PIKETON (AP) — The site of a former uranium enrichment plant tucked away in the hills of southern Ohio has the necessary infrastructure for a nuclear power plant — abundant water, a power grid and bipartisan political backing.

It’s where the former Portsmouth Gaseous Diffusion Plant enriched uranium during the Cold War. Cleanup of the site is still going on, along with construction of a new-technology centrifuge process to enrich uranium for use in nuclear power plants.

President Barack Obama expressed support for clean energy and for workers at the plant during last year’s campaign.

The state’s top elected Democrats and Republicans, many of them longtime backers of atomic energy, are expected at the Piketon site on Thursday for the formal announcement.

They include Gov. Ted Strickland, a Democrat who used to represent the area in Congress, and Rep. Jean Schmidt, a Republican who does now.

Barry Bennett, Schmidt’s chief of staff, has called it ‘‘a major, major plant.’’

Officials declined to release details — cost, capacity, time table — on Wednesday. Sally Thelen, a Duke Energy spokeswoman in Cincinnati, said Duke will be a partner in the plant but declined to say how big a share of ownership Duke would have and who the partners will be.

‘‘Right now we’re just acknowledging the announcement, now that the cat is out of the bag,’’ she said.

But she was willing to talk about Duke’s experience with nuclear plants. The company has two nuclear plants in South Carolina and one in North Carolina.

‘‘We’ve been in nuclear over 30 years — safely, efficiently,’’ Thelen said. ‘‘About 20 percent of our energy is nuclear. It would be new here, where our plants are coal-fired, but in terms of Duke, we’ve done it safely and reliably for over 30 years.’’

The president of the union whose workers are cleaning up the adjacent Piketon site of the former Portsmouth Gaseous Diffusion Plant said he learned several days ago the announcement would be made, and it was tough to try to keep it under wraps.

‘‘It’s going to be a big deal,’’ said Bobby Graff, president of USW Local 5-589. He expects about 400 permanent jobs for his members, but that’s at least a decade down the road.

Financing and licensing could take three to four years. But when it’s begun, construction of the plant could create as many as 4,000 temporary jobs, according to some estimates.

USEC Inc., based in Bethesda, Md., is building the American Centrifuge Plant on a portion of the 3,700-acre Department of Energy site about 80 miles east of Cincinnati.

Spokeswoman Elizabeth Stuckle said even when the centrifuge plant, which still is seeking financing and a $2 billion government loan guarantee, is on line, and when the generating plant is completed, enriched uranium would not pass directly from the centrifuge to the plant.

It has to go elsewhere to be packed into usable fuel pellets or fuel rods, she said.

Marilyn Wall, a spokeswoman for the Sierra Club’s Miami Group office in Cincinnati, said environmental organization remains opposed to construction of nuclear power plants because of several issues, including uranium mining practices and disposal of nuclear waste.

‘‘We don’t see it as a solution or a viable energy policy,’’ Wall said. ‘‘And there are a lot of nuclear issues already in Piketon.’’