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|All Authors / Contributors:||
Eric Mendes; Eric Simoni; Université de Paris-Sud. Faculté des Sciences d'Orsay (Essonne).
|Description:||1 vol., 401 p. : ill. ; 30 cm.|
|Responsibility:||Eric Mendes ; sous la direction de [Eric Simoni].|
A question put within the framework of the nuclear fuel storage worn in geological site is what become to them in the presence of water. The aim of a fundamental program, of PRECCI project (ECA), is to highlight the behaviour of interfaces which can be used as models for the interfaces nuclear spent fuel/water if the fuel is uranium UO2 dioxide. This doctorate is interested in the effect of the alpha activity which is the only one that exist in the spent fuel after long periods. The aim is to identify the mechanisms of alteration and of leaching of surfaces under alpha irradiation. A method is developed to irradiate UO2/H2O interfaces in deaerated conditions with the beam of He2+ produced by a cyclotron. The He2+ ions cross an UO2 disc and emerge in water with an energy of 5 MeV. Leachings under irradiation are carried with a large range of particles flux. The post-irradiation characterization of the surface of the discs realised by micro-Raman spectroscopy allowed to identify the alteration layer. It is made up of studtite UO2(O2),4H2O, and of schoepite UO3,xH2O. The analysis of the solutions shows that the uranium release strongly increases. The electrochemical properties of the interfaces under irradiation strongly differ from those before irradiation. This work allows to propose that the radiolytic species seen by the interface are it during the heterogeneous phase of evolution of the traces and are species of short lives. Modelings show that the radiolytic radicals species can migrate toward the interface and react with the UO2 surface.