Comparison of Advanced Melting Process for HLW Vitrification, Joule-Heated Ceramic-Lined Melter (JHCM) and Cold-Crucible Induction Melter (CCIM)

Abstract

High level waste (HLW) originating from reprocessing of spent fuel commercial power reactors contains more than 40 different elements. Vitrification into borosilicate glass at 1100 ∼1200°C is the process of choice. It is routinely used to immobilize the radioactive waste constituents in a chemically stable matrix for a final geological disposal. Melting process for commercial HLW glasses are variants of two basic designs. (1) The joule-heated ceramic-lined melter (JHCM) originally developed in the United States in 1973 and used in several nuclear sites in the world. (2) The hot-walled induction melter (HWIM), developed in France starting in 1962 and used in France and UK. These technologies, while effective, do pose limitations in waste form compositions and throughput rates. Particularly HLW originating from commercial spent fuel reprocessing usually contains noble metals elements such as ruthenium (Ru), rhodium (Rh), and palladium (Pd) which require special attention when this waste is vitrified. Recent advances to both of these baseline technologies are beginning to be used with large gains to ensure waste form flexibility, throughputs, and noble metals compatibility. The next generation JHCMs use a steeply sloped bottom and a subsidiary-heating bottom drain to allow these noble metals particles to be effectively flushed from the melter with higher waste loadings. Similar melters are being installed near Guangyuan/Sichuan province, China by German consortium team and being developed for the second K-Facility melter at Rokkasho by Japan Nuclear Fuel Limited (JNFL). As another example the advanced JHCMs will be installed in the Hanford WTP project having large glass pool surface area with rapid bubbling. Significant improvements on induction melters have also been implemented. AREVA recently installed a cold-crucible induction melter (CCIM) in combination with a rotary calciner at La Hague in France. This melter uses radio frequency induction to power the glass melt itself and water cooling of the outer surface maintains a frozen glass shell (skull) as the glass contact material. Because no permanent refractories or embedded electrodes are used, this design allows for high-temperature operation and can tolerate more corrosive melts, and uses a water-cooled, motor-driven mechanical stirrer to comply with noble metals behavior. This paper highlights some of these advances and suggests potential advantages and disadvantages of these next generation melter technologies comparing advanced JHCM with updated CCIM. In conclusion, these melters have made the technologies of choice for new HLW vitrification projects around the world.