DEVELOPMENT OF SPENT SOLVENT TREATMENT PROCESS BY A SUBMERGED COMBUSTION TECHNIQUE

An experimental study using a bench-scale equipment of 1 kg-simulated spent solvents per hour has been conducted in order to evaluate the ap plicability of a submerged combustion technique to the treatment of sp ent solvents contaminated with TRU elements. This report describes the experimental results on the combustion characteristics of the simulat ed spent solvents of tri-n-butyl phosphate and/or n-dodecane, and on t he distribution behaviors of combustion products such as phosphoric ac id, Ru, I, Zr and lanthanides as TRU simulants in the submerged combus tion process. Also the experimental results of TRU separation from pho sphoric acid solution by co-precipitation using bismuth phosphate are reported. It was shown that the submerged combustion technique was app licable to the treatment of spent solvents including the distillation residues of the solvent. Based on the experimental data, a new treatme nt process of spent solvent was proposed which consisted of submerged combustion, co-precipitation using bismuth phosphate, ceramic membrane filtration, cementation of TRU lean phosphate, and vitrification of T RU rich waste.