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Mukai, Masayuki; Ueda, Masato; Inada, Daisuke; Yukawa, Kazuhiko; Maeda, Toshikatsu; Iida, Yoshihisa
Proceedings of International Symposium NUCEF 2005, p.219 - 224, 2005/08
For better quantitative understanding of radionuclide migration for safety assessment of geologic disposal, JAERI has been conducting experimental and modeling studies on influences of humic substances, highly alkaline conditions and colloids on sorptive and diffusional behavior of TRU in geologic materials. In the absence of fulvic acid, one of humic substances, diffusion of Am through a tuff sample was not detected. By adding fulvic acid, Am was detected in the downstream cell, which indicates the diffusion through the sample. Highly alkaline conditions arisen from cementitious materials may spread by altering chemical and physical properties of geologic materials. Through-diffusion experiments of alkaline species in granite showed that the effective diffusion coefficient of Ca
and OH
in a cement-equilibrated aqueous solution were found to be higher by almost two orders of magnitude than Na
and OH in a NaOH solution. Radionuclide migration can be enhanced by colloids, and thus a calculation code describing the effect of colloids on radionuclide migration has been required.
Sato, Haruo
Proceedings of International Symposium NUCEF 2005, P. 62, 2005/02
The anisotropy and effect of salinity in the apparent diffusion coefficients (Da) and activation energies (Ea) for I- and Cs+ ions were studied. The diffusion experiments were carried out as a function of smectit's dry density, salinity, temperature and diffusion direction to the orinentated direction of smectite particles. An purified Na-smectite was used in the experiments. I- Ions are considered to mainly diffuse in interstitial pores and Cs+ ions are considered to diffuse in both interlayer and interstitial pores from the changes of the Da- and Ea-values for both ions on dry density, salinity and diffusion direction. Moreover, I- ions are considered to be affected by electrostatic effect from smectite surface, and Cs+ ions are considered to the effect of the decrease in the activity of porewater in addition to the effect of ion exchange enthalpy between Cs+ and I- ions in smectite.