Abstract
Actinide oxalate decomposition under hot compressed water is proposed as a milder production route for nanometric sized (mixed) actinide oxides.
Highlights
Oxalate precipitation is a versatile process often applied in the nuclear fuel cycle for different purposes
The particle sizes were calculated from the X-ray diffraction (XRD) data based on the full width at half maximum of at least six selected peaks in the 2θ range between 25 and 100°
The temperature of the particle formation increases from Pu to Th, i.e. (i) ThO2 NCs can only be obtained at reaction temperatures of 250 °C; (ii) UO2 NCs are nicely formed at temperatures above 150 °C; (iii) for the formation of the NpO2 NCs, a temperature of 160–200 °C was applied; and (iv) the PuO2 NCs are already formed at 95 °C after several days
Summary
Oxalate precipitation is a versatile process often applied in the nuclear fuel cycle for different purposes (e.g. isotopic separation and preconcentration,[1] quantitative recovery of actinide ions from waste solutions,[2] fuel production,[3] spent fuel treatment and reprocessing,[4,5] etc.). By precipitation with oxalic acid, the actinides form micrometre-sized hydrated oxalates, independent of the oxidation state of the actinide Such oxalates can be converted to their corresponding oxides and gaseous products by thermal treatment, and the final products are free of impurities except eventually some residual carbon.[6] Since the decomposition temperature is usually mild (500–800 °C), the final oxide is normally nanosized.[7,8] the final powder consists of plate-like agglomerates, as a consequence of the pseudomorphic oxalate-to-oxide conversion.
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