ML20147A495
| ML20147A495 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Regulatory Research |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1986-031-00 | |
| Download: ML20147A495 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
413/86-031 Event
Description:
Small LOCA forces plant trip Date of Event:
June 13, 1986 Plant:
Catawba 1 EVENT DESCRIPTION Sequence The unit was at 48% power with the variable letdown orifice valve INV849 in service to reduce letdown flow to 30 gal/mmn.
A leak
(>1 gal/min) had been detected at the CCW/CVCS junction at the letdown heat exchanger.
The fixed orifice flow paths were isolated.
At 1100 h a leak of >1.5 gal/min was detected.
At 1500 h an unusual event was declared.
At 1542 h, alarms occurred indicating the loss of motor control center
- 1MXD, which affected control power to valve INV849 and the generator hydrogen-cooler-temperature valve.
The former failed open, and the latter failed closed.
Charging flow suddenly increased to 130 gal/min, and pressurizer level began to fall.
The letdown line had suffered a guillotine rupture at valve INV849's downstream outlet flange as a result of vibration-induced fatigue.
At 1550 h the main-generator hydrogen temperature began to rise.
At 1551 h the letdown orifice valve was closed, but pressurizer level continued to decrease.
Hydrogen temperature continued to increase.
Sump high-level alarms were actuated, and at 1610 h reactor power and turbine load were reduced.
Maximum charging was maintaining pressurizer level, and additional letdown isolation valves were closed.
The leak was contained by 1641 h.
Hot standby was entered at 1700 h.
Cold shutdown was entered at 0257 h the next day.
Corrective Action Repairs were made to the letdown line.
The MCC failure was due to a
name plate that became unglued and caused a short circuit when it fell.
Plant/Event Data Systems Involved:
Electrical and chemical volume and control Components and Failure Modes Involved:
Motor control center transformer -
failed in operation CVCS pipe -
ruptured in operation Event Identifier:
413/86-031 D-130
Component Unavailability Duration:
NA Plant Operating Mode:
1 (48% power)
Discovery Method:
Operational event Reactor Age:
1.4 years Plant Type:
PWR Comments We are assuming a 130 gpm SBLOCA since CP's were able to maintain pressurizer level with this flowrate MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate SBLOCA 0.12 Flow isolable via letdown isolation valves Branches Impacted and Branch Nonrecovery Estimate None Plant Models Utilized PWR plant Class F Event Identifier:
413/86-031 D-131
CONDITIONAL CORE DAHAGE PROBABILITY CALCULATIONS Event Identifier:
413/B6-031 Event
Description:
Small LOCA Forces Plant Trip Event Date:
6/13/86 Plant:
Catawba I INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOCA SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator CV 1.2E-01 Probability LOCA Total
- 1.
- 1.
- 3.
3E-03 ATNS LOCA Total DOMINANT SEQUENCES End State:
CV Conditional Probability:
301 LOCA -RT -AFW -HPI HPR/-HPI -SS.DEPRESS -LPR/-HPI.HPR End State:
CD Conditional Probability:
302 LOCA -RT -AFN -HPI HPR/-HPI -SS.DEPRESS LPR/-HPI.HPR End State: ATWN Conditional Probability:
4.OE-06
- 4.
OE-06 1.5E-03 3.IE-03
- 4.
OE-06 Event Identifier: 413/86-031 D-132
326 LOCA RT SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob 301 302 303 304 326 LOCA -RT
-AFW -HPI HPR/-HPI -SS.DEPRESS -LPR/-HPI.HPR LOCA -RT
-AFW -HPI HPR/-HPI -SS.DEPRESS LPR/-HPI.HPR LOCA -RT -AFN -HPI HPR/-HPI SS.DEPRESS LOCA -RT
-AFW HPI -SS.DEPRESS -LPI/HPI -LPR/HPI LOCA RT Cy CD CD Cv ATWS 1.5E-03 *
- 3.
IE-03 *
- 1.
- 9.
7E-05 4.OE-06 #
N Rec#*
1.2E-01
- 1.
2E-01 1.2E-01 1.OE-01 i.4E-02
- dominant sequence for end state
- 4 non-recovery credit for edited case SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodeI\\pwrbtree.cmp c: \\asp\\newmodel\\cataw.txt c:\\asp\\newmodel\\pwrb.pro No Recovery Limit BRANCH FREDUENCIES/PROBABILITIES Branch TRANS LOOP LOCA Branch Model:
INITOR Initiator Freq:
RT RT/LOOP EMERB.POWER AFW AFW/EMERS.POWER MFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT PORY.OR. BRV.RESEAT/EMERS.POWER SS.RELEAS.TERM SS.RELEAS.TERM/-MFW HPI HPI(FIB)
HPR/-HPI PORV.OPEN SS.DEPRESS COND/MFW LPI/HPI LPR/-HPI,HPR Event Identifier: 413/86-031 System Non-Recov Opr Fail 4.BE-04
- 4.
6E-06 2.4E-06 ) 2.4E-06 1.OE400 3.9E-01 4.3E-01 ) 1.2E-01 2.4E-06 2.BE-04
- 0.
OE+00 2.9E-03
- 3. 8E-04
- 5. OE-02 2.OE-Ot
- 4. OE-02 3.OE-02 3.OE-02 1.5E-02 1.5E-02 I.OE-03 I.OE-03
- 1. 5E-04 I.OE-02 3.6E-02 1.,E+O0 1.5E-04 b.7E-01
- 1.
2E-01 1.0E+00 B.
OE-0I
- 2.
6E-01 3.4E-01
- 3.
4E-01 I.OE+0O
- 5.
OE-02 1.0DEW0
- 3.
- 3.
- 8.
4t-01 B.
- 1.
OE+00
- 1.
OE +00 1.OE +00 3.4E-01 3,4E-01
- 1.
DEW+0
- 4. OE-02
- 4. E-02 V-133
LPR/HP!
1.5E-04
- 1. OE+O0
- branch model file forced Austin 09-11-1987 12:58:13 Event Identifier: 413/86-031 D-134