COLUMBIA, S.C. - The Department of Energy is unsure how it will dispose of some of the plutonium currently being stored at the Savannah River Site and around the country, a recent report says.

A spokesman said Wednesday the agency plans to remove the radioactive metal from the site just outside Aiken, S.C., it just doesn't know exactly how yet.

About 13 metric tons of surplus plutonium "is without a disposition path," according to the agency's report to Congress last month. The report raised concerns from anti-nuclear activists who said it's an indication the agency plans to store plutonium at the Savannah River Site permanently.

Energy Department spokesman Joe Davis said that's not the case.

"Any plutonium that we have brought into this state will be taken out of the state," Davis said. "That's our policy, we're sticking to it. We're not going to bring any plutonium into the state that doesn't have a pathway out."

The agency has two types of plutonium, weapons grade and nonweapons grade, Davis said. The material in question is about 13 metric tons of nonweapons grade plutonium. The United States already has agreed to get rid of 34 metric tons of weapons grade plutonium by converting it into fuel for commercial nuclear reactors.

But the report's uncertainty raises questions about the overall disposition program, said Tom Clements of Greenpeace. Clements has pushed for glass conversion because he says it's a safer alternative to mixed-oxide fuel, or MOX.

"They may claim it's on track or not confused, but the confusion continues," Clements said. "The bottom line is clear, the Savannah River Site is becoming a long-term storage site."

The nonweapons grade plutonium could be converted into MOX fuel or could be turned into glass, a method the agency is currently investigating, Davis said.

Almost half of the 13 metric tons of nonweapons grade plutonium was shipped to the Savannah River Site from the Rocky Flats facility in Colorado.

The agency's uncertainty is hardly surprising, said Frank Avignone, former chairman of the Physics Department at the University of South Carolina.

"On one hand, it's a bad idea to leave it here forever," Avignone said. "On the other hand, I'm not surprised the plan is moving so slowly when the president and the Secretary of Energy and everybody else has their mind on other things."