Experiments and CFD simulations of the LBE loop in HYST: A new concept for irradiation experiments in a fast-reactor-like environment

Abstract

The current work investigates the thermal-hydraulics of a HYbrid fast/thermal core configuration Subcritical Testbed (HYST), a new concept proposed for irradiation experiments in a fast-reactor-like environment. Both the experimental studies and CFD simulations are performed to assist the development of HYST system. The experiments characterize heat transfer and pressure drop in the fast core as well as the heat transfer to thermal core from the fast core, while the CFD simulations only focus on the fast core to reduce the computational cost. The Reynolds-Averaged Navier Stokes (RANS) simulations using ANSYS Fluent are benchmarked through a two-step strategy first by existing data in literature and then by the newly collected data in HYST. By comparing with the existing data, confidence is gained in mesh generation, wire-rod contact modeling, and selected turbulence and Prt models. The mesh independence study in simulating HYST using Fluent indicates that the mesh convergence can be reached. Investigated parameters include the LBE temperature and velocity magnitude in all subchannels, heater rod surface temperature, outlet LBE temperature, and pressure drop between inlet and outlet. The effects of different Prt models and non-uniform power distribution on HYST simulation results are also investigated. Finally, these RANS simulations of HYST are benchmarked by preliminary experimental data in both adiabatic and heated tests. The experimental data of LBE outlet temperature for heated tests compare well with the simulations; however, the pressure drops are underestimated by the correlations and CFD simulations. In the next development phase, more detailed experimental studies and CFD simulations will be performed to assist the design of HYST system.