Characterization of nuclear materials in extreme conditions: The raman spectroscopy approach

In this article, we review our last advances on the Raman spectroscopy characterization of irradiated and/or leached UO₂, PuO₂ and (U,Pu)O₂ samples. For this, three original Raman setups dedicated to the study of nuclear materials were involved. In all cases, irradiation was observed inducing the appearance of Raman defect bands in the 500-750 cm^-1 range. For UO₂, annealing temperature experiment suggests that these defect bands may be the signatures of a medium range structured defect. Besides, the leaching experiments show different behavior between the in situ probed UO₂ ceramic and post mortem probed [UO₂ + (U,Pu)O₂] sample: In the first case we observed the growth of an altered layer made of studtite and schoepite phases. In the second we observed, in one hand the creation of U₃O₈ and studtite phases at the surface of the UO₂ grains, in second hand no Raman signatures of any layer at the surface of the (U,Pu)O₂ grains.