Vitrification of DOE Simulated Radioactive Waste by Induction-Heated Cold-Crucible Melter Technology

Certain waste streams of the US DOE contain radioactive refractory oxides and other components like aluminum zirconium and chromium, which present difficulties during their processing and immobilization. The vitrification of such waste in joule-heated melters at high waste loading is possible only at a temperature exceeding 1150°C. The Khlopin Radium Institute (St.-Petersburg, Russia) jointly with the US Department of Energy has performed a feasibility study on the suitability of the Cold-Crucible Induction Heated Melter (CCIM) technology for the single-stage solidification of a surrogate sludge (C-106/AY-102 HLW Simulant), similar in composition to the High Level Waste (HLW) found at DOE’s Hanford Site (Richland, USA). During the experiments, slurry of simulated sludge and glass formers was metered directly to the CCIM, melted, and the glass product was poured from the melter. The melts were conducted at a mean melt temperature of 1350°C. The experiments produced borosilicate glass wasteforms with a waste oxide loading of 70 weight percent. According to the X-Ray diffraction analysis, the final product had a glass-crystalline structure. The crystalline phase was represented by spinel, (Fe,Mn)Fe₂O₄, uniformly distributed over the wasteform. The chemical durability of the samples was tested by the Product Consistency Test (PCT), and was considered durable according to the DOE specifications for HLW. In the course of the experiments, data were accumulated on the specific electric power consumption and the throughput of the facility.