Water unsaturated buffer materials

PRELIMINARY ANALYSIS ON WATER MOVEMENT AND MASS TRANSPORT IN UNSATURATED BUFFER MATERIAL UNDER THERMAL GRADIENT 3.1 Analysis conditions To demonstrate coupling between T-H-M and mass transport, we carried out preliminary analysis... 

As shown in Figure 4(e), dissolved concentration of NaCl increases in all parts of the sample with time, and is concave downwards. This indicates that the diffusive transport is dominant in unsaturated buffer material. Dissolved concentration of NaCl in the lower part of the sample increases due to decrease in volumetric water content caused by vapor movement from the bottom to top (Figure 4(f)), but is not so large compared to that of infiltrating saline water at the top. Both precipitation of NaCl and local strong increase in dissolved concentration of NaCl are not found in all parts of the sample. 

In this paper, we present the coupled T-H-M-C model and carry out the preliminary analysis on water movement and mass transport in unsaturated buffer material under thermal gradient. Based on the preliminary analysis, it is suggested that salt accumulation in buffer material will not be significant as long as the transport is dominated by diffusion in unsaturated buffer material. As shown by this analysis, numerical experiments on the coupled T-H-M-C processes can support our understanding of the near-field evolution in a HLW repository. 

In this analysis, we used properties of buffer material obtained by laboratory experiments using distilled water, because unsaturated properties of buffer material with NaCl solution have not been well studied yet. 

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