Irradiation Effects on a Calixarene Based Picolinamide Ligand Used in The Partitioning of Minor Actinides

A study of the radiolysis effects on different solutions containing the ligand Hexakis(3-N- picolinamidepropyloxy)calix[6]arene, which is investigated in the frame of the partitioning of minor actinides from spent nuclear fuel, has been performed. The research work exploits the joint use of three different experimental techniques, namely, Solvent Extraction, Electrospray Ionization Mass Spectrometry (ESI-MS), and Electron Paramagnetic Resonance (EPR) spectrometry, in order to investigate the degradation pathway of the aforementioned solutions, irradiated with a 60Co source able to provide a dose rate of about 0.58 kGy/h. In particular, solvent extraction experiments showed that the irradiation at suitable dose of the organic solutions here studied can modify the capability of the calixarene ligand to promote transport of Am3+ and Eu3+ ions from a weakly acidic aqueous phase to the organic phase containing the ligand itself. On the other hand, ESI-MS(-MS) measurements showed that the detection of the stable chemical species formed during the irradiation is possible. However, the results delivered need to be further investigated. In particular, the concern is focused on the detection of the oxidized species derived from the calixarene ligand. Finally, the alcoxynitrossidic radical detected by EPR spectrometry of the irradiated solutions of the calixarene ligand in NPHE (o-Nitrophenyl Hexyl Ether) seems to support the hypothesis that oxidation reactions on the ligand take place