Phase Stability Studies of Unirradiated Al-U-10wt.%Mo Fuel at Elevated Temperature

The phase stability of atomized U-10wt. ％Mo powder and the thermal compatibility of dispersed fuel meats at 40$0^{\circ}C$ and 50$0^{\circ}C$ have been characterized. Atomized U-10Mo powder has a good \ulcorner-U phase stability, and excellent thermal compatibility with aluminum matrix in a dispersion fuel. It is thought that the good phase stability is related to th large supersaturation of Mo atoms in the atomized particles. The reasons for the excellent thermal compatibility have been considered to be as follows. Before thermal decomposition of ${\gamma}$-U in particle, supersaturated Mo atoms at ${\gamma}$-U grain boundaries inhibit the diffusion of Al atoms. After thermal decomposition of ${\gamma}$-U into ${\gamma}$-U and U$_2$Mo, the intermetallic compound of U$_2$Mo seems to retard the penetration of Al atoms. The penetration mechanisms of aluminum atoms in the atomized particles are assumed be classified as (a) diffusion through the reacted layer between fuel particles and Al matrix leaving a kernel-like unreacted island and (b) diffusion along grain boundaries showing several unreacted islands and more reacted regions.