A high-resolution, three-dimensional (3D) image of the interior of the sedimentary rock was obtained by means of nano-focus X-ray computer tomography (X-ray CT). Using computational methods to analyze the 3D microstructure of the rock, we presented the tortuosity and geometrical constrictivity. We also presented results on the tritiated water (HTO) diffusion tests and a mercury intrusion porosimetry (MIP) test performed on the rock. We have compared these results to understand the dominant parameters that control diffusion of HTO in the present system. These results suggest that the dominant parameters in the present system are not the constrictivity but the tortuosity and the diffusion-accessible porosity. The material considered in this study is the siliceous mudstones sampled from 500 m in depth at the Wakkanai formation around Horonobe underground research center in Hokkaido, Japan.

Mixed matrix membranes based on modified polyimides and silicalite-1 were prepared and studied. The novel preparation approach consists in improvement of the interfacial adhesion by employment of the coupling agent 3-aminopropyltriethoxysilane in such a way which leads to forming of chemical bonds between polyimide and silicalite-1. Firstly polyimide chains were endcapped by this agent which subsequently enabled their reaction with groups naturally present on silicalite-1 surface. Membranes with silicalite-1 content up to 60 wt. % were prepared and characterized by SEM, light microscopy and permeation of gases, prevailingly of He. The accessibility of sililicalite-1 pores prior to embedding and after embedding into polymeric matrices was studied by an iodine indicator technique. The permeability of membranes for gases was measured using a semi-open permeation apparatus with a small volume. Helium permeability depended on filler content and increased monotonously with the increasing content of filler. There were, however, significant deviations of the permeability dependences on filler content from shapes predicted by Bruggeman’s model. The qualitative explanation of the data disagreement with the model was proposed based on a stratification of mixed matrix membranes found by SEM.

The goal of our contribution was to develop a method providing morphological (microstructural) descriptors whose values would match total porosity and specific surface obtained other independent methods. The model obtained from limited amount of statistical information, accessible by image analysis of cross-sections, offers an attractive way for the prediction of equilibrium and transport phenomena in natural and man-made macroporous media.

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A point defect model is developed in hyperstoichiometric uranium dioxide, UO2+x,in order to explain some experimental results of deviation from stoichiometry and electrical conductivity existing in the literature. This model takes into account both singly charged uranium vacancy, V''U , and two types of Willis clusters, characterized by two kinds of interstitial oxygen atoms that are located on two different sites and two oxygen vacancies, namely 2(Oi"Oi''Vȯ)4'' and . The electron holes, ḣ , are also introcued to ensure the crystal global electroneutrality. An adjustment procedure of the most convincing experimental data of the literature, corresponding to the temperature and oxygen partial pressure dependencies of departure from stoichiometry,x, and electrical conductivity, [sigma] , has been undertaken. The fit model/experience obtained has been found fairly good, justifying, a posteriori, the relevance of the nature of the selected defects in the model.