Design and Thermal-Mechanical Analysis of a Supporting Structure for a Molten Salt Pump Shaft Seal Test Facility

A shaft seal test facility (SSTF) was designed to evaluate the static and dynamic performance of molten salt pump shaft seal candidates under various molten salt reactor operating conditions. The SSTF design incorporated a structural frame capable of supporting a stainless steel salt tank and enabling passive drainage of molten salt to a storage tank. The structure was required to sustain a load of approximately 500 kg and operate at temperatures up to 650°C. The proposed design consisted of a top plate, four H-bar legs, and four brackets, analogous to a table. A coupled thermal-structural analysis was conducted at both room and elevated temperatures to evaluate the structural integrity of the design. The simulation results revealed three local stress concentration regions: two welding joints and small bolt holes in the top plate. Several design improvements and boundary condition modifications were tested as ways to mitigate the stress concentrations. Thermal stress was identified as the dominant factor at elevated temperatures. Allowing bracket movement accommodated thermal expansion, substantially reducing stress at the bottom welding joint. Further analysis revealed that the elevated stresses and plastic strains at the top welding joint were primarily caused by the mismatch in the thermal expansion coefficients between different materials. Therefore, welding metals with markedly different thermal expansion coefficients should be avoided in high-temperature applications. Increasing the top plate thickness reduced plastic deformation at the bolt holes but concurrently elevated stress at the top welding joint.