Migration and phase change study of leaking molten salt in tank foundation material

•Thermal equilibrium temperature of foundation increases after leakage.•The operating temperature affects significantly migration characteristics.•Migration process of leaking molten salt is investigated experimentally. Molten salt is widely used as a heat transfer and thermal storage medium in concentrated solar power plants. This paper mainly focuses on the migration and phase change characteristics of molten salt leaking from a high-temperature storage tank to the thermal-steady porous foundation materials. The effects of the different conditions, including material structure, leakage pore size, operating temperature and leaking molten salt mass, are investigated via the self-designed experimental system that models the actual leaking process. Results show that the molten salt migrates rapidly in the porous foundation material during the leaking process and begins to solidify on the bottom, hindering molten salt from further flowing down. After molten salt leakage, the thermal equilibrium temperature of foundation material increases. It is found that the molten salt migration depth distinctly decreases with the smaller porosity of the porous material. When the leakage pore size diminishes or the operating temperature increases, the migration depth obviously increases, while the migration diameter decreases. Nevertheless, within a certain range, the leaking molten salt mass has some effect on the migration diameter but has little effect on the migration depth. These results provide quantitative references for the pollution control and disposition of molten salt leakage accidents.