First-principles study of the radiolytic degradation of diglycolamides

Understanding the degradation mechanisms of organic compounds in an extreme radiolysis induced environment is important for designing efficient organic extractants for the separation of radionuclides from used nuclear fuel. In this paper, we present an in-depth computational chemistry-based molecular level analysis of the radiolytic degradation of diglycolamides, with a focus on structural and thermodynamic aspects of the process. The most vulnerable parts of the organic ligands prone to attack and degradation by radicals are identified via electronic density and bond strength analysis. We identified the C-O of the ether group as the weakest bond, which is further weakened by methylation. A plausible degradation path resulting from breaking the C-O bond by H radical attack is obtained by computation of free energy of the process. To investigate realistic reaction conditions, we accounted for the impact of solvation effects on the thermodynamic quantities, including solvation entropy effects. The resulting degradation mechanism is consistent with experimentally observed degradation products.