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Impact of the cationic homogeneity on Th0.5U0.5O2 densification and chemical durability
Journal of Nuclear Materials ( IF 2.8 ) Pub Date : 2018-12-09 , DOI: 10.1016/j.jnucmat.2018.12.009
Laurent Claparede , Nicolas Clavier , Adel Mesbah , Florent Tocino , Stéphanie Szenknect , Johann Ravaux , Nicolas Dacheux

In order to study the effects of cationic homogeneity on the life cycle of Th1-xUxO2 ceramics, including sintering and reprocessing (dissolution) steps, five different ways of preparation were set up, going from the most homogenous oxalic co-precipitation to a mechanical mixture of the parent oxides. Dilatometric experiments evidenced a better sintering capability for the most homogenous compounds obtained through wet chemistry methods while dry chemistry routes led to poor density values (between 80 and 90 %TD). However, the introduction of an additional mechanical grinding step prior to the powders sintering systematically led to the homogenization of the systems. Improved homogeneity also provide a better chemical durability associated with the congruent release of thorium and uranium in solution during dissolution tests of Th0.5U0.5O2 samples. However, heterogeneous samples led to incongruent behaviors that can be lowered by introducing a grinding step before the sintered samples preparation. Since the impact of the cationic homogeneity must be followed carefully during dissolution, in operando observations of evolving solid/solution interface by ESEM were performed. They allowed imaging the preferential dissolution of uranium-enriched zones and confirmed the significant impact over dissolution rate of the presence of chemical heterogeneities at the interface.



中文翻译:

阳离子均一性对Th 0.5 U 0.5 O 2致密化和化学耐久性的影响

为了研究阳离子均质性对Th 1- x U x O 2生命周期的影响陶瓷,包括烧结和后处理(溶解)步骤,建立了五种不同的制备方法,从最均匀的草酸共沉淀到母体氧化物的机械混合物。膨胀测量实验表明,对于通过湿化学方法获得的最均质的化合物,烧结性能更好,而干化学方法导致密度值较差(在80%TD至90%TD之间)。然而,在粉末烧结之前引入额外的机械研磨步骤系统地导致了系统的均质化。在Th 0.5 U 0.5 O 2的溶出度测试中,改善的均质性还提供了与溶液中th和铀的一致释放相关的更好的化学耐久性。样品。但是,异质样品导致不一致的行为,可以通过在烧结样品制备之前引入研磨步骤来降低行为。由于在溶解过程中必须仔细跟踪阳离子均质性的影响,因此操作中通过ESEM观察了不断演变的固/液界面。他们允许对铀富集区的优先溶解进行成像,并证实了界面处化学异质性的存在对溶解速率的重大影响。

更新日期:2018-12-09
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