Journal of Applied Crystallography

Volume 40, Part 6 (December 2007)

research papers

J. Appl. Cryst. (2007). 40, 1064-1075 [ doi:10.1107/S0021889807040010 ]

Evidence for the presence of U-Mo-Al ternary compounds in the U-Mo/Al interaction layer grown by thermal annealing: a coupled micro X-ray diffraction and micro X-ray absorption spectroscopy study

H. Palancher, P. Martin, V. Nassif, R. Tucoulou, O. Proux, J.-L. Hazemann, O. Tougait, E. Lahéra, F. Mazaudier, C. Valot and S. Dubois

Abstract: The systematic presence of the ternary phases U₆Mo₄Al₄₃ and UMo₂Al₂₀ is reported in a U-Mo/Al interaction layer grown by thermal annealing. This work shows, therefore, the low Mo solubility in UAl₃ and UAl₄ binary phases; it contradicts the hypothesis of the formation of (U,Mo)Al₃ and (U,Mo)Al₄ solid solutions often admitted in the literature. Using µ-XAS (micro X-ray absorption spectroscopy) at the Mo K edge and µ-XRD (micro X-ray diffraction), the heterogeneity of the interaction layer obtained on a [gamma] -U_0.85Mo_0.15/Al diffusion couple has been precisely investigated. The UMo₂Al₂₀ phase has been identified at the closest location from the Al side. Moreover, µ-XRD mapping performed on an annealed fuel plate enabled the characterization of the four phases resulting from the [gamma] -U_0.85Mo_0.15/Al and (U₂Mo + [alpha] -U)/Al interactions. A strong correlation between the concentrations of UAl₄ and UMo₂Al₂₀ and those of UAl₃ and U₆Mo₄Al₄₃ has been shown.

Keywords: µ-XRD; µ-XAS; U-Mo/Al interaction; nuclear fuel.