Measurement of diffusion and sorption of radionuclides in rocks.

Abstract

The diffusion of Cs, Sr, Am and Np into granite tablets has been examined. Sorption of these nuclides on the five kinds of rock : granite, granodiorite, basalt, andesite and rhyolite was measured and expressed as a function of interstitial water of the rock. The interstitial water was measured by weighing the penetrated water and also by counting the penetrated 99mTc. Technetium counting represents that the sorption is affected by the rocks and does not correspond linearly to the interstitial water content.The ratio IC, amount of sorbed nuclide per unit of interstitial water divided by amount of nuclide per unit of solution, is introduced to make clear the relationship between nuclide sorption and interstitial water. Results indicate that there is a correlation between the sorption of nuclides and the amount of interstitial water. However, mechanisms that retard the movement of the nuclide are different from each other. Americium shows nearly equal If, values with different rocks. In contrast, Np varies greatly.