Properties and removal of non-metal ions in molten salts

Molten salts have broad applications in high-temperature energy systems such as advanced nuclear reactors and concentrated solar power systems. However, it is known that molten salts are corrosive to most of the structural materials, and the corrosion by molten salts is one of the major concerns in their applications. Impurities, especially, non-metal impurities such as moisture, hydroxide and oxygen, are known to accelerate the material corrosion. The present study focused on measurements of the fundamental data such as diffusion coefficients of non-metal ions and reaction constants of the redox reactions that may influence the corrosion kinetics. The study investigated the following non-metal ions: OH-, O2- and I-. In addition, the study also investigated how to removal these ions from molten fluoride salts electrochemically. It was found that the oxygen ion can be removed by using a graphite anode in the form of carbon oxides, and the iodine ion can be removed by using graphite anode in the form iodine gas. The study also showed the anodic effects on a graphite anode which would affect the separation efficiency for iodine removal from a fluoride molten salt.