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

摘要

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) Al-3 and ( U, Mo) Al-4 solid solutions often admitted in the literature. Using mu-XAS ( micro X-ray absorption spectroscopy) at the Mo K edge and mu-XRD ( micro X-ray diffraction), the heterogeneity of the interaction layer obtained on a gamma-U0.85Mo0.15/Al diffusion couple has been precisely investigated. The UMo2Al20 phase has been identified at the closest location from the Al side. Moreover, m-XRD mapping performed on an annealed fuel plate enabled the characterization of the four phases resulting from the mu-U0.85Mo0.15/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.