ML20156A232
| ML20156A232 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-033-00 | |
| Download: ML20156A232 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER. No. :
327/84-033 Event
Description:
Atmospheric Dump Valve Opens and Causes LOFW Date of Event:
May 11, 1984 Plant:
Sequoyah 1 EVENT DESCRIPTION Sequence During a normal reactor startup on May 11,
- 1984, following a reactor trip on May 10, Unit 1 experienced another reactor trip.,Just prior to the event that occurred at 1400 h CST, Unit 1 was in mode 1 (554*F, 2235 psig) at 21% reactor power with SG level controls in manual.
Atmospheric steam dump valve I-FCV-1-107 spuriously opened, causing a swell of SG levels.
This action resulted in a high-high level in SG 3 that caused a turbine trip and MFW isolation to all f our SGs.
The transient then resulted in shrink of SG levels, causing a reactor trip on low-low level in SG 2.
All equipment and personnel responded as expected, and the unit stabilized at 547'F.
Corrective Action Inspection revealed a broken repositioning linkage on atmospheric dump valve 1-FCV-1-107, allowing the valve to cycle erratically.'
The repositioning linkage was replaced, and the valve was returned to ser-vice.
Plant/Event Data Systems Involved:
Atmospheric dump Valve and MFW isolation Components and Failure Modes Involved:
Atmospheric dump valve -
opened spuriously in operation MFW -
isolated on demand Component Unavailability Duration:
NA Plant Operating Mode:
1 (21% power)
Discovery Method:
Operational event Reactor Age:
3.9 years Plant Type:
PWR Comments None Event Identifier:
327/84-033 D-131
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery Branches Impacted and Branch Nonrecovery Estimate MFW 0.34 Recovery assumed locally at equipment Secondary-side 1.0 No recovery assumed because of damaged release terminated valve linkage Plant Models Utilized PWR plant Class F Event Identifier:
327/84-033 D-132
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 327/84-033 Event
Description:
ASD Valve Opens and Causes LOFW Event Date:
5/11/84 Plant:
Sequoyah 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV 1
.0E+00 Probability TRANS Total 5.3E-04 5.3E-04 CD TRANS Total ATWS TRANS Total 4.SE-06
- 4.
BE-06 3.OE-05
- 3.
OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
109 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI End State: CD Conditional Probability:
103 TRANS -RT -AFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HPI End State:
ATWS Conditional Probability:
5.OE-04 1
.6E-06 HPR/-HPI -SS.DEPRESS LPR/-HPI.HPR 3.OE-05 Event Identifier: 3217/84-033 D-13 33
128 TRANS RT SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
101 TRANS -RT -AFW PORV.OR.SRV.CHALL -PORV.DR.SRV.RESEAT SS.RELE AS.TERt1 HPI 103 TRANS -RT -AFW PORV.OR.SRV.CHALL. PORY.OR.SRV.RESEAT -HPI HP R/-HPI -SS.DEPRESS LPR/-HPI.HPR 104 TRANS -RT -AFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT -HPI HP R/-HPI SS.DEPRESS 109 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI 120 TRANS -RT AFW MFW
-HPI (F/B) -HPR/-HPI PORV.OPEN -SS.DEPRESS COND/MFW 123 TRANS -RT AFW MFW
-HPI(F/B)
HPR/-HPI -SS.DEPRESS COND/MFW 124 TRANS -RI AFW MFW
-HPI(F/B)
HPR/-HPI SS.DEPRESS 126 TRANS -RI AFW tIFW HPI (F/B) -SS.DEPRESS COND/tIFW 127 TRANS -RI AFW MFW HPI(F/B)
SS.DEPRESS 128 TRANS RI Cv CD CD cv CD 2.1E-05 5.2E-01 1.6E-06
- 2.8E-02 9.OE-08 2.8E-02 5.OE-04
- 5.2E-01 2.8E-07 3.1E-02 CD CD CD CD AIWS
- 1.
2E-06 1
.3E-07 I.2E-06 1.4E-07 3.OE-05*
- 1. 7E-02
- 5. 1E-02 1
.6E-62 4.8E-02 I.2E-0 1
- dominant sequence for end state
- non-recovery credit for edited case MODEL:
DATA:
b
- \\PWRBIREE.CMP b :\\SEQUOPRO.CMP No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS LOOP LOCA RI RI/LOOP EMERG.POWER AFW AFW/EMERS.POWER MFW Branch Model: l.OF.1 Train I Cond Prob:
PORY.OR.SRV.CHALL PORY.OR.SRV.RESEAI PORV.OR.SRV.RESEAT/EMERG.POWER SS.RELEAS.TERM Branch Model: 1.OF.1 Event Identifier: 327/84-033 1.OE-03 2.3E-05 4
.2E-06 2.5E-04 0.OE+00 2.9E-03 1
.OE-03 5.0E-02 2.OE-01 )1.OE+00 2.OE-01 >Unavailable 4.0E-02 3.OE-02 3.0E-02 1.5E-02 > 1.OE+00 1
.OE+00 3.4E-01 3.4E-01 1.2E-01 1
.0E+00 5.1E-01 2
.7E-01 3.4E-01 3.4E-01 1.0E+00 5.OE-02 5.0E-02 3.4E-01 > 1.OE+00 D-134
Train 1 Cond Prob:
SE.RELEAS.TERtI/-MFW Branch Model.
l.d1'.1 Train 1 Cond Prob:
HPI HPI (F/B)
HPR/-HPI PORV.OPEN ESS.DEPRESS COND/MFW LPI/HPI LPR/-HPI.HPR LPR/HPI 1.5E-02 ) Failed 1.5E-02 ) 1.OE+OO 1.5E-02 > Failed 1.OE-03 1
.OE-03 3.OE-03 1
.OE-O2 3.6E-02 1
.OE+OO I.OE-03 6.7E-01 1.OE-03 3.4E-01 > 1.OE+OO 5.2E-01 5.2E-01 5.6E-01
- 1. OE+0O 1.OE+OO 3J.E-O1 3.4E-01 1.OE+00 1.OE+00 4.OE-02 4 OE-02 forced Minarick 04-12-1987 16:35:46 Event Identifier: 327/84-033 D-135