High density UO2 and high thermal conductivity UO2 composites by spark plasma sintering (SPS)

A system for preparing a nuclear fuel pellet, comprising:

• a homogeneous dispersion of powders, as a nuclear fuel powder, the homogeneous dispersion of powders comprising uranium dioxide (UO2) and a thermally conductive material selected from a metal or metal alloy, where the homogeneous dispersion of powders comprises 90 to 99 vol % of the UO2 and the thermally conductive material has a thermal conductivity that is greater than 10 W/mK at 100° C.;
• a spark plasma sintering (SPS) apparatus;
• a die assembly loaded with the homogeneous dispersion of powders;
• a power supply associated with the SPS apparatus, the power supply configured to apply a pulsed current to the die assembly;
• and
• the SPS apparatus comprising a sintering chamber that receives the die assembly, where the SPS apparatus depressurizes the sintering chamber and increases temperature of the die assembly to a maximum temperature of 850 to 1600° C. as the pulsed current is applied to the die assembly, where the temperature is increased with a rate of increase of at least 50° C./minute after achieving a temperature of 600° C. and maintained at the maximum temperature for a period of 0.5 to 20 minutes while applying a controlled pressure of 25 to 100 MPa to the die assembly to form the nuclear fuel pellet, where the maximum temperature and the controlled pressure are held during the period until a density of more than 95% TD (theoretical density) of the UO2, an average grain size of at least 4 μm absent inter-granular pores, and a thermal conductivity of at least 8 W/mK at 100° C. is attained.