The quantity of radioactive waste will grow significantly with an increasing interest and use of nuclear-generated energy. There will always be inevitable radioactive waste residues that require disposal, even using an advanced nuclear fuel cycle in the future. Deep geological disposal, one of the most promising final disposal methods, should be validated for its long-term performance and safety assessment. Geotechnical issues related to the deep geological disposal are critical for the sustainable development of nuclear energy. They play challenging roles especially under extreme circumstances that result from deep geological conditions of a repository, extremely long containment time, and the characteristics of nuclear waste itself such as high decay heat, which may primarily affect thermo-hydro-mechanical and geochemical-coupled behavior of a repository for geologic time scales. This paper introduces an overview of deep geological disposal concepts based on Finnish, Korean, Spanish, and Swedish disposal programs, discusses the outstanding research issues in disposal from the aspect of geological and geotechnical engineering, such as Excavation-Damaged Zone (EDZ), cementitious material, long-term gas migration, and self-sealing/healing of fractured rocks with a focus on the state of the art in-situ validation experiments, and additionally presents a numerical modeling of the coupled THMG process in the repository near field, which is one of the major factors concerning the fuel canisters.

Deterioration plays an important part in the life cycle of infrastructure systems. Among all causes of deterioration (aging, chloride ingress, etc.) the action of live organisms has shown to be critical in, for example, underground structures, sewage systems, and at-sea structures. This phenomenon is usually overlooked, in part, because in most cases live organisms accelerate other processes that may eventually lead to unacceptable structural performance or cause failure (e.g., corrosion, cracking). By the direct or indirect action, it has been estimated that biodeterioration-related structural problems cost billions of dollars a year in infrastructure maintenance and repair. The paper shows that for all major civil engineering materials, in the long term and under the appropriate environmental conditions, biodeterioration may severely affect infrastructure components and their ability to perform as designed. This is particularly relevant given the large amount of existing infrastructure that has been exp...

This work presents a fully coupled formulation developed to handle engineering problems in unsaturated (and saturated) soils that present two dominant void levels. The proposed framework assumes the presence of two porous media linked through a mass-transfer term between them. In its more general form, the proposed approach allows the consideration of nonisothermal multiphase flow coupled with the mechanical problem. The double-porosity formulation was implemented in a finite-element code and has been used to analyze a variety of engineering problems. The approach is especially suitable for cases in which the material exhibits a strong coupling between the mechanical and the hydraulic problems in both media, such as with swelling clays. For those types of problems, the proposed formulation is used in conjunction with the mechanical double-structure model already proposed by the authors. This paper presents the coupled formulation and the application of the proposed approach to problems involving e...