[en] The current concept of the EPR (European pressurised water reactor) relies on a sufficiently homogeneous spreading of the melt in order to ensure its coolability after a passive initiation of flooding by water. The conditions under which a complete spreading can be expected are the subject of current theoretical and experimental results. The CORFLOW code allows to treat three-dimensional non-isothermal free surface flow. The influence of cooling on the spreading is modelled by a temperature dependent viscosity. The increase of the viscosity in the thermal boundary layer of the melt can eventually lead to a stop of the melt front. The experimental findings from the KATS series are analysed and CORFLOW results are presented. In addition the available similarity solutions are also used to validate the CORFLOW code. (orig.)