Competitive processes of tributyl phosphate degradation in HNO3-saturated solution in Isopar-M during radiolysis and aging

Highlights: • Hydrolysis is inferior to radiolysis in the efficiency of TBP degradation. • Post-radiation aging promotes the formation of nitroesters at low pH. • Isopar-M protects TBP without increasing the explosiveness of its mixtures. • The chemical and physical protection of TBP increases with the absorbed dose. Radiolytic (8 MeV electron beam, 0.1–2 MGy dose) and post-radiation (3-years aging) transformations in tri-n-butyl phosphate/Isopar-M radiochemical extraction medium saturated with 3.4 M nitric acid are described. The products of nitration, nitroxylation, hydroxylation, dealkylation, carbonylation, carboxylation, and radical dimerization have been identified, and the mechanism of their formation and post-radiation redistribution has been analyzed. The competition between the processes caused by radiolysis, acid hydrolysis, nitration and nitroxylation is discussed. The results indicate an increase in the effect of chemical and physical protection of tri-n-butyl phosphate with an increase in the absorbed dose.