ML20149K338
| ML20149K338 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1989-023-00 | |
| Download: ML20149K338 (5) | |
Text
B-236 ACCIDENT SEQUENCE PRECURSOR PROGRAM EVENT ANALYSIS LER No:
Event
Description:
Date of Event:
Plant:
333/89-023 Reactor scram with HPCI system inoperable while testing SRVs November 12, 1989 Fitzpatrick Summary The reactor scrammed from 10% power during surveillance testing of the safety relief valves (SRVs), and the high-pressure coolant injection (HPCI) system was inoperable at that time. The conditional probability of core damage associated with this event is estimated to be 1.3 x 1i-5. The relative significance of this event compared with other potential events at Fitzpatrick is shown below.
-LER 333/89-023 1E-j1-61E 1E-4 1E-3 1E-2
- LTrip LL0H
[L 36Oh EP
L.precursor cutoff HMC Event Description Fitzpatrick scrammed from 10% power on November 12, 1989, while performing required surveillance testing on the SRVs. The topworks of two SRVs were replaced following a previous scram (LER 333/89-020), and postwork system functional testing was required. An SRV was cycled open and closed, causing a small pressure rise in the main steam system. The pressure rise caused a neutron flux increase to about 14.4%
power. Since the plant was in the startup/hot standby mode of operation, this was sufficient to initiate a high flux scram (nominally set at 15% power).
HPCI had previously been removed from service on November 3, 1989, when a ground was discovered in the speed control circuit for the HPCI turbine (see LER 333/89-019).
B-237 Additional Event-Related Information The HPCI System is a high-pressure injection system designed for small-break LOCAs that do not depressurize the reactor. HPCI is an independent system, uses a turbine-driven pump, and automatically initiates on reactor low water level. HPCI can deliver
-5000 gpm of makeup water to the vessel through the feedwater piping.
The plant scrammed on high neutron flux when an SRV closure caused a pressure spike in the reactor. The rapid pressure rise collapsed voids in the reactor coolant, and the enhanced moderation caused a neutron flux increase.
ASP Modeling Assumptions and Approach This event has been modeled with the assumption that the HPCI system was inoperable during the scram and subsequent recovery operations.
Analysis Results The conditional probability of severe core damage for this event is 1.3 x 1i-5. The dominant core damage sequence associated with the event is a postulated failure of the power conversion system, SRV lift and failure to reseat, failure of feedwater, failure to recover HPCI (probability assumed to be 1.0), and failure to depressurize using ADS.
This sequence is highlighted on the following event tree.
Other LERs that involved HPCI and/or RCIC inoperability in conjunction with power operations are: 333/89-002, -003, -005, -014, -019, -020, and -021. See the event description for LER 333/89-020 for more information.
B-238 I ~ I I
HCI '
I IRHR(SP 4S I TRRN I
IICI CR0 SRVSf PS LC (SOC ICOOLING lENT CK~AL H IC AD MO
~
WDE)
M IODhE)
SEC END No STATE OK OK OK CORE DAMAGE CE OK CORE DAMAGE OK OE CORE DAMAGE Ox CORE DAMAGE 0E OK CORE DAMAGE Ox OK CORE DAMAGE Ox CORE DAMAGE OK CORE DAMAGE CORE DAMAGE CORE DAMAGE GE OK CORE DAMAGE Ox GE CORE DAMAGE OK GE CORE DAMAG3E OK OK CORE DAMAGE OK CORE DAMAGE OK CORE DAMAGE CORE DAMAGE CORE DAMAGE GE OE CORE DAMAGE Ox GE CORE DAMAGE OK OK CORE DAMAGE OK GE CORE DAMAGE OK Gx CORE DAMAGE GE CE CORE DAMAGE CE CORE DAMAGE Gx CORE DAMAGE CORE DAMAGE CORE DAMAGE ATWS Dominant core damage sequence for LER 33 3/89-023
B-239 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
333/89-023 Event
Description:
Scram with HPCI inoperable while testing SRVs Event Date:
11/12/89 Plant:
Fitzpatrick INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator l.OE+00 Probability CD TRANS Total ATWS
- 1. 3E-05
- 1. 3E-05 3.OE-05 3.OE-05 TRANS Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence 28 trans -rx.shutdown pcs/trans srv.chall/trans.-scram srv.close fw/pcs.trans HPCI srv.ads 11 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close
-fw/pcs.trans rhr(sdc) rhr(spcool)/rhr(sdc) 99 trans rx.shutdown
-* non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence 11 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close
-fw/pcs.trans rhr(sdc) rhr(spcool) /rhr(sdc) 28 trans -rx.shutdown pcs/trans srv.chall/trans.-scram srv.close fw/pcs.trans HPCI 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-Rec trans 3.4E-04 1.0E+00 loop 1.6E-05 3.6E-01 loca 3.3E-06 5.OE-01 rx.shutdown 3.OE-05 l.0E+00 rx.shutdown/ep 3.5E-04 l.OE+00 pcs/trans 1.7E-01 1.OE+0C srv.chall/trans.-scram 1.OE+00 1.0E+00 End State CD CD ATWS End State CD CD ATWS Prob 1.2E-05
- 7. 6E-07 N Rec**
2.4E-01 1.OE-01 3.OE-05 1.0E+00 Prob 7. 6E-07 1.2E-05 3.OE-05 N Rec**
l.OE-0l 2.4E-01
- 1. OE+00
- ov Opr Fail Event Identifier: 333/89-023
B-240 arv.chall/loop.-scrazn arv.close emerg.power ep. rec fw/pcs.trans fwlpcs. loca HPCI Branch Model:
1.OF.1 Train 1 Cand Prob:
rcic crd a rv.ads lpcs lpci (rhr) /lpcs rhr (sdd rhr (adc) /-lpci rhr(adc) /lpci rhr(spcool) /rhr(sdc) rhr(spcool) /-lpci. rhr (sdc) rhr(spcool) /lpci.rhr~sdc) rhrsw l.OE+OO
- 3. 6E-02
- 2. 9E-03
- 1. EE-0l
- 4. 6E-01 1.OE+OO 2.9E-02 > l.OE+OO
- 2. 9E-02 6.OE-02 l.OE-02 3.7E-03 3.OE-03 l.OE-03 2.1E-02 2.OE-02 1.OE+OO 2.OE-03 2.OE-03 9.3E-02 2.OE-02
> Unavailable 1.OE+OO l.OE+0O B. OE-O1 l.OE+OO 3.4E-O1 3.4E-01 7.OE-Ol > l.OE+OO 7.OE-O1 l.OE+OO 7.1E-01 3.4E-Ol 7.1E-01 3.4 E-01 3.4 E-01 1.OE+OO 3.4E-01 3.4E-Ol 1.OE+OO 3.4E-01 1.OE-02 1.OE-02 1.OE-03 1.OE-03 1.OE-03 2.OE-03
- branch model file
- forced lMinarick 06-15-1990 13:11:10 Event Identifier: 333/89-023