Fluid Dynamic Model of the Molten Salt Reactor Experiment Using Flownex Simulation Environment

Abstract

Molten salt reactors (MSRs) have recently experienced renewed interest due to their potential for improved economics, safety, and sustainability. Despite their 70-year history, the Molten Salt Reactor Experiment (MSRE) was the only MSR to ever be operated and has become an essential source of experimental data for new MSR designs. This work evaluates available literature on the MSRE to create a model that serves as the basis for a thermalhydraulic analysis of the system. It was proposed to create a model of the MSRE hydraulic experiment with geometric and head loss inputs calculated from first principles and accepted experimental results, as existing thermalhydraulic models tune inputs to match pressure loss and velocity data. Such a model is essential for modelling transient behaviour of the MSRE by ensuring that correct residence and neutron transport times are used for calculations. Minor head losses of components were calculated using accepted literature for similar geometries, and major losses were modified in the core to account for developing flow conditions and the atypical channel geometry. Flownex Simulation Environment is a 1-dimensional software code that provides the ability to model entire nuclear reactor systems. A Flownex network of the MSRE was created to compare results against available MSRE experiment results, and results from the model agreed well in most cases. Pressure loss through the core and the full system were within 2% of experimental values. Velocities and flow rates matched well, except in regions of complex 3-dimensional flow such as the cooling annulus. The model can easily be extended to simulate the full MSRE operating with molten salt, though no experimental data is available for comparison. Further investigation is required to ensure that correct heat transfer correlations and material properties are used. Flownex also has the potential to include neutronics in future simulations for transient studies.