• COOLANT MIXING
• BORON DILUTION
• NUCLEAR SAFETY
• CFD
• ROCOM
• SIMULATIONS
• NUMERICAL INVESTIGATIONS
• Trio_U
• FLUENT

The present work, carried on in the frame of a collaboration agreement between the Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP) of the University of Pisa, and the CEA – Grenoble, deals with the application of the Trio_U CFD code for investigating a boron dilution transient simulated at the ROCOM test facility. In the first chapters of the present document, a rapid introduction to the theoretic and numeric fundamentals of the Computational Fluid Dynamics is reported, as well as a brief description of the test facility and of the Trio_U code. In the following chapters, the various phases of preparation of the numerical simulations (both “production” calculations and sensitivity tests) are described, in particular the creation of the orthogonal-structured mesh grids, the modelling of the most critical parts of the calculation domain (e.g. the perforated drum, which requires the use of a “porosity model” and an adequate implementation of the “head loss model”), the choices made in preparing the input decks for Trio_U. Then, the results of the main calculations are shown and compared to experimental data. Calculated data resulted in a quite good agreement with the experimental ones, almost from a qualitatively point of view. As it was expected, some limitations affected the accuracy of the results, mainly due to the relative coarseness of the mesh grids and to some inadequacies in the models. Those limitations left some open points to be dealt with in further investigation activities.
Finally, a preliminary numerical simulation of ROCOM, performed with the FLUENT CFD code at the DIMNP is described, which constitutes the starting point for an activity aimed to test the capabilities of that code.