▶ Date: 2022. 05. 19(THU)

▶ Time: 16:30pm ~ 17:30pm

▶ Speaker: Prof. Takayuki SASAKI (KYOTO University)

▶ Title: Radionuclide Solubility and Thermodynamics in Aqueous Systems

▶ Abstract:

The geological disposal of highly radioactive waste generated in the nuclear fuel cycle requires a safety assessment of the long-term migration of radionuclides in groundwater over a period of hundreds of thousands of years. The environment of the deep geological formations in which the waste will be isolated affects the parameters used to estimate the apparent solubility, complexation and sorption reactions, and the mobility of radionuclides. Assumptions about the geological environment are based on the aquatic chemistry and thermodynamics understood through experiments and models. In a more realistic subsurface environment, it may also be necessary to consider radionuclide complexation in the presence of natural organic materials such as humic acid (HA). However, as HA does not have a fixed chemical structure, its modeling remains extremely challenging. A semi-empirical fragment model suggests that considering changes in the Gibbs free energy associated with complexation and focusing on the functional groups common to the chemical structures of various HAs could be useful to clarify radionuclide complexation with HA. Note that this model has helped explain the sorption behavior of radionuclides in stagnant deep groundwater irradiated with radiation from wastes. In this talk, I will discuss the solution chemistry in groundwater based on equilibrium reactions, rather than the various recent advanced spectroscopic findings.