ML20156A265
| ML20156A265 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-010-00 | |
| Download: ML20156A265 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
387184-010 Event
Description:
SRV Failure to Close Following Scram Date of Event:
February 25, 1984 Plant:
Susquehanna 1 EVENT DESCRIPTION Sequence On February 25, 1984, at 1848 h, Unit 1 was in mode 1 at 54% power when it was manually scrammed during preplanned testing of the ADS Susquehanna 1 utilizes 16 SRVs; 6 of these valves also function as ADS valves.
A preplanned test requirement was in progress to verify ope~r-ability of the ADS valves wherein each ADS valve was to be manually and sequentially cycled.
During the test sequence, the "M" SRV failed, to close; in accordance with the test procedure, a manual scram was mint-i ated because attempts to close the SRV were unsuccessful.
Each of the ADS SRVs has three independent solenoid-operated coný-
trol valves.
During testing of the "B" solenoid on the "M" SRV, the solenoid valve stuck open, and the instrument gas pressure kept the SRv open.
After 2 min of attempting to close the SRV by a procedure es~pe-cially written for this activity, the reactor was manually scrammed.' At 1 min and 20 s af ter scram, the inboard MSIVs were closed to reduce vessel depressurization.
Vessel pressure dropped from 946 to 682 psig during the transient.
Several minutes later, the "M" SRV closed due to internal spring energy when the instrument gas header isolated for the test dropped to 60 psig.
Corrective Action The "B" solenoid and air valve on the "M" SRV were replaced, and the new solenoid was tested successfully.
Investigation has found this to be a nonrecurring event*
The vendor will inspect the valves to determine the cause of the failure.
The test was continued, and the other SRVs and solenoid valves operated properly.
Plant/Event Data Systems Involved:
Steam relief Event Identifier:
387/84-010 D-217
Components and Failure Modes Involved:
SRV -
failed open in operation Component Unavailability Duration:
NA Plant Operating Mode:
1 (54% power)
Discovery Method:
Testing Reactor Age:
1.4 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 SRV 0.1 Assumed recoverable because of isolated gas header PCs 1.0 Unavailable because of MSIV closure MFW 1.0 Unavailable because of MSIV closure Plant Models Utilized BWR plant Class C Event Identifier:
387/84-010 D-218
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
387/84-010 Event
Description:
SRV Failure to Close Following Scram Event Date:
2/25/84 Plant-Susquehmanna I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1
.OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV TRANS 1
.4E-06 Total 1
.4E-06 CD TRANS 1
.4E-04 Total 1.4E-04 ATWS TRANS 2
.OE-05 Total 2
.OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
4.8E-07 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS
End State:
CD Conditional Probability,.
9.OE-05 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA SRV.ADS End State: ATWJS Conditional Probability:
2.OE-05 Event Identifier: 387/84-010 D-219
173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
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(SBC).RHR(SPCOOL) 110 TRANS -SCRAMI PCS/TRANS SRV.CHA.LL/TRANS.-SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CRD SRY.ADS III TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE -FW
/PCS.LOCA RHR(SDC) RHR(SPCOOL)/-LPCI.RHR(SDC) C.I.AND.V
/RHR(SDC).RHR(SPCOOL) 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM 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) 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(
SDC) 155 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/FCS.LOCA HPCI RCIC/LOCA -SRV.AOS -COND/FW.PCS -RHR(SDC) 159 TRANS SCRAM -SLC.OR.RODS PCS/ TRANS SRV.CLOSE FW/FCS.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.OE-05 1.OE-01 4.5E-06 2.9E-01 3.1E-06 7.6E-03 9.OE-05
- 1.9E-02 4.8E-07
- 1.9E-01 2.5E-07 9.9E-02 4.7E-07 1.3E-02 2.4E-07 6.6E-03 2.OE-05 *
.OE+O0 ATWS
- dominant sequence for end state
- non-recovery credit for edited case MODEL:
DATA:
b
- \\bwrctree.cmp b
- \\susqprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch Systemn TRANS LOOP LOCA SCRAM SLC.OR.RODS PCS/TRANS Branch Model: 1.OF.1 Train 1 Cond Prob:
PCS/LOCA Event Identifier: 387/84-010 1
.1E-03 1
.3Er05 3
.3E-06
- 4.
1IE-04 1.OE-02 1.7E-01 > 1.0E+00 1.7E-01 > Unavailable 1
.OE+O0 Non-Recov 1.OE+00 3.4E-01 3
.4E-01 1.0E400 1.0E+O0 1.OE+00 1.0E+00 Opr Fail 4.OE-02 D-220
SRV.CHALL/TRANS.-SCRAM SRV.CHALL/TRANS.SCRAM SRV.CHALL/LOOP.-SCRAM BRY.CHALL/L00P.SCRAMh SRV.CLOSE Branch Model: 1.GF.1 Train 1 Cond Prob:
EMERG.POWER
.FW/PCS.TRANS Branch Model-. 1.GF.1 Train 1 Cond Prob:
FW/PCS.LOCA HPCI RCIC/TRANS.OR.LOOP RCIC/LOCA CRD SRV.ADS COND/FW.PCS LPCS LPCI (RHR) /LPCS RHRSW/LPCS SLPCI.TRANS RHRSW/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
.OE+00 1.OE+0O 1.OE+00 1.OE+00 5.3E-02 > 1.OE+00 5.3E-02 > Failed 5A.E-04 4.6E-01 > 1.OE+00 4.6E-01 > Unavailable 1.OE+00 1
.OE-01 6.7E-02 1
.OE+00 1.OE-02 6.7E-03 1.OE+00 3.OE-03 4.OE-04 5.DE-01 5.OE-01 5.OE-01 2.OE-02 2.OE-02 L.OE+00 2.OE-02 5.21-01 1.OE+00 1
.OE+00 L.OEOO 1
.OE+00 I.OE+00 1.OE+00 > 1.OE-01
- 5.
IE-01 3.4E-01 > 1.OE+00 3A.E-01 5J.E-01 5.7E-01 1.OE+00 1.GE+00 I
.OE+00 3A.E-01 3.4E-01 3.4E-01 I.OE+00 l.OE+00 1
.OE+00 3.4E-01 3A.E-01 1.OE+00 I.OE+00 1.OE+00 3A.E-01
- 4.
OE-02 4.OE-02 4 OE-02 4 OE-02 4 OE-02 forced Minarick 04-12-1987 12: 14 :04 Event Identifier: 387/84-010 D-221