ML20149K389
| ML20149K389 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1988-002-00 | |
| Download: ML20149K389 (5) | |
Text
B-9 7 Accident Sequence Precursor Program Event Analysis LER No:
Event
Description:
Date of Event:
Plant:
286 /88-002 Plant trip and one of three AFW pumps fails March 31, 1988 Indian Point Unit 3 Summnary While at 100% power, a main boiler feed pump tripped'due to maintenance activities, which subsequently caused an automatic plant trip.
Both motor-driven auxiliary feedwater pumps started as designed; however, one tripped on overcurrent as a result of excessive flow caused by a damaged flow controller.
The conditional probability of core damage estimated for the event is 1.0 x 10-5.
The relative significance of this event compared to other potential events is shown below.
Event Description During routine maintenance operations, cycling of main feedwater recir-culation valve FCV-1116 for MFW pump 32 was performed to test a faulty limit switch on the valve operator.
The cycling was performed with the isolation valve closed, causing a water hammer. The water hammer vibra-tion caused MFW pump 32 to trip off when a false "discharge valve not fully open" signal was generated.
The operators took manual control of the plant and started AFW pumps 31 and 33.
.Turbine runback was also initiated.
SC levels initially decreased and then began to increase.
The operators were unable to pre-vent a plant trip on high SC level in SC 31. During the post-trip recovery, AFWP 33 tripped on overcurrent.
The operators had previously closed its recirculation valve to control the flow.
When the valve was
B-9 8 placed in auto operation, it erroneously opened full due to undetected damage to its flow controller (broken glass faceplate, cause unknown).
The subsequent runout flow condition caused the pump to trip on over-current.
Event-Related Plant Design Information Indian Point 3 has three auxiliary feedwater trains.
Two of these trains are motor driven and one is turbine driven.
The turbine-driven auxiliary feedwater pump was available during the trip had it been required.
ASP Modeling Assumptions and Approach The event has been modeled as a transient with main feedwater unavail-able and one of three auxiliary feedwater trains failed.
Analysis Results The conditional probability of core damage associated with the event is estimated at 1.0 x 10-5.
The dominant sequence involves unavailability of AEW (p = 1.4 x 10-3), failure to recover main feedwater (p = 0.34),
and failure of feed and bleed (p =0.02). This sequence is highlighted on the following event tree.
B-9 9 PORV/
PORV/
PORV TRANS R
AFW MFW SRV SRV HPI HPR OPEN ElllilICHAL RESEAT SEQ END NO STATE OK OK 11 CD 12 CD OK OK OK 13 CD 14 CD OK 15 16 17 18 OK CD CD CD ATWS Dominant Core Damage Sequence for LER 286/88-002
B-100 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 286/88-002 Event
Description:
Trip and one ARW pump fails to run Event Date:
03/31/88 Plant:
Indian Point 3 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRAN S
- 1. GE-*G SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS
- 1. GE-OS Total
- 1. GE-OS AIMS TRANS 3.4E-05 Total
- 3. 4E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State
- Prob, N Rec'-
15 trans -rt ARM MRM -hpl(flb) -hpr/-hpi porv.open COý 4.8E-06 8.8E-02 17 trans -rt ARM MRM hpl(f/b)
CO 4.8E-06 7.4E-02 16 trans -rt ARM MFW -hpi(flb) hpr/-hpl CD 5.3E-07 8.8E-02 11 trans -rt -ARM porv.or.srv.chall porv.or.srv.reseat -hpi hpr/
CD l.OE-08 1.1E-02
-hpi 12 trans -rt -ARM porv.or.srv.chall porv.or.srv.reseat hpl CD 2.2E-09 9.2E-03 13 trans -rt ARM -MRM porv.or.srv.chall porv.or.srv.reseat -hpl CO 9.2E-12 1.9E-03 hpr/-hpi 14 trans -rt ARW -MRM porv.or.srv.chall porv.or.srv.reseat hpi CD 2.OE-12 1.6E-03 18 trans rt AIMS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
11 trans -rt -ARM porv.or.srv.chall porv.or.srv.reseat -hpl hpr/
CO 1.OE-O8 l.1E-O2
-hpi 12 trans -rt -ARM porv.or.srv.chall porv.or.srv.reseat hpi CD 2.2E-09 9.2E-03 13 trans -rt ARM -MRW porv.or.srv.chall porv.or.srv.reseat -hpi CD 9.2E-12 1.9E-03 hpr/-hpi 14 trans -rt ARM -MRM porv.or.srv.chall porv.or.srv.rcsear hpi CD 2.OE-12 1.6E-03 15 trans -rt AFM MFM -hpi(f/b) -hpr/-hpi porv.open CO 4.8E-06 8.8E-02 16 trans -rt ARM MRM -hpi~f/b) hpr/-hpi CO 5.3E-07 B.BE-02 17 trans -rt ARM MRM hpi(f/b)
CD 4.8E-06 7.4E-02 18 trans rt AIMS 3.4EO05 1.2E-01
-- non-recovery credit for edited case SEQUENCE MODEL:
c: \\asp\\sealmod\\pwrbseal.cmp BRANCH MODEL:
c:\\asp\\sealmod\\indpoint.sll PROBABILITY FILE:
c:\\asp\\sealmod\\pwr bsll.pro No Recovery Limit BRANCH RREQUENCIES/PROBABILITIES Event Identifier: 286/88-002
B-101 Branch trans loop loca rt rt/ loop emerg.power AFW Branch Model:
l.OF.3+ser Train 1 Cond Prob:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
afw/emerg.power MFW Branch Model:
1.OF.1 Train 1 Cond Prob:
porv.or.srv.chall porv.or.srv. reseat porv.or.srv.reseat/emerg.power seal.boca ep.rec (sl) ep. rec hpi hpi (f/b) hpr/-hpi porv. open
- branch model file
- forced Minarick 11-13-1989 15: 25:4 6 System 4.6E-04 3.l1E-05 2.4E-0 6 2.8E-04 0.0E+ 00 5.4E-04 3.8E-04 > 5.3E-03 2.00-02 > Failed
- 1. 00-01
- 5. 0E-02 2.8E-04 5.0 E-02 2.00-01 > 1.00+00 2.00-01 > Unavailable 4.0E-02 2. OE-02 2.00E-02 2.1E-01 6.00-01
- 5. 6E-02
- 3. 0O0-04
- 3. 0OE-04 1.50-04 1.00-02 Non -Recov 1.00+00 1.70-01 4.30-01 1.20-01 1.00+00 8.00-01
- 2. 6E-01 3.40-01 3.4E-01 1.00+00 1.10-02 1.00+00 1.00+00 1.00+00 1.00+00 8.40-01 8.40-01 1.00+00 1.00+00 Opr Fail 1.00-02 1.00-03 4.00-04 Event Identifier: 286/88-002