COLUMBIA- Construction will continue this year at a nuclear reactor fuel project at the Savannah River Site, but plans to mothball the multibillion dollar program eventually are still in the works, federal authorities said Tuesday.

Those plans mean work at the mixed-oxide fuel facility will go on through the fiscal year that ends Sept. 30. In a budget request submitted to Congress earlier this year, the Obama administration proposed suspending the project known as MOX, saying it is too expensive and that another method needs to be found to dispose of the plutonium.

"We will continue with construction activities through 2014, retaining the key nuclear engineers and other highly-skilled workers that will be needed regardless of the path forward," Josh McConaha, spokesman for the National Nuclear Security Administration, said in a statement to The Associated Press.

Construction began in 2007, but the project has undergone years of delays as costs have continued to rise to nearly $8 billion. The facility is slated to open in 2016, and federal officials now say it will cost about $30 billion over the years it's in use.

The project is intended to help the United States fulfill an agreement with Russia to dispose of 34 tons each of weapons-grade plutonium - an amount that officials have said is equal to 17,000 warheads. It would be the first of its kind in the United States.

Reiterating the Obama administration's commitment to honoring that agreement, McConaha said the government was exploring other ways to dispose of the plutonium.

Some of those alternatives were contained in an Energy Department report obtained Tuesday by AP. Among them are so-called fast reactors - which the U.S. doesn't currently have - or mixing it with other waste to make it unusable. According to the report, using the reactors would have a life cycle cost of more than $50 billion, and the process known as "downblending" would cost more than $16 billion.

Other options such as immobilizing the plutonium in glass or irradiating it in another kind of reactor would each cost more than $30 billion.

Members of South Carolina's congressional delegation have been vocal in their support of keeping MOX on track. U.S. Sens. Lindsey Graham and Tim Scott and U.S. Rep. Jim Clyburn quickly issued statements hailing the administration's decision. Gov. Nikki Haley, who has said the closure of MOX would both harm international relations and the state's workers, said U.S. Energy Secretary Ernest Moniz had called her earlier Tuesday to notify her of the decision.

"This is a commitment that the federal government made to South Carolina," Haley told AP by phone. "Our voices got loud and will continue to be loud."

South Carolina has also filed a federal lawsuit seeking to keep the U.S. Energy Department from withdrawing funding for the program, saying that the administration can't use money intended to build the plant to shut it down. On Tuesday, Haley said the state must press forward with the lawsuit to keep MOX viable in the long term.

"I think we can't let up," Haley said. "We are not going to be a dumping ground in South Carolina."

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Matt Daly in Washington contributed to this report. Kinnard can be reached at http://twitter.com/MegKinnardAP