ENS Event | |
|---|---|
15:24 Feb 1, 2008 | |
| Title | Loss of Spent Fuel Pool Cooling |
| Event Description | Millstone Unit 1 is in a decommissioning status but still maintains spent fuel in the spent fuel pool. On January 30, 2008, the normal power to the Unit 1 spent fuel pool was lost due to a fault (overcurrent trip) in the "Trayer Switch" (an auto disconnect switch) in the electrical supply line to the spent fuel pool cooling bus. A backup diesel generator was started and was being used to power the spent fuel pool cooling system until the "Trayer Switch" was repaired. At approximately 0840 EST today (2/01/08), alarms were received indicating low decay heat pump low flow and low spent fuel pool cooling pump low flow and discharge pressure. Investigation revealed that the backup diesel generator was operating at a frequency of 57.5 Hz rather than the normal 60 Hz. The technical staff was unable to get the diesel generator to maintain the normal 60 Hz output frequency. The licensee elected to secure the spent fuel pool cooling system pumps at 1024 EST based on concerns that the pumps could be damaged if operated at under frequency for an extended period of time.
Licensee technicians are currently engaged in repairing the diesel generator frequency controls and estimate that it could be returned to service this afternoon. The licensee has also ordered a temporary skid mounted diesel generator which should also arrive this afternoon. The repairs to the normal power source are not anticipated to be completed until Monday (2/04/08). The spent fuel pool temperature has increased 1 degree to 86 F in approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The tech spec limit on spent fuel pool temperature is 150 F. The licensee states that other unit electrical systems powered off the diesel, such as lighting and rad monitors, continue to operate normally at the reduced output frequency of the diesel. One security tower has been slightly impacted but appropriate compensatory measures were implemented. A Millstone Unit 2/3 Resident Inspector has been notified. The licensee has attempted to contact the Regional Inspector. |
| Where | |
|---|---|
Millstone  Connecticut (NRC Region 1) | |
| Reporting | |
| Other Unspec Reqmnt | |
| Time - Person (Reporting Time:+-1.62 h-0.0675 days <br />-0.00964 weeks <br />-0.00222 months <br />) | |
| Opened: | Lenny Mauspeller 13:47 Feb 1, 2008 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Feb 1, 2008 |
| 43951 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Decommissioned (0 %) |
| After | Decommissioned (0 %) |
WEEKMONTHYEARENS 439512008-02-01T15:24:0001 February 2008 15:24:00
[Table view]Other Unspec Reqmnt Loss of Spent Fuel Pool Cooling 2008-02-01T15:24:00 | |