ML20161A171
| ML20161A171 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-036-00 | |
| Download: ML20161A171 (4) | |
Text
B-165 PRECURSOR DESCRIPTION SHEET LER No.:
424/87-036 Event
Description:
Auxiliary feedwater system is inoperable twice Date of Event:
6/3/87 and 6/15/87 Plant:
Vogtle Unit I
-EVENT DESCRIPTION Sequence Plant personnel disabled the auxiliary feedwater valve actuation circuitry by pulling incorrect fuses.
Personnel incorrectly used and interpreted a procedure during MFW pump maintenance during which it was intended to only block auto AFW initiation on MFW pump trip.
This occurred twice. On 6/3/87 the AFW system was inoperable for -49 h and on 6/15/87 the AFW system was inoperable for -11 h.
Corrective Action The fuses were replaced, the procedure was corrected, and personnel were instructed on the importance of performing a detailed review of system clearances and the importance of procedure compliance as well as correct procedure interpretation.
Plant/Event Data Systems Involved:
Auxiliary feedwater system Components and Failure Modes Involved:
AFW unavailable Component Unavailability Duration:
49 h and 11 h Plant Operating Mode:
3 (0% power)
Discovery Method:
Operator observation Reactor Age:
0.3 y Plant Type:
PWR Comment~s None.
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated LOOP, Base case nonrecovery
424/87-036
B-166 Branches Impacted and Branch Nonrecovery Estimate AFW 0.34 Recoverable locally AFW/Emergency 0.34 Recoverable locally Power Plant Models Utilized PWR plant Class B Event Identifier:
424/87-036
B-167 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
424/87-036 Event
Description:
Auxiliary feedwater system is inoperable twice Event Date:
06/03/87 Plant:
Vogtle 1 UNAVAILABILITY, DURATION= 60 NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS LOOP LOCA SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator 2. 9E-02 I.IE-04 6.2E-05 Probability CD CV TRANS LOOP LOCA Total TRANS LOOP LOCA Total 5.4E-06 8.8E-07 5.8E-10 6.3E-06 9.2E-06
( 4.9E-l0 5.4E-07 9.7E-06 ATWS TRANS LOOP LOCA Total o.OE+O0
- 0. OE+00
- 0. OE+00 0.OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 126 trans -rt AFW mfw hpi(f/b) -ss.depress cond/mfw 120 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 212 loop -rt/loop
-emerg.power AFW hpi(f/b) 210 loop -rt/loop
-emerg.power AFW -hpi(f/b) -hpr/-hpi porv.open 127 trans -rt AFW mfw hpi(f/b) ss.depress 121 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open ss.depress 123 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress cond/mfw 125 trans -rt AFW mfw hpi(f/b) -ss.depress -cond/mfw 119 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 316 loca -rt AFW mfw -hpi -hpr/-hpi -ss.depress cond/mfw 122 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw End State CD CD CD CD CD CD CD CV CV CV CV Prob 2.4E-06 2.2E-06 4.0E-07 3.7E-07 2.6E-07
- 2. 5E-07
- 2. 5E-07
- 4. 5E-06 4.2E-06
- 4. 8E-07 4.7E-07 N Rec**
- 3. 3E-02 3.9E-02 1.1E-01 1.3E-01
- 9. 7E-02 1.2E-01
- 3. 9E-02
- 6. 4E-02 7.6E-02
- 1. 7E-02
- 7. 6E-02
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQU ENCE ORDER)
Sequence End State 119 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress -
CV cond/mfw Prob N Rec*
4.2E-06 7.6E-02 Event Identifier:
424/87-036
B-168 120 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open -ss.depress cond/mfw 121 trans -rt AFW mfw -hpi(f/b) -hpr/-hpi porv.open ss.depress 122 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress -cond/mfw 123 trans -rt AFW mfw -hpi(f/b) hpr/-hpi -ss.depress cond/mfw 125 trans -rt AFW mfw hpi(f/b) -ss.depress -cond/mfw 126 trans -rt AFW mfw hpi(f/b) -ss.depress cond/mfw 127 trans -rt AFW mfw hpi(f/b) ss.depress 210 loop -rt/loop -emerg.power AFW -hpi(f/b) -hpr/-hpi porv.open 212 loop -rt/loop -emerg.power AFW hpi(f/b) 316 loca -rt AFW mfw -hpi -hpr/-hpi -ss.depress cond/mfw
- non-recovery credit for edited case CD CD Cv CD CV CD CD CD CD Cv 2.2E-06 3.9E-02 2.5E-07
- 4. 7E-07 2.5E-07 4.5E-06 2.4E-06 2.6E-07 3.7E-07 4.OE-07 4.8E-07 1.2E-01 7.6E-02
- 3. 9E-02
- 6. 4E-02 3.3E-02 9.7E-02
- 1. 3E-01 I.1E-01 1.7E-02 Note:
For unavailabilities, 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.
SEQUENCE MODEL:
BRANCH MODEL:
PROBABILITY FILE:
c:\\asp\\newmodel\\pwrbnew.cmp c:\\asp\\newmodel\\vogtle.new c:\\asp\\newmodel\\pwrbnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans loop loca rt rt/loop emerg.power ep.rec AFW Branch Model:
l.OF.3+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
AFW/EMERG.POWER Branch Model:
I.OF.l Train 1 Cond Prob:
mfw porv.or.srv.chall porv.or.srv.reseat porv.or.srv.reseat/emerg.power ss.releas.term hpi hpi(f/b) hpr/-hpi porv.open ss.depress cond/mfw lpi/hpi lpr/-hpi.hpr lpr/hpi 4.BE-04 4.6E-06 2.4E-06
- 2. SE-04 O.OE+00 2.9E-03 I.OE+00 3.8E-04 > 1.OE+00 2.OE-02 > Unavailable 1.OE-01 > Unavailable 5.OE-02 > Unavailable 2.8E-04 5.OE-02 > 1.OE+00 5.OE-02 > Unavailable 2.0E-01 4.OE-02 2.OE-02 2.OE-02 1.5E-02 1.OE-03 1.OE-03 1.5E-04 1.OE-02 3.6E-02 1.OE+O0 1.5E-04 6.7E-01 1.5E-04 1.OE+00 3.9E-01 4.3E-01 1.2E-01 1.OE+00 8.OE-01 1.7E-01 2.6E-01 > 3.4E-01 3.4E-01 3.4E-01 1.OE+00 1.IE-02 1.OE+00 3.4E-01 8.4E-01 8.4E-01 1.OE+00 1.OE+00 1.0E+00 3.4E-01 3.4E-01 1.OE+00 1.OE+00 1.OE-02 1.OE-03 4.OE-04 1.OE-02 branch model file
- forced Minarick 05-16-1989 07:02:46 Event Identifier:
424/87-036