ML20161A157
| ML20161A157 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 06/09/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1988-028-00 | |
| Download: ML20161A157 (5) | |
Text
B-222 Accident Sequence Precursor Program Event Analysis LER No:
Event
Description:
Date of Event:
Plant:
344/88-028 Trip with one safety injection pump out for mainte-nance September 16, 1988 Trojan Summuary A trip from 100% power occurred while one train of the safety-injection system was out of service for maintenance.
The conditional core damage probability estimated for this event is 1.9 x 10-6.
The relative sig-nificance of this event compared with other potential events at Trojan is shown below:
-LER 344/88-028 1 E-8 I1E-7 1E-6 I E-5 I E-4 I1E-3 1 E-2 I
Trip -
L EP Unavail Trip w/1 AFW (360 hrs)
Train Unavail LOOP AFW Unavail (360 hrs)
Event Description While establishing conditions necessary for replacement of a failed pressurizer pressure transmitter, a technician erroneously tripped the input bistable from another pressurizer pressure transmitter.
This satisfied the two out of four overtemperature delta temperature (OTDT) trip logic, causing a reactor trip from 100% power.
The trip occurred at approximately 0830.
At that time, safety injection pump "B" was out of service for maintenance.
Trains "A" and "B" of auxiliary feedwater (AFW) started.
At 0905, it was discovered that the AFW control valve (CV-3004A1) for the "A" steam generator could not be throttled from the control room, due to a motor operator clutch lever being depressed by the motor power conduit.
The conduit was improperly routed over the valve operator.
The valve was properly positioned to deliver the correct AFW flow rate, however, and the cable was subsequently moved off the lever.
.1-223 ASP Modeling Assumptions and Approach This event was modeled with one train of safety injection unavailable following a trip.
Because all trains of the AFW system were providing the required flow, the control valve that could not be throttled was not considered to be faulted.
Analysis Results The conditional probability of severe core damage estimated for this event is 1.9 x 10-6.
The dominant sequence for core damage involves a failure of auxiliary feedwater (p =
8.5 x 10-4) and main feedwater (p = 0.07) following trip, and failure of feed and bleed (p =
0.018, including failure to initiate).
This sequence is highlighted on the following event tree.
B-224 TAS FT AW MW PORV/
PORV/
PORV SEQ END TRPW 9 RV SRV HPI HPR OPN O
Z E I
CHAL REETOE O
STATE OK OK CD 12 CD OK OK OK 13 CD 14 CD OK OK 156 CD 16 CD 17 CD 18 ATWS Dominant Core Damage Sequence for [ER 344/88-D28
3-225 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
Event
Description:
Event Date:
Plant:
344/88-028 Trip with one Safety Injection 09/16/88 Trtojan pump unavailable INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS
- 1. 0E+00 End State/Initiator Probability CD TRANS Total ATWS TRANS Total
- 1. 9E-06
- 1. 9E-06
- 3. 4E-05
- 3. 4E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER) 17 15 12 16 Sequence trans -rt afw mfw HPI(F/B) trans -rt afw mfw -HPI(F/B) -hpr/-hpi porv.open trans -rt -afw porv.or.srv.chall porv.or.srv.reseat
((PI trans -rt afw mfw -HPI(F/B) hpr/-hpi End State Prob CD CD CD CD
- 1. 1E-06
- 6. 1E-07
- 7. 4E-08
- 6. BE-08 N Rec**
- 2. OE-02
- 2. 4E-02
- 9. 2E-03 2.4E-02 i8 trans rt AIMS 3.4E-05 1.2E-01
-- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob 12 15 16 17 is trans -rt trans -rt trans -rt trans -tt trans tt
-afw porv.or.srv.chall porv.or.srv.reseat HPI afw rnfw -RPI(F/B( -hpr/-hpi porv.open afw mfw -HPI(F/B(
hpr/-hpi afw mfw HPI(F/B)
CO CD CD CD ATWS
- 7. 4E-08 6.1lE-07
- 6. 81-08
- 1. 1E-06
- 3. 4E-05 N Rec**
- 8. 21-03 2.4E-02 2.4E-02 2.OE-02 1.2E-01
-non-recovery credit for edited case SEQUENCE NODEL:
BRANCH MODEL:
PROBABILITY FILE:
a: \\seaimod\\pwrbseal.cmp a:\\sealmod\\trojan.sll a:\\sealmod\\pwr bsll.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch trans loop inca rt rt/ loop eme rg. power afw Event Identifier: 344/88-028 System
- 5. 6E-04
- 3. 6E-01 4.3E-01 1.2E-01
- 1. SE+SS 8.01-01 3.4 E-01 Opt Fail
9-226 afw/emerg.power mfw porv.or.srv.chall porv.or.srv. resent porv.or.srv.rescat/emerg.power seal. loca ep. rec si) ep. rec HPI Branch M~odel:
l.OF.2 Train 1 Coed Prob:
Train 2 Cond Prob:
522 (FIB)
Branch M4odel:
1.OF.2+opr Train 1 Cond Prob:
Train 2 Coed Prob:
hprl-hpi porv. pen 2.5E-03 1.00+00 4.00E-02 2.0E-02 2. 00-02 2.3E-01
- 5. 9E-01
- 6. 1E-02 1.00-03 > 1.OE-02 1.00-02 1.0Z-01 > Failed 1.OE-03 > 1.OE-02 1.0 E-02 1.00-01 > Failed 1.5E-04 1.0E-02
- 3. 4E-01 7.0E-02 1.00+/-00
- 1. 10-02
- 2. 0E+-00 1.00+00 1.00+00 1.00+00 8.40-01 8.40-01
- 1. 00+/-00 1.00+00 1.00-02
- 1. OE-03 4.00-04 branch model file
- forced Minarick 11-12-1989 21:56:28 Event Identifier: 344/88-028