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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 µm in size. The matrix was composed of fine laminar structure of about 0.15 µm in thickness. U grains became finer from about 30 µm in conventionally cast fuel slug to about 2 µm in atomized powder. Laminar structure became so fine from 0.2 µm in conventionally cast fuel slug to 0.1 µm 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 © 2012 John Wiley & Sons, Ltd.