The CHALMEX process, adapted specifically from the second cycle of the GANEX (Grouped ActiNide Extraction) process, aims to streamline nuclear fuel recycling by simultaneously extracting all actinides in a single, efficient step. Traditional processes frequently utilize tributyl phosphate (TBP) as an extractant, which encounters limitations such as extractant degradation and undesirable co-extraction of fission products, consequently reducing recycling efficiency and increasing secondary waste.
This study explores the potential of Di-Butyl Octenyl Amide (DBOA), an N,N-dialkylamides extractant compliant with the CHON (carbon, hydrogen, oxygen, nitrogen) principle, as a replacement for TBP. DBOA was selected due to its expected stability, selectivity, and reduced secondary waste generation, aiming to significantly enhance actinide extraction efficiency in the CHALMEX framework.
The solvent extraction system utilized in this research included a diluent combined with two extractants—DBOA and CyMe4-BTBP—pre-equilibrated with 3–4 M nitric acid. Additionally, two masking agents, Bimet and Mannitol, were chosen due to their proven capabilities in selectively reducing co-extraction of specific fission products. The aqueous phase simulated spent nuclear fuel, incorporating realistic concentrations of lanthanides, transition metals (D elements), and trace levels of uranium (U), neptunium (Np), americium (Am), curium (Cm) and plutonium (Pu).
Laboratory-scale solvent extraction experiments were conducted using equal 500 µL volumes for each phase. Results demonstrated superior performance of DBOA, particularly in extracting tetravalent plutonium (Pu(IV)) and hexavalent uranium (U(VI)). Notably, the distribution ratios for Pu(IV) with DBOA were substantially higher than those observed with TBP, indicating significant enhancement in actinide recovery efficiency.
Following extraction, a scrubbing stage utilizing 0.5 M nitric acid and a stripping stage employing 0.5 M glycolic acid at pH 4 were integrated into the process flow sheet. These stages were crucial for improving the purity of the actinide-rich product, decreasing secondary waste, and enhancing overall sustainability.
Comprehensive analytical assessments were conducted using alpha spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), and high-purity germanium (HPGe) gamma spectrometry. These techniques confirmed the effectiveness of the extraction and purification stages, ensuring accurate characterization of the final product composition.
The outcomes of this research underscore DBOA’s effectiveness as a robust and superior alternative to traditional extractants like TBP, especially within the complex second raffinate cycle of the CHALMEX process. Enhanced actinide- separation efficiency, coupled with significantly reduced secondary waste production.
In conclusion, this study investigate DBOA as a more sustainable and optimal extractant for improving nuclear fuel recycling practices, contributing meaningfully to sustainable and efficient nuclear fuel cycle management.