Abstract
The main aim of this paper is to simulate a safety analysis related to the SB LOCA (Small Break Loss of Coolant Accident) using a CFD (Computational Fluid Dynamics) code, where the investigated part is a section of VVER 440 reactor. SB LOCA can be regarded as one of the accidents disrupting the normal operation and its investigation is essential for the safety evaluation of the entire plant. Solved scenario assumes a small break on the hot leg where the coolant leaks. Lost coolant is compensated by safety systems injecting water from the emergency tanks with significantly lower temperature in comparison with the coolant. A major part of this paper is dedicated to the modelling and to the mesh generation. This part deals with the modelling of the involved components, which was done using Design Modeler. Complex components were adjusted, simplified or omitted in order to generate a suitable mesh. This process was done using ANSYS-Meshing by the application of the appropriate algorithms. Attention was also paid to the number of cells and their quality as the crucial parameter affecting the accuracy and the length of calculation. ANSYS-Fluent r14 was chosen as the CFD solver that allows 3D solution of a transient scenario. Input parameters representing boundary conditions were obtained from the simulation tool RELAP where the investigated analysis was performed for the entire primary circuit. The result of this analysis principally provides of the determination of the maximal and minimal temperature in the regions, that are prone to the brittle fracture, namely welds at the inlet nozzles and the weld nearby the core.
