ML20161A163
| ML20161A163 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-019-00, LER 1985-021-00 | |
| Download: ML20161A163 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
Event
Description:
Date of Event:
Plant:
250/85-019, 021 Multiple AFW Train Failures Following LOFW from Hot Standby July 22-24, 1985 Turkey Point 3 EVENT DESCRIPTION Sequence Three events occurred in close sequence.
While in hot standby and recovering from a prior reactor trip, a MFW bypass valve failed to open. The trip had occurred because of a lightning strike that caused a spurious signal.
A low SG level resulted in AFW autostart.
AFW trains A and C failed on demand because of governor problems.
Train B oscillated near its trip set point but did not actually fail.
Train A was restarted in 5 min.
During the subsequent recovery, a MFW bypass valve failed to close, resulting in a high SG level and a trip of the only operating MFW pump.
AFW autostarted, but train B's flow control valve failed open.
Later, during restart, two ANW train flow control valves failed to open during testing.
The valves all failed because of moisture in the instrument air lines.
Corrective Action Repairs were made.
The plant remained shut down until repairs were com-pleted.
Plant/Event Data Systems Involved:
ANW and MFW Components and Failure Modes Involved:
MFW bypass valves -
failed on demand AFW`
pumps and flow control valves
-failed on demand and in operation Event Identifier:
250/85-019, 021 E-5 1
Component Unavailability Duration:
NA Plant Operating Mode:
3 (0% power)
Discovery Method:
Operational event Reactor Age:
12.6 years Plant Type:
PWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery assumed Branches Impacted and Branch Nonrecovery Estimate AFW Base case Two of three trains failed MFW Base case Failed Plant Models Utilized PWR plant Class E Event Identifier:
250/85-019, 021 E-52
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:
Event
Description:
Event Date:
Plant-250/85-019,021 Multiple AFW Train Failures Following LDFW 6/22/85 Turkey Point 3 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV TRANS Total CD TRANS Total ATWS TRANS Total 1.000E+00 Probability
- 1.
- 1.
- 8.
- 8.
- 3.
OOOE-05
- 3.
OOOE-05 DOMINANT SEQUENCES End State:
CV Conditional Probability:
125 TRANS -RT AFN MFW HP.I(F/B) -SS.DEPRESS -COND/MFW End State:
CD Conditional Probability:
126 TRANS -RT AFW MFW HPI(F/B) -SS.DEPRESS COND/MFW End State: ATWS Conditional Probability-128 TRANS RT
- 7.
- 3.
624E-04 3.OOOE-05 Event Identifier: 250/85-019,021 E-5 3
SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prab Non-Recovit 119 TRANS -RI AFW IIFW
-HPI(F/B)
-COND/MFW 120 TRANS -RI AFW MFW -HPI (F/B)
COND/MFW 122 TRANS -RI AFW MFW -HPI (F/B) 123 TRANS -RI AFW MFW -HPI (F/B) 124 TRANS -RI AFW IIFW
-HPI (F/B) 125 TRANS -RI AFW MFW HPI(F/B) 126 TRANS -RI AFN MFW HPI(F/B) 127 TRANS -RI AFW MFW HPI(F/B) 128 TRANS RI
-HPR/-HPI PORV.OPEN -SS.DEPRESS
-HPR/-HPI PORV.OPEN -SS.DEPRESS HPR/-HPI -SS.DEPRESS -CONDIMFW HPR/-HPI -SS.DEPRESS COND/MFW HPR/-HPI 95. DEPRESS
-SS. DEPRESS -COND/IIFW
-SS. DEPRESS CONDINFW SS. DEPRESS CV ED 1.612E-04 5.579E-02
- 8.
- 2.
874E-02 CV CD CD Cv CD Cd AIWS
- 6.
998E -04
- 3.
- 3.
960E -05 7.035E-04 I 3.624E-04 I
- 3.
- 3.
OOOE-05 I
- 3.
- 1.
- 5.
- 2.
- 1.
- 3.
829E-03 1.200E-01 I dominant sequence for end state It 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:
b:pwrbtree.4 DATA:
b:turkprob.i No Recovery Limit BRANCH FREgUENCIES/PROBABILIIIES Branch cop EMP system TRANS LOOP LOCA RI RI/LOOP EMERG. POWER AFW Branch Model:
1.0F.3 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
AFW/EMERG. POWER Branch Model:
1.OF.3 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
- 1.
- 2.
- 4.
- 2.
- 0.
OOOE+00
- 2.
B50E-03 1.500E-03 > 3.OOOE-01 5.000E-02 > Failed l.000E-01 > Failed
- 3.
000E-01 1.500E-03 > 3.000E-01 5.OOOE-02 ) Failed 1.OOOE-01 > Failed
- 3.
OOOE-01 Non-Recov
- 1.
000E+00
- 3.
- 3.
- 1.
200E-01 1.O00E+00 5.100OE-01
- 2.
700E-01 2.700QE-01 Opr Fail Event Identifier: 250/85-019,021 E-54
MFW Branch Model:
1.OF.1 Train 1 Cond Prob:
PGRY.QR. SRV. CHALL PORV.OR. SRV. RESEAT PIJRV. OR. SRV. RESEAT/EMERS. POWER
HPR/-HPI PORY. PEN SS. DEPRESS COND/MFW IPI /HPI LPR/-HPI.HPR LPR/HPI It$ forced Ad harris 10-03-1986 13:32:01 Event Identifier: 250/85-019,021 1.900E-01 > i.OO0E+00 1.900E-01 > 1.OO0E+00
- 4.
OOOE-02
- 2.
- 2.
O0OE-02 1.500E-02 1.500E -02
- 3.
000E-04 3.OOOE-04 3.OOOE-03 1.00OE-02
- 3.
600E-02 1.000E+00 1.OOOE-03
- 6.
700E-01 1.OOOE-03
- 3.
- 1.
OOOE+00
- 5.
- 5.
OOOE-02
- 3.
- 3.
- 5.
- 5.
200E-01 5.600EC-01 1.000E+00 1.000E+00 3.400E-01
- 3.
400E-01 1.000E+00
- 1.
OOOE+00
- 4.
OOOE-02
- 4.
OOOE-02 E-55