Natural Tracer Profiles Across Argillaceous Formations

The CLAYTRAC Project

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This technical report describes the results of the Nuclear Energy Agency's CLAYTRAC project, in which natural tracer data from nine sites was evaluated to assess potential impacts of disposal of radiological waste in geological repositories. It shows scientific information from numerous sites and applies robust analytical methods to improve the understanding of radionuclide migration and evolution of sites for deep geological disposal. These results improve the understanding of sites, and thus the confidence in safety, for geological disposal of radioactive waste.



Appendix A3

Specific Aspects Related to Diffusion Coefficients

Nuclear Energy Agency

Most values for diffusion coefficients were obtained on the basis of laboratory experiments conducted at ambient temperature. In-situ temperatures may deviate significantly from the laboratory temperature. In the case studies considered here, the most significant deviations are identified in borehole MAR501 in the Couche Silteuse de Marcoule (29.5 °C) and in Opalinus Clay at Benken (34.5 °C). In a generic way, the temperature dependence of diffusion coefficients can be described by the Stokes-Einstein equation (Li & Gregory 1974)


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