ML20149K482
| ML20149K482 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-013-00 | |
| Download: ML20149K482 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.: 339/84-013 Event
Description:
Forced Shutdown Due to Two Inoperable Emergency Diesel Generators Date of Event: December 9, 1984 Plant: North Anna 2 EVENT DESCRIPTION Sequence At 1215 h the "2J" EDG was started to determine operability, while the "2H" EDG was tagged out for the maintenance. At 1321 h the "2J" EDG tripped on high crankcase pressure. Preventive maintenance was immedi-ately stopped on the "2H" EDG. The "2H" EDG was started,. loaded, and determined operable at 1605 h pursuant to testing requirements. The "2WH" EDG was placed on an 8-h surveillance testing schedule as required. At 0637 h on December 9, 1984, the "*2H" EDG was started for surveillance testing. At 0652 h the "2H" EDG tripped on high crankcase pressure and was declared inoperable.
As a 'result of having two inoperable EDGs, a plant shutdown was initiated.
Corrective Action Maintenance personnel and technical representatives from the Fairbanks Morse, EDG manufacturer, investigated the causes of the EDG trips and performed corrective maintenance. The Nos. 2, 3, and 11 upper pistons and the D11 liner were replaced because of possible leaks on the "2J" EDG. As a result of the failures, a root cause was sought. It is believed to be due to a fault in the Technical Specifications surveil-lance requirement.
Plant/Event Data Systems Involved:
Emergency power Components and Failure Modes Involved:
DG 2H1 - failed in test DG 2J - failed in test Component Unavailability Duration: First time 2.5 h; second time; 53 h; 9 h assumed for analysis Plant Operating Mode: 1 (100% power)
Discovery Method: During testing Reactor Age: 4.5 years Plant Type: PWR Event Identifier: 339/84-013 D- 175
Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated LOOP Base case Branches Impacted and Branch Nonrecovery Estimate EPS 1.0 No recovery assumed possible Plant Models Utilized PWR plant Class A Event Identifier: 339/84-013 D- 17 6
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 339/84-013 Event
Description:
Forced Shutdown Due to Two Inoperable Diesel Generators Event Date: 12/9/84 Plant: North Anna 2 UNAVAILABILITY, DURATION-- 9 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP 7.OE-05 SEQUENCE CONDITIONAL PROBABILITY SUIMS End State/Initiator Probability CV LOOP 3.5E-07 Total 3.5E-07 CD LOOP 1.2E-06 Total 1.2E-06 ATWS LOOP 0.OE+00 Total 0.OE+00 DOMINANT SEQUENCES End State: CV Conditional Probability: 3.4E-07 219 LOOP -RT/LDOP EP -AFW/EP -PORV .OR.SRV .CHALL SS .RELEAS .TERM End State: CD Conditional Probability: 1.2E-06 220 LOOP -RT/LDOP EP AFW/EP SEQUENCE CONDITIONAL PROBABILITIES Event Identifier: 339/84-013 D-177
Sequence SeueceEnd State Prob N Rec**
217 LOOP -RI/LOOP EP -AFW/EP PORV.OR.SRV.CHALL -PORV.OR.SRV.RESE Cv 1.4E-08 l.lE-0l AT SS.RELEAS.TERM 219 LOOP -RI/LOOP EP -AFW/EP -PORV.OR.SRV.CHALL SS.RELEASTERM Cv 3.4E-07
- 4non-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 inrisk compared to a similar period without the existing failures.
MODEL: b:\PWRATREE .CMP DATA: b:\NANNAPRO.CMP No Recovery Limit BRANCH FREWJE NCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.OE-03 I.OE+00 LOOP 2.3E-05 3.4E-01 LOCA 4.2E-06 3.4E-01 RI 2.5E-04 1.2E-01 RI/LOOP 0.0E+00 I .0OE+00 EP 2.9E-03 > 1.0E+00 5.IE-01 > 1.OE+00 Branch Model : 1.DF.2 Train 1 Lond Prob: 5.0E-02 > Failed Train 2 Land Prob: 5.7E-02 > Failed AFW 1.0E-03 2.7E-01 AFW/EP 5.0E-02 3.4E4)1 MFW 1.9E-01 3.4E-01 PORV .OR .SRV .CHALL 4.E-02 I.0E+00 PORV .OR.SRY .RESEAT 2.OE-02 5.0E-02 SS .RELEAS .TERM 1.5E-02 3.4E-0 I SS .RELEAS .TERPI/-NFW 1.5E-0'2 3.4E-01 SS .DEPRESS 3.6E-02 1.0E+00 COND/MFW 1.0E+00 3.4E-01 HPI 2.3E-03 5.2E-01 HPI (F/B) 2.3E-03 5.2E-01 4.OE-02 PORY .OPEN 1.OE-02 1.OE+00 HPR/-HPI 3.OE-03 5.6E-01 4.OE-02 CSR 3.OE-03 3.4E-01 4.E-02 LPI/HPI I.OE-03 3.4E-01 LPR/-HPI 6.7E-01 I.0E+00 LPR/HPI 2.OE-03 I .OE+00 Event Identifier: 339/84-013 D-178
- forced Minarick 04-12-1987 10:29:45 Event Identifier: 339/84-013 D-179