ENS 41137
ENS Event | |
|---|---|
02:10 Oct 20, 2004 | |
| Title | Unusual Event Declared Due to Unexplained Decrease in Spent Fuel Pool Water Level |
| Event Description | An uncontrollable decrease in water level in the spent fuel pool occurred. All fuel assemblies remained covered. Current plant conditions DO NOT threaten public safety. Level decrease is secure. Valve lineup caused level decrease to BWST. Approximately 24 feet above fuel maintained. Secured fuel transfer canal drain lineup.
Unit 3 is currently defueled. The licensee was attempting to perform a spent fuel pool makeup while there was another valve lineup in progress which drained the deep end of the fuel transfer canal. This exposed some piping that allowed a flow path from the spent fuel pool to the BWST and resulted in the transfer of slightly less than 1 ft. level in the spent fuel pool, or approximately 10,000 gallons. Operators immediately recognized the decrease in spent fuel pool level and took appropriate steps to secure other activities in order to identify the drain path. This included securing the RCB wash downs in progress inside containment to eliminate a source for the observed increase in RB sump levels and secured equipment drain downs in progress in the Aux Building to eliminate these as a source for the observed increase in the high activity waste tank level. Spent fuel pool level decreased from 0.3 ft above to about 0.7 ft below the normal. During the transient, a 24 ft. level was maintained above the spent fuel. No increase in radiation levels following the decreasing in water level was observed. The licensee had recently started three spent fuel pool cooling pumps and due to a decrease in spent fuel pool temperature some shrinkage had occurred. The drain down to the BWST was initiated at approximately 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br />. At 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br />, Operators recognized the problem and entered the applicable Abnormal Procedure. At 2210 hours0.0256 days <br />0.614 hours <br />0.00365 weeks <br />8.40905e-4 months <br /> the Licensee declared an Unusual Event and took actions to secure the valve lineup which allowed the drain down. These actions were completed by 2215 hours0.0256 days <br />0.615 hours <br />0.00366 weeks <br />8.428075e-4 months <br /> at which time the Unusual Event was terminated. By 2224 hours0.0257 days <br />0.618 hours <br />0.00368 weeks <br />8.46232e-4 months <br /> a level increase due to makeup was observed. Current spent fuel pool level is - 0.15 ft and increasing. The Licensee will continue makeup until the level reaches + 0.5 which is estimated to occur at approximately 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on 10/20/04. No offsite radioactive release occurred. The licensee will inform the NRC resident inspector. |
| Where | |
|---|---|
Oconee  South Carolina (NRC Region 2) | |
| Reporting | |
| Emergency class: | Unusual Event |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration | |
| Time - Person (Reporting Time:+-3.12 h-0.13 days <br />-0.0186 weeks <br />-0.00427 months <br />) | |
| Opened: | Steve Godfrey 23:03 Oct 19, 2004 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Oct 19, 2004 |
| 41137 - NRC Website | |
WEEKMONTHYEARENS 557332022-02-05T08:57:0005 February 2022 08:57:00
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