ENS 42576
ENS Event | |
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14:59 May 15, 2006 | |
Title | Momentary Loss of Dhr Due to Automatic Actuation of the Keowee Emergency Power Supply |
Event Description | Event: At 10:59 hours on 5-15-06, while in Mode 6 following completion of refueling activities, Oconee Unit 3 experienced a lockout of CT-3, the transformer for the Startup power source, which was in service at the time. This resulted in a momentary loss of AC power to the unit. Keowee Hydro Station, the Oconee emergency power source received an automatic emergency start signal, started, and closed in to supply power via the Underground Emergency Power path within approximately 40 seconds.
Initial Safety Significance: Initial conditions of significant systems: Normal power via backcharge of main transformer was not available. The Fuel Transfer Canal was full and valves open connecting it to the Spent Fuel Pool. Time to core boil was 58 minutes per procedure. The Equipment Hatch was open. The initial loss of power resulted in interruption of Decay Heat Removal (DHR) Cooling, Spent Fuel Pool Cooling, and other support systems. Power was automatically restored and the affected systems returned to service promptly. Therefore there was no safety significance to this event. Reactor Coolant System heated up from approximately 80F to approximately 89.5F during this event. Corrective Action(s): As stated, Keowee started and supplied power automatically. The appropriate Abnormal Procedures were entered to restore power and restart these systems. DHR was restored at 11:13. Actions were initiated to achieve Containment Closure due to the loss of DHR. The Equipment Hatch was closed by 11:40. Backup power is available from Central Switchyard via CT-5. The cause of the initiating transformer lock out is under investigation. The licensee informed the NRC Resident Inspector. |
Where | |
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Oconee South Carolina (NRC Region 2) | |
Reporting | |
10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
Time - Person (Reporting Time:+-1.18 h-0.0492 days <br />-0.00702 weeks <br />-0.00162 months <br />) | |
Opened: | Randy Todd 13:48 May 15, 2006 |
NRC Officer: | Steve Sandin |
Last Updated: | May 15, 2006 |
42576 - NRC Website
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WEEKMONTHYEARENS 571592024-06-03T04:51:0003 June 2024 04:51:00
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