In separate legal documents at the NRC, they denied allegations by pro-repository groups that they had pre-judged the case by comments they made at a Senate confirmation hearing in February.

"Considering all relevant facts and circumstances, a reasonable person would not conclude that my testimony demonstrates pre-judgment of the issues now before the commission or raise doubts about my ability to consider the issues ... fairly and impartially," Magwood said.

The announcement by the commissioners is a precursor to an NRC ruling that many attorneys expect to be issued this month in the closely watched Yucca case.

The decision is expected to be a key milestone in the Department of Energy's bid to shut down the project that fell out of favor with President Barack Obama.

The states of Washington and South Carolina, and White Pine County in Nevada and Aiken County in South Carolina had asked three commissioners to step aside on the vote.

They pointed to comments given by Magwood, Ostendorff and commissioner George Apostolakis when they were asked by Sen. Barbara Boxer, D-Calif., at their confirmation hearing whether they would "second guess" the DOE decision to terminate the nuclear waste project. All three said "no."

Apostolakis said in July he would recuse himself from voting on Yucca Mountain, not because of what was said at the Senate hearing but because he had taken part in a scientific review of the Yucca program for Sandia National Laboratories in 2007 and 2008.

In his six-page filing, Magwood said he knew at the time of the hearing the Obama administration wanted to shut down the program. But, he said, he was not aware of the legal questions surrounding the issue or the NRC process to rule on them.

"While there may have been some ambiguity about the meaning of 'second guess,' I certainly did not understand Senator Boxer's question in any sense to ask for my commitment to ignore the law," Magwood said.

Ostendorff said in a six-page document he had "only limited knowledge" of Yucca Mountain licensing at the time. While he would not question the repository shutdown as a policy issue, he said he had no knowledge of the legal issues involved.

"It was not my belief, nor do I think that any reasonable person could conclude as such in light of all the facts and circumstances, that Senator Boxer was asking for my opinion as to whether the application could be withdrawn as a matter of law," Ostendorff said.

Contact Stephens Washington Bureau chief Steve Tetreault at stetreault@stephensmedia.com or 202-783-1760.