Spark plasma sintering of diamond-reinforced uranium dioxide composite fuel pellets.

In an effort to increase the thermal conductivity of UO 2 fuel pellets, high density UO 2 –5 vol% diamond composite pellets were fabricated using the spark plasma sintering (SPS) technique. Diamond particles with nano-size (0.25 μm) and several micro-sizes (3 μm, 12 μm and 25 μm) were mixed with UO 2 powder and sintered using SPS at 1300–1600 °C with a hold time of 5 min. The resultant density, chemical reaction, microstructure, thermal conductivity and Young's modulus of the sintered pellets were investigated. The pellets with 3 μm diamond particles had a uniform distribution of particles as well as better thermal and mechanical properties compared to others. An increase in thermal conductivity of up to 41.6%, 38.3% and 34.2% at 100 °C, 500 °C and 900 °C, respectively, was measured in the UO 2 –diamond composite pellets compared to the pure UO 2 fuel pellets. [ABSTRACT FROM AUTHOR]