05000219/LER-2004-001
| Event date: | 05-17-2004 |
|---|---|
| Report date: | 07-13-2004 |
| 2192004001R00 - NRC Website | |
Plant Operating Conditions Before the Event:
Oyster Creek was operating in the RUN Mode at 100% power with no safety systems out of service.
Description of Event:
At 03:10 on 05/17/04 Operations commenced the scheduled biweekly #1 EDG Load Test surveillance.
During the surveillance, at 04:40, an operator reported that the #1 EDG was making an unusual noise and vibration was noted on the cooling fan belt drive shaft. A field supervisor was dispatched to investigate.
Upon evaluating the condition of the fan bearing, the field supervisor advised the control room to secure the diesel. After the diesel was secured, shift entered a 7-day LCO at 05:00.
At approximately 07:30 the Outage Control Center was staffed to support the development of a schedule and prepare a plan to repair the cooling fan pillow block bearing. Parallel to the activities associated with the recovery plan, an investigation into the cause of the cooling fan bearing support loose bolts commenced. Included in the investigation was a review of the total number of hours that the #1 EDG was run since the 24-month inspection in late April, a review of the procedures and documentation that were used to perform the cooling fan maintenance and interviews with the individuals that performed the fan work during the overhaul. In addition, an extent of condition was performed to evaluate other fasteners that could have been disturbed during the 24-month inspection.
A work order and a clearance were prepared to complete the repairs to the cooling fan bearing support.
The clearance was applied at approximately 12:20. The scope of the work order included reinstallation and torquing of the cooling fan pillow-block bearing bolts, re-verification of torques that were applied to all disturbed fasteners during the recent inspection and incorporation of other associated minor repairs which had been identified during subsequent #1 EDG walk downs. The pillow block bearing was inspected and reinstalled. No damage to the bearing occurred.
All repairs were completed at approximately 17:12 on May 17 and the clearance was removed.
Immediately following the repairs, #1 EDG Load Test was again performed as the cooling fan post maintenance test and to validate operability. In addition, vibration readings were also taken to ensure no abnormal cooling fan pillow-block bearing frequencies were observed. Normal frequencies were observed with no anomalies noted. The surveillance test was completed satisfactorily and the diesel was declared operable on May 17 at 20:25.
Analysis of Event
There were no actual safety consequences associated with this event. At the time of discovery of the #1 EDG problem, #2 EDG was operable along with all of its associated engineered safeguard loads and capable of performing its safety function.
A 7-day LCO was entered on May 17, 2004 based on TS 3.7.C.2 for one diesel generator inoperable during power operation. An evaluation in accordance with the significance determination process (SDP) of the event is not yet completed. An evaluation of the #1 EDG is in progress to determine if the EDG was operable, but degraded, with the condition that was identified and would have been available for a time sufficient to perform its intended safety function.
Cause of Event:
The root cause of this human performance event was the failure of plant personnel to follow the implementing procedure for the Diesel Generator 24-month inspection.
A contributing factor to this event was that individual preventative maintenance (PM) tasks were not prepared in accordance with the guidance in the surveillance test (ST).
Corrective Actions
Interim Actions:
- The loose bolt fasteners on the pillow-block bearing assembly were replaced and torqued to the proper value.
- Extent of condition was performed on all bolted fasteners that were disturbed as part of the 24 month inspection and proper torque values were verified.
- Maintenance Department Stand-down conducted to review expectations for performance and the use of fundamentals to prevent human error.
Long Term Actions:
- Evaluate and create PM tasks for the 24-month diesel inspection, including the specific tasks identified in the "Component Replacement Schedule" (Appendix 1, page E2-1) of Surveillance Test (ST) 636.1.010.
- Revise the ST and the applicable vendor Maintenance Instructions into Level 1 (Continuous Use) Maintenance Procedures. These procedures should provide the necessary details, verifications and human factoring. In addition, data sheets for entering readings such as "as left" torque values; clearances, M&TE and other pertinent information should be provided.
- Planners will be trained and reinforced in the expectation to provide torque specifications and appropriate verifications in work packages.
- A follow up work package quality assessment will be performed prior to the upcoming refuel outage (1R20).
Additional Information
A. Failed Components:
No components were damaged other than the threads on one of the bolts. Examination of the bearing revealed no damage and after reassembling the components the #1 EDG was successfully run for surveillance, examined for vibrations and determined to be operable.
B. Previous similar events:
None.
C. Identification of components referred to in this Licensee Event Report:
Components IEEE 805 System ID�IEEE 803A Function Emergency Diesel Generator EK� DG