Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

A pump start-up experiment with the presence of a tracer slug, conducted on a Gidropress mixing facility in the framework of TACIS Project R2.02/02, was simulated with the CFD code ANSYS CFX. The numerical results were compared against the experimental data, which consist in tracer concentration measurements at several locations at the core inlet. The results showed an good agreement with the experiment from the qualitative point of view: in particular, the morphology of the tracer concentration distribution at the core inlet was correctly described. This qualitative agreement is quite an important achievement, since the addressed scenario is featured by a complex, highly three-dimensional, flow distribution in the downcomer. From a quantitative point of view, the results in terms of maximum perturbation (and related timing), core-averaged perturbation are also satisfactory. The perturbation peak is over-predicted by 5%, which is comparable with the experimental uncertainty. The predicted time history of the core-averaged perturbation shows a less smooth trend than the experiment, which seems to indicate a less effective mixing.