"The Department of Energy should not be in the business of propaganda and trying to persuade schoolchildren that storing nuclear waste at Yucca Mountain is OK," Berkley said.

"Yucca Mountain Johnny is like Joe Camel was to cigarettes," Berkley said, referring to the once-ubiquitous cartoon pitch-camel who was dropped by the RJ Reynolds tobacco company in 1997 under pressure from Congress and health groups.

Defending the site, Energy Department spokeswoman Megan Barnett said the Yucca Mountain Youth Zone drew 20,000 page views from January through May.

Barnett said the site has been valued by "students and adults around the globe on nuclear physics, geology, engineering and complex science." "We intend to keep this educational tool available," Barnett said, "and we look forward to working with Congress on this issue."

The Yucca site has games and activities, suggested curricula for teachers, and discussions about "the nuclear waste problem" and how science is used to find "solutions." Aimed at students of varying grade levels, the entry pages link to more detailed science discussions deeper within the site.

The Web site is among dwindling "public outreach" elements of the Yucca program, which has been squeezed by declining budgets. Public tours of the Yucca site, 100 miles northwest of Las Vegas, have been curtailed, and the Energy Department this spring closed the Yucca Mountain Project Science Center on Meadows Lane in Las Vegas.

Berkley went after the Web site last year but lost a 271-147 vote after Republican committee leaders came to Yucca Mountain Johnny's defense.

This year, the chairman of the House energy and water subcommittee is a Democrat, Peter Visclosky of Indiana, who accepted Berkley's amendment without debate.

The amendment was added to a fiscal 2008 spending bill for the Energy Department. The Senate also will debate the bill, with final decisions expected later this year on the bill and the fate of Yucca Mountain Johnny.