ML20149K384
| ML20149K384 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-016-00 | |
| Download: ML20149K384 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
247/85-016 Event
Description:
LOOP Due to Operator Error During Trip Recovery and AFW Pump Trip Date of Event:
December 12, 1985 Plant:
Indian Point 2 EVENT DESCRIPTION Sequence A reactor trip occurred at 0637 h because of a loss of two out of three reactor coolant flow signals in reactor coolant loop No. 21.
During recovery activities, the normal supply of offsite 138-ky power was disrupted at 0800 h because an operator attempted to clear a relay contactor on a 345-ky pilot wire by "tapping" the relay cover.
An adjacent relay actuated, which, in turn, tripped a second relay.
The second relay tripped the offsite power breakers and deenergized all 6.9-and 480-V buses.
The diesel generators started and reestablished power to the 480-V safeguard buses.
Natural circulation was established within the RCS.
Of fsite power was reestablished at 0820 h. At 0835 h the No. 24 reactor coolant pump was started to establish forced cooling.
During this recovery period, the No. 23 AFW pump (one of two 1/2-capacity, motor-driven pumps) tripped several times after being manually reset.
only one motor-driven AFW pump (No. 22) was required for decay heat removal.
The full-capacity, turbine-driven pump (No. 21) and the other motor-driven pump (No. 22) remained operable.
ANW pump No. 23 was returned to operable status at 1725 h.
Corrective Action A capacitor and a transformer in the bistable circuit of the low-flow reactor coolant instrument channel were repaired.
The relays associated with the interruption of off site power were in-vestigated, and no failures were detected.
The LOOP is attributed to operator interaction.
An open coil on a -relay on AFW pump No. 23 was repaired, and the pump was returned to operable status.
Event Identifier:
247/85-016 E-46
Plant/Event Data Systems Involved:
Primary cooling, AFW, high-voltage ac power system Components and Failure Modes Involved:
Reactor coolant ioop flow instrumentation -
failed in operation AFW pump -
failed to start Trip relay -
transferred tripped (fails in operation)
Component Unavailability Duration:
ANW pump, 7 h; trip relay, 20 min; reactor coolant loop flow instrumentation, 17 h Plant Operating Mode:
3 (0% power)
Discovery Method:
Operational event Reactor Age:
12.6 years Plant Type:
NWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP Base case Base case nonrecovery assumed Branches Impacted and Branch Nonrecovery Estimate AFW Base case one motor-driven train failed Plant Models Utilized PWR plant Class H (assumed equal to class B, C, E, and F for this calculation)
Event Identifier:
247/85-016 E-47
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:
Event
Description:
Event Date:
Plant:
247/85-016 LOOP Due to Opr Error During Trip Recovery and AFN Pump Trip 12/12/85 Indian Point 2 INITIATING EVENT NON-RECOVRABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator
- 3.
400E-01 ProbabilIi ty CV LOOP Total
- 2.
- 2.
- 5.
- 5.
- 0.
OOOE+00
- 0.
OOOE+00 DOM INANT SEQUENCES End State:
CV Conditional Probability:
2.378E-06 217 LOOP -RT/LOOP ENERG.POWER -AFN/ENERG.PONER -PORV.OR.SRV.CHALL SS.RELEAS.TERN End State:
CD Conditional Probability:
2.210E-05 214 LOOP -RT/LOOP -ENERG.PONER AFW HPI(F/B)
SEQUENCE CONDITIONAL PROBABILITIES Event Identifier: 247/85-016 E-48
Sequence SeueceEnd State Seq. Prob Non-Recovi 203 LOOP -RTILOOP -EMERG.POWER -AFN PORV.OR.SRY.CHALL PORV.OR.SR V.RESEAT -HPI HPR/-HPI -SS.OEPRESS -LPR/-HPI.HPR 212 LOOP -RTILOOP -ErIERG.POWER AFN -HPI(FIBJ -HPR/-HPI PORV.OPEN 213 LOOP -RI/LOOP -EMERG.POWER AFW -IIPI(F/B)
HPR/-HPI 214 LOOP -RI/LOOP -EMERB.POWER AFN HPI(F/B) 215 LOOP -RI/LOOP EMER6.P0WER -AFW/EMER6.POWER PORV.OR.SRV.CHALL
-PORV.OR.SRV.RESEATIEMERS.POWER SS.RELEAS.TERM 217 LOOP -RT/LOOP EMERG.POWER -AFW/EMER6.POWER -PORV.OR.SRV.CHALL SS.RELEAS.TERM 218 LOOP -RI/LOOP EIIERG.POWER AFW/ENERG. POWER CY CD CO CD CV CY CD 1.793E-07 1.00GE-03
- 4.
- 2.
164E-05 2.210E-05
- 9.
- 8.
4 51 E-02
- 5.
- 4.
- 5.
B23E-02 2.37BE-06
- 5.62SE-02 8.401E-06 5.896E-02 Idominant sequence for end state 44non-recovery credit for edited case Note:
Conditional probability values are differential values which reflect the added risk due to failures associated with an event.
Parenthetical values indicate a reduction in risk compared to a similar period without the existing failures.
MODEL:
b:pwrbtree.cmp DATA:
b: IPPROB.CMP No Recovery Limit BRANCH FREGtJENCIESIPROBABILITIES Branch System TRANS LOOP LOCA RT RT/ LOOP EMER6. POWER AFW Branch Model:
1.OF.3+ser Train!I Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Probability:
AFNIENERG. POWER PORV. OR.SRV. CHALL PORV. OR. SRV. RESEAT PORV. OR.SRV.RESEAT/EMER6.POWER SS. RELEAS. TERM SS. RELEAS. TERK/-MFN HPI HPI (F/B)
Event Identifier:
247/85-016
- 1.
- 2.
- 4.
170E-06 2.500E -04
- 0.
OOOE+00
- 2.
850E-03 1.020E-03 > 5.915E-03 2.O0OE-02 ) Failed
- 1.
OOOE-01
- 5.
OOOE -02 7.200E-04
- 5.
- 2.
OOOE-01
- 4.
OOOE-02
- 2.
OOOE -02
- 2.
OOOE-02 1.500E-02 1.500E-02
- 1.
500E-03 1
.500E-03 Non-Recov
- 1.
OOOE+00
- 3.
- 3.
- 1.
- 1.
O00E+00 5.100OE-01
- 2.
700E-01 Opr FailI
- 3.
- 3.
4O0E-0 I 1.0OOE+00
- 5.
OOOE-02 5-OOOE-02
- 3.
- 3.
- 5.
- 5.
- 4.
OOOE-02 E-49
HPR/-HPI PORV. OPEN SS. DEPRESS CDND/MFN LPI/HPI LPR/-HPI.HPR LPR/ HP I
- forced Austin 08-11-1986 17:08:35 Event Identifier: 247/85-016
- 3.
OOOE -03 1.000E-02
- 3.
- 1.
OOOE+00
- 1.
DOOE-03
- 6.
- 1.
OOOE-03
- 5.
- 1.
OOOE+00
- 1.
OOOE+00
- 3.
- 3.
- 1.
OO0E+00
- 1.
OOOE+00
- 4.
OOOE-02 E-50