WASHINGTON – US anti-nuclear groups Monday condemned a project to build a plant where plutonium from weapons would be reprocessed into fuel for nuclear power plants, saying the plan was costly, dangerous and would benefit mainly the French group, Areva.

A mixed-oxide, or MOX, plutonium reprocessing plant that is being built in South Carolina has become "an expensive effort that enriches contractors, led by the French government-owned company Areva," Tom Clements of Friends of the Earth said at the launch of a report by an anti-nuclear alliance.

"In my opinion, it is primarily because of Areva's influence inside the Department of Energy that the US is pursuing a plutonium fuel program and it's because of Areva's influence that there's a push for the US to also reprocess commercial spent fuel to remove plutonium, like France does," he said.

According to Areva's website, the reprocessing plant will help the United States to fulfill an agreement struck in 2000 with former Cold War foe Russia, under which each country committed to eliminating 34 metric tons of surplus military plutonium by recycling it as fuel for civil nuclear applications.

After some delays, construction of the reprocessing plant in South Carolina began in August 2007, the report by the Alliance for Nuclear Accountability (ANA) says.

Once finished, the 600,000-square-foot facility will be able to turn 3.5 metric tons of weapons-grade plutonium into MOX fuel assemblies each year, and the facility will be licensed for 20 years and operate into the 2030s, Areva says.

The plant, on the Department of Energy's Savannah River site, is roughly one-third finished and three times over budget, with a price tag so far of $4.9 billion dollars, Clements maintained.

But even as the nuclear disaster in Japan highlights the dangers of MOX fuel -- which the ANA report says was used in one of the reactors at Japan's crippled Fukushima power plant -- the US government is failing to rethink construction of the South Carolina facility, Clements told reporters.

"As plutonium leaks from the damaged reactors in Japan, the US Department of Energy (DoE) continues planning for the use of dangerous mixed-oxide fuel in US nuclear reactors of the same design as the Fukushima reactors in Japan," Clements said.

MOX fuel pellets "make reactors harder to control and, in the case of a severe accident, the radiation plutonium releases will be worse than uranium fuel," said Clements.

But Areva spokesman Jarret Adams told AFP there was "not a significant difference" between weapons-derived MOX fuel and MOX made from recycled nuclear fuel.

The latter is currently being used "in about 40 reactors in five different countries, and the performance of MOX fuel has been widely tested," Adams said.

He defended the US MOX fuel facility being built by Areva and Shaw as an "important project to help convert former weapons material into useable material for American power plants.

"It removes former weapons material from possible future use," Adams said.

Anti-nuclear activists would prefer encasing the plutonium left over from dismantled US nuclear weapons in glass, and then storing it as high-level waste.

That method, called vitrification, is "cheaper, quicker and safer" than converting plutonium into MOX fuel, says the report released Monday by ANA, a network of three dozen organizations.