Water and Lead-Bismuth Experiments for Megapie: Fluent and Star-Cd Simulation

WATER AND LEAD-BISMUTH EXPERIMENTS: FLUENT AND STAR-CD SIMULATION

Alberto Peña

Gustavo A. Esteban

Alberto Abánades

Universidad del país Vasco/Euskal Herriko Unibertsitatea

C/ Alameda de Urquijo S/N 48013 Bilbao, Spain

Summary

In the framework of the ASCHLIM project, a group of European experts in thermalhydraulic calculation has been clustered to evaluate the state of the art of CFD codes applied to ADS design. The work of this group, supported by the Vth Framework Program of the European Union, has been focused on CFD analysis of the experiments that includes thernalhydraulic phenomenology associated to current transmutation design options. Some experimental data related to the MEGAPIE project (MEGAwatt PIlot Experiment) were analyzed. This paper includes the CFD calculations performed in our institution in that sense.

Different geometries for target windows are being tested and numerically simulated, in order to analyze the feasibility of the CFD methods in the particular case of the liquid metals within ASCHLIM project.

Parallel to these liquid metals experiments water experiments have been performed in a plexiglass test module, using approximately the same 1:1 geometry and similar hydraulic Reynolds number. This allows visualization techniques, impossible to use in the Lead-Bismuth experiments and prevents corrosion and elevated operating temperatures in an initial exploratory experiment. The experiment with water is called HYTAS.

The experiments dealing with liquid metal will be performed in the THEADES loop of the KALLA laboratory of the Institute of Nuclear and Energy Technologies (IKET) at Forschungzentrum Karlsruhe (FZK) (Germany). Two experiments with liquid lead bismuth will be performed, characterized by a rectangular by-pass jet. The first one investigates the turbulent mixing, and in the second one the KILOPIE (KILOwatt PIlot Experiment) experiment will be performed. The geometry is identical to the window design (MEGAPIE) in both experiments. However, the second experiment includes an inner rising tube whose inlet has been slanted to break even more drastically the axi-symmetry of the problem.

The University of the Basque Country (UPV-EHU) has performed the benchmark calculations to simulate the mentioned experiments with the two codes available at the institution (STAR-CD and FLUENT). No data is available at the moment for the liquid lead bismuth configuration, but these pre-test CFD calculations have been done to predict the future experimental results.

Some recirculation is predicted in the CFD calculations in the experiments with liquid metals and water. Concerning thermal aspects, STAR-CD computes higher temperatures than FLUENT. The discrepancy may be explained by the different near wall treatment employed by both codes for the thermal boundary layer behavior.

The codes are not sensitive to different inlet region configurations, and although the coolability of the window seems to be guaranteed (no hot points are foreseen), the flow pattern is not properly driven into the inner tube.

Mass flow rates are higher in the heated jet experiment compared with the HYTAS experiment. This can contribute to the better flow patterns obtained. Fewer critical points appear in the heated jet experiment calculations.