An environmental group charged yesterday that the Energy Department's tentative plans for transporting and processing nuclear waste would increase the risk of accidents and radiation contamination.

The Environmental Policy Institute, a nonprofit group with its headquarters here, yesterday released 13 maps of tentative railroad and trucking routes that DOE has prepared for transporting high-level nuclear waste from around the nation to a temporary storage and treatment facility in Oak Ridge, Tenn. The maps were obtained through a Freedom of Information Act request.

The institute said the maps reveal that cities and states around Tennessee will face the greatest exposure to the nuclear waste. The maps also show that the bulk of the spent fuel will be transported from nuclear plants in the East.

DOE recommended in April that the temporary storage site be established in Oak Ridge, where the canceled Clinch River breeder reactor was located.

Under DOE's proposal, the Oak Ridge plant, known as a Monitored Retrievable Storage (MRS) Facility, is intended to repackage and store spent fuel rods from nuclear power plants until permanent disposal facilities are completed in 1998 in Texas, Nevada and Washington.

The Tennessee plant, which Energy officials say could be completed by 1996, would cost $1 billion and could store as much as 15,000 tons of nuclear waste from the nation's 88 commercial nuclear plants. Most nuclear waste is now stored at the site where it is produced.

Fred Millar, director of the institute's Nuclear and Hazardous Materials Transportation Project, said at a news conference that the plan is designed "not to reduce the risks of nuclear transport but merely its public visibility."

"Nuclear waste shipments are simply concentrated on a fewer number of states, thereby placing a whole new set of communities at greater risk," he said.

He said some cities would suffer the double risk of having nuclear waste pass through on the way to Oak Ridge and, after it has been processed, on the way to a final resting site in Texas, Nevada or Washington.

Millar forecast that the 80 rail shipments to and from the Oak Ridge facility each year "could go out like regular freight and be subject to the same percentage of derailments as regular freight."

He predicted that if 1 percent of the contents of a nuclear cask were to leak from an accident near an urban area, thousands of cancer fatalities could result many years afterward.

But Roger Gale, director of DOE's Office of Policy, Integration and Outreach, said that only the best rail lines would be employed to transport the used fuel rods.

"The overall risks to which the public is subjected would be reduced under MRS," he said in an interview after the news conference. If it were riskier, he said, "then we wouldn't do it."

About 85 percent of the fuel wastes would come from the East and about 10 percent would arrive from the West, Gale said.

Millar estimated that as many as 1,300 rail and truck shipments would be made annually to the Tennessee facility.

He also said the 17 casks now used to ship nuclear material are unreliable.

Gale said the casks' safety has been certified by the Nuclear Regulatory Commission.