Thermal gradient mass transport corrosion in NaCl-MgCl2 and MgCl2-NaCl-KCl molten salts

Abstract

A small scale natural circulation loop, or microloop , has been developed at TerraPower for the evaluation of material corrosion via thermal gradient mass transfer with molten chloride salts. Molten chloride salts are high temperature, low vapor pressure heat transfer fluids with applications in advanced nuclear, solar thermal power generation, and energy storage. As of now, forty nine loops have operated or are currently operating, accruing over nine flow–years of data with nine different commercially available alloys. Results indicate that only molybdenum is impervious to chloride salt attack, with extended circulations forming a molybdenum-rich corrosion microstructure in certain alloys. Out of the alloys tested, only three had corrosion results of less than 100 μ m yr −1 : alloy 600, alloy C-276, and alloy N. This report aims to discuss the design and operating characteristics of the microloop platform, while exploring thermal gradient mass transport corrosion results in NaCl-MgCl 2 and MgCl 2 -NaCl-KCl eutectics—two typical chloride salts of interest.