The utilisation of molten glass coating for the safe, efficient densification of loose simulant radioactive ashes has been investigated. As part of the h2020 PREDIS project, our work focused on the pre-disposal thermal treatment of organic material, we have investigated several glass formulations to maximize the waste load incorporation inside the glassy matrix. Short term lixiviation tests have been performed to assess the performances of such matrices.
The ashes arise from processing organic materials surrogates (simulating materials contaminated by α-emitting actinides) within the IRIS process (Installation for Research on Incineration of Solids) in CEA Marcoule France. It is a multi-step process able to treat high chloride containing wastes via a combined pyrolysis and calcination process. Simulant inactive ashes arising from the IRIS process are comprised of a calcium-zinc aluminosilicate rich material, with a very low level of residual carbon – making these ashes ideal candidates for HIP (Hot Isostatic Pressing) processing.
Molten glass coating trials were undertaken by mixing IRIS ashes into glass powder at low melting temperatures, resulting in a 30 to 40 % waste loading. Post-processing characterisation revealed the formation of a polycrystalline material. These trials have demonstrated the suitability of molten glass process towards the processing of such ash materials, resulting in a solidified product. Though forming a solid product, substantial porosity remains within the final product, creating potential for wasteform improvements. Further wasteform optimisation is ongoing to investigate the impact of the glass composition, along with studies into the long-term aqueous durability of these materials.