Close to 2,000 temporary employees will be imported to work in Claiborne County in February, when Grand Gulf Nuclear Station begins the power upgrade that will make it the most powerful nuclear reactor in the country, a spokesman with Entergy Nuclear told the Vicksburg Rotary Club Thursday.

The upgrade, which will see most of the 25-year-old plant’s systems replaced, will bump the plant’s power output 13 percent but also infuse the local economy with increases to hotel, meal and other spending for about 2 1/2 months, said Dillon Allen, the project control specialist for the project.

“It will add to our existing capacity and meet the increased demand for electricity that we see coming down the road, without increasing our capital costs greatly,” Allen said. “For our workers, it’s also replacing things that were built in the 1970s and 1980s that have been in use for 30 years.”

The station normally employs about 350 employees, but at its height, the upgrade will see 2,200 or more total workers there, both staff and contracted, from electricians and welders to engineers and other professionals, he said.

“A lot of those people will be staying here in Vicksburg,” Allen added.

The Grand Gulf station is about 25 miles south of Vicksburg, just off U.S. 61 South.

No estimates of what Entergy expects to provide for hotel and meal allowances were available, but Grand Gulf’s last refueling outage early in 2010 — bringing about 1,000 temporary workers — was credited for a nearly 15 percent increase in Vicksburg hotel and bed and breakfast occupancy rates over the same period in the previous year.

The temporary workers are expected to remain until early summer.

The upgrade was planned for Grand Gulf’s regular scheduled refueling outage, Allen said.

“Other (nuclear power) sites are scheduled and make sure they remain operating to provide the necessary power,” he said. “We schedule them for the spring and the fall because it has the smallest impact, when there is less demand for electricity.”

Following the upgrade, Grand Gulf’s total electrical output will go from about 1,300 to 1,450 megawatts, Allen said. “We’ll essentially be ripping out the insides of the plant and putting in all new systems.”

Components to be replaced include a high-pressure turbine rotor, control room systems, main transformer, the entire main generator and numerous pieces of auxiliary equipment.

Following construction in the 1970s and 1980s, Grand Gulf began operating in 1985. The plant uses a controlled nuclear reaction to generate heat to boil water. The resulting steam is piped under pressure to a turbine, which spins to generate electricity that goes onto a grid with power from other plants.

The station is in the process of obtaining license renewal to operate for another 20 years, Allen said.