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Abstracts
4) 40165 – THOR® Steam Reforming Technology for the Treatment of Ion Exchange Resins and More Complex
Wastes such as Fuel Reprocessing Wastes
J. Brad Mason, Corey Myers, Studsvik, Inc. (USA)
The THOR fluid bed steam reforming process has been successfully operated for more than 10 years in the USA 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 primarily ion exchange resins but various liquids, sludges and solid
organic wastes have also been treated. The primary advantages of the THOR process include: (a) maximum volume
reduction on the order of 5:1 to 10:1 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.
Over the past five 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 U. S. Department
of Energy (DOE) environmental remediation activities, the THOR dual bed steam reforming process was successfully
demonstrated to process: Idaho National Laboratory (INL) Sodium-Bearing Waste (SBW); Savannah River Tank 48
High Level Waste (HLW); and Hanford Low Activity Waste (LAW) and Hanford Waste Treatment Plant Secondary
Waste (WTP SW) liquid slurry simulants. The THOR process has been demonstrated in pilot plant operations to
successfully process various simulated liquid, radioactive, nitrate-containing wastes into environmentally safe,
leach-resistant solid mineral products. The solid products incorporate normally soluble ions, such as sodium, potassium,
cesium, technetium, and sulfate, chloride and fluoride salts into an alkali alumino-silicate mineral matrix that inhibits the
leaching of those ions into the environment. The solid mineral products produced by the THOR process exhibit durability
and leach resistance characteristics that are 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 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.
5) 40257 – Phase Behavior and Reverse Micelle Formation in Supercritical CO2 with DTAB and F-pentanol for
Decontamination of Radioactive Wastes
Kensuke Kurahashi, Osamu Tomioka, Yoshihiro Meguro, JAEA (Japan)
Decontamination of radioactive wastes is useful for the volume reduction and re-categorization of them. However, a
large amount of secondary wastes are often generated from a wet decontamination using traditional solvents. Therefore,
the development of decontamination method decreasing the secondary wastes is required. Supercritical CO2 (scCO2),
which is gaseous matter at ordinary conditions, has the potential to minimize the amount of solvent wastes. However,
neat scCO2 is not suitable for the separation of polar materials, such as metal compounds, because non-polar scCO2
cannot dissolve them. A reverse micelle is a stable aggregate of amphiphilic surfactants surrounding a water pool in a
non-polar solvent. Polar materials can be dissolved in the water pool and dispersed in the nonpolar solvent. Therefore, the
formation of reverse micelle in scCO2 could increase the availability of scCO2 as a solvent for separation of
radionuclides from radioactive wastes. In the present study, we investigated the reverse micelle formation in scCO2 with
dodeceytrimethylammonium bromide (DTAB) and 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (Fpentanol). After putting a
mixture of DTAB, F-pentanol and water in a high pressure view cell of 54 cm3 at 45 °C, CO2 was introduced into the
cell slowly. When the mixture was dissolved completely in the scCO2, the pressure was measured as the cloud point
pressure (CPP). When 1.08 mmol DTAB were employed, 13.5 mmol H2O could be dissolved in scCO2 with 6.3 vol%
F-pentanol at 20.9 MPa. Formation of reverse micelles was confirmed by dissolving an aqueous solution of methyl
orange into the scCO2 with DTAB and water. The CPP values were determined for various volume of water. The CPP
values increased slowly with an increase of water concentration in the cell less than 0.35 mol/dm3. The increase of water
concentration led the growth of reverse micelle size, and then the CPP value would rise. On the other hand, the CPP did
not simply increase with the water concentration more than 0.35 mol/dm3 and a sharp and concave peak appeared in the
relationship between the CPP value and the water concentration. This suggests that the state of water in the scCO2
changed before and after the water concentration of 0.35 mol/dm3. The water concentration giving the CPP peak
depended on the F-pentanol concentration but was independent of the DTAB concentration. From this fact, it is expected
that the interaction between F-pentanol and water affects the state of water in the scCO2.
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