Speaker
Description
Advanced partitioning strategies are essential to enable sustainable closed nuclear fuel cycles and reduce the long-term radiotoxicity of spent nuclear fuel. Among these strategies, the AmSel process targets the separation of americium and curium. This represents a key step for advanced management strategies, as curium exhibits high neutron emission and decay heat, imposing stringent safety measures, while americium dominates long-term radiotoxicity in high-level waste. Despite their different behaviors, chemical similarity in the trivalent oxidation state makes their separation highly challenging [1].
Hydrometallurgical approaches exploit reverse selectivity: TODGA in the organic phase extracts lanthanides and curium, while americium is retained in the aqueous phase through a selective hydrophilic ligand. To address industrial and environmental constraints, CHON-compliant extractants are of particular interest. CHON ligands reduce secondary waste generation and allow solvent destruction by incineration. Moreover, advanced partitioning processes are carried out under high radiation fields, where radiolytic solvent degradation can strongly influence extraction efficiency and long-term process reliability. Previous AmSel studies mainly relied on sulfonated BTBP extractants, which, although providing good selectivity, showed limited compliance with CHON requirements and limited long-term stability [2].
In this work, bis-triazolyl phenanthroline-based ligands with bis-ethoxy (BTzphen) side chains are investigated. The role of the bis-ethoxy chains is examined to test their effect on extraction selectivity and radiolytic stability, while preserving the typical selectivity of nitrogen-donor phenanthroline systems.
To evaluate their suitability for application in the AmSel process, distribution ratios and separation factors were determined through batch solvent extraction experiments by varying ligand concentration, nitric acid molarity, and competing ions, using an organic phase based on TODGA diluted in a kerosene-octanol mixture. Preliminary extraction results show Am/Cm separation factors in the range of approximately 2.4-3.1 under optimized conditions.
The radiolytic stability of the ligand is evaluated through gamma irradiation experiments performed at absorbed doses from 10 to 100 kGy, representative of advanced reprocessing conditions. Degradation pathways are investigated using HPLC-MS analysis to identify radiolysis products and degradation mechanisms, while Raman spectroscopy is envisioned to monitor structural modifications of the ligands after irradiation.
The obtained results show that Am/Cm separation can be improved by the presence of this molecule, even when realistic lanthanide concentrations are introduced into the feed solution, indicating a potential for further optimization under process-relevant conditions.
This is work is funded by the European Union through the EURATOM research and training programme, project TRANSPARANT (Technological Research Action Necessary for Safe PARrtitioningand Nuclear Transmutation), Grant Agreement: 101166386.