Papers by Keyword: Interaction Layer

Abstract: UMo/Al dispersion fuel is one of the prospective materials as a high uranium density fuel for high performance research reactors due to its excellent stability during irradiation. In this paper, An overview is provided of current development activities of UMo/Al dispersion fuel at abroad and home, including: the development reasons, this fuel fabrication technology, and the irradiation test. A comprehensive summary is given on the irradiation test, the existing problems and the solution recently obtained by the different countries. Early irradiation experiments with uranium alloys showed promise of acceptable irradiation behavior if these alloys could be maintained in their cubic γ-U crystal structure. The further development of this fuel was delayed due to an unacceptable volume expansion caused by UMo/Al interaction layer (IL) formation and a subsequent gross pore formation at the interface between UMo particles and matrix Al when severe irradiation conditions are reached. In order to alleviate or eliminate the swelling of UMo/Al dispersion fuel,several potential remedies are available to correct the swelling problems. These range from relatively minor changes to the fuel and matrix chemistry, to replacement of the aluminum matrix with another material, or to eliminate the matrix altogether. All of these variations are currently being investigated in the world.

Abstract: New nuclear fuel material with high density in uranium is envisaged for intense irradiation research reactors. The alloy U-Mo has been researched as a feasible candidate to be used in such reactors. This nuclear fuel is conceived to be used encapsulated in aluminum matrix. Nevertheless, there are interaction products of U-Mo/Al which form porosity during irradiation, leading to routine operation harms in research reactors. This interaction is due to solid solution interdiffusion of species, mainly of Al towards U-Mo region forming reaction products. This interaction could be studied by on-pile method, observing the occurrence of formed products during irradiation, but this method is costly and used only for long term experiments in very few reactors in the world. For this, several out-of-pile studies using heat treatments of diffusion pairs are carried out at adequate temperatures and times, just below the -phase eutectoid temperature to simulating the interdiffusion and formation U-Mo-Al phases. In the present study, it was employed a new developed assembling method to prepare interdiffusion pairs by immersing sliced U-10Mo sticks inside molten Al. These samples are made by induction furnace, in temperature range ~660-670 °C, under controlled argon atmosphere, in order to entrap molten Al around U-Mo sticks and so keeping this entangled structure after solidification. The interdiffusion pairs are then cut and prepared for treatments. This novel sample preparation guarantees full contact between the U-Mo and Al without oxidation contact, creating so, the ideal conditions for interdiffusion investigation of the interfaces of Al/U-Mo. Preliminary results to study interaction products where achieved by heat treatments during 5h at 550°C. Observations and calculations from SEM/EDS microstructures and XRD diffractograms revealed few microns interaction layer between the matrix and the fuel material, resembling phases reported in the literature for the interaction products between U-Mo-Al. This layer is mainly composed by Al and U, Mo phases, probably (U, Mo)Al3 and phases containing Si, as U3Si5 and a proposed one Al2Si3U3 that fits better to XRD spectrum of experimented diffusion pairs.