The main objective of long-term management of radioactive wastes is to protect man and environment from the risks linked with existing wastes, during industrial exploitation of storage site as on long-term. The geological repository’s safety relies on a multi-barrier strategy and on a multifunctional concept, involving the complementary properties of the geological site, the design provisions and the primary package. Each of the safety functions concerns flow management in a global system composed of the repository and its environment. One of the most important fluxes, the radioactive nuclide flux, is here phenomenologically described from its source, after alteration of wastes packages, to the biosphere.