In an effort to increase the thermal conductivity of UO<inf>2</inf> fuel pellets, high density UO<inf>2</inf>-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<inf>2</inf> 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<inf>2</inf>-diamond composite pellets compared to the pure UO<inf>2</inf> fuel pellets.
Chen, Z., Subhash, G., & Tulenko, J. S. (2015). Spark plasma sintering of diamond-reinforced uranium dioxide composite fuel pellets. Nuclear Engineering and Design, 294, 52–59. https://doi.org/10.1016/j.nucengdes.2015.08.021