LEI PhD student Audrius Graževičius participated in a traineeship at Nuclear Research and Consultancy Group (NRG) center, in Peten (the Netherlands), during the period of 3rd of June – 1st of December 2018. The traineeship was organized by implementing the European Nuclear Education Network mobility project. The objective of this scientific traineeship is to improve the methodology of Computational Fluid Dynamics (CFD) modelling devoted for numerical investigation of gas mixture processes occurring in the containment atmosphere of a nuclear power plant during a severe accident. To achieve this objective the experiment TH-27 (carried out at THAI+ facility, Becker Technologies GmbH, Eschborn, Germany) was selected. During the TH-27 experiment the natural convection with water steam and helium injections, and condensation were investigated using ANSYS Fluent software.
During his traineeship A. Graževičius improved the existing and developed new user defined functions (UDF’s) with the help of which it is possible sufficiently precisely repeat the actual experiment results. He also conducted the analysis of numerical model mesh, number of iterations per time step, time step size, heat transfer coefficient, condensation process, turbulence models and other impact for calculation results. On the basis of obtained results and research conclusions the CFD modelling methodology was improved towards software modelling of the gas mixture processes occurring in the containment atmosphere of a nuclear power plant.