"We want a good, safe environmental consideration," Hodges attorney William Want told a three-judge panel of the Richmond-based 4th U.S. Circuit Court of Appeals.

Mr. Want said the Energy Department didn't know enough about Savannah River Site's long-term storage capacity before it decided in April to move weapons-grade plutonium to it from the Rocky Flats nuclear weapons plant near Denver.

An attorney for the government disagreed, saying a study conducted in February was sufficient.

"You don't need a new environmental assessment as long as you studied a range of options," said Jeffrey B. Clark, the deputy assistant U.S. attorney general.

The panel did not rule after the two-hour hearing.

The Energy Department plans to transfer six metric tons of plutonium to the Aiken site. Federal officials hope to convert the material into commercial nuclear fuel called mixed oxide, but they have not committed to doing so.

Fearing that the storage will become permanent, Mr. Hodges has fought the plan since last summer, holding highway roadblock exercises and vowing to lie in front of trucks to keep the shipments from crossing the state line.

U.S. District Judge Cameron Currie, of Aiken, last month denied Mr. Hodges' request to stop the shipments. If his appeal fails, Mr. Hodges has promised to press his case to the Supreme Court.

On Wednesday, the appeals panel questioned the lawyers about the extent of the environmental study and the potential ramifications of storing plutonium in South Carolina indefinitely.

When Mr. Want suggested DOE did not sufficiently examine how long the Aiken site could hold plutonium after 10 years, Judge Paul Niemeyer asked him to prove it.

Mr. Clark said the February study by DOE examined the storage risks for a 50-year period.