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

Abstract

U3Si2-UO2 composite fuel combines the advantages of high uranium density and thermal conductivity of U3Si2 and excellent stability of UO2 under light water reactor (LWR) condition. Since commercialized pressureless sintering of UO2 is usually performed above the melting point of U3Si2, spark plasma sintering (SPS) is considered as a convenient method to produce U3Si2-UO2 composite fuel. However, the potential interaction between U3Si2 and UO2, an important aspect for composite materials, has not been sufficiently investigated. In this report, U3Si2-UO2 pellets with 1:1 wt ratio were fabricated by SPS. Next, the interaction between U3Si2 and UO2 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 U3Si2 and UO2 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).