In-Situ Drying for Major Volatility Containment in Melter During Vitrification of Low and Intermediate Level Waste (LILW)

Vitrification technology is emerging as the most competitive solution against Cementation; currently the only conditioning method being employed in Pakistan for low and intermediate level waste immobilization. Vitrification significantly improves the stability and durability of the final waste form and reduces the repository volume requirements. Hence considerable technological and financial benefits are foreseen. Small scale in-active Vitrification experiments have been carried out to verify the feasibilities to opt for Vitrification as immobilizing technique for LILW. To cater for entrainment of radionuclides / waste salts in the off-gas system, a novel In-situ drying procedure is identified to enhance volatility control in the melter. Initially, we have opted pot/in can melter vitrification technique for small scale experimentation due to its easy handling and low throughputs. In-situ drying procedure reduces the volatiles in off gas during subsequent melting operations to meet with the true essence of Vitrification i.e. to fix the activity in the immobilizing matrix. In the first stage, canister is filled with glass frits then at an In-situ drying temperature around 150-2000C, single batch waste volume is fed and dried out. Waste flow rate and In-situ drying temperature are optimized in such a way that the boiling surface in the canister remains below glass frits level. The bed height above boiling surface acts as a packed bed column, thus, provides decontamination for entrained salts present in the off-gas. Series of experiments are planned to verify the feasibility of In-situ drying during Vitrification of LILW. Results obtained will be helpful for major volatility containment in melter and consequently, minimizing secondary waste generation during off gas treatment. (author)