ML20140A206
| ML20140A206 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/19/2020 |
| From: | NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1993-005-00, LER 1993-007-00 | |
| Download: ML20140A206 (13) | |
Text
A. 14-1 A. 14 LER Nos. 498/93-005 and -007 Event
Description:
Unavailability of One Emergency Diesel Generator and the Turbine-Driven Auxiliary Feedwater Pump Date of Event: December 29, 1992, through January 22, 1993 Plant:
South Texas Project, Unit I A. 14.1 Summary For a period of -25 d, South Texas Project (STP) Unit 1 operated with one emergency diesel generator (EDG) and the turbine-,driven auxiliary feedwater (TDAFW) pump inoperable. The EDG was rendered inoperable because of binding of the fuel metering rods. The TDAFW pump was inoperable because of water intrusion into the turbine, which would have prevented the automatic start of the TDAFW pump.
During this same period, a second EDG was removed from service for maintenance for a period of 61 h.
The conditional core damage probability for this event is 1. 2 x 10 The relative significance of this event compared to other postulated events at STP Unit 1 is shown in Fig. A. 14. 1.
LER 498/93-005, -007 LTRIP I
'LOOP L-6 hE Precuarsor Cutoff L360 h AFW LOFW + I1MD AFW Fig. A. 14. 1 Relative event significance of LER Nos. 498/93-005 and -007 compared with other potential events at South Texas Project I A. 14.2 Event Description STP Unit 1 was operating at 95% power on January 20, 1993, when EDG 13 failed to start during a monthly surveillance test. The EDG had been painted during a 3-d period beginning December 29, 1992. Paint applied to the fuel injection pumps ran into the fuel metering ports, which caused the binding of the fuel metering rods. An operability test of the EDG was not performed after the completion of the painting.
Following repair of the EDG, it was returned to service on January 22, 1993, -25 d after it initially had been rendered inoperable. During the time period that EDG 13 was inoperable, EDG 12 had also been removed from service for 61 h.
The TDAFW pump was also inoperable for the 25-d period that EDG 13 was inoperable. During the fourth refueling outage, the TDAFW turbine trip/throttle valve, which had been leaking before the outage, was disassembled for repair. Although the disc and stem had steam cuts, no replacement parts could be located, so the valve was reassembled and returned to service. On December 27, 1992, the day after the end of the fourth refueling outage, the pump was tested as part of a post-maintenance test. The turbine oversped and tripped. The pump was then successfully slow started and was declared operable. Two other slow starts were successfully performed on December 31, 1992, using the anticipated transient-without-scram (ATWS) mitigation system actuation circuitry (AMSAC). The next test of the TDAFW pump was on January 28, LER Nos. 498/93-005 and -007
A. 14-2 1993. Following maintenance, the turbine tripped during a fast start. The next day the turbine tripped during a slow start. Following repairs to the governor and a number of successful starts, the pump was returned to service on January 30, 1993. On February 1, 1993, the TDAFW pump again failed its surveillance test.
Two days later the TDAFW turbine for Unit 2 oversped and tripped following a Unit 2 plant trip. A review of the maintenance history on the Unit 2 TDAFW pump also revealed problems with the overspeed trip device that rendered the pump inoperable for 4 d. This led to the decision to shut down Unit 1. The cause of the TDAFW pump overspeed events at both units was water intrusion into the turbine.
A. 14.3 Additional Event-Related Information The STP units utilize a three-train safety system arrangement. Any train of equipment is sufficient to accomplish safe shutdown of a unit for most design basis accidents. For each unit, there are three EDGs, each supplying a separate and independent load group. The AFW scheme consists of four pumps. Three of the pumps are motor driven and are supplied by their associated safeguards bus and EDG. The fourth pump is a turbine-driven pump using steam from the steam generators to provide its motive force. All four of the AFW pumps are 100% capacity pumps.
A. 14.4 Modeling Assumptions This event is modeled as a potential loss-off-offsite power (LOOP) event from December 29, 1992, to January 22, 1993. EDG 13 was assumed to be inoperable from the time that painting was begun on December 29, 1992, until the EDG was returned to service on January 22, 1993 (a total of 597 h). EDG 12 was inoperable for 61 h during this period. When an EDG is inoperable, the equipment associated with that EDG is also inoperable during a potential LOOP event where offsite power is not recovered. The model was revised to reflect this by failing variously one or two trains of equipment dependent on emergency power. The EDG failure was modeled by assuming that the other EDGs were not susceptible to the same failure mode. In this event, the EDG failure from the painting process was discovered before the other EDGs were exposed to the same failure mechanism.
The licensee determined that the TDAFW pump was inoperable from the end of the fourth refueling outage (December 26, 1992) until the plant was shut down on February 3, 1993. This encompasses the time period when the EDGs were inoperable. The recovery value for the AEW system was not changed because the failures related to the TDAFW pump were, for the most part, recoverable by starting the pump after the overspeed was reset. In these cases, the initial start attempt cleared the condensate from the steam admission line and the turbine casing and prewarmed the turbine, increasing the likelihood of successful start on subsequent attempts.
Two cases were run for the Unit 1 unavailabilities. Case 1 was calculated as a LOOP with EDG 13 and the TDAFW pump inoperable (but recoverable) for 536 h (597 - 61 h). An hourly LOOP frequency of 2 x 10-5 was multiplied by 536 h and a short-term nonrecovery probability of 0.43 (see below) to obtain a LOOP frequency for the period of interest of 4.6 x 10-3. A similar calculation was performed (Case 2) for the 6 1-h period during which EDGs 12 and 13 and the TDAFW pump were inoperable, and a LOOP frequency of 5.2 x 104was estimated.
Nominal battery life at South Texas is 2 h. But, by shedding unnecessary loads, battery life may be extended to perhaps 8 h. To credit this strategy, each of the two cases was further decomposed to reflect the core damage probability with and without battery load shed. (Cases IA and 2A use 2-h battery lifetimes, and Cases 11B and 2B3 use 8-h battery lifetimes.) As the actions involved in load shedding appeared to fall into ASP recovery class R3, a probability of failure to shed battery loads when required of 0. 12 was assumed LER Nos. 498/93-005 and -007
(a~
~~~~~~~~~~~A decito1fteAPreoeycassmyb 4fudi-pedxA3URGC-64 o
7 n
a weighted core damage probability was calculated for each case:
- 0. 12 x p(cd I 2-h battery life) + (I - 0. 12) x p(cd I 8-h battery life).
The LOOP frequency and electric power recovery probabilities for South Texas were calculated according to the methods detailed in ORNL/NRC/LTR-89/1 IRI1, Revised LOOP Recovery and Seal LOCA Models, October 1993. For both the 2-h and 8-h battery lifetime cases, a short-term LOOP nonrecovery probability of 0.43 was calculated. The seal LOCA probability was estimated to be 0.31 and the probability of nonrecovery of ac power in the long term given a seal LOCA was estimated to be 0. 7. The probability of ac power nonrecovery given that no seal LOCA occurred was estimated to be 0. 11 for the 2-h battery lifetime case. For the 8-h battery lifetime case, a probability of nonrecovery of AC power prior to battery depletion of 0.012 was calculated.
To credit the use of the positive displacement (PD) charging pump with power supplied by the Technical Support Center diesel, the base seal LOCA probability of 0.31 was multiplied by a nonrecovery value of
- 0. 17 [0. 12 (ASP operator nonrecovery class R3) + 0.05 (ASP probability that the EDG fails to start on demand, PD pump failure rate presumed to be small relative to EDG failure rate)] to obtain a reduced seal LOCA probability of 0.05.
The conditional core damage probability is calculated as follows:
- 0. 12 x p(cdl 2-h battery life) + (1-0. 12) x p(cdl 8-h battery life)
(0. 12)(4.3 x 10-6) + (0. 88)(3.8 x 10-6) = 3.9 x 1 0-6 (0. 12)(9. 1 X 10-6) + (0.88)(7.9 x< 10-6 )=
8.0x 10-6 3.9 x10-6 + 8. 0 x10-6 = 1.2 x10-5 The Unit 2 plant trip with the subsequent overspeed trip of the TDAFW pump was also modeled. It was modeled as a transient with the TDAFW pump failed, but recoverable. The inoperability of the Unit 2 TDAFW pump was not modeled because it was treated as a loss of redundancy.
A. 14.5 Analysis Results The conditional core damage probability for the time period when just EDG 13 and the TDAFW pump were inoperable (Case 1), weighted to reflect the likelihood and effects of successful battery load shed, is calculated to be 3.9 x 10-6. Similarly, the conditional core damage probability for the time period when 6
EDGs 12 and 13 and the TDAFW pump were inoperable (Case 2) is 8.0 x 10-. Therefore, the total conditional core damage probability for the event is 1.2 x 10-. The dominant core damage sequence for LER Nos. 498/93-005 and -007
A. 14-4 both cases involves a postulated LOOP with failure of emergency power and AFW, and is highlighted on the event tree shown in Fig. A. 14.2.
6 The modeling of the Unit 2 transient resulted in a value < 1 x 10-. This is below the cutoff value for events in the ASP Program. Therefore this event is not a precursor. Additional information concerning this event is included in Augmented Inspection Team report 50-498/93-07; 50-499/93-07.
LER Nos. 498/93-005 and -007
A. 14-5 RTI IA PORVI PORVIII SEAL EP REC Pl HR PORV E
LOOP LOOP EP AW SRV SRV LOCA (LONG)
PI PR OPEN ICHAL JRESEAT INO END STATE OK OK CD CD OK OK CD CD CD OK CD CD CD OK CD CD OK CO CD CD OK CD CD ATWS Fig. A. 14.2 Dominant core damage sequence for LER 498/93-005 LER Nos. 498/93-005 and -007
A. 14-6 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 498/93-005 and 498/93-007 Event
Description:
EDG and AFW Pump Unavailability (Case 1A)
Event Date:
12/29/92 - 1/22/93 Case:
EDG 13 and TDAFW Pump inoperabLe; 2 hr battery Lifetime Plant:
South Texas 1 UNAVAILABILITY, DURATION= 536 NONRECOVERABLE INITIATING EVENT PROBABILITIES LOOP 4.6E-03 SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator Probabili ty CD LOOP 4.3E-06 Total 4.3E-06 ATWS LOOP O.OE+OO Total O.OE+OO SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
55 Loop -rt/Loop EMERG.POWER AFW/EMERG.POWER CD 3.5E-06 1.2E-01 54 loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL -
CD 5.OE-07 2.3E-01 seal.Loca ep.rec 53 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLl CD 1.7E-07 2.3E-01 seaL.Loca ep.rec(sL)
- nonrecovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
53 Loop -rt/loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL CD 1.7E-07 2.3E-01 seaL.Loca ep.rec(sL) 54 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL -
CD 5.OE-07 2.3E-01 seaL.Loca ep.rec 55 loop -rt/loop EMERG.POWER AFW/EMERG.POWER CD 3.5E-06 1.2E-01
- nonrecovery credit for edited case Note:
For unavailabitities, 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:
s:\\asp\\prog\\modeLs\\pwrbseaL.cmp BRANCH MODEL:
s:\\asp\\prog\\models\\southtex.stl PROBABILITY FILE:
s:\\asp\\prog\\modeLs\\pwr-bsil.pro No Recovery Limit BRANCH FREQUENC IES/PROBABILITIES Branch System Nonrecov Opr Fail trans 6.4E-04 1.OE+00 Loop 2.OE-05 4.3E-01 Loca 2.4E-06 4.3E-01 rt 2.8E-04 1.2E-01 rt/loop O.OE+OO 1.OE+0O LER No. 498/93-005 and -007
A. 14-7 EMERO.POWER Branch Model:
1.OF.3 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
AFW Branch Model:
1.OF.4+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Train 4 Cond Prob:
Serial Component Prob:
AFW/EMERG.POWER Branch Model:
1.OF.1 Train 1 Cond Prob:
mfw porv.or.srv.chal I porv.or.srv. reseat porv.or.srv. reseat/emerg.power seatl
.Ioca ep.rec(sL) ep. rec HP I Branch Model:
1.OF.3 Train I Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
HPI( F/B)
Branch Model:
1.OF.3+opr Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
HPR/-HPI Branch Model:
1.OF.3+opr Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
porv. open 5.4E-04 > 2.9E-03 5.OE-02 5.7E-02 1.9E-01 > Failed 3.1E-04 > 2.3E-03 2.OE-02 1.OE-O1 3.OE-01 > Failed 5.OE-02 > Failed 2.8E-04 5.OE-02 > 1.OE+OO 5.OE-02 > Failed 1.OE+OO 4.OE-02 2.OE -02
- 2.
OE-02 3.E-O1 > 5.0E-02(1) 7.OE-O1 1.1E-01 3.OE-04 > 1.OE-03 1.OE-02 1.OE-O1 3.OEO01 > Failed 3.OE-04 > 1.OE-03 1.OE-02 1.OE-01 3.OE-01 > Failed 1.5E-05 > 1.5E-04 1.OE-02 1.5E-02 1.OE-01 > Failed 1.OE-02 B.OE-01
- 2.
6E-01 3.4E-01 7.OE-02 1.OE+OO 1.1E-02 1.OE+00 1.OE+OO 1.OE+00 1.OE+00 8.4E-01 8.4E-01 1.OE+0O 1.OE+OO 1
.OE-03 1
.OE-02 1.OE-03 4.OE-04
- branch model file
- forced NOTES (1)IncLudes positive displacement pump LER No. 498/93-005 and -007
A. 14-8 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
Event
Description:
Event Date:
Case:
Plant:
498/93-005 and 498/93-007 EDG and AFW pump unavailability (Case 1B) 12/29/93 -
1/22/93 EDG 13 and TDAFW pump inoperable; 8 hr battery lifetime South Texas 1 UNAVAILABILITY, DURATION= 536 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator LOOP Total ATWS LOOP Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER) 4.6E-03 Probability 3.8E-06 3.8E-06
- 0.
OE+OO
- 0.
OE+00 Sequence End State Prob N Rec**
55 Loop -rt/loop EMERG.POWER AFW/EMERG.POWER 53 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chalL seat.loca ep.rec(sl)
CD CD 3.5E-06 1.2E-01 1.7E-07 2.3E-01
- nonrecovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
53 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chal I seaL.loca ep.rec(sL) 55 Loop -rt/Loop EMERG.POWER AFW/EMERG.POWER CD CD 1.7E-07 2.3E-01 3.5E-06 1.2E-01
- nonrecovery credit for edited case 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:
No Recovery Limit s :\\asp\\prog\\mode I s\\pwrbseaLI. cmp 5 :\\asp\\prog\\modeLs\\southtex.stl1 s:\\asp\\prog\\modeLs\\pwr~bs~ll.pro BRANCH FREQUENCIES/PROBABILITIES Branch trans Loop I oca rt rt/ loop System 6.4E-04 2.OE-05 2.4E-06 2.8E-04 O.OE+0O Nonrecov 1.OE+OO 4.3E-01 4.3E-01 1.2E-01 1.OE+00 Opr Fai l LER No. 498/93-005 and -007
A. 14-9 EMERG.POWER Branch Model:
1.OF.3 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
AFW Branch Model:
1.OF.4+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Train 4 Cond Prob:
Serial Component Prob:
AFW/EMERG.POWER Branch Model:
1.OF.1 Train 1 Cond Prob:
mfw porv.or.srv.chal i porv.or.srv. reseat porv.or.srv. reseat/emerg.power seal.tIoca ep.rec(sl) ep. rec HP I 5.4E-04 > 2.9E-O3 5.OE-O2 5.7E-02 1.9E-01 > Failed 3.1E-04 > 2.3E-03 2.OE-02 1.OE-01 3.OE-O1 5.OE-O2 2.8E-04 5.OE-O2 Fai Led Fai led 1.OE+00 8.OE-O1 2.6E-01 3.4E-O1 7.OE-O2 1.OE+00 1.1E-02 1.OE+00 1.OE+00 1 COE+00 1.OE+OO
- 8. E -01 Branch Model:
Train 1 Cond Train 2 Cond Train 3 Cond HPI( F/B)
Branch Model:
Train 1 Cond Train 2 Cond Train 3 Cond HPR/-HPI Branch Model:
Train 1 Cond Train 2 Cord Train 3 Cond porv. open 1.OF.3 Prob:
Prob:
Prob:
1.OF.3+opr Prob:
Prob:
Prob:
1.OF.3+opr Prob:
Prob:
Prob:
5.OE-O2 > Failed 1.OE+OO 4.OE-02 2.OE-02 2.OE-O2 3.1E-O1 > 5.OE-O2(1) 7.OE-O1 1.1E-O1 > 1.2E-02(2) 3.E-O4 > 1.OE-O3 1.OE-O2 1.OE-O1 3.OE-O1 > Failed 3.OE-O4 > 1.OE-O3 1-~OE-02 1.OE-O1 3.OE-O1 > Failed 1.5E-05 > 1.5E-04 1.OE-O2 1.5E-02 1.OE-O1 > Failed 1.OE-O2 1.OE-03 8.4E-01 1.OE+OO 1.OE+00 1.OE-O2 1.OE-03 4.OE-O4
- branch model file
- forced NOTES (1)Includes positive displacement pump (2)Reflects 8 hr battery lifetime LER No. 498/93-005 and -007
A. 14-10 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATION4S Event identifier: 498/93-005 and 498/93-007 Event
Description:
EDG and AFW Pump UnavaiLabitities (Case 2A)
Event Date:
12/29/92 - 1/22/93 Case:
EDGs 12 and 13 and TDAFW Pump inoperable; 2 hr battery Lifetime Plant:
South Texas 1 UNAVAILABILITY, DURATION= 61 NONRECOVERABLE INITIATING EVENT PROBABILITIES LOOP 5.2E-04 SEQUENCE CONDITIONAL PROBABILITY SUNS End State/initiator Probabi lity CD LOOP 9.1E-06 Total 9.1 E-06 ATWS LOOP O.OE+OO Total O.OE+OO SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
55 Loop -rt/Loop EMERG.POWER AFW/EMERG.POWER CD 7.1E-06 1.2E-01 54 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL -
CD 1.4E-06 2.3E-01 seaL.Loca ep.rec 53 Loop -rt/Loop ENERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL CD 4.6E-07 2.3E-01 seaL.Loca ep.rec(sL)
- nonrecovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
53 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL CD 4.6E-07 2.3E-01 seaL.Loca ep.rec(sL) 54 Loop -rt/Loop ENERG.POWER -AFW/ENERG.POWER -porv.or.srv.chalL -
CD 1.4E-06 2.3E-01 seaL.Loca ep.rec 55 Loop -rt/Loop EMERG.POWER AFW/EMERG.POWER CD 7.1E-06 1.2E-01 nonrecovery credit for edited case 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:
s:\\asp\\prog\\modeLs\\pwrbseaL.cmp BRANCH MODEL:
s:\\asp\\prog\\modeLs\\southtex.sLl PROBABILITY FILE:
s:\\asp\\prog\\modeLs\\pwr~bsLl.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 6.4E-04 1.OE+OO Loop 2.OE-05 4.3E-01 Loca 2.4E-06 4.3E-01 rt 2.8E-04 1.2E-01 rt/Loop O.OE+O0 1.OE+OO LER No. 498/93-005 and -007
A. 14-11 EMERG.POWER Branch Model:
Train 1 Cond Train 2 Cond Train 3 Cond AFW 5.4E-04 > 5.OE-02 8.OE-O1 1.OF.3 P rob:
Prob:
Prob:
5.OE-O2 5.7E-02 >
1.9E-01 >
3.1E-04 >
Fai Led Fai Led 2.OE-O2 Branch Model:
1.OF.4+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Train 4 Cond Prob:
Serial Component Prob:
AFW/EMERG.POWER Branch Model:
1.OF.1 Train 1 Cond Prob:
mfw porv. or. srv. chal porv.or.srv. reseat porv.or.srv. reseat/emerg.power seal. Loca ep.rec(sl) ep. rec HP I 2.OE-02 1.OE-O1 > Failed 3.OE-O1 > Failed 5.OE-02 > Failed 2.8E-04 5.OE-02 > 1.OE+OO 5.OE-02 > Failed 1.OE+OO 4.OE-02 2.OE-02 2.OE-02 3.1E-01 > 5.OE-O2(1) 7.OE-O1 1.1E-01 3.OE-04 > 1.OE-02 2.6E-01 3.4E-01 7.OE-02 1.OE+OO 1.1E-02 1.OE+OO 1.OE+OO 1.OE+OO 1.OE+OO
- 8.
- 8.
4E-01 1.OE+OO 1.OE+0O Branch Model:
Train 1. Cond Train 2 Cond Train 3 Cond HPI( F/B)
Branch Model:
Train 1 Cond Train 2 Cond Train 3 Cond HPR/-HPI Branch Model:
Train 1 Cond Train 2 Cond Train 3 Cond porv. open 1
.OF.3 Prob:
Prob:
Prob:
1
.OF.3+opr Prob:
Prob:
Prob:
1
.OF.3+opr Prob:
Prob:
Prob:
1.OE-02 1.OE-01 3.OE-O1 3.OE-04 1.OE-02 1.OE-01 3.OE-O1 1.5E-05 Fai Led Fai Led 1.OE-02 FailIed Fai Led 1.OE-02 1
.OE-03 1.OE-02 1.OE-03 4.OE-04 1.OE-02 1.5E-02 > Failed 1.OE-O1 > Failed 1.OE-02
- branch model file
- forced NOTES (1Includes positive displacement pump LER No. 498/93-005 and -007
A. 14-12 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
Event
Description:
Event Date:
Case:
Plant:
498/93-005 and 498/93-007 EDG and AFW pump unavailabiLities (Case 2B) 12/29/93 -
1/22/93 EDGs 12 and 13 and TDAFW pump inoperable; 8 hr South Texas 1 battery lifetime UNAVAILABILITY, DURATION= 61 NONRECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS 5.2E-04 End State/Initiator Probability CD LOOP Total ATWS 7.9E-06
- 7. 9E-06
- 0.
OE+OO O.OE+00 LOOP Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 55 Loop -rt/loop EMERG.POWER AFW/EMERG.POWER 53 Loop -rt/Loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chaLL seaL.loca ep.rec(sL)
End State Prob N Rec**
CD CD 7.1E-06 1.2E-01 4.6E-07 2.3E-01
- nonrecovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 53 Loop -rt/loop EMERG.POWER -AFW/EMERG.POWER -porv.or.srv.chal I seaL.loca ep.rec(sL) 55 Loop -rt/Loop EMERG.POWER AFW/EMERG.POWER nonrecovery credit for edited case End State CD Prob N Rec**
4.6E-07 2.3E-01 7.1E-06 1.2E-01 CD Note:
For unavaitabilities, conditional probability values are differential values which reflect 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:
s:\\asp\\prog\\models\\pwrbseaL.cmp BRANCH MODEL:
s:\\asp\\prog\\modeLs\\southtex.s~l PROBABILITY FILE:
s:\\asp\\prog\\models\\pwr~bs~ll.pro No Recove 'ry Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 6.4E-04 1.OE+00 Loop 2.OE-05 4.3E-01 Loca 2.4E-06 4.3E-01 the rt rt/ loop EMERG. POWER Branch Model:
1.OF.3 Train 1 Cond Prob:
2.8E-04
- 0.
OE+OO 5.4E-04 > 5.OE-02 1.2E-01 1.OE+OO
- 8. OE -01 5.OE-02 LER No. 498/93-005 and -007
A. 14-13 Train 2 Cond Prob:
Train 3 Cond Prob:
A FW Branch Model:
1.OF.4+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Train 4 Cond Prob:
Serial Component Prob:
AFW/EMERG.POWER Branch Model:
1.OF.1 Train 1 Cond Prob:
mfw porv.or.srv.chatlI porv.or.srv. reseat porv.or.srv. reseat/emerg.power seal. loca ep.rec(sl) ep. rec HPI Branch Model:
1.OF.3 Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
HPI( F/B)
Branch Model:
1.OF.3+opr Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
HPR/- HP I Branch Model:
1.OF.3+opr Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
porv. open 5.7E-02 1.9E-01
- 3. 1 E-04
" Fai Led
" Failed
" 2.OE-02 2.OE-02 1.OE-01 > Failed 3.OE-O1 > Failed 5.OE-02 > Failed 2.8E-04 5.OE-02 > 1.OE+OO 5.OE-02 > Failed 1.OE+OO 4.OE-02 2.OE-02 2.OE-02 3.E-O1 > 5.OE-02 7.OE-01 1.1E-01 > 1.2E-02' 3.OE-04 > 1.OE-02 (1)
(2)
- 2. 6E-01 3.4E-O1 7.OE-02 1.0OE+00 1.1E-02 1 O0E+00 1.OE+00 1.0OE+00 1.OE+O0 8.4E-01
- 8. E -01 1 O0E+00 1.OE+00 1.OE-02 1.OE-01 3.OE-01 3.OE-04 1.OE-02 1.OE-01 3.OE-01 1.5E-05 Fai Led Fai Led 1.OE-02 Fai led Fai Led 1 O0E-02 1 O0E-03 1 O0E-02 1.OE-03 4.OE-04 1.OE-02 1.5E-02 > Failed 1.0E-01 > Failed 1.0E-02
- branch model file
- forced NOTES (1includes positive displacement pump (2)Reflects 8 hr battery Lifetime LER No. 498/93-005 and -007