ML20149K408
| ML20149K408 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1987-030-00 | |
| Download: ML20149K408 (4) | |
Text
B-114 PRECURSOR DESCRIPTION SHEET LER No.: 369/87-030 Event
Description:
Emergency power system is unavailable Date of Event: 9/8/87 Plant: McGuire 1 EVENT DESCRIPTION Sequence While a crew was labeling components in the diesel fuel oil system, they incorrectly labeled two valves due to an error in the procedure.
This action resulted in the inadvertent closure of the lB tank valve when the 1A valve was intended to be closed. The 1A fuel tank was then taken out of service for its mandatory 10-y cleaning. The DC day tanks were still available, but held only 1 h of fuel. The EPS was essen-tially unavailable since only one DC was available and it had only 1 h of fuel. DC lB would have operated for approximately 1 h before running out of fuel.
Corrective Action The lB valve was immediately opened, and repairs were completed on the DC 1A fuel tank.
Plant/Event Data Systems Involved:
Emergency power Components and Failure Modes Involved:
Fuel valve to DC IB was closed by error DC 1A fuel tank was out for its 10-y cleaning Component Unavailability Duration: 72 h Plant Operating Mode: 5 (0%)
Discovery Method: Testing Reactor Age: 6.1 y Plant Type: PWR Comments Since the day tank valve was labeled incorrectly, it was assumed that an operator would not have discovered that the wrong valve was closed in the event a low-level alarm occurred in the day tank. If the DC had ever run out of fuel, it would be a lengthy process to restart it
(>1 h).
MODELING CONSIDERATION AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated LOOP Base case nonrecovery Event Identifier: 369/87-030
B- 115 Branches Impacted and Branch Nonrecovery Estimate EPS 1.0 Assumed nonrecoverable Plant Models Utilized PWR plant Class F Event Identifier: 369/87-030
B-I 16 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 369/87-030 Event
Description:
Emergency power system is unavailable Event Date: 09/08/87 Plant: McGuire 1 UNAVAILABILITY, DURATION= 72 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 1.3E-04 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CD LOOP 2.4E-05 Total 2.4E-05 CV LOOP 5.3E-07 Total 5.3E-07 ATWS LOOP O.OE+O*O Total 0.OE+00 SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)
Sequence End State Prob N Rec**
217 loop -rt/loop EMERG.POWER ep.rec CD 2.2E-05 6.6E-02 216 loop -rt/loop EMERG.POWER -ep.rec afw/emerg.power CD 1.BE-06 1.1E-01
- non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)
Sequence End State Prob N Rec**
216 loop -rt/loop EMERG.POWER -ep.rec afw/emerg.power CD 1.8E-06 1.1E-01 217 loop -rt/loop EMERG.POWER ep.rec CD 2.2E-05 6.6E-02
- 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 compared to a similar period without the existing failures.
SEQUENCE MODEL: c:\asp\newmodel\pwr_bnew.cmp BRANCH MODEL: c:\asp\newmodel\mcguire.new PROBABILITY FILE: c:\asp\newmodel\pwr_bnew.pro No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail trans 4.BE-04 1.0E+00 loop 4.6E-06 3.9E-01 Event Identifier: 369/87-030
B-117 loca 2 .4E-06 4.3E-01 rt 2. 8E-04 1.2E-O1 rt/loop 0. OE+00 1.OE+00 EMERG.POWER 2.9E-03 > l.OE+00 8.OE-01 > 1.OE+00 Branch Model: 1.OF.2 Train 1 Cond Prob: 5. OE-02 > Unavailable Train 2 Cond Prob: 5.7E-02 " Unavailable ep.rec 1. OE+O0 1.7E-01 afw 3. 8E-04 2.6E-01 a fw/emerg .power 5.OE-02 3.4E-01 mfw 2. OE-OI 3.4E-01 porv.or.srv.chall 4. OE-02 1.OE+O0 porv.or.srv.reseat 3. OE-02 1.1E-02 porv.or.srv-.reseat/emerg.power 3.OE-02 I.OE+00 ss.releas.term 1. 5E-02 3.4E-01 hpi I.OE-03 8.4E-01 hpi(f/b) 1. OE-03 8.4E-01 1.0E-02 hpr/-hpi 1.5E-04 1.OE+00 1 .OE-03 porv.open 1. OE-02 I.OE+00 4 .OE-04 ss.depress 3. 6E-02 1.OE+O0 cond/mfw 1.OE+00 3.4E-01 1.OE-02 lpi/hpi 1.5E-04 3.4E-01 lpr/-hpi.hpr 6.7E-01 1.OE+00 lpr/hpi 1.5E-04 1.OE+00
- branch model file
- forced Minarick 05-16-1989 06:55:11 Event Identifier: 369/87-030