MICROSTRUCTURAL ANALYSIS OF A GLASS DEDICATED TO THE RADIOACTIVE WASTE CONFINEMENT BY RAMAN AND FTIR SPECTROSCOPY

This study deals with the structural changes occurring in a Mo-reach glass dedicated to the confinement of Moreach radioactive waste that contains different contents of Cs2O oxide, ranging from 0.3 to 0.6 wt.%. The glass synthesis was carried out by the double melting method at 1380 degrees C, followed by a stage of 2 h at 600 degrees C. Neodymium was an actinide simulator. The glasses were characterized by their physical and microstructural properties using different spectroscopic techniques. As the experiment shows, the glass geometrical density varies between 1.96 and 2.75 g/cm(3). X-ray diffraction (XRD) analysis shows amorphous features, with traces of crystalline germs, identified as the CaMoO4 powellite phase, which probably formed during glass cooling. Fourier transform infra-red (FTIR) analysis reveals the main chemical bounds in the glasses: Si-O-Si and O-Si-O in SiO4, B-O-B in BO3, and Al-OAl in AlO4. The addition of Cs2O raises the rate of polymerization in the glass network and then decreases the number of no-bridged oxygens (NBO). Raman spectroscopic analysis reveals the absorption bands of MoO42- in CaMoO4. It shows that the Mo environment is altered by the addition of increasing contents of Cs2O in the glass. This is evidenced by the absorption bands shifts at 319, 792, and 844 cm(-1). The absorption band located at 700 cm(-1), ascribed to the elongation of SiO4 and AlO4, is attenuated for 0.4 and 0.6% of the Cs2O content. It shifts to 680-900 cm(-1) due to the glass high Mo content but increases in intensity with the Cs2O content, thus disturbing the alkali positions of Ca and Na, with Cs remaining soluble in the glass. One can conclude that a little rise in the Cs2O content inhibits the phase separation of both Na and Ca molybdates. The glasses analyses do not show particular changes in the lanthanide valences, which are probably in a +III oxidation state. The addition of Cs2O in this kind of glass network remains an issue with respect to the coherence of its microstructure. However, about 0.6 wt.% of Cs2O has been incorporated in the glass network, with no Cs2O phases segregation.