Radiolytic degradation of selective actinide extractants from the bis-1,2,4-triazine family in cyclohexanone solutions

Abstract

Early stages of radiolysis of solutions with 2,6-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4]triazin-3-yl)pyridine (CyMe4-BTP) and 6,6′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4-]triazin-3-yl)-[2,2′]bipyridine (CyMe4-BTBP) ligands in cyclohexanone, proposed as a solvent for selective actinide extraction, were studied by means of the pulse radiolysis technique with spectrophotometric detection. Transient UV-vis spectra of excited triplet states of ligands, formed by energy transfer from cyclohexanone excited triplet states to ligands, were recorded for the first time. The influence of typical extraction conditions (the presence of diluted acid and O₂ from air) on the mechanisms of reactions in the system studied was assessed. It was shown that an addition of benzophenone in high concentrations to the system together with its continuous saturation by O₂ could partially protect ligands from radiation damage, caused by the high-energy radiation emitted by the spent nuclear fuel.