Realistic modeling approach for radionuclide transport in heterogeneous fractured crystalline rocks

Tachi, Yukio  ; Ito, Tsuyoshi*; Fukatsu, Yuta  ; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

To develop a realistic model and reliable parameters for long-term safety assessments of geological disposal, it is necessary to understand and quantify the effects of heterogeneities around the fractures on radionuclide transport in fractured crystalline rocks. This paper presents a comprehensive approach developed for coupling laboratory tests, microscopic observations and modelling in order to understand and quantify tracer transport occurring in natural fracture, using different types of fractured granodiorite sample from the Grimsel Test Site, Switzerland. Realistic model incorporating heterogeneities around the fracture, and their properties such as porosity, sorption and diffusion parameters, provided a much better interpretation for experimental results of several tracers with different transport properties. Mechanistic understanding and detailed modeling considering the effects of heterogeneities around a natural fracture should improve confidence for the safety assessment in fractured crystalline rocks.