Effect of residual carbon on the sintering behavior of MOX pellets

From uranium(IV) oxalate to sintered UO 2 : Consequences of the powders' thermal history on the microstructure

“…On the one hand, several authors reported the presence of carbonated or oxocarbonated species when converting actinide oxalates under inert or reducing atmospheres [20]. Such compounds could still exist in some of the samples fired at the lowest temperatures (typically below 600 • C), and are expected to delay and/or hinder the sintering processes [39]. However, the residual carbon content is more likely to be present in an amorphous state as the formation of defined oxycarbide species could be excluded considering the carbon amount in the samples (typically less than 10 wt.%) [40].…”

Direct sintering of UO2+x oxides prepared under hydrothermal conditions

“…This morphological feature can limit the powder flowability when shaping pellets for ceramic fabrication, and then induce some mechanical defects after sintering. Also, oxide based powders coming from oxalate precursors generally incorporate residual traces of carbon, typically from around 100 ppm when calcined under air [13] up to several thousands of ppm for thermal conversion performed under inert or reducing atmosphere [12], which have been associated to dedensification processes [14], [15].…”

Hydrothermal Conversion of Thorium Oxalate into ThO2·nH2O Oxide

“…%) coming from the decomposition of the organic fraction during the calcination step. It can even exceed the required levels for fuel fabrication (around 100 ppm) , and impact the sintering process. Also, powders frequently inherit the initial platelet morphology of the initial precursor, which could hamper the flowability of the powder during shaping process leading to green fuel pellets.…”