Tritium, a radionuclide produced through neutron capture by lithium and other elements in molten salts, presents unique challenges to radionuclide release for both fusion energy breeder blankets and molten salt fission reactors due to its low solubility, small molecular size, and electronic structure, which allows it to readily permeate through hot structural materials. The fundamental understanding of tritium transport is crucial to the safe design and operation of these reactors. The Molten Salt Tritium Transport Experiment (MSTTE) currently under construction at Idaho National Laboratory (INL) aims to investigate tritium transport phenomena using a forced-convection fluoride salt loop. This loop is designed to study various transport mechanisms, such as permeation through metals and gas-liquid interactions, and is intended to support future research on Tritium Extraction Units (TEUs). A critical aspect of the MSTTE loop design is ensuring a fully developed velocity profile before the fluid reaches the permeation test section where measurements are made to understand the semi-integral phenomena of tritium permeating through structural materials in flowing salt. This study employs Computational Fluid Dynamics (CFD) to model the salt flow behavior within the MSTTE permeation test section. A realizable k-e turbulent model with enhanced wall treatment (EWT) is used to simulate the single-phase, vertical upward flow of molten salt FLiNaK under isothermal conditions. Simulation results indicated flow distortion and underdeveloped profiles at all planned flow rates within the test section, due to the 85-degree sharp bend. To address this issue, reduced diameter with a reducer and expander as well as a flow conditioner (FC) are investigated to achieve fully developed flow. Analysis showed that the flow conditioner successfully corrected the flow profile, achieving fully developed behavior at a flow rate of 50 NLM. This research enhances our understanding of flow dynamics in molten salt systems and contributes to optimizing tritium transport control technologies.
