Characterization of U-Nb-Zr dispersion fuel prepared by centrifugal atomization process

The characterization of atomized U-5 wt% Nb-3 wt% Zr and U-9 wt% Nb-3 wt% Zr dispersion fuel has been carried out in order to increase the applicability of atomization technology. The atomized powders showed a generally spherical shape with smooth surface, irrespective of alloy composition. The heat treatment results revealed that the 9 wt% Nb alloy powder had relatively higher g -phase stability than the 5 wt% Nb alloy powder. A lamella structure consisting of an a -U phase and g -phase mainly observed at the grain boundaries with heat treatment. However, further annealing of the 5 wt% Nb powder at 500 deg. C showed that fine lamella morphology was formed completely throughout the whole matrix, whereas in the 9 wt% Nb powders, a metastable g-Phase was still retained in the grain. The 5 wt% Nb fuel meat exhibited a slightly larger volume expansion than the 9 wt% Nb specimen at any temperature. The reaction product of (U,Nb,Zr)Al3, was generally formed at the particle surface, with a kernel-like shape by the unreacted g-Phase islands left. On the other hand, phase decomposition to an a -U from a metastable g phase occurred simultaneously at the grain boundaries in the unreacted fuel core, at which the aluminum could diffuse with an increased rate; consequently the U-Nb-Zr alloys exhibited an enhanced swelling rate. (author)