U₃Si₂ is regarded as one of the most promising accident-tolerant nuclear fuels for light water reactors and is expected to replace the UO₂ nuclear fuel in the future. Currently, spark plasma sintering (SPS) is an advanced technique for preparing U₃Si₂ pellets; however, the influence of SPS parameters on the performance of the pellets is unclear.

This study aims to investigate the effects of different sintering parameters (temperature and pressure) on the mechanical and thermal properties of the U₃Si₂ pellets prepared using SPS technology.

The thermal diffusivity of U₃Si₂ pellets was measured using a laser flash apparatus, and the thermal conductivity of the pellets was calculated. The mechanical properties of the pellets, including hardness, Young's modulus, and fracture toughness, were measured using nanoindenter. Thereafter, the influence of different sintering temperatures in the range of 1 000~1 300 ℃ and pressures in the range of 30~90 MPa on the mechanical and thermal properties of U₃Si₂ pellets were carefully examined.

The measurement results show that the thermal conductivity of the as-synthesized pellets increases linearly with temperature in the range 27~700 ℃. Moreover, increasing the sintering temperature and pressure improves the thermal conductivity of the U₃Si₂ pellets. The hardness and Young's modulus of the pellets increase with an increase in sintering temperature. They also exhibit a trend of first increasing and then stabilizing with increasing pressure, and tend to fully stabilize at 60 MPa. Moreover, the fracture toughness of the pellets decreases with the increase of sintering temperature and increases with increasing pressure.

Based on the above results, optimized SPS parameters for the U₃Si₂ pellets are proposed, and this study provides a reference for the preparation of high-performance U₃Si₂ pellets.