WASHINGTON–Sen. Barbara Boxer upbraided the Nuclear Regulatory Commission Thursday over delays in increasing security against terrorist threats, refusing to hand over documents that Boxer and Republican David Vitter of Louisiana had requested and a lack of transparency in employees’ travel and expenses,.

The NRC had denied a request for documents from Boxer, chairman of the Senate Committee on Environment and Public Works, based on “nonspecific constitutional separation of powers,” Boxer said.

“The privilege you are suggesting is absolutely off the wall,” Boxer said. “The arrogance of that is unbelievable because you wouldn’t be here without the Congress. You have to be subjected to oversight and we have a right to documents.”

NRC Chairman Allison Macfarlane offered no further explanation.

“We have nothing to add to the discussion about the papers Senator Boxer has requested,” David McIntyre, a public affairs officer at the NRC, wrote in response to a request for clarification.

Macfarlane and the other commission members, appearing before the Senate committee Thursday, also blundered under questioning on the NRC’s vote to delay a recommendation by its own staff that two people be present when nuclear materials are handled to prevent an insider terrorist attack. The commissioners could not recall how or why they had voted to delay the decision, which they did unanimously in May 2013.

The commission voted in accordance with Commissioner William Magwood’s suggestion that the two-person rule be delayed because it required a cost benefit analysis.

“The commission decided not to move forward with that,” Macfarlane said. When asked why she said, “It was a commission decision. I’m not sure what the vote was.”

Boxer expressed concerns and frustrations with the decision, saying that in 2011 the Department of Homeland Security had warned that “violent extremists had obtained inside positions in utilities” and posed a significant threat.

“This business of a cost benefit analysis when you’re dealing with a potential terror attack and the takeover of a nuclear plant—you’ve got to be kidding me,” Boxer said. “The cost of preventing someone from stealing nuclear weapon materials is pretty much priceless.”

Vitter also criticized the NRC for being too process-oriented and “losing the forest through the tree.

NRC Commissioner George Apostolakis conceded slow progress in implementing new reactor designs.

“On the face of it, I must admit I agree it doesn’t look good,” Apostolakis said.

The committee also criticized the slow pace of the post-Fukushima seismic evaluations, which has taken the NRC three years to conduct. If seismic risk is found in the evaluations, the NRC permits an additional three years for analysis.

“Earthquakes aren’t going to wait until your paperwork is done,” Boxer said.

Boxer also called commissioners’ travel into question, calling it “excessive.” Although NRC commissioners agreed to be in town one week each month, they reaffirmed their desire to keep their travel records “nonpublic,” citing national security.

“You’re not above the American people,” Boxer said. “I hope you will change your attitude about openness, about transparency.”