Densification mechanism of U3Si2 consolidated by spark plasma sintering

The high uranium density and good thermal conductivity at high temperature render U3Si2 an excellent candidate for accident tolerant fuels (ATF). Spark plasma sintering (SPS) is a convenient method to produce U3Si2 fuel and U3Si2-X fuels. However, the densification mechanism of U3Si2 by SPS has been rarely investigated. In this work, U3Si2 pellets were fabricated by SPS with 2 sets of different sintering parameters (the soak samples and the ramp samples). The grain size of U3Si2 pellets sintered by SPS persisted-25 & mu;m when soaked at 900-1300 degrees C and increased to-35 & mu;m at 1400 degrees C. The morphology of the 900 degrees C soak sample was supposed to be due to spark plasma and plastic deformation. Utilizing the Helle-Granger model, the apparent activation energy (Q) and the stress exponent factor (n) can be determined. The soak samples exported n as 2.88, 3.16, and 3.55 (average 3.20) at 900, 1000, and 1100 degrees C, respectively. The ramp samples exported Q as 355.57, 325.48, 343.04, and 377.04 kJ/mol (average 350.28 kJ/mol) and n as 4.67, 4.22, 4.04, and 3.52 (average 4.11) at 65, 70, 75, and 80%TD, respectively. The n values of the two set of samples were both consistent with the suspected deformation hints in SEM. These results suggest that densification of SPS-sintered U3Si2 occurred via plastic deformation controlled by dislocation motion.

Automated summary

U3Si2 is an excellent candidate for accident tolerant fuels (ATF) due to its high uranium density and good thermal conductivity at high temperature. In this study, U3Si2 pellets were fabricated by spark plasma sintering (SPS) and the densification mechanism of U3Si2 by SPS was investigated. The results showed that the densification of SPS-sintered U3Si2 occurred via plastic deformation controlled by dislocation motion.