Port Gibson — Grand Gulf Nuclear Station put its figurative hand on the dimmer switch Sunday.

Employees at the Port Gibson power plant began reducing power to enter a scheduled refueling outage.

During the outage, workers will perform hundreds of maintenance activities, a Grand Gulf officials said, and replace more than one third of the fuel in the reactor.

A new turbine rotor and refurbished main generator will also be installed to increase the station’s electrical output by approximately 13 percent.

The total cost of the expansion, $724 million, will be shared among the joint owners of Grand Gulf, including Entergy Mississippi and the South Mississippi Electric Power Association, Grand Gulf communication specialist, Suzanne Anderson said in December.

The work is requiring extra employees and dozens of contracted companies. More than 4,000 people will be involved in the work, the release said.

“This is a milestone for Grand Gulf as we will be significantly upgrading major equipment in the plant and positioning Grand Gulf to safely operate for the long-term,” said Site Vice President Mike Perito.

The outage and work at the Entergy plant is expected to last several weeks.

Both Entergy and local officials expect the work to have an economic impact in the Miss-Lou.

“Anytime anybody is spending nearly $800 million, it’s is tremendous,” Natchez Inc. Executive Director Chandler Russ said in December. “It truly is a regional project.”

Refueling outages are required for all nuclear reactors every 18 to 24 months.

For business reasons, Entergy does not publicly discuss anticipated outage durations in detail, according to a company press release.

The outage will be the plant’s 18th.