Separation of Minor Actinides and Rare Earths from a Simulated High Activity Liquid Waste by Two Macroporous Silica‐based Polymeric Composites

Abstract

To eliminate the long‐lived minor actinide (MA) elements from high activity liquid waste (HLW), a group partitioning from a simulated HLW solution containing 14 typical elements and 3.0 M HNO3 was performed. It was done by utilizing two macroporous silica‐based polymeric N,N,N′,N′‐tetraoctyl‐3‐oxapentane‐1,5‐diamide (TODGA) and octyl(phenyl)‐N,N‐diisobutylcarbamoylmethylphosphine oxide (CMPO) composites (TODGA/SiO2‐P and CMPO/SiO2‐P). It was found that in the first column packed with TODGA/SiO2‐P, the tested elements were separated to (1) Cs, Ru, and Mo (non‐sorption group), (2) minor actinides (MAs), rare earths (REs), Sr, and Pd (MA‐RE‐Sr‐Pd group), and (3) Zr, respectively, by eluting with 3.0 M HNO3, 0.01 M HNO3, 0.05 M DTPA‐pH 3.75, and 0.5 M H2C2O4 at 298 K. MA were considered to flow into MA‐RE‐Sr‐Pd group along with Gd and Dy because of their similar sorption and elution behavior towards TODGA/SiO2‐P. In the second column packed with CMPO/SiO2‐P, the MA‐containing effluent was separated to (1) Sr‐Pd group and (2) MA‐RE group, respectively by eluting with 3.0 M HNO3 and water at 323 K. MA was believed to flow into MA‐RE group. Based on the results obtained, a process entitled GPEC (Group Partitioning of HLW by Extraction Chromatography) for effective partitioning of minor actinides and rare earths from HLW utilizing two macroporous silica‐based polymeric composites was proposed.