Advanced numerical methods for thermalhydraulics

New applications have been found for advanced best estimate codes, due to the needs for industrial studies and safety studies, and due also to the appearance of new generations of computers, as powerful work stations. Thus developments have been focused on the optimization of the numerical performance of thermal-hydraulics codes based on two-fluid six equation model. The first field of investigation is to minimize the computing time. Comparisons of existing methods demonstrate that a fully implicit scheme is suitable to be optimized. The second field of investigation is to develop powerful three-dimensional module with advanced numerical method, as multistep method, conjugate gradient method for the solver and in future non-structured meshing. (authors). 6 tabs., 8 refs