Coupled Neutronics-Thermal-Hydraulic Modeling of a Molten Salt Reactor: The Aircraft Reactor Experiment

The CEA multiphysics tool combining the deterministic neutronics code APOLLO3® and the computational fluid dynamics (CFD) platform TRUST/TrioCFD is used to model the first-ever-built molten salt nuclear reactor, the Aircraft Reactor Experiment (ARE). A neutronics model and a thermal-hydraulic model of the reactor were created and coupled. Steady-state and transient simulations were performed in order to reproduce experiments realized on the ARE. The simulation results and experimental data are compared as a way of validating the multiphysics tool. The nominal state of the ARE is reproduced first; significant discrepancies were observed regarding the liquid sodium flow. Variations of βeff with the fuel flow rate were then studied. While the simulation was in very good agreement with the experimental data for high flow rates, some discrepancies were observed at low and null flow rates. Finally, a transient simulation of a rod withdrawal was reproduced. While the beginning of the transient simulation was in good agreement with the experimental data, oscillations appeared in the second half of the simulation.