ML20156A238
| ML20156A238 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-008-00 | |
| Download: ML20156A238 (4) | |
Text
B-137 PRECURSOR DESCRIPTION SHEET LER No.: 400/87-008 Event
Description:
LOFW and a RWST isolation valve fails closed Date of Event: 2/27/87 Plant: Harris 1 EVENT DESCRIPTION Sequence While at 49% power during surveillance testing of the main turbine control valves, governor valve No. 3 was found failed. While the valve was being examined, a generator load swing from 358 to 315 MW(e) over a 2-s period occurred followed by an increase to 400 MW(e) over a 12-s period. All MFW system pumps except the lB condensate pump had tripped off. The test engineer had inadvertently shorted two terminals causing the valve to close and then open, thus creating the load swing. The MFW pumps tripped off as a consequence of the valve closure.
All systems responded as designed. Due to the RCS cooldown and inventory volume shrinkage, the charging pump switched suction from the volume control tank to the RWST on low VCT level. One RWST suction valve (two in parallel) failed to open. The valve motor failed on demand. An attempt to restart MFW was unsuccessful.
Corrective Action Repairs were made.
Plant/Event Data Systems Involved:
Main feedwater RWST Components and Failure Modes Involved:
MFWPs fail in operation RWST suction valve fails on demand Component Unavailability Duration: N/A Plant Operating Mode: 1 (49%)
Discovery Method: Operational event Reactor Age: 0.1 y Plant Type: PWR Comments None.
MODELING CONSIDERATION-AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient No recovery Event Identifier: 400/87-008
B-138 Branches Impacted and Branch Nonrecovery Estimate MFW 1.0 No recovery HPI Base case One of two isolation valves failed to open HPI (B&F) Base case One of two isolation valves failed to open LPI Base case One of two isolation valves failed to open Plant Models Utilized PWR plant Class B Event Identifier: 400/87-008
B-139 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 400/87-008 Event
Description:
LOFW and a RWST isolation valve fails closed Event Date: 02/27/87 Plant: Harris 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 1.7E-06 Total 1.7E-06 CV TRAN S 1.4E-04 Total 1.4E-04 ATWS TRANS 3.4E-05 Total 3.4E-05 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec*
126 trans -rt afw MFW HPI(F/B) -ss.depress cond/mfw CD 1.2E-06 7.4E-02 120 trans -rt afw MFW -HPI(F/B) -hpr/-hpi porv.open -ss.depress CD 3.3E-07 8.8E-02 cond/mfw 127 trans -rt afw MFW HPI(F/B) ss.depress CD 1. 3E-07 2 .2E-01 121 trans -rt afw MFW -HPI(F/B) -hpr/-hpi porv.open ss.depress CD 3.7E-08 2.6E-01 123 trans -rt afw MFW -HPI(F/B) hpr/-hpl -ss.depress cond/mfw CD 3.7E-08 B.BE-02 109 trans -rt -afw -porv.or.srv.chall ss.releas.term HPI CV 1.3E-04 2.9E-01 101 trans -rt -afw porv.or.srv.chall -porv.or.srv.reseat ss.releas CV 5.3E-06 2. 9E-01
.term HPI 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
101 trans -rt -afw porv.or.srv.chall -porv.or.srv.reseat ss.releas CV 5. 3E-06 2.9E-01
.term HPI 109 trans -rt -afw -porv.or.srv.chall ss.releas.term HPI CV 1.3E-04 2.9E-01 120 trans -rt afw MFW -HPI(F/B) -hpr/-hpi porv.open -ss.depress CD 3. 3E-07 8.8E-02 cond/mfw 121 trans -rt afw MFW -HPI(F/B) -hpr/-hpi porv.open ss.depress CD 3.7E-08 2. 6E-01 123 trans -rt afw MFW -HPI(F/B) hpr/-hpi -ss.depress cond/mfw CD 3.7E-08 8.8E-02 126 trans -rt afw MFW HPI(F/B) -ss.depress cond/mfw CD 1.2E-06 7.4E-02 127 trans -rt afw MFW HPI(F/B) ss.depress CD 1. 3E-07 2.2E-01 128 trans rt ATWS 3.4E-05 1.2E-01
- non-recovery credit for edited case Event Identifier: 400/87-008
B-140 SEQUENCE MODEL: c:\asp\newmodel\pwrbnew.cmp BRANCH MODEL: c:\asp\newmodel\harris.new PROBABILITY FILE: c:\asp\newmodel\pwrbnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 4.8E-04 1.OE+00 loop 4. 6E-06 3.9E-01 loca 2.4E-06 4.3E-01 rt 2.8E-04 1.2E-01 rt/loop O.OE+00 1.OE+00 emerg .power 2.9E-03 8.OE-01 ep.rec 1.OE+00 1.7E-01 afw 3.8E-04 2.6E-01 afw/emerg .power 5.OE-02 3.4E-01 MFW 2.OE-01 > 1.OE+00 3.4E-01 > I.OE+00 Branch Model: 1.OF.1 Train 1 Cond Prob: 2.OE-01 > Unavailable porv.or. srv.chall 4.OE-02 1.OE+00 porv.or. srv.reseat 3.OE-02 1.IE-02 porv.or. srv. reseat/emerg.power 3.OE-02 1.0E+00 ss. releas.term 1.5E-02 3.4E-01 HPI 1.5E-03 > 3.1E-02 8.4E-01 Branch Model: 1.OF.3+ser Train 1 Cond Prob: 1.OE-02 > Failed Train 2 Cond Prob: 1.OE-01 Train 3 Cond Prob: 3.0E-01 Serial Component Prob: 1.2E-03 HPI (F/B) 1.5E-03 > 3.1E-02 8.4E-01 1.OE-02 Branch Model: 1.OF.3+ser+opr Train I Cond Prob: 1.OE-02 > Failed Train 2 Cond Prob: 1.OE-01 Train 3 Cond Prob: 3.OE-01 Serial Component Prob: 1.2E-03 hpr/-hpi 1.5E-04 1.OE+00 1.OE-03 porv.open 1.OE-02 1.OE+00 4.OE-04 ss.depress 3.6E-02 1.OE+00 cond/mfw 1.0E+00 3.4E-01 1.OE-02 LPI/HPI 1.5E-04 > 1.5E-02 3.4E-01 Branch Model: 1.OF.2 Train 1 Cond Prob: 1.OE-02 > Failed Train 2 Cond Prob: 1.5E-02 lpr/-hpi .hpr 6.7E-01 1.0E+00 lpr/hpi 1.5E-04 1.OE+00
- branch model file
- forced Minarick 05-16-1989 06:53:13 Event Identifier: 400/87-008