CHALLENGES IN RETROFITTING OF CERAMIC MELTER IN PLACE OF LIQUID FED METALLIC MELTER

摘要

A modified pot glass process using induction heated liquid-fed metallic melter is adopted in India for vitrification of high-level radioactive wastes.Although all the operational vitrification plants are using this technology presently,it is recognized that induction of ceramic melters in place of metallic melters would be advantageous.The liquid fed metallic melter has limitations with respect to processing throughput and also calls for frequent remote replacement of the process pot.This replacement puts a heavy demand on the operations and is also not cost effective.Adoption of liquid fed ceramic melters in place of metallic melters calls for their retrofitting in the vitrification cell initially designed for metallic melter.This retrofitting is being carried out in one of the operating vitrification plants. rnConsiderations had to be given right from design to decommissioning of the ceramic melter, which had to be made compact without sacrificing the enhanced throughput.This involved critical analysis and design of the main electrodes with respect to their geometry and configuration.The options of slurry and frit feeding both had to be carefully designed keeping in view of the limited cell height.Side pouring of the molten glass from the melter could not be considered because of the constricted cell geometry and thus redundancy had to be provided by incorporating an additional bottom drain as stand by.In view of the compactness cylindrical geometry of the melter as against rectangular geometry was also considered. rnThe compactness of the melter was also dictated from decommissioning considerations.In view of the space constraints in the existing cell,it is necessary to lift the entire melter unit through the cell top and decommission it in a shielded environment,elsewhere.This called for limiting the entire weight of the melter including refractories within 10 tonnes and this was dictated by the availability of the material handling system in the existing cell. rnExisting waste management facilities are co-located with the reprocessing facilities at various reactor sites in India and as such do not call for vitrification plants with very high processing capacities.On successful operation of this ceramic melter,replacement of existing metallic melters with ceramic melters will be carried out in a phased manner. rnWM’04 Conference,February 29–March 4,2004,Tucson,AZ