OLYMPIA — The state of Washington is questioning whether the Department of Energy should be considering steam reforming as an alternative to vitrification for Hanford's low-activity waste held in underground tanks.
"We're very, very skeptical," said Jane Hedges, manager of the Nuclear Waste Program of the state Department of Ecology, which is the regulator for tank waste treatment.
DOE has proposed steam reforming as one technology in a suite of technologies new to Hanford that it believes has the potential to reduce the cost of environmental cleanup of Hanford tank waste by billions of dollars and accelerate cleanup.
Hanford has 53 million gallons of radioactive waste held in tanks until it can be treated for disposal. DOE's plan is to divide the waste into high-level and low-activity waste streams.
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All of the high-level waste will be turned into a stable glass form at the vitrification plant. It had been planned to be disposed of at Yucca Mountain, Nev., in a deep geological repository.
But the majority of the volume would be low-activity waste and the vitrification plant never was planned to be large enough to treat all of the low-activity waste in a time frame that DOE and regulators consider reasonable.
The treated low-activity waste would be buried at Hanford without the extra protection to the environment provided by a deep geological repository.
For a time it looked like a technology called bulk vitrification, which produces blocks of glassified waste the size of a land-sea shipping container, would be used to treat the excess low-activity waste.
Construction at Hanford for a bulk vitrification pilot plant began in 2005 with DOE touting glass production within a year. But the pilot plant did not advance beyond the pouring of concrete pads. Testing of a nonradioactive waste simulant continued to show problems with how well the finished product would contain radioactive waste long-term, engineering fixes were needed and the cost of the project kept rising.
Now it seems unlikely that DOE will be able to prove that steam reforming is a viable technology in a reasonable amount of time, Hedges said. The state requires treatment of waste by 2022.
That can be accomplished by adding a second Low Activity Waste Facility to the vitrification plant now under construction, which the state has favored.
"There's been a long-standing commitment to glass," said Suzanne Dahl, tank treatment section manager for the Department of Ecology. "Why spend money for something that already has a solution?"
Vitrification of low-activity waste is a mature technology that is ready to be used with no more testing and it produces a well-understood waste form that is extremely protective of the environment, the state wrote in the forward to DOE's Draft Tank Closure and Waste Management Environmental Impact Statement.
Immobilizing low activity waste in glass through vitrification is required in the legally binding Tri-Party Agreement as the result of the 2010 settlement agreement, the state pointed out in a letter to DOE commenting on steam reforming. It also is the technology in an agreement with the Nuclear Regulatory Commission to allow the treated low-activity waste to be disposed of in a landfill, the letter said.
Current plans call for 90 percent of the tank waste by volume to be treated and buried in a new landfill at Hanford above ground water that feeds the Columbia River, according to the state.
Several decades were spent to prove glass as a viable waste form and proving steam reforming also produces a viable waste form would have to be done in one to three years, which seems unlikely, according to the state.
There also are operational issues to consider, according to the state. While a second Low Activity Waste Facility could be designed that largely is a copy of the first with some improvements, no such blueprint exists for steam reforming, according to the state.
The steam reforming technology uses super-heated steam and charcoal to combine clay and waste into a mineral structure. It requires temperatures of about 1,150 to 1,330 degrees Fahrenheit, but that's still much lower than the approximately 2,100 degrees proposed for vitrification.
The granular ceramic waste that results then would be combined into a solid monolith for disposal.
DOE likes the technology because the lower temperatures are less likely to drive one of the waste constituents, radioactive technitium, out of the waste during processing.
However, the state believes that's a nonissue because tests have shown that technitium can be incorporated into the glass produced at the vitrification plant, Dahl said.
DOE is looking at steam reforming after a committee of the National Academies' National Research Council recommended in an interim report that DOE look at new waste forms that might be better or more efficient to produce.
The council identified steam reforming as a robust and a mature technology for processing waste. It has been used commercially in the United States for more than a decade, including to treat radioactively contaminated resins from commercial nuclear facilities.
"No one makes low-activity waste glass in the rest of the world," said Shirley Olinger, DOE environmental management associate principal deputy.
Steam reforming could be less expensive than vitrification, but more importantly, it could allow treatment of tank waste sooner, she said. It also would allow some of the waste to be treated independently of the vitrification plant, she said.
However, more work is needed to investigate the technology and DOE must settle on a treatment for the remainder of the low activity tank waste by 2015 to meet a Tri-Party Agreement deadline and keep high level radioactive waste treatment on schedule.
"If we can't prove it in time, it is not a viable technology," Olinger said.
In the meantime, treatment plans -- what DOE calls its baseline -- will not be changed until DOE is convinced steam reforming is a viable technology, she said. If it proves out, DOE will work with its Hanford regulators on a path forward, she said.
Steam reforming might be in its early stages at Hanford, but it is close to being used at DOE's Idaho site, she said.
But waste treated with steam reforming in Idaho will not be buried in a landfill at Idaho, Dahl said.
Instead, it is expected to be disposed of in a deep geologic repository, unlike Hanford's treated low activity waste. The state also argues that although steam reforming is used commercially, it is not used to produce the ceramic waste form proposed for Hanford.
w Annette Cary: 582-1533; firstname.lastname@example.org