Cerium Neodymium Oxide Solid Solution Synthesis as a Potential Analogue for Substoichiometric AmO2 for Radioisotope Power Systems

The European Space Agency (ESA) is sponsoring a research programme on the development of americium oxides for radioisotope generators and heater units. Cubic AmO2-(x/2) with an O/Am ratio between 1.65 and 1.75 is a potentially suitable compound for pellet sintering. C-type (Ia-3) Ce1-xNdxO2-(x/2) oxides with 0.5 < x < 0.7 could be used as a surrogate for some Ia-3 AmO2-(x/2). A new Ce1-xNdxO2-(x/2) production process has been investigated where a nominally selected x value of 0.6 was targeted: Ce and Nd nitrates and oxalic acid were added drop-wise into a vessel, where they continuously reacted to create oxalate precipitates. The effect of temperature (25 C, 60 C) of the reactants (mixed at 250 revolutions per minute) on oxalate particle shape and size were investigated. Oxalates were calcined at 900 C to produce oxide particles. Oxalate particle properties were characterised as these are expected to influence oxides particle properties and fuel pellet sintering.