Characterization of Nuclear Materials in Extreme Conditions: Raman Spectroscopy Approach

A review is given of our last advances on Raman spectroscopy characterization of irradiated and/or leached UO₂, PuO₂ and (U,Pu)O₂ samples. For this purpose, three original Raman setups dedicated to the study of nuclear materials were involved. In every case, irradiation-induced Raman defect bands in the 500 - 750 cm^-1 range was observed. For UO₂, an annealing temperature experiment suggests that these defect bands could be the signatures of medium-range structured defects. Besides, the leaching experiments show different behavior between the irradiated in situ probed UO₂ ceramic and post mortem probed [UO₂ + (U,Pu)O₂] sample: The growth of an altered layer made of studtite and schoepite phases was monitored at the surface of UO₂ ceramic, while post-mortem studies reveal the presence of U₃O₈ and studtite phases at the surface of the UO₂ grains of the binary sample. No alteration layer was observed at the surface of the leached (U,Pu)O₂ grains.