This study presents numerical simulations of radionuclides (RN) release from a concrete container performed with a chemo-transport model, which describes simultaneously radionuclides (RN) migration in concrete and concrete leaching. The mathematical description of leaching is based on the generalized transport equation of calcium in concrete. The equation is solved numerically using the CAST3M code. 2D simulations of concrete leaching with the possibility to account for the influence of cracking have been performed. A second transport equation has also been implemented in the CAST3M code to determine the extent of radionuclide diffusion in (partially) leached concrete. The radioactive decay and the retention of the RN in concrete are taken into account. Results show that leaching is particularly important for RN having long decay periods. The crack depth appears to be the most important geometric parameter (compared to the crack opening and the crack width) with respect to RN diffusion.