Fluid-structure interaction (FSI) behavior of a VVER-1200 nuclear reactor vessel under normal operating conditions

Maintaining the structural integrity of nuclear reactor pressure vessels (RPVs) during both normal operating conditions and postulated accidents is an important safety concern in the field of nuclear reactor design. Development of numerical techniques has been needed in order to solve complex phenomena which happen in nuclear power plants. So, accurate descriptions of the heat transfer and the coolant flow within a nuclear reactor for the safety and performance concerns are always desirable. In particular, fluid-structure interaction (FSI) analysis must be resolved for accurate investigation and design of nuclear reactor pressure vessel internals which are completely submerged in coolant. In this particular study, the one-way partitioned FSI effect of the light water as a moderator on RPV wall in a typical Russian design VVER-1200 nuclear reactor has been investigated. The aim was the characterization of the FSI phenomena occurring between the reactor vessel structure and the inner pressurized fluid. Due to computational limits, some simplifications in the geometry of the RPV were applied. The deformation of the RPV wall caused due to the coolant temperature has been analyzed. Both the imported pressure and the imported temperature loads from the ANSYS Fluent solvers has been used as an input in the reactor vessel structural analysis. As a result of the analyses, the reactor vessel wall deflection, radial stress (X), axial stress (Y), hoop stress (Z), and Tresca stress have been found. Based on these studies, the analyses show that the structural integrity of the RPV is provided throughout the normal operating conditions. The obtained results validate that it is possible to perform more analysis for asymmetric operating or accident conditions using the FSI simulation knowledge obtained.