^(125)Ⅰ在压实北山花岗岩粉中毛细管内扩散

Diffusion of ^(125)Ⅰ in Compacted Beishan Granite Research of Capillary In-Diffusion Method

为了解^(129)Ⅰ在我国深地质处置库重点研究区围岩中的迁移行为,为选址预评价提供基础数据,利用批式吸附实验法和改进的毛细管内扩散法研究了碘离子在北山花岗岩粉中的吸附和扩散行为,分析了不同控制条件对碘离子的表观扩散系数(Da)的影响。结果表明:在固液比为20g/L,碘离子在北山花岗岩粉上的吸附几乎可以忽略;扩散实验中^(125)Ⅰ-的Da值为8.2×10^(-11)~1.4×10^(-9)m^2/s,表明碘离子在压实北山花岗岩岩粉中的扩散速率很快;^(125)Ⅰ-的Da值随扩散温度的升高而变大,随扩散源液离子强度的增加而变大,随同位素载体浓度的升高而变大,^(125)Ⅰ-的扩散速率随溶液pH值的上升整体有减小的趋势。

In order to understand the migration behavior of 129I in the host rock of China＇s key potential deep geological repository, and to provide basic data for the pre-safety assess- ment of the site, the effect of different experimental conditions on the adsorption and diffu- sion of iodine ion was investigated using a batch sorption method and a modified capillary in- diffusion method. The results suggest that the adsorption of iodide onto Beishan granite is almost negligible under solid/liquid ratio of as high as 20 g/L. According to the capillary experimental results, Da values of 125I- are between 8.2×10^（-11） and 1.4×10-9 m2/s, which suggests that the diffusion rate of iodide ion in compacted Beishan granite powder is very high. There is a positive correlation between the Da with temperature, isotopic carrier con- centration and ionic strength, which can be explained by Brownian motion and electrieai double layer structure of granite surface. While Da value of 125I witness an overall decrease with the increase of pH values due to the granite surface charge. As can be seen, the capil- lary method is a fast and easy method which can be used to investigate the migration of radio- nuclide in compacted mineral powders.