ML20147A486
| ML20147A486 | |
| 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 1987-012-00 | |
| Download: ML20147A486 (4) | |
Text
B-55 DESCRIPTION SHEET LER No.: 317/87-012 Ri Event
Description:
LOOP and one AFW train fails Date of Event: 7/23/87 Plant: Calvert Cliffs 1 and 2 EVENT DESCRIPTION Sequence While at 100% power, a phase to ground fault developed on phase C' on one of two 500-kV transmission lines (line 5052) connecting the station to the Waugh Chapel power grid. Breakers tripped open as designed to isolate the fault. The second 500-kV line breakers (line 5051) tripped spuriously on sensing the fault due to a failed relay circuit card. A loss of station offsite power occurred. The units tripped. All three station DGs started and loaded. The LOOP lasted -2 h until partial offsite power was restored.
Trouble was experienced in attempting to manually start the No. 11 TD AFW pump. It failed to start on the first two attempts due to an out-of-adjustment trip linkage. It started on the third attempt. There was no attempt to start the motor-driven AFW pump. The operators employed manual start to minimize diesel generator loading.
The initial line 5052 fault was caused by a tree making contact with the line.
Corrective Action All trees in the area were cut down. The TD AFW pump's trip link-age was adjusted.
Plant/Event Data Systems Involved:
Electrical Components and Failure Modes Involved:
Relays fail in operation Turbine AFW pump No. 11 twice failed to start on high vibration.
Component Unavailability Duration: N/A Plant Operating Mode: 1 (100%)
Discovery Method: Operational event Reactor Age: 12.8 and 10.6 y, respectively Plant Type: PWR Event Identifier: 317/87-012 RI
B-56 Comments This event was modeled assuming one TD AFW pump failed to initially start. The LER employs the word "pumps" when referring to the attempted start but does not explicitly mention the second TD AFW pump nor the motor-driven AFW pump (See LER p. 3 of 3P).
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP No recovery Branches Impacted and Branch Nonrecovery Estimate AFW Base case One of three trains fails on demand AFW/EP Failed 0.04 (0.12 for first turbine-driven AFW pump
- 0.34 for local start of second turbine-driven pump).
Plant Models Utilized PWR plant Class C Event Identifier: 317/87-012 R1
B-57 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 317/87-012R1 Event
Description:
LOOP and one AFW train fails Event Date: 07/23/87 Plant: Calvert Cliffs 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 1.OE+00 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD LOOP 4.8E-04 Total 4.BE-04 CV LOOP l.IE-05 Total I.IE-05 ATWS LOOP O.OE+O0 Total O.OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
217 LOOP -rt/loop emerg.power ep.rec CD 3.9E-04 1.4E-01 216 LOOP -rt/loop emerg.power -ep.rec AFW/EMERG.POWER CD 7.8E-05 2.7E-02 215 LOOP -rt/loop emerg.power -ep.rec -AFW/EMERG.POWER -porv.or.srv CV 8.9E-06 2.2E-01
.chall ss.releas.term 209 LOOP -rt/loop -emerg.power -AFW -porv.or.srv.chall ss.releas.te CV 1.2E-06 2.9E-01 rm hpi 213 LOOP -rt/loop emerg.power -ep.rec -AFW/EMERG.POWER porv.or.srv CV 3.6E-07 2.2E-01
.chall -porv.or.srv.reseat/erserg.power ss.releas.term
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
209 LOOP -rt/loop -emerg.power -AFW -porv.or.srv.chall ss.releas.te CV 1.2E-06 2.9E-01 rm hpi 213 LOOP -rt/loop emerg.power -ep.rec -AFW/EMERG.POWER porv.or.srv CV 3.6E-07 2.2E-01
.chall -porv.or.srv.reseat/ermerg.power ss.releas.term 215 LOOP -rt/loop emerq.power -ep.rec -AFW/EMERG.POWER -porv.or.srv CV 8.9E-06 2.2E-01
.chall ss.releas.term 216 LOOP -rt/loop emerg.power -ep.rec AFW/EMERG.POWER CD 7.BE-05 2.7E-02 217 LOOP -rt/loop emerg.power ep.rec CD 3.9E-04 1.4E-01
- non-recovery credit for edited case SEQUENCE MODEL: c:\asp\newmodel\pwrgnew.cmp BRANCH MODEL: c:\asp\newmodel\calvert.new PROBABILITY FILE: c:\asp\newmodel\pwr_bnew.pro Event Identifier: 317/87-012R1
B-58 No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 4.8E-04 1.0E+00 LOOP 4.6E-06 > 4.6E-06 3.9E-01 > 1.OE+00 Branch Model: INITOR Initiator Freq: 4.6E-06 loca 2.4E-06 4.3E-01 rt 2.8E-04 1.2E-01 rt/loop O.OE+00 1.0E+00 emerq .power 2.9E-03 8.OE-01 ep. rec 1.0E+00 1.7E-01 AFW 3.BE-04 > 2.3E-03 2.6E-01 Branch Model: 1.OF.3+ser Train 1 Cond Prob: 2.OE-02 Train 2 Cond Prob: 1.OE-01 Train 3 Cond Prob: 5.OE-02 > Failed Serial Component Prob: 2.8E¶04 AFW/EMERG'.POWER 5.OE-02 > 1.oE+oo 3.4E-01 > 4.1E-02 Branch Model: l.OF.l Train 1 Cond Prob: 5.OE-02 > Failed mfw 2.OE-01 3.4E-01 porv.or.srv.challi 4.OE-02 1.OE+00 porv.or.srv.reseat 2.OE-02 1.1E-02 porv. or. srv. reseat/emerg .power 2.OE-02 1.OE+00 as. releas .term 1.5E-02 3.4E-01 ss.depress 3.6E-02 1.OE+00 cond/mfw 1.OE+00 3.4E-01 1.OE-02 hpi 3.OE-04 8.4E-01 hpi (f/b) 3.OE-04 8.4E-01 1.OE-02 porv. open 1.OE-02 1.OE+00 4 .OE-04 hpr/-hpi 1.5E-04 1.OE+00 csr 2.OE-03 3.4E-01
- branch model file
- forced Minarick 05-16-1989 12:20:03 Event Identifier: 317/87-012RI