ML20149K393
| ML20149K393 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1986-023-00 | |
| Download: ML20149K393 (4) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
409/86-023 Event
Description:
LOOP occurs due to lightning strike at coal-fired unit Date of Event:
July 10, 1986 Plant:
LaCrosse EVENT DESCRIPTION Sequence With the plant in the cold shutdown condition, at 0630 h, the following opened:
the 69-kV tie line breaker, 2NBI1; the reverse transformer supply breaker, 25NB4; and the 480-V main feed breakers, 452 MIA and 452 MIB.
Both EDGs started and supplied the I-A and 1-B 480-V essential buses.
The containment building also isolated.
The 1-A high-pressure service-water diesel pump started when service-water pressure dropped to the low-pressure set point.
A severe thunderstorm was in progress at the time.
The operations center informed the plant that the adjacent coal plant's auxiliary switchyard had been hit by lightning.
The operators reset the lockout relays.
At 0642 h they closed breakers 2NBII and 25NB4; at 0645 h they shut the 480-V main feed breakers and opened the EDG's output breakers.
The 480-V essential bus breakers automatically
- closed, completing the electrical lineup restoration.
At 0659 h the I-A high-pressure service-water DG was secured and returned to automatic.
At 0702 h the EDGs were secured and returned to automatic.
An unusual event was declared due to the loss of offsite power.
The plant was without offsite power for 12 min.
The lightning had hit a static wire in the adjacent coal plant's auxiliary switchyard.
The 69-kV tie line supplies power to LaCrosse's reserve transformer and the coal unit's reserve auxiliary transformer.
When the lightning struck, the 69-kV tie line breaker and both transformers' supply breakers opened.
The LaCrosse 480-V main feed breakers tripped on undervoltage.
Undervoltage also started the EDGs and tripped the 480-V essential bus main feed breakers, which caused the emergency DGs' output breakers to close to supply the essential buses.
If this incident had occurred while the reactor was at 100% power, a loss of load transient would have resulted.
This is a design-basis transient, and the plant would still have been in a safe condition.
Corrective Action The breakers were closed.
Event Identifier:
409/86-023 D-126
Plant/Event Data Systems Involved:
Electrical Components and Failure Modes Involved:
Breakers -
failed open in operation Component Unavailability Duration:
NA Plant Operating Mode:
4 (0% power)
Discovery Method:
Operational event Reactor Age:
17.6 years Plant Type:
BWR Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP Base case nonrecovery multiplied by 0.75 for occurring at power Branches Impacted and Branch Nonrecovery Estimate None Plant Models Utilized Unique BWR class Event Identifier:
409/86-023 D-127
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS
, Event Identifier:
409/86-023 Event
Description:
LOOP Due to Liqhtning Strike at Coal-Fired Unit Event Date:
7/10/16 Plant:
LaCrosse INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 2.7E-01 Probability CD LOOP Total
- 2. OE-05
- 2. OE-05 CV LOOP Total
- 0.
OE+00
- 0.
OE+00 ATNS LOOP Total 5.3E-06
- 5.
3E-06 DONINANT SEQUENCES End State:
CD 205 LOOP -ENERG.PONER
-SCRAM HPCS End State:
ATWS 206 LOOP -EMERG.POWER SCRAM -HPCS SEQUENCE CONDITIONAL PROBABILITIES Conditional Probability:
HPSw Conditional Probability:
SLC.OR.RODS 6.7E-06 4.7E-06 Event Identifier: 409/86-023 D-128
Sequence End State Prob N Recof 202 LOOP -EMERB.POWER
-SCRAM HPCS -HPSW
-SRVCLOSE SHUTDOWN.COND ENSER HANUAL, DEPRESS 204 LOOP -EMERB.POWER
-SCRAM HPCS -HPSW SRV.CLOSE MANUAL.DEPRES CD CD 1.6E-06 2.7E-0l 1.6E-06 2.7E-01 205 206 207 209 210 211 212 S
LOOP -EMER6.POWER
-SCRAM HPCS HPSW LOOP -EMERG.POWER SCRAM -HPCS SLC.OR.RODS LOOP -EMERG.POWER SCRAM HPCS LOOP EMERS.POWER -SCRAM
-HPSW -SRV.CLOSE SHUTDOWN.CONDENSER MANUAL.DEPRESS LOOP EMERG.POWER -SCRAM
-HPSW SRV.CLOSE LOOP EMER6.POWER -SCRAM HPSW LOOP EMER6.POWER SCRAM CD ATWS ATWS CD CD CD ATiWS 6.7E-06
- 4.7E-06
- 4.7E-07 7.3E-07
- 6.
IE-06
- 3.
IE-06 2.2E-07 2.7E-01 2.7E-01 2.7E-01 2.2E-01 2.2E-01 2.2E-01 2.2E-01
- dominant sequence for end state 4* non-recovery credit for edited case SEQUENCE MODEL; BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\lactree.cmp c:\\asp\\newmodel\\lacrosse.txt c:\\asp\\newodeI\\bwrc.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch TRANS LOOP Branch Model:
INITOR Initiator Freq:
LOCA SCRAM SLC.OR.RODS EMER.,POWER FN HPSW SHUTDOWN.CONDENSER HPCS LPCS SRV.CLOSE OH MANUAL.DEPRESS
- branch model file
- forced Event Identifier: 409/86-023 System Non-Recov Opr Fail S.
6E-04 2.OE-05 > 2.OE-05 2.OE-05 3.3E-06 3.5E-04 1.OE-02 2.9E-03 I.OE-01 5.OE-03 I.OE-02 5.OE-03 I.OE-03 i.OE-02 I.OE-02 1.2E-01
- 1.
OE+0O 3.6E-01 >2.7E-01 5.OE-01 I.
OE+00 1.0E+00
- 8.
OE-01
- 3.
4E-01 1.0E+00 I.OE+00 1.0E+00 1.0E+00 1.0E+00 J.OE+00 1.0E+00 4.OE-02 D-129