Measuring the diffusion and sorption of the trace elements and radionuclides in soil, clay and bentonite

Abstract

Diffusion is an important migration mechanism of trace elements and radionuclides in the biosphere, soils, clays, river sediments. Naturally, in the last few years there has increased also the relevance to diffusion of trace elements and radionuclides and methods of its determination in bentonite. Bentonite is proposed as sealing and backfill material in the near-field of deep repositories of spent nuclear fuel and of radioactive wastes. This paper presents capillary modification of measuring diffusivity, some of its results in porous natural materials and barrier materials of repositories for wastes.

Sorption behaviour of caesium on a bentonite sample

“…At the contact with the clayed backfill engineered barriers, Cs is submitted to two processes: sorption and diffusion. If it percolates through the clay barrier, it is expected to be further retarded by the geosphere [1,2]. Consequently, in order to predict (via a thermodynamic model) the behaviour of Cs in terms of transport, the sorption phenomena have to be understood on a large range of Cs concentration and chemical conditions, consistent with those encountered in the near field of a repository.…”

Use of Composite Barrier in Radioactive Waste Repositories

“…The buffer materials should be designed to adsorb more radionuclides having a long half-life. Furthermore, the buffer materials should be designed with high chemical, physical and structural properties such as low permeability, high plasticity, and high cation exchange capacity [3][4][5][6][7][8]. 79 Se and 126 Sn are remarkable radionuclides in the waste packages because they are long half-live fission products and radiologically harmful in the spent nuclear fuel [9][10][11].…”