ML20156A219
| ML20156A219 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1983-099-00 | |
| Download: ML20156A219 (4) | |
Text
B.40-1 B.40 LER No. 362/83-099 Event
Description:
Date of Event:
Trip with Turbine-Driven AFW Pump Inoperable October 31, 1983 Plant:
San Onofre 3 B.40.1 Summary San Onofre 3 was operating at 62% power when a loss of main feedwater caused a reactor trip. An emergency feedwater actuation signal (EFAS) was generated, but the turbine-driven emergency feedwater (EFW) pump failed to start. The conditional core damage probability estimated for the event is 1.5 x 105.
B.40.2 Event Description During Mode 1 operation at 62% power, San Onofre Unit 3 experienced a loss of feedwater and tripped after the feed pumps experienced problems with their suction supply. An EFAS signal was generated when the unit tripped, but the turbine-driven EFW pump failed to start. The pump was found to be tripped, was reset, and was successfully restarted. The reason for the EFW pump trip was unknown at the time of the licensee event report (LER), but investigation was ongoing.
B.40.3 Additional Event-Related Information None.
B.40.4 Modeling Assumptions This event was modeled as a loss of feedwater with the turbine-driven EFW pump inoperable.
B.40.5 Analysis Results The conditional core damage probability estimated for this event is 1.5 x 10'. The dominant sequence for this event, highlighted on the event tree in Figure B.40. 1, involves a failure of main and emergency feedwater, and failure to supply makeup from the condensate system.
LER No. 362/83-099
lI-000 w*
n.-
0 w
z w CO ccJO 0
0 1:
>it I=
.J 0
I--
z 0-B.40-2 0 0 0 8 0 8 8 0
0 0 0 0 8
0 0 0 0 0 0 0 0 0 o o Figure B.40.1 Dominant core damage sequence for LER 362/83-099 LER No. 362/83-099
B.40-3 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
362/83-099 Event
Description:
Trip with turbine-driven AFW pump inoperable Event Date:
October 31. 1983 Plant:
San Onofre 2 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.0E+O0 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 1.5E-05 Total 1.5E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
119 trans -rt AFW MFW -srv.reseat cond CD 1.2E-05 1.5E-OI 508 trans rt -prim.press.limited AFW/ATWS CD 1.IE-06 I.OE-OI 118 trans -rt AFW MFW -srv.reseat -cond rcs.cooldown CD 6.6E-07 1.5E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
118 trans -rt AFW MFW -srv.reseat -cond rcs.cooldown CD 6.6E-07 1.5E-O1 119 trans -rt AFW MFW -srv.reseat cond CD 1.2E-05 1.5E-01 508 trans rt -prim.press.limited AFW/ATWS CD 1.1E-06 I.OE-OI
- non-recovery credit for edited case SEQUENCE MODEL:
c:\\asp\\1982-83\\pwrh8283.cmp BRANCH MODEL:
c:\\asp\\1982-83\\sanono2.82 PROBABILITY FILE:
c:\\asp\\1982-83\\pwr8283.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 1.7E-03 1.OE+O0 loop 2.OE-05 5.8E-01 loca 2.4E-06 5.4E-01 LER No. 362/83-099
B.40-4 sgtr rt rt(loop)
Event Identifier: 362/83-099 AFW Branch Model:
1.OF.3+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
AFW/ATWS Branch Model:
1.OF.1 Train 1 Cond Prob:
afw/ep MFW
,Branch Model:
1.OF.1 Train 1 Cond Prob:
cond srv.chall srv.chall/afw srv.chall/loop srv.chall/sbo srv.reseat srv.reseat(atws) hpi rhr hpr ep seal.loca offsite.pwr.rec/seal.loca offsite.pwr.rec/-seal.loca sg.iso.and.rcs.cooldown rcs.cooldown rcs.cool.below.rhr prim.press.limited emrg.boration 1.6E-06 2.8 E- 04 0.OE+00
- 1.
OE+00 1.OE-01
- 1.
OE+00 3.8E-04 > 2.3E-03 2.OE-02 1.OE-01 5.0E-02 > Failed 2.8E-04 4.3E-03 > 4.OE-02 4.3E-03 > 4.0E-02 5.0E-02 2.0E-01 > 1.OE+00 2.0E-01 > Failed 2.5E-02 4.OE-02 1.OE+00 1.OE-01 1.OE+00 2.OE-02 1.OE-01 3.OE-04 7.1E-03 2.OE-03 2.9E-03 5.5E-02 7.6E-01 3.4E-01 1.OE-02 1.0E-03 3.0E-03 8.8E-03 0.OE+00 4.5E-01
- 1.
OE+00 3.4E-01 3.4E- 01
- 1.
OE+00 1.OE+00 1.OE+00 1.OE+00
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00 8.9E-01 5.7E-02 1.OE+00 8.9E-01
- 1.
OE+00
- 1.
OE+00
- 1.
OE+00 1.OE-01
- 1.
OE+00 1.OE+00
- 1.
OE+00 1.OE+00 1.0E-02 1.OE-03 1.OE-03
- 3.
OE -03 1.0E-02
- branch model file
- forced LER No. 362/83-099