CFD-simulation of the VVER thermal hydraulic benchmark V1000CT–2 using ANSYS CFX

Plant measured data from VVER-1000 coolant mixing experiments were used within the OECD/NEA and AER coupled code benchmarks for light water reactors to test and validate CFD codes. The task is to compare the various calculations with measured data, using specified boundary conditions and core power distributions. The experiments, which are provided for CFD validation, include single loop cooling down or heating-up by disturbing the heat transfer in the steam generator (SG) through the steam valves at low reactor power in the range of 5-14% and with all main coolant pumps (MCP) in operation. They were conducted during the plant commissioning phase at Kozloduy-6, Bulgaria and Kalinin-1, 2, Russia. CFD calculations have been performed for the thermal hydraulic benchmark V1000CT-2 using ANSYS CFX. The numerical grid model was generated with the grid generator ICEM-CFD and contains 4.7 Mio. tetrahedral elements. The Best Practice Guidelines (BPG) in using CFD in Nuclear Reactor Safety Applications has been used. Different advanced turbulence models were utilized in the numerical simulation. The best agreement with the Kozloduy heating-up experiment at the core inlet shows the Detached Eddy Simulation (DES). The results show a clear sector formation of the affected loop at the downcomer, lower plenum and core inlet. The maximum local values of the relative temperature rise in the experiment amount 97.7% and in the calculation 97.3%. Uncertainties are still the estimation and interpolation of experimental values at the core outlet to the core inlet.