ML20147A491
| ML20147A491 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Reactor Regulation |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1986-006-00 | |
| Download: ML20147A491 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
Event
Description:
Date of Event:
Plant:
318/86-006 Trip occurs, and one atmospheric dump valve fails to close September 5, 1986 Calvert Cliffs 2 EVENT DESCRIPTION Sequence While the reactor was at 100% power, a surge capacitor in the 21A RCP failed and shorted to ground.
The RCP tripped off, which led to an automatic reactor trip on low flow.
The cooldown rate was faster than expected because an atmospheric steam dump valve was stuck open.
It was closed manually after 22 min.
Corrective Action The solenoid valve associated with found to be leaking high-pressure air by materials were replaced.
the atmospheric dump valve was its seats.
The solenoid valve Plant/Event Data Systems Involved:
RCS and atmospheric steam dump Components and Failure Modes Involved:
RCP -
failed in operation Atmospheric steam dump valve -
failed to close on demand Component Unavailability Duration:
NA Plant Operating Mode:
1 (100% power)
Discovery Method:
Operational event Reactor Age:
9.8 years Plant Type:
PWR Comments None Event Identifier:
318/86-006 D-96
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 Nonrecoverable Branches Impacted and Branch Nonrecovery Estimate SS release 1.0 Atmospheric dump valve failed to close terminated from control room and is not closed locally for 22 min Plant Models Utilized PWR plant Class G Event Identifier:
318/86-006 D-97
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
318/86-006 Event
Description:
Trip and One ASD Valve Fails to Close Event Date:
9/5/86 Plantl Calvert Cliffs 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV l.0E+00 Probability TRANS Total 2.5SE-04 2.5E-04 CD TRANS Total l.BE-O6 1.SE-06 ATWS TRANS Total DOMINANT SEQUENCES End State:
CV Conditional Probability:
104 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI End State:
CD Conditional Probability:
102 TRANS -RI -AFW PORV.DR.SRV.CHALL PDRV.OR.SRV.RESEAT -HPI End State:
ATWS Conditional Probability:
3.4E-05 3.4E-05 2.4E-04 1.6E-06 HPR/-HPI 3,.4E-05 Event Identifier: 318/86-006 D-98
121 TRANS RT SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
101 TRANS -RT -AFW PORV.OR.SRV.CHALL -PORV.OR.SRV.RESEAT SS.RELE ASTERM HPI 102 TRANS -RT
-AFW PORV.OR.SRVCHALL PDRV.OR.SRV.RESEAT -HPI HP R/-HPI 104 TRANS -RT
-AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI 116 TRANS -RT AFN MFW -HPiF/B)
HPR/-HPI -SS.DEPRESS COND/MFW 119 TRANS -RT AFW MFW HPI(F/B) -SS.DEPRESS CONDIMFW 121 TRANS RT CV CD 1.0E-05 8.4E-01 I.bE-06
- 5.OE-02 CV CD CD ATWS 2-.4E-04
- 8.5SE-08 8.9E-08 3.4E-05 4 8.4E-01
- 3. OE-02 2.5E-02 1.2E-01
- dominant sequence for end state
- non-recovery credit for'edited case SEQUENCE MODEL:
c:\\asp\\newaodel\\pwrqtree.cmp BRANCH MODEL:
c:\\asp\\newmodel\\caIvert.txt PROBABILITY FILE:
c:\\asp\\newmodel\\pwr~b.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS LOOP LOCA RT RT/LOOP EMERS.POWER AFW AFW/EMERB.POWER MFW PORV.OR. SRV. CHALL PORV.OR.SRV.RESEAT PORV.OR.SRV.RESEAT/EMERG.POWER SS.RELEAS.TERM Branch Model:
I.OF.1 Train I Cond Prob:
SS.RELEAS.TERM/-MFW 89.DEPRESS COND/MFW HPI HPI(F/B)
PORV.OPEN Event Identifier: 318/86-006
- 4. BE-04 4.6E-06 2.4E-06 2.8E-04 O.OE00 5.4E-04 3.BE-04 5.0E-02 2,OE-01
- 4. 0E-02
- 2.
- 2. OE-02 1.5E-02 > 1.0E+00 1.5E-02 > Failed
-1.5E-02 3.6E-02 1.0E+00 3.OE-04 3.OE-04 I.OE-02
- 1.
OE+00
- 3.
- 4.
- 1.
2E-01 1.0E+400 B.
OE-01 2.6E-01
- 3.
4E-01 3.4E-01 J,0E+00 S. OE-02
- 1. OE+00 3.4E-01 > 1.0E+00 3.4E-01 1.OE+00 3.4E-01 B. 4E-01 B.
- 1. OE+00 4.OE-02 D-99
NPR/-HPI CSR