Heat transfer experiments in rod bundles cooled by lead-bismuth uutectic (LBE)

Heavy liquid metals (HLMs), such as lead-bismuth eutectic (LBE) and pure lead are prominent candidate coolants for critical assemblies and accelerator-driven systems based on fast neutrons. With a strong focus on safety, key thermal-hydraulic aspects of these systems must be considered. The main challenge for modeling the heat transfer in liquid metals is given by their characteristically low Prandtl number (Pr << 1), separating the scales of turbulent transfer of momentum and heat. For that reason, specific experimental investigations are required for validating according models, particularly for complex geometries such as rod bundles. This work presents the experimental evaluation of two tests sections, both consisting of electrically-heated 19-pin hexagonal bundles, although with different characteristics. The setup #1 has grid spacers and a relatively large pitch-to-diameter ratio P/D=1.4. In this recently completed experimental campaign, extensive heat transfer and pressure drop information was obtained at typical reactor conditions of temperature (up to 450 °C), power density (up to 1.0 MW m ) and bulk velocity (2.2 m s ). With a good repeatability, these results agree well with information available in literature and are a suitable source of data for the validation of predicting models. The setup #2 is a similar bundle, with wire spacers and P/D=1.28. It is currently in the last stages of construction and commissioning. Its main characteristics, instrumentation and envisaged experiments are presented in this work.