Abstract
The safe isolation of high-level radioactive waste from the human environment is a key requisite in the nuclear fuel cycle. Deep geological repositories (i.e. >500m) in a suitable rock mass, involving both engineered and natural barriers is currently the most favoured option for the disposal of high-level nuclear waste. Complex Thermal-Hydro-Mechanical and Chemical (THMC) phenomena are anticipated during the repository lifetime. The formation of gasses (e.g., as a result of oxidation processes) and their possible migration through the engineered barrier system (EBS) could jeopardise the main barrier functions. This paper focuses on the experimental study of the gas flow process through clay-barrier materials, particularly on the effect of degree of saturation, clay initial dry density, and confinement stress on gas permeability. It is shown that the initial dry density of the clay has a significant impact on gas flow, especially at low saturations. As expected, lower gas permeability values were obtained near saturation. Confinement has a minor impact on gas flow, at least for the range of stresses investigated in this paper.
Highlights
The final and safe disposal of high-level nuclear waste (HLW) is a problem that still needs to be solved
This paper presents results from this project related to gas permeability tests conducted on specimens of a compacted bentonite intended as barrier materials for the disposal of HLW
For a given confinement and saturation degree the specimens prepared at a higher dry density (1.6g/cm3) are less permeable to gas than the ones compacted at a lower dry density sample (1.3g/cm3)
Summary
The final and safe disposal of high-level nuclear waste (HLW) is a problem that still needs to be solved. Properties of this clay make it a very appropriate barrier material, namely, extremely low permeability, selfhealing ability, low ion transport capacity, high chemical stability, and high swelling potential [14] This is why the MX-80 bentonite has been adopted in several research projects aimed at investigating the performance of EBS in the context of HLW disposal Particular attention is paid to the effect of the sample initial dry density, degree of saturation and confinement on gas permeability These experiments focused on gas flow through the ‘intact’ compacted clay, results related to the gas migration through clayed-materials discontinuities (drying cracks) and interfaces between dissimilar materials are presented in [12] and [13], respectively
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
