CFD benchmark for a heavy liquid metal fuel assembly

As part of a Department of Energy International Nuclear Energy Research Initiative (1-NERI), the Dutch Nuclear Research and consultancy Group (NRG), the Belgian Nuclear Research Centre (SCKCEN), Ghent University (UGent) in Belgium and the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) are collaborating with Argonne National Laboratory (ANL) to perform and compare a series of thermal hydraulic simulations representative of a heavy liquid metal fast reactor fuel assembly. Such a widely spaced wire-wrapped fuel assembly is a complex configuration for which few flow data are available for verification and validation of computational fluid dynamics (CFD) simulations. For this benchmark a 19-pin wire-wrapped rod bundle with characteristics representative of the MYRRHA flexible fast research reactor, under design at SCK'CEN in Belgium, is modeled. The heat conduction in the cladding of the fuel rods and the spacer wires is taken into account by conjugate heat transfer. UGent, ENEA and NRG performed their Reynolds Averaged Navier-Stokes (RANS) simulations with commercially available CFD codes. The high-fidelity ANL Large-Eddy Simulation (LES) was performed with Nek5000, used for CFD in the Simulation-based High-efficiency Advanced Reactor Prototyping (SHARP) suite. The paper will show and discuss the comparison of the thermal and hydraulic RANS results and the reference Nek5000 LES results. The comparison with the LES results will indicate to which extent the current liquid metal modeling methods are sufficient and help to highlight remaining issues. The results of the study are very valuable in the design and licensing process for MYRRHA.