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    Artigo IPEN-doc 29094
    Effects of aluminum distearate addition on UO2 sintering and microstructure
    2022 - FREITAS, ARTUR C. de; COSTA, DIOGO R.; JARDIM, PAULA M.; LEAL NETO, RICARDO M.; CARVALHO, ELITA F.U. de; DURAZZO, MICHELANGELO
    Uranium dioxide (UO2) is widely used as a fuel in commercial nuclear light-water reactors (LWRs). Rigorous control of density, pore, and grain size of UO2 pellets are important prerequisites for fuel performance. Solid lubricants, frequently used in pellets manufacturing, minimize structural defects on compaction such as cracks and end-capping, promoting grain growth during sintering. This work presents and discusses the effects of the aluminum distearate (ADS) addition on the sintering behavior and microstructure of UO2 fuel pellets. UO2 and UO2-0.2wt% ADS pellets were sintered at 1760 °C for 5.7 h for comparison purposes. The results show that the densification rate increases using the solid lubricant, but the shrinkage is lowered by 0.7% due to low homogenization. The average grain size was increased by about 35% during sintering. Based on our results and a literature review, a mechanism for grain growth by aluminum addition is proposed.
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    Artigo IPEN-doc 25088
    Sintering behavior of UO2-Er2O3 mixed fuel
    2018 - DURAZZO, MICHELANGELO; FREITAS, ARTUR C.; SANSONE, ALBERTO E.S.; FERREIRA, NILDEMAR A.M.; CARVALHO, ELITA F.U. de; RIELLA, HUMBERTO G.; LEAL NETO, RICARDO M.
    The incorporation of burnable neutron absorbers into nuclear fuel pellets is important regarding reactivity compensation, which enables longer fuel cycles. The dry mechanical blending route is the most attractive process to accomplish absorbers incorporation because of its simplicity. By using this route, the present work has investigated the sintering behavior of UO2Er2O3 mixed fuel. A comparison with UO2Gd2O3 sintering behavior was presented. The behavior of UO2Er2O3 fuel sintering was similar to that reported for UO2Gd2O3 fuel, e.g. two-stage sintering with two peaks in the shrinkage rate curves. The effect showed to be less pronounced for Er2O3. This was attributed to the characteristics of the Er2O3 powder particles used as raw-material, whose agglomerates can be more easily broken and thus better homogenized during the blending with UO2 powder. These results confirmed that sinterability depends directly on the quality of the homogenization of the powders, as seen previously. A second phase was experimentally detected in the UO2Er2O3 system, but its impact on the sintering behavior of this mixed fuel has not yet been clarified.