Mobility of Zinc in the Callovo-Oxfordian Claystone

Abstract

The diffusion of zinc was studied in the Callovo-Oxfordian claystone, which is a potential host rock for the retrievable disposal of high-level radioactive wastes. Two in-diffusion laboratory experiments were performed with initial zinc concentrations of 4 10−5 mol L−1 and 8 10−6 mol L−1 (resp.) for 35 days. The zinc rock profile was acquired using an original technique, the μLIBS, with a high resolution (10μm), calibrated with the abrasive peeling method.The experimental data, i.e. Zn concentration monitoring in the source reservoir and Zn rock profile, were successfully reproduced using a chemical-transport code. In that code, the sorption of Zn was described by a multisite ion- exchange model, with only the effective diffusion coefficient value being adjusted (De=8 10−11 m2 s−1). This De value, 2 times higher than that of tritiated water, indicates that zinc, like most cations, is also subject to enhanced diffusion in clayrocks.