Characterisation of 3000 ppm Cr2O3 doped UO2 and its precipitates

The thermochemical state of UO2‐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 UO2. 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 Cr3O4 phase. We aim to use chromium precipitates as in situ oxido‐reduction indicators for the thermochemical characterisation of UO2 nuclear fuel, but a preliminary characterisation of these precipitates was necessary. Raman mapping of a chromium‐doped UO2 enabled the localization of chromium oxide precipitates using principal component analysis. Their Raman spectrum was measured, and its interpretation allowed us to propose that these chromium oxide precipitates would be uranium stabilised Cr3O4.