ML20147A487
| ML20147A487 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter Office of Nuclear Reactor Regulation |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1989-005-00 | |
| Download: ML20147A487 (7) | |
Text
B- 125 ACCIDENT SEQUENCE PRECURSOR PROGRAM EVENT ANALYSIS LER No: 317/89-005 Event
Description:
Failure of instrument air boundary check valve Date of Event: March 14, 1989 Plant: Calvert Cliffs 1 Summary An instrument air boundary check valve was discovered to be leaking excessively at Calvert Cliffs 1. This could have resulted in saltwater pump runout in situations where containment sump recirculation was required following a loss of offsite power. The conditional core damage probability estimated for this event is 1.4 x 10-6. The relative significance of this event compared with other postulated events at Calvert Cliffs is shown below.
LER 3 17/89-005 1E-7 1E-6ý 1E-5 1E-4 1E-3 1E-2 Thpl LOWl )p L3 E 1/20z precursor cutoff Event Description At 2100 on March 14, 1989, a test determined that an excessive amount of back-leakage existed through an instrument air (IA) boundary check valve (IA-650). This allowed air to leak into the nonessential piping and components of the IA system, which would be depressurized following a LOOP. The check valve failed due to material wear, causing a poor seating surface. The repair and leak testing of the replacement check valve has shown that the valve type was inappropriately chosen for its intended application. This valve was to be replaced with a different check valve better suited for its intended use.
B- 126 Additional Event-Related Information In the event of a LOOP, the saltwater (SW) air compressors are powered from the diesel generators. Because of the backflow through IA-650,, the SW air system (which has limited capacity) would be rendered inoperable. Four SW heat exchanger discharge valves would initially orient to their required positions because of accumulators associated with the valves. However, once sump switchover occurs, heat exchanger discharge must be throttled to prevent SW pump runout. For throttling, a continual source of air must be provided to the valves. Since this would not be available with IA-650 failed, SW pump failure could eventually occur, resulting in a loss of component cooling water and service water.
ASP Modeling Assumptions and Approach The event was modeled as a postulated LOOP in which sump recirculation is required either because of a transient-induced LOCA or because of the need for feed and bleed.
The exposure time was assumed to be 1 year. In the event of sump recirculation, SW pump runout is assumed to fail the pumps, resulting in high-pressure recirculation (HPR) failure, since discharge valve throttling would not be available. Since SW pump runout is only postulated if offsite power is unavailable, only LOOPs with durations longer than the time at which sump switchover would be expected to occur have been addressed.
This time was assumed to be 6 h for transient-induced LOCAs and feed and bleed. Local recovery of heat exchanger discharge valve position was assumed.
(To only address LOOPs not recovered in 6 h, two separate initiator-based calculations were performed with LOOP recovery set to the frequency of LOOPs at Calvert Cliffs >6
- h. The core damage probability was estimated by subtracting the second reference calculation, from the first calculation, as described in Appendix A.)
.Analysis Results The conditional core damage probability estimated for this event is 1.4 x 10-6. The dominant sequence, highlighted on the following event tree, involves a postulated LOOP with emergency power and AFW success, failure of a demanded PORV to close, successful HPI, and failure of sump recirculation.
B- 127 LOOP RTt-OOP EP AFW I SRV ISRV SEAL EP REC HPI HPR OPEN CR] SEQ END CHALL RESEAT LOCA (LONG)OPNIC NO STATE OK<
OK 41 CO 42 CO OK OK 56 CO 43 CO 44 CO 45 CO OK 46 CO 47 CO 48 CO OK 49 CO 50 CO OK 51 CO 52 CO 53 CO OK 54 CO 55 CO 40 ATWS Dominant core damage sequence for LER 317/89-005
B-128 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 317/89-005 Event
Description:
Failure of instrument air boundary check valve (caic 1)
Event Date: 03/14/89 Plant: Calvert Cliffs 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 3. 6E-03 SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator Probability CD LOOP 1.9E-06 Total 1.9E-06 ATWS LOOP 0. OE+00 Total 0.OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
41 LOOP -rt/loop, -emerg.power -afw porv.or.srv.chall porv.or.srv. CD 9.8E-07 1.2E-03 reseat/emerg.power -hpi NPR/-NPI 56 LOOP -rt/loop -emerq.power afw -hpi(f/b) -HPR/-NPI -porv.open CD 2.3E-07 6.2E-04 CSR 53 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall CD 2.OE-07 2.8E-03 seal.loca ep.rec(al) 55 LOOP -rt/loop emerg.power afw/emerg.power CD 1.4E-07 9.8E-04 44 LOOP -rt/ioop -emerg.power afw -hpi(f/b) NPR/-NPI CD 1.2E-07 3.2E-04 54 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall - CD 1.OE-07 2.8E-03 seal.loca ep.rec 51 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall CD 5.2E-08 9.7E-04 seal.loca -ep.rec(sl) -hpi NPR/-NPI
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
41 LOOP -rt/loop -eslerg.power -afw porv.or.srv.chall porv.or.srv. CD 9.8E-07 1.2E-03 reseat/erserg.power -hpi HPR/-NPI 56 LOOP -rt/loop -emerg.power afw -hpi(f/b) -NPR/-NPI -porv.open CD 2.3E-07 6.2E-04 CSR 44 LOOP -rt/loop -emerg.power afw -hpi(f/b) NPR/-NPI CD 1.2E-07 3.2E-04 51 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall CD 5.2E-08 9.7E-04 seal.loca -ep.rec(sl) -hpi NPR/-NPI 53 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall CD 2.OE-07 2.8E-03 seal.loca ep.rec(sl) 54 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall - CD 1.OE-07 2.8E-03 seal.loca ep.rec 55 LOOP -rt/loop emerg.power afw/emerg.power CD 1.4E-07 9.8E-04
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\l989\pwrgseal.cmp BRANCH MODEL: c:\aap\1989\calvertl.sll PROBABILITY FILE: c:\asp\1989\pwrbsll.pro Event Identifier: 317/89-005
B- 129 No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Faill trans 5.OE-04 1.OE+00 LOOP 1.6E-05 > 1.6E-05 5.3E-01 > 3.6E-03 Branch Model: INITOR Initiator Freq: 1.6E-05 loca 2.4E-06 4. 3E-01 ri 2.8E-04 1.2E-01 rt/ loop 0.0E--00 1. OE+00 emerg. power 2. 9E-03 8. OE-01 afw 3.8 E-04 2.6E-01 afw/emerg.power 5.OE-02 3.4E-01 mfw 2.OE-0l 3.4E-01 porv.or.srv.chall 4.0 E-02 1. OE+00 porv.or. srv. reseat 2. OE-02 1. lE-02 porv.or.srv. reseat/emerg.power 2.0 E-02 1.OE+00 seal.loca. 4.6E-02 1.0E+00 ep. rec Cal) 5.7E-01 1. OE+0O ep. rec 1.4E-02 1. OE+00 hpi 3.0 E-04 8.4 E-01 hpi (f/b) 3.OE-04 8.4 E-01 1.OE-02 porv .open 1.0 E-02 1.0 E+00 4 .OE-04 HPR/-HPI 1.5E-04 > 1.OE+00 1.0E4-00 > 3.4E-01 Branch Model: l.OF.2 Train 1 Cond Prob: l.0E-02 > Unavailable Train 2 Cond Prob: 1.5E-02 > Unavailable CSR 2.OE-03 > l.OE+00 3.4E-01 > 1.OE+00 Branch Model: l.OF.2 Train 1 Cond Prob: 2.0E-02 > Unavailable Train 2 Cond Prob: l.0E-01 > Unavailable
- branch model file
- forced Minarick 06-21-1990 17:38:54 Event Identifier: 317/89-005
B-130 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 317/89-005 Event
Description:
Failure of instrument air boundary check valve (caic 2)
Event Date: 03/14/89 Plant: Calvert Cliffs 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 3. 6E-03 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD LOOP 4.8BE-07 Total 4. 8E-07 ATWS LOOP 0.01+00 Total 0. OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
53 LOOP -rt/loop emerg.power.-afw/emerg.power -porv.or.srv.chall CD 2.OE-07 2.8E-03 seal.loca ep.rec(sl) 55 -LOOP -rt/loop emerg.power afwi/emerg.power CD 1.4E-07 9.8E-04 54 LOOP -rt/loop, emerg.power -afw/emerg.power -porv.or.srv.chall - CD 1.01-07 2.8E-03 seal.loca ep.rec 48 LOOP -rt/loop, emerg.power -afw/emerg.power porv.or.srv.chall - CD 8.3E-09 2.8E-03 porv.or.srv.reseat/emerg.power seal.loca ep.rec(sl) 50 LOOP -rt/loop exnerg.power -afw/emerg.power porv.or.srv.chali CD 6.5E-09 2.8E-03 porv.or.srv. reseat/emerg.power
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
48 LOOP -rt/loop emerg.power -afw/emerq.power porv.or.srv.chall - CD 8.3E-09 2.8E-03 porv.or.srv.reseat/emerg.power seal.loca ep.rec(sl) 50 LOOP -rt/loop emerg.power -afw/eme rg.power porv.or.srv.chall CD 6.51-09 2 .8E-03 porv.or.srv. reseat/emerg.power 53 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall CD 2.OE-07 2.8E-03 seal.loca ep.rec(sl) 54 LOOP -rt/loop emerg.power -afw/emerg.power -porv.or.srv.chall - CD 1.OE-07 2.8E-03 seal.loca ep.rec 55 LOOP -rt/loop emerg.power afw/emerg.power CD 1.4E-07 9.8E-04
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\1989\pwrgseal .cmp BRANCH MODEL: c: \asp\1989\calvertl .sll PROBABILITY FILE: c: \asp\1989\pwr bsil .pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail Event Identifier: 317/89-005
B-131 trans 5.OE-04 1.OE+OO LOOP 1.6E-05 > 1.6E-05 5.3E-01 > 3.6E-03 Branch Model: INITOR Initiator Freq: 1.6E-05 loca 2.4E-06 4 .3E-01 rt 2.8E-04 1.2E-01 ri/loop O.OE+OO 1.OE+OO emerg.power 2.9E-03 S.OE-Ol afw 3.8E-04 2.6E-O1 afw/emerg.power 5.OE-02 3.4E-Ol mfw 2.OE-Ol 3.4E-01 porv.or.srv.chall 4.OE-02 1.OE+OO porv.or.srv.reseat 2.OE-02 1.1E-02 porv.or.srv. reseat/emerg.power 2. OE-02 l.OE+OO seal.loca 4.6E-02 l.OE+OO ep.rec(sl) 5.7E-01 l.OE+0O ep.rec 1.4E-02 1.OE+OO hpi 3.OE-04 8.4E-Ol hpi(f/b) 3.OE-04 8.4E-Ol l.OE-02 porv.open l.OE-02 1.OE+OO 4.OE-04 hpr/-hpi 1.5E-04 l.OE+OO csr 2.OE-03 3.4E-01
- branch model file
- forced Minarick 06-21-1990 17:39:-46 Event Identifier: 317/89-005