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

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.