WASHINGTON - The Energy Department is committed to removing 99 percent of the nuclear waste in underground tanks at weapons sites, and anything less is "off the table," the head of the cleanup program told lawmakers Thursday.
Assistant Energy Secretary Jessie Roberson told a Senate hearing that she saw no chance that as much as 10 percent of the waste might be kept in the tanks even if the department is allowed to keep residual sludge at the bottom of the buried containers.
The assurance came as Ms. Roberson was pressed by senators about the cleanup of highly radioactive waste left over from decades of plutonium production for nuclear weapons at the Energy Department's Hanford complex in Washington state and at sites in South Carolina and Idaho.
The department would like to reclassify the residual sludge that will be left at 177 buried tanks at Hanford and in dozens of similar waste tanks at the Savannah River Site in South Carolina and the INEEL facility in Idaho as having a "low level" of radioactivity.
The proposal, which would require Congress to change the nuclear waste law, has been met with concern in Washington state and Idaho, where officials argue that the sludge should be buried in a special repository to be built in Nevada for high-level radioactive defense waste. The department wants to mix the sludge with a cementlike grout and not remove it.
Ms. Roberson, who is leaving her job next month for personal reasons, sought to allay some of the states' concerns at a hearing by the Energy and Natural Resources Committee.
Sen. Ron Wyden, D-Ore., told Ms. Roberson he had been informed that the department was considering leaving as much as 10 percent of the waste and "dangerously high" levels of radiation in the Hanford tanks.
Unless the state agrees to something different, Ms. Roberson said, "99 percent is what we're living by ... I don't see any chance that we're gong to go to 90 percent."
Mr. Wyden said he was encouraged but not totally satisfied by the assurance and asked for it in writing. And Sen. Maria Cantwell, D-Wash., also wanted a guarantee that the Energy Department would stick to the 1 percent.
"That is our commitment," Ms. Roberson said.
Some environmentalists, when asked to respond to Ms. Roberson's assurances, questioned the significance.
"One percent of what?" said Tom Cochran, a nuclear waste expert at the Natural Resources Defense Council. He argued that a small amount of waste volume left in the tanks could have a large percentage of the radioactive intensity in a tank.
Geoff Fettus, an defense council lawyer who brought the successful lawsuit challenging the DOE's attempt to reclassify tanks waste without congressional action, said "what they plan to leave behind in the tanks has been a moving target."
In court papers, they said they would remove "as much as economically and technically feasible," Mr. Fettus said.
On a related issue, Sen. Jeff Bingaman, D-N.M., told Ms. Roberson that, should residual radioactive sludge be allowed to be kept in the tanks, he was concerned that the Energy Department - and not the Nuclear Regulatory Commission - would determine whether the grout-sludge mixture met the commission's criteria for low-level waste.
"I would feel much more comfortable if the NRC made the decision on whether its own criteria had been met," Mr. Bingaman said.
Ms. Roberson said she was confident that waste left in the tanks would have a low enough radioactive intensity to classify it as low-level once mixed with the grout.
The DOE announced earlier this week that Ms. Roberson was resigning as head of the cleanup program, effective July 15, after three years on the job.
Asked about the resignation Thursday, she denied that her departure involved policy issues, criticism by some lawmakers of the tank cleanup plan, or the recent resignation of two other senior DOE officials involved in environmental cleanup issues.
She said "a little ruffling" at a hearing would not cause her to quit. "I leave for personal reasons, and they are unconnected to anyone else but my family."
Ms. Roberson worked at SRS during the early 1990s as deputy assistant manager for environmental research and solid waste, DOE spokesman Rick Ford said. She was responsible for speeding up cleanup at the site, and encouraged the department to tear down unneeded buildings to save taxpayer money, Mr. Ford said.
"She wasn't just our boss; she was our friend," he said.
Staff Writer Josh Gelinas contributed to this report.
Assistant Energy Secretary Jessie Roberson will resign next month.