The certification starts a clock ticking on the project's next phase. By law, DOE officials can apply to build a nuclear waste repository at the Nevada site six months after the backup documents have been certified.

DOE officials have pledged that their application will be ready by June 30.

The actions on Friday suggests officials might be running ahead of schedule and could file by April. Two weeks ago, the department issued two major draft environmental impact studies for the project, which DOE officials said further signified progress, although many other funding and scheduling challenges remain.

Yucca documents have been posted to the database, known as the Licensing Support Network, in large batches over the past several years.

Analysts and attorneys hired by the state of Nevada, which is fighting the project, have been scrutinizing the documents looking for holes.

State officials have said they suspect key material still might be missing, setting the stage for a new legal fight. The state has 10 days to file a complaint with the Nuclear Regulatory Commission.

"We will undertake an immediate review of the database to confirm its completeness or lack of completeness," state attorney Charles Fitzpatrick said Friday. "If we conclude it is incomplete, we will take the necessary action."

The Energy Department tried to certify a Yucca document database in 2004, but it was thrown out by judges at the NRC for being incomplete.