR(SPCOOL) 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAtI SRV.CLOSE FW
/PCS.LOCA. HPCI RCIC/LOCA SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS -RHR(SDC) 135 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS RHR(SDC) -
RHR(SPCGOOL)/-LPCI.RHR(SDC) 138 TRANS SCRAM -SLC.OR..RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FW.PCS -LPCS -RHR(
SOC) 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 CV 2.4E-04 *
.1E-01 1.4E-05 6.5E-02 9.5E-06 7.6E-02 4.BE-05 1.9E-01 4.9E-07
- 2.1E-01 2.OE-08 7.3E-02 2.5E-07 1.1E-01 2.4E-07 1.2E-01 1.2E-07 6.4E-02 2.OE-05
- 1.0E+00 ATWS
- dominant sequence f or end state
- non-recovery credit for edited case MODEL:
DATA:
b :\\bwrctree.crnp b :\\susqprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch TRANS LOOP LOCA SCRAM System 1
.1E-03 1.3E-05 3.E-06
- 4. 1 E-04 Non-Recov 1.OE+O0 3.4E-01 3.4E-01 1.0E400 Opt' FailI Event Identifier: 388/84-006 D-23 1
SLC.GR.RODS PCSI TRANS Branch Model:
1.01.1 Train 1 Land Prob:
PCS/LOCA SRV.CHALL/TRANS.-SCRAII SRV.CHALL/TRANS.SCRAM SRV.CHALL/LOOP.-SCRAtI SRV.CHALL/LOOP.SCRAM SRV.CLOSE EMERG.PWER FW/PCS.STRANS Branch Model.
1.01.1 Train 1 Land Prab:
FW/PCS.SLOLA HPCI RLIC/TRANS.OR LOOP RCIC/LOCA CRD SRV.ADS
,COND/FW.PCS LPCS ILPCI(RHR)/LPCS Branch Model: 1.OF.2 Train 1 Cond Prob:
Train 2 Cond Prab:
RHRSW/LPCS.LPLI.STRANS RHRSW/LPCS.LPCI SLOOP RHRSW/LPCS.LPLI.LOCA RHR (SDL)
Branch Model: 1.OF.2+ser
.Train 1 Land Prob:
Train 2 Land Prab:
Serial Component Prob:
RHR (SDC) /-LPCI RHR (SOC) /LPCI RHR(SPCOOL)/-LPCI..RH(SDC)
C.! AND.V/RHR(SDC).RHR(SPCOOL)
- forced tMinarick 04-12-1987 12:26:50 Event Identifier: 3B8/84-006 I.OE-02 1.7E-01 > 1.OE+OO 1.7E-01 > Unavailable 1.0E+00 1.0E+00 1.OE+00 1
.0E+00 1.OE+00 5.3E-02 5A.E-04 4.6E-01 > 1.OE+00 4.6E-01 > Unavailable I
.OE+00 1.OE-01 6.7E-02 1.OE+00 I.OE-02 6.7E-03 1.OE+00 3.OE-03 4.OE-04 > 1.OE-01 4.OE-03 > Failed I.OE-0I 5.0E-01 5.OE-01 5.OE-01 2.OE-02 ) 1.2E-01 4.OE-03 > Failed 1.OE-01 2.OE-02 2.OE-02 1.OE+00 2.OE-02 5.2E-01 1.OE+00 I.OE+00 1.0E+00 4 OE-02 I.OE+00 1.OE+00 1.OE+00 1.OE+00 I. E+00 1.OE+00 5AE-01 3.4E-01 >'
1.OE+00 3.E-01 5.7E-01 5.7E-01 1.OE+00 I.OE+00 1.OE+06 3A.E-01 3A.E-01 3.4E-01 4 OE-02 4 OE-02
- 1. OE+00 1.OE+00 1.OE+00 3A.E-01 4.E-02 4 OE-02 4.OE-02 3.4E-01 I.OE+00 I OE+00 1.OE+00 M.E-01 D-2 32