Investigation of Dialkylamides (DBOA) as a Potential Extractant Agent for Uranium and Plutonium in the CHALMEX Process

The CHALMEX (Grouped ActiNide Extraction) process, derived from the GANEX process, aims to improve upon existing nuclear fuel recycling methods by co-extracting all the actinides in one step. In this study, the use of dibutyl octanamide (DBOA) as an alternative extractant to Tributyl phosphate (TBP) in the CHALMEX process is demonstrated. A solvent extraction system composed of DBOA, FS-13, and CyMe4-BTBP was tested. Promising performance of DBOA in extracting tetravalent Pu(IV) and hexavalent U(VI) was observed. The distribution ratios for Pu(IV) were significantly higher than those achieved with TBP, indicating improved actinide recovery efficiency. Future investigation of this behavior under high loading conditions would provide valuable insights into the applicability of this system for Pu-rich raffinate in the GANEX second cycle. The radiolytic stability of DBOA was investigated up to 300 kGy, and distribution ratios showed dose-dependent changes. However, some challenges remain, notably the slight increase in co-extraction of lanthanides by CyMe4-BTBP compared with the TBP system, as well as the need for further optimization of hydrodynamic properties to ensure efficient phase separation. Despite these issues, the results build upon existing research by showing the strong potential of DBOA to address key limitations of conventional extractants, particularly in the CHALMEX process.