The Department of Energy is preparing to submit a construction application early next month for a nuclear waste repository at the Nevada site even as the EPA has yet to finalize its radiation health standard.

The EPA proposed draft regulations in August 2005 as to how much radiation should be allowed to escape the repository and enter the environment as the waste decays over thousands of years into the future.

At a Senate hearing in March 2006, the EPA's acting assistant administrator for air and radiation William Wehrum said agency officials hoped to release a final Yucca Mountain regulation by the end of that year, but nothing was forthcoming.

Since then EPA officials have been mum as to when the final rules would be issued.

The silence has given rise to speculation that the regulations are ready but the Bush administration is holding off on making them public to delay the all-but inevitable lawsuits from repository opponents.

Johnson, speaking to reporters at a roundtable organized by the Platts energy trade publications, said there was no strategic reason for taking so long.

"As any major regulation it is important and necessary for us to reflect on it and go through an interagency process," he said. "We are in the midst of reviewing things."

Johnson said he could not say when the Yucca standard would be made final. It appeared to be at the White House for review within the Office of Management and Budget.

The regulation was received by OMB on Dec. 15, 2006, and its status was listed on the agency's Web site as "review extended."

"My expectation is to have a decision certainly by the time I leave office," said Johnson, who is expected to step aside by the time a new president is inaugurated next January.

The EPA's draft regulation proposed to limit radiation exposure near the repository 100 miles northwest of Las Vegas to 15 millirems a year for 10,000 years, then increasing the allowable limit to 350 millirems a year for up to 1 million years. By comparison, a chest X-ray is 10 millirems.

Energy Department officials said their computer calculations show the Yucca repository could meet that standard. Critics including officials in Nevada charge the standard would not protect public health.

The EPA issued an earlier set of radiation rules in June 2001, after a 22-month review process. Those rules were rejected by a federal appeals court in July 2004, prompting EPA to embark on a rewrite.