Abstract

Two kinds of U_3Si powders and U_3Si dispersed nuclear fuel meats have been prepared by conventional comminution process and a newly developed rotating disk atomization process. In contrast to angular shape and broad size distribution of the conventionally processed powder, the atomized powder was spherical and showed narrow size distribution. For the atomized powder, the heat treatment time for the formation of U_3Si by a peritectoid reaction was reduced to about one tenth, thanks to microstructure refinement by rapid cooling of about 5times104 K/s. The extruding pressure of atomized U_3Si powder and Al powder mixture was lower than that of comminuted U_3Si and Al powder mixture. The elongation of the atomization processed fuel meats was much higher than that of the comminution processed fuel meats and remained over 10% up to 80wt.% of U_3Si powder fraction in the fuel meats. It appears therefore that the loading density of U_3Si in fuel meat can be increased by using atomized U_3Si powder. The atomized spherical particles were randomly distributed, while the comminuted particles with angular and longish shape were considerably aligned along the extrusion direction. Along the transverse direction of the extraction the electrical conductivity of the atomization processed fuel meats was appreciably higher than that of comminution processed fuel meats. This tendency became pronounced as U_3Si content increased. Because the thermal conduction which is believed to be proportioned to the electrical conduction in the nuclear fuel meats occurs in radial direction, the atomization processed fuel can be better used in research reactors where high thermal conductivity is required.