Application of Modelica/TRANSFORM to system modeling of the molten salt reactor experiment

The molten salt reactor (MSR), being a liquid-fueled reactor, exhibits a strong coupling between neutronics and thermal hydraulics originating from the simultaneous utilization of the fuel as the coolant. Analysis of the dynamic behavior of MSRs thus necessitates the use of coupled multiphysics tools. This work leverages the multiphysics capabilities of the Modelica-based, open-source component library Transient Simulation Framework of Reconfigurable Modules (TRANSFORM) and demonstrates its ability to simulate the behavior of an MSR with the focus on modeling the Molten Salt Reactor Experiment (MSRE). The model employs 1D thermal-hydraulic components with a coarse radial and axial discretization of the active core region approximating the design of the MSRE. The power generation within each node is determined by neutron point kinetics which are modified to account for the effects of fuel circulation. Using the developed model, neutronic and thermal-hydraulic behavior under steady-state conditions is characterized and compared to experimental data and alternative computational codes. Some discrepancies are found but most of them are explained by the modeling choices and uncertainties in input data. Performance of the model under transient conditions is then investigated by simulating experiments conducted on the MSRE; the results are again benchmarked against reference data. Overall, good agreement is attained.