SCRIBA, NY – On October 29 at 9 p.m., Nine Mile Point Unit 1 experienced an automatic reactor shutdown.
The shutdown was caused by an electrical grid disturbance that caused the unit’s output breakers to open. When the unit’s electrical output breakers open, there is nowhere to “push” or transmit the power and the unit is appropriately designed to shut down under these conditions.
“Our preliminary investigation identified a lighting pole in the Scriba switchyard that had fallen onto an electrical component. This is believed to have caused the grid disturbance. We continue to evaluate conditions in the switchyard,” said Jill Lyon, company spokesperson.
The plant responded according to design and automatically shut down with all safety systems responding appropriately, she said, adding the plant is in a safe and stable condition.
“Our Operators, using detailed procedures and their training, took the appropriate actions to respond to plant conditions,” Lyon said. “All nuclear power plants are designed with a defense-in-depth approach to ensure safety. As such, they are designed to automatically shut down in response to certain indications and conditions.”
The unit had been at 100% power when the shut down occurred.
The unit will be returned to service when the required work scope has been successfully completed and tested. The specific duration for this outage isn’t known.
Unit 2 continues to operate safely at 100% power.