THOR® Steam Reforming Technology for the Treatment of Ion Exchange Resins and More Complex Wastes Such as Fuel Reprocessing Wastes

The THOR^® fluidized bed steam reforming process has been successfully operated for more than 10 years in the United States for the treatment of low- and intermediate-level radioactive wastes generated by commercial nuclear power plants. The principle waste stream that has been treated is ion exchange resins (IER) and Dry Active Waste (DAW), but various liquids, sludges, and solid organic wastes have also been treated. The principle advantages of the THOR^® process include: (a) high volume reduction on the order of 5:1 to 10:1 for IER and up to 50:1 for high plastic content DAW streams depending on the waste type and waste characteristics, (b) environmentally compliant off-gas emissions, (c) reliable conversion of wastes into mineralized products that are durable and leach-resistant, and (d) no liquid effluents for treatment of most radioactive wastes. Over the past ten years, the THOR^® process has been adapted for the treatment of more complex wastes including historic defense wastes, reprocessing wastes, and other wastes associated with the fuel cycle. As part of the U.S. Department of Energy (DOE) environmental remediation activities, the THOR^® dual bed steam reforming process has successfully processed: (a) Idaho National Laboratory (INL) Sodium-Bearing Waste (SBW), (b) Savannah River Tank 48 High Level Waste (HLW), (c) Hanford Low Activity Waste (LAW), and (d) Hanford Waste Treatment Plant Secondary Waste (WTP-SW) liquid slurry simulants. The THOR^® process has been shown in pilot plant operations to successfully process various simulated liquid, radioactive, nitrate-containing wastes into environmentally safe, leach-resistant, solid mineralized products. These mineralized products incorporate normally soluble ions (e.g. - Na, K, Cs, Tc), sulfates, chloride salts, and fluoride salts into an alkali alumino-silicate mineral matrix that inhibits the leaching of those ions into the environment. The solid mineralized products produced by the THOR^® process exhibit durability and leach resistance characteristics superior to borosilicate waste glasses. As a result of this work, a full-scale THOR^® process facility is currently under construction at the DOE’s Idaho site for the treatment of SBW and a full-scale facility is in the final design stage for the DOE’s Savannah River Site for the treatment of Tank 48 high level waste. Recent work has focused on the development of new monolithic waste formulations, the extension of the THOR^® process to new waste streams, and the development of modular THOR^® processes for niche waste treatment applications. This paper will provide an overview of current THOR^® projects and summarize the processes and outcomes of the regulatory and safety reviews that have been necessary for the THOR^® process to gain acceptance in the USA.