Pre-test CFD analysis of the rod bundle experiment in the HLM facility NACIE-UP

At ENEA-Brasimone R.C., large experimental facilities exist to study HLM free, forced and mixed convection in loops and pools: e.g. NACIE-UP is a large scale LBE loop for mixed convection experiments. In the context of the SEARCH FP7 project, an experiment has to be performed in the NACIE-UP facility to assess the coolability of a 19-pin wire-wrapped electrical bundle (Fuel Pin Simulator, FPS), with heat flux up to 1 MW/m2. The bundle is representative of the one adopted in the MYRRHA concept. The present paper is devoted to the Computational Fluid Dynamic (CFD) analysis of Heavy Liquid Metal (HLM) cooled Fuel Bundles to be adopted in the Gen-IV nuclear reactors. A CFD analysis of fluid flow and heat transfer was carried out in the heavy liquid metal (LBE) cooled bundle test section of the NACIE-UP facility. The model includes the details of the wire-spacers as well as the entry region of the test section. A turbulence closure approach is adopted for all the simulations with ≈ 3.5∙107 nodes and a resolution of y+ = 1