Results and interpretation of bentonite resaturation experiments with liquid water and water vapour
Most countries favour compacted air-dry bentonite for engineered barriers in final repositories for nuclear waste. While the hydrophilic properties of bentonite appear to be ideally suited for minimising any contact of water with the waste the process of resaturation is not fully understood yet. In order to investigate the dynamics of water uptake several resaturation experiments with liquid water as well as with water vapour have been performed. A series of tests concerning the uptake of liquid water in compacted MX-80 bentonite samples has been completed recently. The experiments provide uptake rates and moisture distributions as a function of time. Analogous experiments with water vapour are presently running. Some first results are presented. The data gained is used to check new conceptual models which explain resaturation by flow of liquid water and by diffusion of water vapour, respectively. In the new models the effects of hydration on the local pore water content and the change of porosity corresponding to the amount of hydrated water are considered. The results strongly suggest that vapour diffusion plays a significant - if not dominant - role in the resaturation process of bentonite.
KeywordsResaturation Experiment GHULYHG IURP
Unable to display preview. Download preview PDF.
- Börgesson L (1984): Water Flow and Swelling Pressure in Non-Saturated Bentonite-Based Clay Barriers. Clay Barriers for Isolation of Toxic Chemical Wastes, International Symposium, May 28–30, StockholmGoogle Scholar
- Börgesson L (2001) Compilation of laboratory data for buffer and backfill materials in the Prototype Repository. SKB, International Progress Report IPR-01-34Google Scholar
- Huertas F, Fuentes-Cantillana JL, Jullien F, Rivas P, Linares J, Farina P, Ghoreychi M, Jockwer N, Kickmaier W, Martinez MA, Samper J, Alonso E, Elorza FJ (2000) Full-scale engineered barriers experiment for a deep geological repository for high-level radioactive waste in crystalline host rock (FEBEX project). European Commission, final report EUR 19147 ENGoogle Scholar
- Kahr G, Kraehenbuehl F, Müller-Vonmoos M, Stoeckli HF (1986) Wasseraufnahme und Wasserbewegung in hochverdichtetem Bentonit. NAGRA, Technischer Bericht 86–14Google Scholar
- Kröhn K-P (2003) New conceptual models for the resaturation of bentonite. Applied Clay Science, Vol. 23Google Scholar
- Mooney R W, Keenan AG, Wood LA (1952) Adsorption of Water Vapour by Montmorillonite; I: Heat of Desorption and Application of BET Theory. Journal of the American Chemical Society, Nol. 74, No. 6Google Scholar
- Pusch R (1980) Water uptake, migration and swelling characteristics of unsaturated and saturated, highly compacted bentonite. KBS Report 80-11, SKBF, StockholmGoogle Scholar
- Pusch R, Kasbohm J (2001) Can the Water Content of Highly Compacted Bentonite be Increased by Applying a High Water Pressure? SKB, Technical Report 01-33Google Scholar
- Pusch R, Yong R (2003) Water saturation and retention of hydrophilic clay buffer-microstructural aspects. Applied Clay Science, Vol. 23Google Scholar