Interface reaction of U3Si2-UO2 composite pellets during spark plasma sintering

U 3 Si 2 -UO 2 composite fuel combines the advantages of high uranium density and thermal conductivity of U 3 Si 2 and excellent stability of UO 2 under light water reactor (LWR) condition. Since commercialized pressureless sintering of UO 2 is usually performed above the melting point of U 3 Si 2 , spark plasma sintering (SPS) is considered as a convenient method to produce U 3 Si 2 -UO 2 composite fuel. However, the potential interaction between U 3 Si 2 and UO 2 , an important aspect for composite materials, has not been sufficiently investigated. In this report, U 3 Si 2 -UO 2 pellets with 1:1 wt ratio were fabricated by SPS. Next, the interaction between U 3 Si 2 and UO 2 during the sintering process was examined with X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that U 3 Si 2 and UO 2 reacted to yield USi as the main product. The reaction occurred at a relatively low temperature of 1100 °C, at which the composite fuel was less than 90% theoretical density (TD).