05000331/LER-2007-008
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No 05000 | |
| Event date: | 04-11-2007 |
|---|---|
| Report date: | 06-11-2007 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3312007008R00 - NRC Website | |
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Duane Arnold Energy Center 05000331 YEAR
I.Description of Event:
The 'B' Emergency Diesel Generator (EDG) Lube Oil Filter (LOF) o-ring was replaced on 2/12/07 during a cylinder liner replacement during Refuel Outage (RFO) 20. The LOF o-ring replacement was conducted by vendor service mechanics.
The 'B' EDG was operated between 2/12/07 and 3/24/07 for greater than 52 hours6.018519e-4 days <br />0.0144 hours <br />8.597884e-5 weeks <br />1.9786e-5 months <br /> with no indication of any leak from the LOF.
On 3/25/07 during the performance of Surveillance Test Procedure (STP) 3.8.1-04, "Standby Diesel Generators Operability Test," a minor leak was identified. At the time, the leak was identified as minor with no effect on operability. Corrective Work Order (CWO) A77495 was initiated to repair the minor leak when scheduled.
On 4/11/07, during a performance of STP 3.8.1-04, following preplanned maintenance, a 0.21 gallon per minute lube oil leak from the LOF was observed. Specifically, during the initial start for the STP, the o-ring joint for the LOF developed a significant leak and the engine was shutdown.
The engine remained inoperable until the leak was repaired later on 4/11/07.
II.Assessment of Safety Consequences:
A detailed past operability evaluation was completed. Although the EDG was not capable of performing its Technical Specification (TS) mission time of 7 days, the EDG was proven by analysis to operate for 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> without any operator intervention prior to failure.
Since the diesel generator past operability evaluation proved that the EDG would operate for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> without manual actions, there is no noticeable risk impact due to the degradation of the diesel generator. The risk impact is negligible because the probability of losing offsite power for a time period longer than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is very low. In addition, many other onsite and offsite resources become available to mitigate any undesirable conditions (e.g., repairing of any deficient equipment or using alternate means of achieving safety functions).
The 'A' EDG has same LOF and o-ring configuration. No issues involving leaks on that LOF have been identified. That o-ring was replaced during the last 2-year inspection (not at the same time as the 'B' EDG). No concern exists based on the time in-service.
This event did not result in a Safety System Functional Failure.
III.Cause of Event:
An investigation into this event was completed under Apparent Cause Evaluation (ACE) 1719.
The ACE determined the apparent cause for the 'B' EDG LOF leak was the installation of the wrong o-ring during RF020.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Duane Arnold Energy Center 05000331 YEAR NUMBER NUMBER The following possibilities as to why the wrong sized o-ring could have been installed were investigated and eliminated as the cause:
1. Wrong o-ring supplied to warehouse from vendor 2. Wrong o-ring provided by warehouse to workers 3. Wrong o-ring brought in by vendor 4. Wrong o-ring returned to stock Therefore, based on the results of the investigation, the exact cause of using the wrong sized o-ring could not be determined. However, the process of using commercial grade soft goods is being reviewed.
IV. Corrective Actions:
Actions to Correct the Condition:
CWO A77913 replaced the LOF o-ring for the 'B' EDG. Following the replacement of the o-ring the engine was run with no identified leaks.
Corrective Action to Address the Apparent Cause:
Review O-Rinq procurement and quality level process The evaluation will review the procurement and quality level process for o-rings.
Development of the lessons learned from the cylinder liner work in RF020.
This event will be incorporated into the work planning for the cylinder liner replacement on the 'A' EDG in RFO21. This CA will incorporate all improvements for oversight and pre-job brief expectations.
V. Additional Information:
Previous Similar Occurrences:
From LER reviews over the previous 5 years, the following similar occurrence was identified:
with LPCI in an LCO for Suppression Pool Cooling El IS System and Component Codes:
LA - Diesel Lube Oil System FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Duane Arnold Energy Center 05000331 YEAR NUMBER� NUMBER Reporting Requirements:
This report is being submitted pursuant to 10CFR50.73(a)(2)(i)(B).