Abstract
Freeze plug is an important safety system that can be used in Molten Salt Reactors (MSRs). Capable of removing the decay heat of the fuel in the core by draining the liquid fuel in the core to the safety tank located underneath the core by gravity, with no use of a mechanical valve or operator and electrical supply. The better understanding of designing the freeze plug system, the more efficient the MSRs safety system will be. The opening time of the freeze plug is one of the major importance in ensuring the passive safety of the MSRs. In this study, systematic numerical simulations are carried out to understand the solidification and melting processes of salt in MSRs freeze plugs. The simulation results from a previous study showed that the steady-state form of the frozen salt in the solidification process has a big impact on the opening time of the plug in the melting process. Based on these results, a simple method to estimate the opening time using the thermal conduction theory was developed. It was found that the opening time of the simulation results has a good agreement with the opening time from the analytical equation. Thus, it was demonstrated that this method is useful to estimate the performance of well-designed freeze plugs.
