In the context of high-level radioactive waste repository simulations, specific waste repository system properties require the use of a highly heterogeneous and anisotropic diffusion tensors. Classical finite volume or mixed hybrid finite element schemes produce non-physical negative concentrations and therefore are unsuitable for simulations which couple transport and chemical reactivity models. In this article, the authors use a new finite volume scheme satisfying a minimum and maximum principle to solve the transport equations and demonstrate that this scheme avoids the negative concentration values generated by other schemes.