EXTRACTION AND EXTRACTION CHROMATOGRAPHIC-SEPARATION OF MINOR ACTINIDES FROM SULFATE BEARING HIGH-LEVEL WASTE SOLUTIONS USING CMPO

Bench-Scale studies on the partitioning and recovery of minor actinides from the actual and synthetic sulphate-bearing high level waste (SBHLW) solutions have been carried out by giving two contacts with 30% TBP to deplete uranium content followed by four contacts with 0.2M CMPO + 1.2M TBP in dodecane. The acidity of the SBHLW solutions was about 0.3M. In the case of actual SSHLW, the final raffinate contained about 0.4% alpha-activity originally present in the HLW whereas with synthetic SBHLW the or-activity was reduced to the background level, Ce-144 is extracted almost quantitative in the CMPO phase, Ru-106 about 12% and Cs-137 is practically not extracted at all. The extraction chromatographic column studies with synthetic SBHLW (after two TBP contacts) has shown that large volume of waste solutions could be passed through the column without break-through of actinide metal ions. Using 0.04M HNO3 > 99% Am(III) and rare earths could be eluted/stripped. Similarly > 99% Pu(IV) and U(VI) could be eluted/stripped using 0.01M oxalic acid and 0.25M sodium carbonate, respectively, In the presence of 0.16M SO42- (in the SBHLW) the complex ions AmSO4+. UO2SO4, PuSO42+ and Pu(SO4)(2) were formed in the aqueous phase but the species extracted into the organic phase (CMPO+TBP) were only the nitrate complexes Am(NO3)(3) . 3CMPO, UO2(NO3)(2) . 2CMPO and Pu(NO3)(4) . 2CMPO. A scheme for the recovery of minor actinides from SBHLW solution with two contacts of 30% TBP followed by either solvent extraction or extraction chromatographic techniques has been proposed.