WASHINGTON -- The Department of Energy on Monday began explaining proposed changes to the Yucca Mountain nuclear waste site. But activists and representatives for Nevada grumbled that few details were available at a public meeting.

Energy Department organizers called the event a listening session as they start environmental impact studies of the proposals. After an hour, 46 people had signed in, mostly professionals representing interest groups, federal agencies, members of Congress and potential contractors.

The department is embarking on new designs for waste-handling facilities at Yucca Mountain and on a study of a possible railroad path that would carry radioactive waste through counties in western Nevada.

Information on new designs for waste canisters and blueprints of the above-ground parts of the tunnel repository were on poster boards, with presenters standing nearby to answer questions.

The same format is to be used in public meetings scheduled in Nevada over the next two weeks. More of them will focus on the proposed Mina railroad corridor across Northern Nevada and through Lyon, Mineral and Esmeralda counties.

Critics of the Yucca program said the agency's presentation was unhelpful.

"There was not enough detail to offer an intelligent comment," said Marty Malsch, an attorney for the state. "Nobody could have a way to know whether they would be affected or not."

The information "is all scattered," said Kevin Kamps, nuclear waste specialist at the Nuclear Information and Resource Service. "We can't talk to each other, we can't hear from each other about concerns. It think it is by design."

Michele Boyd, legislative director of the Public Citizen energy program, said how the Energy Department proposed to load nuclear waste at reactors using new multi-purpose canisters was unclear.

"The pictures were completely useless," Boyd said.

Others defended what some called the low-key format and said it was designed to encourage citizens to ask questions and offer suggestions out of the spotlight. Formal public hearings will be held after the draft studies are completed, they said.

"This lets the department talk one-on-one with the public and answer questions and learn better what the concerns are," said Jane Summerson, DOE document manager for one of the impact studies.