Effects of Thimble Leak on the Thermal Characteristics of Water-cooled Fuel Drain System in Molten Salt Reactor

The  fuel drain system is feasible and safety important.  [Purpose]: This study aims at the water-cooled fuel drain system of MSRE (Molten Salt Reactor Experiment) to analyze the effects of thimble leak on thermal characteristics and key factors.  [Methods]: First, a computational fluid dynamics simulation was conducted to establish a multiphase heat transfer flow model, which was employed to study the impact of leak on the heat transfer performance of bayonet tube.

Then, sensitivity analyses of leak sizes (2 mm to 7 mm), leak locations (above the bottom of thimble, ranging from 0.01 m to 1.25 m), and the pressure difference between the annular gas space and the fuel drain tank (ranging from 20684 Pa to 48258 Pa) were conducted.  [Results]: The results indicate that when thimble leak occurs, the molten salt flowed into the annular gas space. The heat transfer capacity of a single bayonet tube increased more than 500%.