ML20149K491
| ML20149K491 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-006-00 | |
| Download: ML20149K491 (4) | |
Text
B-44 PRECURSOR DESCRIPTION SHEET LER No.: 287/87-006 Event
Description:
HPI is unavailable Date of Event: 9/10/87 Plant: Oconee 3 EVENT DESCRIPTION Sequence During plant shutdown for minor repairs (LER 287/87-004), plant personnel opened the breakers to the HPI suction valve motors from the borated water storage tank, thus isolating the water source. The breakers were tagged open by personnel without informing the control room of these actions. The procedures employed in the shutdown process were unclear as to what actions needed to be performed. During the sub-sequent startup, operators incorrectly believed that the HPI system was available. Three different checks for HPI operability were made, the first two failing to detect its inoperative status. The operators and station personnel failed to adequately communicate with each other during the shutdown and startup processes. The procedures employed con-tained deficiencies.
Corrective Action The valves were restored to service and the procedures were revised.
Plant/Event Data Systems Involved:
HPI Components and Failure Modes Involved:
Isolation valves are unavailable Component Unavailability Duration: 26 h Plant Operating Mode: 4 (0%)
Discovery Method: Operational event Reactor Age: 13.0 y Plant Type: PWR Comments None.
Event Identifier: 287/87-006
B-45 MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated LOCA, LOOP, Base case nonrecovery transient Branches Impacted and Branch Nonrecovery Estimate HPI 1.0 No recovery HPI (B&F) 1.0 No recovery Plant Models Utilized PWR plant Class D Event Identifier: 287/87-006
B-46 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 287/87-006 Event
Description:
HPI is unavailable Event Date: 09/10/87 Plant: Oconee 3 UNAVAILABILITY, DURATION- 26 NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 1.2E-02 LOOP 4.7E-05 LOCA 2.?E-05 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD TRANS 3.5E-08 LOOP 4.6E-09 LOCA 1.OE-06 Total 1.OE-06 CV TRANS 6.3E-05 LOOP 2.4E-07 LOCA 2.6E-05 Total 8.9E-05 ATWS TRANS O.OE+0O LOOP O.OE+00 LOCA O.OE+00 Total O.OE+O0 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec-307 loca -rt -afw HPI as.depresa CD 9.9E-07 4.3Em-01 109 trans -rt -afw -porv.or.srv.chall sa.relean.term BPI CV 5.8E-05 3.4E-01 304 loca -rt -afw HPI -as.depress -lpi/hpi -lpz/hpi CV 2.6E-05 4.3E-01 101 trans -rt -afw porv.or.srv.chall -poiv.or.srv.reaeat ss.releas CV 5.lE-06 3.4E-01
.term HPI
- 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 as.releas CV 5.lE-06 3.4E-01
.term HPI 109 trans -rt -afw -porv.or.srv.chall ss.releas.term HPI CV 5,8E-05 3,4E-01 304 loca -rt -afw HPI -ss.depress -lpi/hpi -Ipr/hpi CV 2.6E-05 4.3E-01 307 loca -rt -afw HPI ss.depress CD 9.9E-07 4.3E-01
- non-recovery credit for edited case Note: For unavailabilities, conditional probability values are differential values which reflect the added risk due to failures associated with an event. Parenthetical values indicate a reduction in risk Event Identifier: 287/87-006
B-4"7 compared to a similar period without the existing failures.
SEQUENCE MODEL: c:\asp\newmodel\pwrdnew.cmp BRANCH MODEL: c:\asp\newmodel\oconee.new PROBABILITY FILE: c:\asp\newmodel\pwr bnew.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 0.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 3.4E-01 porv.or.srv.chall 8.0E-02 1.OE+00 porv.or.srv.reseat 1.OE-02 1.IE-02 porv.or.srv.reseat/emerg.power 1.OE-02 1.OE+00 ss.releas.term 1. 5E-02 3.4E-01 HPI 3.OE-04 > 1.0E+00 8.4E-01 > 1.0E+00 Branch Model: 1.OF.3 Train 1 Cond Prob: .1.OE-02 > Unavailable Train 2 Cond Prob: 1.OE-01 " Unavailable Train 3 Cond Prob: .31. OE-01 > Unavailable HPI (F/B) 3.OE-04 " 1.0E+00 8.4E-01 > 1.OE+00 l.OE-02 Branch Model: l.OF.3+opr Train I Cond Prob: i,.6E-02 " Unavailable Train 2 Cond Prob: l.OE-01 " Unavailable Train 3 Cond Prob: 3.OE-0l > Unavailable hpr/-hpi 1.5E-04 1.0E+00 1 .OE-03 ss.depress 3. 6E-02 1.0E+00 cond/mfw 1.OE+00 3.4E-01 1.0E-02 lpi/hpi 1.5E-04 3.4E-01 lpr/-hpi.hpr 6.7 E-01 1.0E+00 lpr/hpi 1. 5E-04 1.0E+00
- branch model file
- forced Minarick 05-16-1989
.06:51:51