CFD analysis of a wire-wrapped infinite sub-channel using temperature-dependent LBE properties

Abstract

Once a significant number of LMFRs (liquid-metal cooled fast nuclear reactors) employ wire-wrapped fuel assemblies, considerable attention should be directed to this engineering feature. Given the many contact points and tight gaps, wire-wrapped fuel assemblies are difficult to analyze without numerical tools, out of which CFD (computational fluid dynamic) is the leading tool in the field. This work presents a CFD analysis of a wire-wrapped infinite sub-channel, based on MYRRHA’s fuel assembly geometry and with LBE (lead bismuth eutectic) coolant properties implemented as temperature-dependent polynomial curves. Periodic boundary conditions were applied, and the turbulence model chosen was k-w SST. All calculations were run on ANSYS Fluent R19.3. Following good engineering practices for CFD simulations, a GCI (grid convergence index) analysis was carried out, in order to ensure grid/mesh independence on the results. Ultimately, the main goal of this work was to evaluate if the implementation of temperature-dependent thermal-physical properties for LBE coolant would lead to any different results, when compared to the static properties. However, no significant result change was observed in this case, only an increase in computational time, which leads to the conclusion that for small domains with periodic boundaries, the implementation of temperature-dependent coolant properties is not justifiable.