The project No. CZ.01.1.02/0.0.0/18_215/0016493 has been carried out in cooperation between the Faculty of Mechanical Engineering at the University of West Bohemia and TES. The project was focused on the development of CFD model presenting downcomer of the VVER-440/213 pressure vessel including the cold leg. The model enables to analyze the events which may endanger reactor pressure vessel integrity by the physical phenomena called “cold stripe”. The results should also facilitate obtaining the reference data for innovation and validation of computational models of the programs and methodologies for safety analyses performance using RELAP5 and TRACE computer codes. The project was co-financed by European Union under the Operational Programme for Enterprise and Innovations for Competitiveness.