Keywords: boron dilution, computational fluid dynamics, CFD, pressurised water reactors, PWRs, coolant mixing models, simulation, Germany, conductivity measurements, wire mesh sensors, velocity measurements, LDA, turbulent flow, reactor safety analysis, nuclear safety, nuclear energy, nuclear power
Numerical simulation of coolant mixing in a pressurised water reactor with different CFD methods based on complex meshes
This paper describes the numerical simulation of coolant mixing in the downcomer and the lower plenum of the Rossendorf test facility, ROCOM. ROCOM is a 1:5 scale Plexiglas model of a German pressurised water reactor, allowing conductivity measurements by wire mesh sensors and velocity measurements by the LDA technique. The CFD calculations were carried out with the CFD codes CFX-4 and CFX-5. In the case of stationary mixing, the maximum value of the averaged mixing scalar at the core inlet was found in the sector below the inlet nozzle, where the tracer was injected. The comparison of a very detailed mesh (CFX-5) and a mesh with simplifications and additional physical models (CFX-4) showed that in the referred case, the use of these models are allowed. For turbulent flows, CFX-4 and CFX-5 were validated in accordance with the Best Practice Guidelines and can be used in the reactor safety analysis. A better description of the mixing processes inside the RPV is the basis of a more realistic safety assessment.