Workers at Southern Company are trying to determine what caused a nuclear reactor at Plant Vogtle in Waynesboro to shut down on Monday night.

The company, which operates Vogtle, says an electrical switchgear may have tripped a turbine at the reactor, although the incident is still under investigation. A spokeswoman says the shutdown happened automatically as a safety measure, and that no one was in danger.

Such stoppages are uncommon at Vogtle.

Each of the two reactors there generates about 1215 megawatts of electricity, supplying power to about 303,000 homes. The company says other sources of energy are filling out the power grid while the reactor is down, including the company's coal and natural gas plants.

Southern says it's unsure how the shutdown will affect its revenue. The reactor was still offline this afternoon.

Vogtle's other reactor is still online.

Georgia Power, Plant Vogtle's majority owner, is currently seeking to build two new reactors there. They would be among the first built in the U.S. in more than 20 years.

Tags: Georgia, Augusta, Southern Company, nuclear reactors, nuclear energy, reactors, Plant Vogtle, nuclear reactor