Electrochemical Methods for Continuous Metal Corrosion Monitoring in Molten Salts

摘要

Molten eutectic LiCl-KCl is used for electrorefining of spent nuclear fuels using pyroprocessing technology that is currently being developed most notably in the United States and Republic of Korea. Stainless steels are the preferred materials for fabrication of components and other structural constituents . The presence of impurities within the system need to be addressed to minimize possible corrosion of these steels in the salt . Such corrosion can lead to contamination of the electrolyte and/or degradation of the electrorefining vessel. The contaminated salt will lead to a contaminated product, while degradation of the vessel components will shorten vessel life. However, formation of corrosion products may also lead to a protective passivation layer .Corrosion of these pseudo protective coatings has been studied inside molten salts but not in a continuous manner . Typically the use of sacrificial coupons is utilized to investigate corrosion in chloride salts. These coupons then undergo analysis such as scanning electron microscopy or x-ray diffraction . The downfall of these techniques is the lag time between a corrosion event to discovery of corrosion. It would be advantageous to monitor corrosion continuously and in real time to observe what changes have occurred that result in corrosion. One type of change or impurity within electrorefiners is the presence of water.