. Finite element/mixed-hybrid formulation of a discrete fracture network model. Key words. fracture flow, stochastic discrete fracture network, mixed-hybrid formulation of the finite element method 1. Introduction. Nuclear energy produced on the Earth has reached 16% of the world's energy production and it is generated by almost 500 nuclear reactors. The weakest link in the production of the energy by this way is a safe storage of highly radioactive spent fuel. This text deals with suggestion of a mathematical model describing percolation of groundwater in the fractured matrix of a solid rock, medium supposed as possible repository of dangerous nuclear waste. In general, there are three main possible accesses to the problem of modelling the fracture flow. When only a large-scale model is required and if there is no need to know detail flow and transport behavior in any site subarea, it is possible to use equivalent porous medium models. More complex than single continuum models are ..