The Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) at SCK•CEN is being designed as a pool-type fast reactor prototype cooled by Lead-Bismuth Eutectic (LBE). Operating in critical mode, MYRRHA will demonstrate the Lead Cooled Fast Reactor technology which is one of the Generation IV reactor concepts. It will minimize the radioactive waste production and bring transuranic elements into shorter-lived waste thanks to the partitioning and transmutation technology.
Thermal hydraulics is recognized as a key aspect in the design and safety analyses of this kind of pool-type system: three-dimensional flows of liquid metal in natural and forced convection regimes need to be carefully investigated. Experiments are used to validate the numerical codes and models.
The correct prediction of temperature profiles on structural materials has a fundamental role in supporting the design of the reactor to avoid possible drawbacks such as thermal striping, stagnation and stratification. The prediction is less evident because of the limited experience in general with fluids with high thermal conductivity (low Prandtl number) as the liquid metals used here
As complex geometries as a full reactor are not practical to investigate basic heat transfer models, single effect cases are setup to get more insight. One of the single effect cases that are relevant for the MYRRHA reactor are mixing jets. This flow regime can be found at many locations in large components characterized by interconnected volumes at different temperatures (i.e. upper and lower plena).
The existing turbulent heat transfer models for industrial computational fluids dynamics have not been developed to reliably predict the temperature fields in in liquid metals due to the limited interest in general applications. Hence, there is the need to enhance the knowledge about single- and multiple-jet mixing phenomena to low Prandtl number fluids.