Abstract : Safety analysis of innovative reactor designs, such as generation IV concepts, requires three dimensional modeling to ensure a sufficiently realistic description. Moreover, if precise solutions of local physical phenomena (DNBR, cross flow, form factors,...) are to be found then the use of accurate 3D coupled neutronics/thermal-hydraulics codes becomes essential. In this paper we present the development and simulation results of such coupling capabilities using the code MURE (MCNP Utility for Reactor Evolution), which automates the preparation and computation of successive MCNP calculations either for precision burn-up and/or thermal-hydraulics/thermics purposes. Thermal-hydraulics calculations are performed with the code COBRA, a sub-channel code that allows steady-state and transient analysis of reactor cores. The goal is a generic, non system-specific code, for both burn-up calculations and safety analysis at any point in the fuel cycle since the eventual trajectory of an accident scenario will be sensitive to the initial distribution of fissile material and neutron poisons in the reactor (axial and radial heterogeneity). The MURE code is open-source, portable and manages all the neutronics and the thermal-hydraulics/thermics calculations in background: control is provided by MURE or the user can interact directly with the codes if desired. MURE automatically builds input files and other necessary data, and manages all necessary code communications. Consequently accurate 3D simulations of power plants on both global and pin level of detail with thermal feedback can be easily performed (radial and axial meshing grids are managed by MURE).