ABSTRACT
U(Mo) alloys are being studied to be applied as a fuel for research and test reactors. When U(Mo) particles are dispersed in an Al matrix, it is known that an interdiffusion during fabrication process and / or irradiation. In this sense, irradiation tests have shown that this IL has a bad behavior under irradiation coming up the addition of Si to Al as one of the most promising solutions.
Several out of pile experiences have been performed with U(Mo)/Al(Si) diffusion couples in which U(Al,SI)3, U3Si5, USi2, USi2-x, Al20Mo2U and/or Al43Mo4U6 are the phases identified as conforming the IL. In some cases, U3Si5 was identified considering modified lattice parameters, which can be justified assuming that the U3Si5 phase would accept a small amount of Al in solution. However, although the Al-Si-U ternary system has been extensively studied, there are no previous experimental results to correlate lattice parameters modification with Al solubility in U3Si5, USi2 y USi2-x phases.
From previous paragraphs, it is important to study the Al-Si-U ternary system especially in the environment of U3Si5, USi2 and USi2-x phases. With this aim, ten alloys were fabricated. Nine of them were isothermally treated at 550 ºC and microstructurally characterized. The Main results show the presence of needle-like morphology in the alloys with concentrations around that of the U3Si5 phase. From th fact that this kind of morphologies is characteristic of a displacive transformation, which occur during cooling process, the use of a dynamic identification transformation technique (as differential scanning calorimetry) came up as mandatory in this research
In this new stage, nine alloys were studied with the calorimeter using two heating/coolig rates (± 1 ºC/min and ± 10 ºC/min). Transformation temperatures and enthalpy of formation of compounds were determined. The samples were also microstructurally characterized after testing.
Keywords
Nuclear fuels; Uranium silicides; Phase identification; calorimetry
