A reactor at the Browns Ferry Nuclear Plant is shut down because of a problem that occurred while it was being returned to operation after refueling.
A report from the Nuclear Regulatory Commission says Unit 3 shut down automatically late Tuesday while at 35 percent power.
The reactor had been idle for refueling and it was being brought back into service.
A spokesman for the regulatory agency, Roger Hannah, said today the problem occurred with a turbine, which is on the non-nuclear side of the unit.
Workers replaced 288 fuel assemblies during the outage, and they also replaced and refurbished other parts of the reactor and its generating turbine.
The plant's other two reactors are still at full power.