Characterisation of 3000 ppm Cr₂O₃ doped UO₂ and its precipitates

Abstract

The thermochemical state of UO 2 -based nuclear fuel is a key parameter for which experimental data are difficult to obtain. A new experimental procedure using in situ oxido-reduction indicators was applied to irradiated fuel, and we aim to use it with chromium-doped unirradiated UO 2 . Nevertheless, we had first to characterise the chemical state of the chromium precipitates in our sample before. Here, we present the method we used for statistical characterisation of these precipitates using several methods, amongst which Raman spectroscopy plays a major role. Moreover, the Raman spectra of the precipitates were interpreted as evidence of a uranium stabilised Cr 3 O 4 phase.

Deconvoluting Cr states in Cr-doped UO2 nuclear fuels via bulk and single crystal spectroscopic studies

“…Recent high resolution transmission electron microscopy analysis of Cr-doped UO 2 has further identified the significant enrichment of Cr and structural disorder found in precipitate grain boundary regions 46 . Further recent studies by Devillaire et al 47 found evidence for Cr 3 O 4 in these precipitates via Raman spectroscopy, which would involve Cr +2 . It has also been proposed the possibility of Cr +2 occurring within the UO 2 lattice matrix itself with some redox mechanisms between it and Cr +3 which should be observable at ambient conditions.…”