Uranium dioxide - Molybdenum composite fuel pellets with enhanced thermal conductivity manufactured via spark plasma sintering

Highlights: • Successful manufacture of UO₂–Mo composites using spark plasma sintering. • Thermal conductivity improvements achieved with modest Mo inclusions. • Development of dis-continuous Mo channels throughout UO₂ microstructure. • High density composite fuel manufactured with short process times. - Abstract: Fuel for nuclear reactors with an increased thermal conductivity offers the potential for lower fuel operating temperatures and reduced fission gas release rates. Uranium dioxide (UO₂) based composites could provide a method of achieving a higher thermal conductivity and molybdenum (Mo) has been identified as a potential candidate for use in such composites. Uranium dioxide composites containing Mo were manufactured via spark plasma sintering with concentrations of up to 10 vol% Mo. The composites were characterised on their microstructural properties and the thermal conductivity was determined by laser flash analysis. The composites achieved densities greater than 95 %TD but lower than typical grain size. The microstructure contained channel like structures of Mo, due to the use of an agglomerated UO₂ precursor powder. An increased thermal conductivity, proportional to the concentration of Mo, was determined for the composites. At the maximum measurement temperature of 800 ^∘ C the increase was found to be 65% and 117% in the 5 and 10 vol% composites respectively.