Two technologies that heat radioactive waste show promise as an alternative to treating some waste that might otherwise be glassified at the vitrification plant under construction at Hanford, according to CH2M Hill Hanford Group.

The contractor has been studying three ways to dispose of some of the low-activity waste now stored in Hanford's underground tanks.

The two thermal processes -- bulk vitrification and steam reforming -- have some problems that would have to be overcome. But one is likely to be picked for further study in a pilot project.

The third method, cast stone, would allow too much radioactive material to leach into the soil, according to the study conducted for the Department of Energy. Conclusions were reached in part based on complex modeling done on Pacific Northwest National Laboratory's supercomputer.

The worst of the nuclear waste from Hanford's underground tanks will be melted into a glasslike material when the $5.7 billion vitrification plant is completed. But the plant cannot process all the 53 million gallons of waste generated by 50 years of production of plutonium for nuclear weapons by a 2028 deadline.

DOE is interested in using alternative technologies to dispose of 10 million to 26 million gallons of low-activity waste.

But first it must prove to regulators that the product would be as environmentally safe as the glass logs of waste to be produced at the vit plant, or, in the project's catch phrase, "as good as glass."

The third technology studied would bind waste into containers of cast stone that's less porous than marble. But studies showed that water would still leach radioactive technetium, which is easily moved by water, out of the stone.

"The performance was not comparable to glass," said Richard Raymond, director of treatment and disposal at CH2M Hill Hanford Group.

However, CH2M Hill recommended that DOE continue to evaluate the stone casting method to treat waste produced by other treatment methods. When the tank waste is heated to be turned to glass, radioactive iodine tends to convert to a gas and would not be captured in the glass.

The cast stone might prove a good way to dispose of secondary wastes, which would be primarily iodine 129, from glassification processes, according to CH2M Hill.

The next step in the project is asking vendors to propose solutions to the problems found with the two most promising alternative technologies.

Bulk vitrification would used electrodes to melt a combination of soil and tank waste into a large block of shiny black glass within a standard, 20-foot shipping container.

However, tests showed about 0.3 percent of technetium migrated to the insulating layer of sand at the top of the shipping container.

"It's not incorporated in the glass, so it leaches very rapidly," said Billie Mauss, DOE's Office of River Protection manager for supplemental technologies.

Using a different type of insulation, such as a solid ceramic, might solve that problem.

The other technology that shows promise, steam reforming, would use high-pressure steam to turn a mixture of clay and waste into BB-sized particles.

However, CH2M Hill was concerned that hundreds of years from now when no one remembers that the waste is buried at Hanford, underground containers of beads could be disturbed by drilling. Those that end up on the ground could be easily crushed and inhaled.

Using glue or grout to turn the beads into a solid block could solve that problem, Raymond said.

CH2M Hill also is concerned that limited data is available on steam reforming of the type of nuclear waste in Hanford tanks and would like more studies completed.

Bulk vitrification and steam reforming would have similar estimated costs. Bulk vitrification could cost $1.2 billion to $1.3 billion, and steam reforming could cost $900 million to $1.3 billion.

Once contractors provide information on possible solutions to the problems identified, a recommendation is expected to be made on which technology should be tested at a pilot project at the Hanford tank farm. The pilot project could be operating a year from now.

All data will be included in a report delivered to the state by Jan. 30, 2005. The Tri-Party Agreement, which covers Hanford's environmental cleanup, does not address alternative technologies. If the agreement is modified to allow steam reform or bulk vitrification of waste, the process could start in January 2011.