Molten Salt Reactors (MSRs) are among the promising Generation-IV nuclear reactor concepts due to their inherent safety characteristics, high thermal efficiency, and capability for passive safety operation. One of the important passive safety components in MSRs is the freeze plug system, which is designed to melt intentionally during abnormal operating conditions and allow the molten salt to drain into passively cooled dump tanks. Accurate prediction of freeze plug melting behavior is essential for ensuring reliable reactor safety performances. In the present study, an experimental investigation and Computational Fluid Dynamics (CFD) validation of transient molten salt melting in a freeze plug are carried out to analyze the thermal and phase change behavior of the system.

Experimental investigations were performed under controlled heating conditions to study the transient melting characteristics of molten salt within the freeze plug configuration. Temperature variation and melting progression were monitored to evaluate the thermal response during the phase transition process. A CFD-based transient numerical model incorporating solidification and melting physics was subsequently developed to simulate the melting behavior of

the molten salt.

The numerical predictions were validated against the experimental observations through comparison of thermal response and melting characteristics. The results demonstrated good agreement between the experimental and numerical analyses, indicating the capability of the CFD model to accurately predict transient melting behavior in freeze plug systems. The validated computational model developed in the present work can further be utilized for predictive thermal analysis and future design assessment of molten salt freeze plug configurations. The study contributes toward the development of experimentally validated CFD methodologies for phase change analysis in molten salt thermal systems.

• Keywords—Molten Salt,Freeze Plug,Phase Change Heat Transfer,Transient CFD Analysis