Neutron Diffraction Study of the in Situ Oxidation of UO2
Résumé
The oxidation of UO2 into U3O8 is described by the accumulation of cuboctahedra into the UO2 lattice. In U4O9, the highly symmetric cuboctahedra are isolated one from the other. In U3O7, they are distorted because of mutual interaction. U3O8 is formed when the topological frustration induced by the disordered cuboctahedra cannot be accommodated by the fluorite structure. The oxidation kinetics and the oxidation mechanism are discussed in connection with this structural description.