KNOXVILLE, Tenn. (AP) - The Unit 1 reactor at the Tennessee Valley Authority's Watts Bar Nuclear Plant in Spring City tripped due to a turbine problem, and the Nuclear Regulatory Commission says the cause of the turbine problem is under investigation.

An NRC statement Tuesday said the plant's lone reactor tripped Sunday, and "all systems functioned as designed with the exception of pressurizer backup heaters."

The statement says the electrical system was in normal shutdown alignment until the system restarted Tuesday and there were no abnormal radiological conditions.

The NRC statement says TVA notified the NRC resident inspector. A TVA spokesman said there was no immediate comment.

A second reactor is being built at the plant.

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