Thermal Analysis of the One-Stage Melting Converter and Related Equipment for Vitrification of High-Level Radioactive Wastes

One-stage melting-converter method for the vitrification of high-level radioactive wastes (HLRAW) was developed and investigated. This method includes the concentration (evaporation), calcination, and vitrification of the HLRAW in one-stage process inside a melting converter. Converter consists of a water-cooled conical metal melting chamber. Capacity for the saturated salty solution is 200 l/h and the capacity for the glass-HLRAW mixture is about 100 kg/h. Calculations showed that at a melt temperature of 1150°C, a cooling-water temperature of 20°C and a thickness of the melt lining of 15 mm the heat flux through the walls is about 75 kW/m² and wall temperature is about 55°C. Thermal analysis showed that at the burner heat transfer rate of 460 kW the heat transfer rate for heating and melting of the charge is 20 kW, the heat transfer rate for evaporation of water from the solution is 100 kW, and the heat losses are 240 kW. Therefore, a thermal efficiency of the converter is about 26%. To keep a melt lining on the vault of converter and around a burner nozzle the special design two-phase closed thermosyphons are used. Design and heat transfer characteristics of these thermosyphons are discussed. Calculations have been made for heat removal of the melted glass and fissionable nuclides poured into the metal containers during first 500 hours.