Raman signatures from age-dating PuO2 since last calcination

Abstract

Abstract The self-irradiation of PuO2 has been shown to affect the attributes of fifteen vibrational bands in the Raman spectrum. The vibrational bands correspond to the Raman allowed vibrational mode T2g, overtones, defects, and bands from electronic origin. Defects in the crystal lattice from low-calcination temperature and alpha decay origins are responsible for the changes in the band attributes (band position, full-width half maximum (FWHM), intensity). Crystal lattice defects are also responsible for the growth of the defect bands. The temporal behavior of the vibrational bands can be used to estimate the age of the material since last calcination. Laser annealing was used to reset the material to full crystallinity prior to the aging study. 240PuO2, with an alpha decay rate of 3.67 greater than the decay rate of 239PuO2, was primarily used to assess the alpha decay-induced damage within 3 years. The aging study focused on the time-dependent properties of the T2g band and the growth of defect bands. The FWHM of the T2g band and the ratio of the areas of the defect bands/T2g band were measured through a time period in excess of 3 years. The data from this study were found very close to the data describing the temporal evolution of the lattice constant measured with the X-ray diffraction (XRD) technique. The local physical properties of the material measured with Raman spectroscopy and the lattice parameter constant measured with XRD indicates a strong correlation between the two techniques. Although both techniques provide similar age-dating information, in contrast to the few milligram quantities required for XRD, Raman spectroscopy requires a 10 µm diameter PuO2 particle to provide an estimate of the material age since last calcination.