Microstructural characterization of U-Zr alloy fuel slugs for sodium-cooled fast reactor

In order to investigate a fabrication process of metallic fuel for sodium-cooled fast reactor, U-Zr fuel slugs were fabricated with gravity casting and injection casting. In order to reduce the formation of radioactive wastes, and to have a fine microstructure, spherical powder of U-Zr alloy was also fabricated by centrifugal atomization. The microstructural characteristics were investigated by using electron microscopes and energy-dispersive electron X-ray spectroscope. U-10wt.%Zr fuel slugs had some dispersion phases of Zr precipitates and Zr compounds of about 5 mu m in size. The matrix was composed of fine laminar structure of about 0.15 mu m in thickness. U grains became finer from about 30 mu m in conventionally cast fuel slug to about 2 mu m in atomized powder. Laminar structure became so fine from 0.2 mu m in conventionally cast fuel slug to 0.1 mu m in atomized powder. It is possible for atomized metallic fuel to have a fine microstructure, resulting in a higher fission gas release rate during irradiation. Copyright (C) 2012 John Wiley & Sons, Ltd.