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| Entered date | Event description | |
|---|---|---|
| ENS 42914 | 17 October 2006 17:02:00 | Unit HPCI system declared inoperable. During performance of the quarterly surveillance, HPCI pump operability, the HPCI system was secured when the "HPCI Turbine Oil Pressure Low" alarm was received and confirmed. Turbine governor end bearing oil pressure was 2 PSIG. The alarm setpoint is 6 PSIG and procedure limit is 10-12 PSIG. Pressure adjust valve was throttled open to raise pressure to 11 PSIG. The HPCI system was not immediately declared inoperable since an evaluation was being performed to determine if 2 PSIG turbine bearing oil pressure was adequate. Evaluation by the vendor will not be complete until 10/18/06. At 1655 hours, HPCI declared operable after a successful run with adequate oil pressure. HPCI is a single train system. The licensee notified the NRC Resident Inspector.
Original report was entered in error on 10/17/06 with Unit 2 versus Unit 1. Changed EN #42914 to accurately reflect the affected unit (Unit 1).
EN #42914 was submitted by Southern Nuclear Operating Company based upon a conservative decision to declare the HPCI system inoperable pending further evaluation to support its operability. Southern Nuclear Operating Company retracts EN #42914 based on the following discussion. During a subsequent review of the parameters by the HPCI Turbine Vendor, Dresser-Rand, and site engineering it was concluded that the HPCI system would have been capable of performing its intended safety function with the lower turbine governor end bearing oil pressure. During the operation of the system, the visual local indication was approximately 2.5 PSIG oil pressure at the governor end bearing. A review of the data showed that with a governor end oil pressure of the procedural minimal of 10 PSIG, the predicted oil flow rate would be 1.08 gpm with a minimum film thickness of 0.48 mils and a maximum bearing temperature of 228 deg F. With a degraded oil pressure of 2.5 PSIG, the predicted oil flow rate would be 0.54 gpm with a minimum film thickness of 0.46 mils and a maximum bearing temperature of 233 deg F. Based on the calculated data, the turbine governor end bearing would have performed satisfactorily for at least 8 hours at an oil pressure of 2.5 PSIG. Using the design basis success criteria, HPCI operation is successful if the system can inject water through the core Feedwater line for a total of 4 hours over a 24 hour period. The 4 hour mission time for HPCI is based on the design basis - if HPCI fails, it is backed up by the Automatic Depressurization System (ADS) in combination with Core Spray and Low Pressure Coolant Injection. The HPCI system is not credited for long term injection or late injection. Although the oil flow rate was reduced by 50% and the minimum film thickness reduced by 4%, the bearing temperatures were predicted to only increase a maximum of 5 deg F. Supporting this conclusion is the fact that the bearing was not damaged during the operation with low oil pressure when the turbine was run for 9 minutes at 2.5 PSIG governor end bearing oil pressure. The licensee will notify the NRC Resident Inspector. |
| ENS 41086 | 3 October 2004 10:46:00 | During a review of outage clearances, it was discovered that a Caution tag out for Service Air to the Drywell was active and the valves were open. This rendered the valves inoperable and Technical Specification 3.6.1.3 action B for one penetration with two inoperable PCIVs was entered. The action was to isolate the penetration by closing one valve within one hour. The event was discovered at 0530 and the outboard valve was closed at 0655 . Since the one hour time limit was exceeded, Technical Specification 3.6.1.3 action E (Mode 3 in 12 hours and Mode 4 in 36 hours) was entered at 0630 and exited at 0655. Technical Specification 3.6.1.3 action A, which is the Tech. Spec. for one inoperable isolation valve will remain in effect. The plant entered Mode 3 at 1530 on 10/01/04. Mode 3 requires primary containment and all PCIVs to be operable. This condition of non-compliance existed from 1530 on 10/01/04 until 0655 on 10/03/04. The licensee notified the NRC Resident Inspector. |