UPDATE: The Nine Mile Point Unit 1 reactor shut down automatically at 11:18 a.m. Tuesday

Officials with Constellation Energy Nuclear Group, the plant’s owner, originally thought the turbine that spins to make electricity had tripped. But the Nuclear Regulatory Commission said late Tuesday the shutdown was due to a high neutron flux in the plant’s reactor.

The cause of the condition is still under review. All plant safety systems responded as designed and there were no complications.

NRC resident inspectors assigned to Nine Mile Point monitored the shutdown and they will review the company’s evaluation of what happened and any corrective actions.

Scriba, NY -- Nine Mile Point Unit 1 nuclear plant automatically shut down Tuesday morning.

Constellation Energy Nuclear Group spokeswoman Jill Lyon said all equipment at the plant is working as it should during the shutdown and all safety systems are in order. She said preliminary data shows the turbine that spins to make electricity tripped at 11:18 a.m.

The exact cause of the shutdown has not yet been identified.

She said the plant responded according to design and automatically shut down with all safety systems responding appropriately. "The plant is in a safe and stable condition," she said.

Unit 1 had been at 100 percent power when the shut down occurred. Lyon said plant personnel are working to identify the cause of the shut down and will determine what, if any, repairs or actions will be required.