Microwave Vitrification of Radioactive Wastes

Abstract

There are indisputable advantages to using microwave radiation in technological processes for reprocessing liquid wastes, and they have been partially or completely realized in the apparatus developed. Testing of the apparatus has confirmed that it holds great promise for liquifying radioactive wastes with a complicated composition in a large range of the salt concentration in the initial solution.Microwave melting is a promising method for reprocessing almost all types of wastes except metallic wastes. The fundamental difference between microwave melting and other types of melting is that the microwave source can be placed in a safe service zone. Only individual parts of the melter structure, which are made of corrosion-resistant materials, are in contact with the material being processed. These parts are made so as to allow for decontamination and, as necessary, disassembly. During microwave heating, a one-time-use metal crucible-container which is used to store the wastes to be reprocessed can be used.The main advantage of microwave heating combined with a crucible-container is that only the stationary cover and crucible-container are placed in a hot chamber or canyon. This method will permit doing the following:• simplify the reprocessing of radioactive wastes, since all stages of the process from water evaporation to the formation of the glass mass can be performed in the same crucible-container, which is then buried; • eliminate from the technological process the stage of repouring of the fused glass mass; • choosing efficiently the scheme and regimes for feeding the wastes into the crucible-container; and • improve the ecological conditions. A different composition of the glass matrix can be used at the vitrification stage. Depending on the nature of the physicochemical state of the materials being processed, the process can be conducted in a wide temperature range. The final product can be obtained in the form of a glass block with the required chemical stability. Preliminary work [1, 2] on the vitrification of some forms of liquid and pulp wastes from radiochemical operations on a microwave setup with a 5-kW generator at 2375 MHz has confirmed that such wastes can in principle be processed in an approximately 20-liter metal crucible-container.The purpose of the present work is to check the solidification of liquid radioactive wastes with complicated chemical composition and different concentration in a single-stage technological process in replaceable one-time-use crucible-con-

Using Vitrification for Sewage Sludge Combustion Ash Disposal

“…Melting methods Description References 1 Melting in a crucible furnace A cyclical process waste mixed with fine glass is melted in a crucible that also serves as a tank for the vitreous phase [56] 2 Melting in an induction furnace A continuous process waste mixed with fine glass is melted by induction in steel containers limited durability of the furnace due to corrosion of the tank [68] 3 Resistance melting by Joule A continuous process waste and fine glass are melted in a ceramic crucible using an electric current of high intensity the liquid phase collects on the walls of the crucible, and then is discharged to a separate tank [62] 4 Induction melting in a crucible A continuous process used a water-cooled induction furnace the liquid phase collects on the walls of the ceramic crucible replacing the steel crucible ceramic refractory materials significantly extends the life of the induction furnace [60] 5 Plasma melting The use of very high temperatures disadvantage is the limited lifetime of the plasma-generating torch used in the United States to vitrify contaminated soils [65] 6 Microwave melting A cyclical process melting and collecting the liquid phase takes place in the same container the method is energy-saving as a microwave furnace is small and can be installed at the waste location [69] 7 Volume melting A cyclical process it is used in a large steel vessel lined with refractory material, in which the melting process occurs along with the collection of the liquid phase [70] 8 Induction electrodeless melting Alternative method single melting system in the basic convertor furnace [71] applications in car body structures. Glass microspheres have major advantages in comparison with conventional fillers such as composites of polypropylene and polyamide, including improved resistance to scratches and abrasion.…”

Calcination and vitrification processes for conditioning of radioactive wastes

“…The bench-scale MW equipment was developed to perform vitrifi cation of simulated waste from NPP with VVER reactor in the form of sodium borophosphate glass (Komarov et al, 2005). The main parameters of the equipment used are given in Table 5.4.…”