Reports by two panels of the National Academies urged the Energy Department to revamp its massive $140 billion clean-up plans for defense nuclear waste with the goal of transporting less of it to a central facility.

This would allow clean-up activities to be completed sooner and cost less, the panels said. The current clean-up schedule, involving dozens of sites, envisions most waste treatment and disposal to be finished in 20 years.

But the scientists also called for greater involvement outside of the Energy Department in determining what wastes should be left in place and what should be transported to a geological repository. The report said the department's credibility on decisions involving waste disposal is hampered because the DOE both proposes and approves waste disposition plans.

''DOE should not attempt to adopt these changes unilaterally,'' said the panel, suggesting the Environmental Protection Agency or Nuclear Regulatory Commission and perhaps an independent group of experts get involved in assessing how radioactive wastes should be treated.

This approach was applauded by some environmentalists Tuesday, who have argued that DOE has too much power in making waste disposal decisions. The report ''clearly sent a message that Congress must rein in DOE and address the mess that it has made of nuclear waste clean-up policy,'' said Geoff Fettus, a lawyer for the Natural Resources Defense Council.

States with some of the biggest clean-up challenges - including Washington, Idaho and South Carolina - and have argued that high-level defense nuclear waste should be taken away for deep geological burial.

But a National Research Council panel, asked to review the government program, concluded that the ''recovery of every last gram'' of such waste ''will be technically impractical and unnecessary.''

In some cases removing waste could lead to increased human exposures to radiation, the panel said. It also said the expense associated with retrieval, immobilization and disposition of some of the waste in a central repository ''may be out of proportion with the risk reduction achieved, if any.''

An attempt to recover all of this waste - such as the hardened ''heel'' waste attached to the inside of buried tanks at the Hanford site in Washington state - could lead to more contamination than if it were left in place, the report said.