The expected application will top 8,000 pages and include about 100,000 pages of supporting references and associated environmental studies. The application filing is expected next month.

The 30-day clock to challenge the application starts ticking after NRC staff decide to docket the application. That decision would be expected in the fall.

"Reviewing the (license application) will be a monumental task, unlike one that any potential NRC party has ever faced," attorneys said in the motion, filed Monday. "The 30-day period is grossly inadequate."

State officials have estimated they might prepare a record 250 to 500 challenges to the science research and engineering designs for the repository, as well as the Energy Department's program management.

Some challenges probably will be consolidated or dismissed by NRC administrative judges before being heard, attorneys have acknowledged.

Nevada's five-member congressional delegation added its support of the extension request in a letter sent to the NRC on Wednesday, saying more time to review and respond to the mountains of material would be "in the interest of fairness and good public policy."