IAEA Benchmark CRP - I31038: Open Phase Liquid-Metal CFD Results for Fuel Pin Simulator

Abstract

In the IAEA Coordinated Research Project “Benchmark of Transition from Forced to Natural Circulation Experiment with Heavy Liquid Metal Loop” (CRP - I31038) participants benchmark their simulation capabilities versus the experimental data obtained in the NACIE-Up facility (NAtural CIrculation Experiment-UPgrade) at ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development). The fuel pin simulator consists of 19 wire-wrapped pins. The liquid metal coolant first passes through an unheated cold section and then through an electrically heated section. In the heated section either all pins or only a fraction of the pins are heated to simulate power gradients in a nuclear reactor. During the experiments both the axial and the lateral temperatures are measured at suitable locations. Twelve results from different organizations contributed to the open phase benchmarking, where specifically the heating of all 19 pins, 9 pins and the 7 inner pins was studied. This will contribute to the validation and verification of the computational fluid dynamic tools for reactor design. We have tried to deliver results that require minimal numerical resources, well-resolve all relevant geometric features and match the accuracy of the provided experimental data. In the second benchmark meeting at IAEA the results of the contributors were compared. It was confirmed that our modelling strategy leads to credible and accurate results at low numerical cost. In the paper we present details on the modelling approach and compare the numerical results to experimental data and preliminary CFD data resulting from all participants in the work package. Our simulation is ranked among the most reliable results.