Dynamics of radionuclide electromigration in intact granite: An kinetic adsorption-advection-dispersion model and its application

Xiaojie Li; Kaixuan Tan; Longcheng Liu; Yongmei Li; Shuo Meng; Xiaodong Li; Chunguang Li; Xinyu Wang; Yunting Tian

doi:10.1016/j.scitotenv.2024.173534

Dynamics of radionuclide electromigration in intact granite: An kinetic adsorption-advection-dispersion model and its application

Sci Total Environ. 2024 May 25:173534. doi: 10.1016/j.scitotenv.2024.173534. Online ahead of print.

Authors

Xiaojie Li¹, Kaixuan Tan², Longcheng Liu³, Yongmei Li⁴, Shuo Meng⁵, Xiaodong Li⁶, Chunguang Li⁴, Xinyu Wang⁷, Yunting Tian¹

Affiliations

¹ School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China.
² School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China. Electronic address: nhtkx@126.com.
³ R&D and Modelling Center for Treatment and Disposal of Radioactive Waste, University of South China, Hengyang 421001, China; School of Nuclear Science and Technology, University of South China, Hengyang 421001, China. Electronic address: lliu@kth.se.
⁴ School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China; R&D and Modelling Center for Treatment and Disposal of Radioactive Waste, University of South China, Hengyang 421001, China.
⁵ R&D and Modelling Center for Treatment and Disposal of Radioactive Waste, University of South China, Hengyang 421001, China; School of Nuclear Science and Technology, University of South China, Hengyang 421001, China.
⁶ Department of Chemistry-Radiochemistry, University of Helsinki, 00014 Helsinki, Finland.
⁷ School of Nuclear Science and Technology, University of South China, Hengyang 421001, China.

PMID: 38802020
DOI: 10.1016/j.scitotenv.2024.173534

Abstract

Granite, as the natural barrier for the disposal of high-level radioactive waste, plays an important role in ensuring environmental and public safety. The safety assessment of the repository depends on the reliable migration parameters of radionuclides in granite. In this study, we developed a kinetic adsorption-advection-dispersion model based on first-order adsorption kinetics. It introduces a first-order adsorption rate coefficient to describe the kinetics of adsorption process and accounts for other crucial mechanisms affecting the migration of radionuclide ions, namely, the electromigration, electroosmosis, and dispersion. This model is then applied to interpret the experimental results of electromigration of tracer ions in intact granite. The results show that for the weakly adsorbed radionuclides studied, iodide and selenite, the effective diffusion coefficients and formation factors calculated by this model are in constant with those derived from the classical advection-dispersion model based on linear adsorption equilibrium. By contrast, for the moderately or strongly adsorbed tracer ions studied, including cobalt, cesium, and strontium, the migration parameters calculated by this model exhibit significantly less uncertainty than those obtained from the advection-dispersion model simulations. The advection-dispersion model based on the first order adsorption kinetics introduces the first order adsorption rate coefficient, and considers the influence of electromigration, electroosmosis and dispersion mechanism, which helps to explain the migration mechanism of nuclide ions in intact granite more accurately.

Keywords: A first-order adsorption rate coefficient; Electromigration experiments; Medium-to-strong adsorbed nuclide; The effective diffusion coefficients.