Mössbauer study and structural characterization of UO2-Gd2O3 sintered compounds

Abstract Samples of UO 2 and up to 10 wt% of Gd 2 O 3 were prepared by solid-state reaction under a reducing atmosphere, in a thermal path comprising ramps and dwell times in the temperature range of 900–1750 °C. The sintered material was analyzed by X-ray diffraction and 155 Gd Mossbauer spectroscopy. The results showed that for samples annealed up to 900 °C, the gadolinium sesquioxide remained unreacted. However, when the temperature was increased to 1300 °C, a solid-state reaction took place forming mixed oxides. For the more severe sintering condition, at 1750 °C, gadolinia left urania partially unreacted producing a material consisting of two compositions, UO 2 (with no dissolved gadolinium) and (U, Gd)O 2 . The proposed heating cycle provided pellets free from Gd 2 O 3 phase and may be used by the nuclear fuel industry as a suitable sintering process.