ENS 51179
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ENS Event | |
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08:01 Jun 25, 2015 | |
Title | Secondary Containment Pressure Increase Due to Voltage Transient |
Event Description | At approximately 0301 [CDT] on 6/25/15, the Main Control Room received numerous annunciators that indicated a trip of the Emergency Reserve Auxiliary Transformer (ERAT) Static VAR Compensator (SVC) caused by a voltage transient on the 138 kV feed due to thunderstorms in the area. The Division 1 Safety Bus was manually aligned from the reserve source to its normal source. As a result of the voltage transient, the Division 1 Fuel Building Ventilation (VF) system isolation dampers closed causing a trip of VF supply and exhaust fans. With no running VF fans, secondary containment differential pressure rose to slightly greater than 0 inches water gauge and which exceeded the Technical Specification requirement of greater than 0.25 inches vacuum water gauge. The Control Room entered EOP-8, Secondary Containment Control. This event is being reported as a condition that could have prevented fulfillment of a safety function under 10 CFR 50.72(b)(3)(v)(C). Secondary Containment differential pressure was restored within Technical Specification requirements at 0319 [CDT] by reopening the VF isolation dampers and restarting the VF supply and exhaust fans. The ERAT SVC was returned to service at 0457 [CDT].
The NRC Resident Inspector has been notified. |
Where | |
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Clinton Illinois (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
Time - Person (Reporting Time:+1.43 h0.0596 days <br />0.00851 weeks <br />0.00196 months <br />) | |
Opened: | Paul Sanders 09:27 Jun 25, 2015 |
NRC Officer: | Jeff Herrera |
Last Updated: | Jun 25, 2015 |
51179 - NRC Website | |
Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (99 %) |
After | Power Operation (99 %) |
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