Résumé
Research about the oxidative dissolution of nuclear fuels under storage as a result of the generation of highly reactive species from radiolysis (H2O2 , HO• , HO2• etc.) has been a subject of considerable interest in recent years. Hydrogen peroxide (H2O2 ) can particularly contribute in the corrosion of UO2-based matrices and promote the dissolution and release of radionuclides in the surroundings through the formation of uranyl peroxide precipitates. In this work we propose an original approach to investigate the behaviour of UO2 materials in the presence of H2O2 . With some analogies with radiolysis, sonochemistry allows the generation of radicals and hydrogen peroxide in aqueous solution under mild conditions. Well-known additional physical effects occurring during sonochemical treatment of solids (erosion, mass transfer, fragmentation...) may contribute in the observation of interesting additional effects on actinide-based materials. After the preparation and thorough characterization of UO2 platelets by the oxalic route, their partial or complete conversion into (meta-)studtite [(UO2(O2)(H2O)2)-xH2O] was observed in pure water and dilute acidic media sonicated under oxygenated atmosphere. Investigations on solid residues revealed the formation of (meta-)studtite structures on the surface of the UO2 platelets with a preservation of the initial morphology suggesting a complex formation mechanism. Interestingly, platelets were further provided with a central void which will be also discussed during the presentation