Actinide Partitioning with a Modified TODGA Solvent: Counter-Current Extraction Studies with Simulated High Level Waste

Abstract

Actinide partitioning studies with improved N,N,N',N'-tetraoctyl diglycolamide (TODGA) solvent (0.05 M TODGA + 5% iso-decanol in n-dodecane) has been explored in order to achieve better decontamination from fission products. The distribution behavior of various metal ions, viz. Am, Pu, U, Eu, Sr, Pd, Cs, Tc, Fe, and Mo with improved TODGA solvent was investigated. Lower concentration of TODGA (0.05 M as compared to previously proposed 0.1 M or 0.2 M) exhibited required extraction properties for actinide partitioning from pressurized heavy water reactor high level waste (PHWR-HLW). Counter-current extraction studies with simulated PHWR-HLW spiked with different radio-tracers (viz. 241Am, 152Eu, 137Cs, 85,89Sr, 59Fe, 106Ru, 109Pd, 95Zr, and 99Mo) suggested that > 99.9% of the trivalent actinides and lanthanides could be extracted in six stages and stripped in four stages. The decontamination factor for various fission products with respect to Am was: 3918 (Cs), 2990 (Sr), 1150 (Zr), 1407 (Ru), 1185 (Pd), and 3250 (Mo). The counter-current extraction studies with the irradiated solvent (500 kGy) reflected a significant amount of Mo extraction.