ENS 41386
ENS Event | |
|---|---|
15:20 Feb 8, 2005 | |
| Title | Steam-Driven Auxiliary Feedwater (Afw) Pump Declared Inoperable Due to Design Issue |
| Event Description | The following information was obtained from the licensee via facsimile:
At 0920 [hrs.] CST, on February 8, 2005, Fort Calhoun Station declared the steam driven auxiliary feedwater (AFW) pump (FW-10) inoperable due to discovery of a design problem with the pump turbine. The station entered the appropriate technical specification action statement at that time. The pertinent action statements for auxiliary feedwater ([T.S.] 2.5.1) read as follows: B (Action statement): With one AFW train inoperable for reasons other than condition A, restore the AFW train to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. C (Action statement: If the required action and associated completion times of condition A or B are not met, then the unit shall be placed in MODE 2 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, in MODE 3 in the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and less than 300 [degrees] F without reliance on the steam generators for decay heat removal within the next 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />. A change to the design basis is in progress to allow the pump to be made operable within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The design problem is due to the AFW pump drains. The manufacturer states that the drain lines must drain below the level of the AFW turbine. The current configuration is that the drains are aligned to the condenser which is approximately 18 feet above the elevation of the AFW turbine. This is not a problem during normal AFW turbine operation as the condenser would most likely be in service. However, the condenser cannot be relied upon during all accident conditions that require AFW actuation. The licensee has notified the NRC Resident Inspector.
The licensee faxed the following retraction: Fort Calhoun Station (FCS) has conducted a thorough engineering evaluation of the effects on water in the turbine exhaust housing of the steam driven feedwater pump (FW-10). It was concluded that FW-10 was able to perform its design function based on the results of the evaluation. FW-10 was determined to be operable as required during past plant operation whether or not condenser vacuum was available. The conclusion was based on four points: 1. The preparer's experience with a multi-stage turbine that was started with water up to the centerline of the rotor and sustained no damage. 2. OPPD's strong evidence that FW-10 has been operated multiple times with some water in the casing. 3. A simple conservative analysis of the forces on a turbine blade when operated in a water submerged condition. The blade stresses were determined to be well below allowables for the loading condition presented with the blade moving through the static water volume during a startup event. 4. In addition, inspection of the turbine in 1998 and 2005 does not show any adverse indications of stress or wear. Therefore this notification is being retracted.. The plant is presently in a scheduled refueling outage. The licensee will notify NRC Resident Inspector. |
| Where | |
|---|---|
Fort Calhoun  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.42 h0.0592 days <br />0.00845 weeks <br />0.00195 months <br />) | |
| Opened: | Erick Matzke 16:45 Feb 8, 2005 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Mar 27, 2005 |
| 41386 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |