ML20149K336
| ML20149K336 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1989-003-00 | |
| Download: ML20149K336 (5) | |
Text
B-192 ACCIDENT SEQUENCE PRECURSOR PROGRAM EVENT ANALYSIS LER No:
Event
Description:
Date of Event:
Plant:
333/89-003 Inadvertent safety relief valve actuation with HPCI inoperable March 6, 1989 Fitzpatrick Summary A reactor safety relief valve was inadvertently opened during testing required because of LTPCI inoperability at Fitzpatrick. The plant was at 100% power at the time of the event.
The operator performing the test realized his mistake and quickly closed the valve. The event has been evaluated as a potential scram with open SRV had the inadvertent valve opening not been detected. The conditional probability of core damage associated with this event is estimated to be 6.5 x 10-6. The relative significance of this event compared with other potential events at Fitzpatrick is shown below.
LER 333/89-003 1E-7 1E-6 1E-5 IE-4 IE-3 1E-2
- LTY~P 360 hHPCI
[L L"i6oE
+
+RCIC LOFW+
precursor cutoff HPCI Event Description Fitzpatrick was performing required plant Technical Specification surveillances when an operator accidently turned the wrong switch and opened an SRV. The operator recognized his error and closed the valve. The valve was open for a total of 5 s. The surveillance was a safety system logic functional test required because the high-pressure coolant injection (HPCI) system was inoperable. HPCI had been declared inoperable on March 2, 1989, following a routine in-service surveillance test on the turbine stop valve.
The valve opening stroke time had exceeded allowable limits, and the system start time was greater than that allowed by Tech Specs. Extensive testing was performed to determine the time required to achieve rated flow and valve stroke times. The HIPCI ramp
B-193 generator was found to be miswired.
Additional Event-Related Information There are 11 SRVs, 7 of which are designated for automatic depressurization system (ADS) service, at Fitzpatrick. The ADS serves to back up the HPCI system under LOCA conditions, in the event that the HPCI is inoperable. The HPCI system is a high-pressure injection system designed for small-break LOCAs that do not depressurize the reactor.
The HPCI system is independent, uses a turbine-driven pump, and automatically initiates on reactor low water level.
ASP Modeling Assumptions and Approach The event has been modeled as a potential trip with open SRV and HPCI unavailable.
The likelihood that flow through the open SRV would not be terminated was assumed to be 3.3 x 10-3 This is the failure to close probability for BWIR relief valves used in ASP analyses. Because of the plant response following the open SRV, it has been assumed that the operators will attempt to close the valve, and no additional operator error contribution has been added to the valve failure to close probability. In addition, reactor vessel isolation was assumed to occur.
Analysis Results The conditional probability of severe core damage estimated for this event is 6.5 x 10-6.
The dominant sequence for the event, highlighted on the following event tree, involves the postulated trip with unavailable PCS, open SRV and unavailable HPCI, and failure of automatic depressurization.
Other LERs that involved HPCI and/or RCIC inoperability in conjunction with power operations are: 333/89-002, -005, -014, -019, -020, -021, and -023. See the event description for LER 33 3/89-020 for more information.
B-194 RET HT
~
-I iC LN1OHE__
R sH I RMR I MRR(SP I MRSW I
DOWNT P CS A
I o RCS C
DS (MR MSODE COOD BI HCSII I
I (s
~ohE SEO E14D NO STATE OK OK OK CORE DAMAGE CORE DAMAGE OK OK CORE DAMAGE COREDMG OK OK GOE DMG CORE DAMAGE OK CORE DAMAGE OK CORE DAMAGE GOE DMG CORE DAMAGE CORE DAMAGE CORE DAMAGE CORE DAMAGE OK OK CORE DAMAGE OK CORE DAMAAGE GOEDMG CORE DAMAGE CORE DAMAGE CORE DAMAGE OK OK CORE DAMAGE OK COKRE DAMAGE OK GE CORE DAMAGE OR CORE DAMAGE GE CORE DAMAGE OK CORE DAMAGE OK OORE DAMAGE COKEAM CORE DAMAGE ATWS Dominant core damage sequence for LER 333/89-003
B-195 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 333/89-003 Event
Description:
Inadvertant SRV actuation with NPCI unavailable Event Date:
03/06/89 Plant:
Fitzpatrick INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator
- 6. 5E-06 6.5E-06
- 9. 9E-08
- 9. 9E-08 TRANS Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 28 TRANS -rx.shutdown PCS/TRANS srv.chall/trans.-scram SRV.CLOSE fw/pcs.trans NPCI srv.ads 99 TRANS rx.shutdown non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 28 TRANS -rx.shutdown PCS/TRANS srv.chall/trans.-scram SRV.CLOSE fw/pcs.trans NPCI srv.ads 99 TRANS rx.shutdown non-recovery credit for edited case SEQUENCE MODEL:
c:\\asp\\1989\\bwrcseal.cmp BRANCH MODEL:
c:\\asp\\1989\\fitzpatr.sll PROBABILITY FILE:
c:\\asp\\1989\\bwr_csll.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Re TRANS 3.4E-04 > 3 4E-04 I10E+fl End State CD ATWS End State CD ATWS Prob N Rec**
6.5E-06 8.OE-04
- 9. 9E-08 Prob
- 6. 5E-06
- 9. 9E-08
- 3. 3E-03 N Rec**
8. OE-04
- 3. 3E-03
- ov 0 > 3.3E-03 Dpr Fail Branch Nodel:
INITOR Initiator Freq:
loop loca rx.shutdown rx.shutdown/ep PCS/TRANS Branch Nodel:
l.OF.l Train 1 Cond Prob:
srv.chall/trans.-scram Event Identifier: 333/89-003 3.4 E-04
- 1. 6E-05
- 3. 3E-06
- 3. OE-05
- 3. 5E-04 1.7E-01 > 1.OE+00 1.7E-01 > Unavailable
- 1. OE+00
- 3. 6E-01 5.OE-0l
- 1. OE+00
- 1. 0E400
- 1. OE+00 l.OE+00
B-196 srv.chall/loop.-scram SRV. CLOSE Branch Model:
1.OF.1 Train 1 Cond Prob:
emerg.power ep. rec fw/pcs.trans fw/pcs. loac HPC I Branch Model:
1.OF.l Train 1 Cond Prob:
rcic c rd s rv. ads lpcs lpci (rhr) /lpcs rhr (sdc) rhr (sdc) /-lpci rhr (sdc) /lpci rhr (spcool) /rhr (sdc) rhr(spcool) /-lpci.rhr(sdc) rhr(spcool) /lpci.rhr(sdc) rhrsw l.OE+00 3.6E-02 > l.OE+00 *
- 3. 6E-02
- 2. 9E-03 1..6E-01
- 4. 6E-01
- 1. OE+00 2.9E-02 > 1.OE+00 2.9E-02 > Unavailable 6.OE-02 1.00-02 3.7E-03 3.OE-03 l.OE-03 2.1E-02 2.00-02
- 1. OE+00
- 2. OE-03
- 2. OE-03
- 9. 3E-02 2.0 E-02
- 1. 0E+00
- 1. OE-400 S. OE-0l 1.00+00
- 3. 4E-01
- 3. 4E-01 7.OE-0l
> l.0E+00
- 7. OE-0l
- 1. OE+00
- 7. LE-01 3.4E-01 7.1E-01 3.4E-01 3.4E0-01
- 1. OE+00 3.40-01 3.40-01 1.00+00
- 3.
E-01 1.00-02 1.00-02
- 2..0-03 1.00-03 1.OE-03 2.OE-03
- branch model file
- forced Minarick 0 6-1.4-1990 12:20:11 Event Identifier: 333/89-003