Corrosion

Fluoride salt selection is one important aspect for Molten Salt Reactors (MSRs). Due to its good heat transfer performance, the FLiNaK eutectic is recommended as one of the most promising heat-transfer fluids for MSRs. Fluoride salts are potentially corrosive to many reactor structural materials at high temperatures due to the removal of surface protective oxide layers. Therefore, it is necessary to investigate corrosion behavior of materials in FLiNaK at elevated temperatures for their application in FHRs.

 

Stainless steel 316H is a potential candidate as a high-temperature resistant alloy for fluoride salt test facilities. In our study, FLiNaK with a 99% purity level is used. The salt is dehydrated at 250 °C for four hours to remove most of moisture in a nitrogen inert glove box. Corrosion behavior of coupons made of SS 316H is investigated in FLiNaK that had been dried under an argon-covered environment in a stainless-steel 316H crucible. The coupon weight loss is identified over a 100-hour test at temperatures over 700 °C. The corrosion on the SS 316H coupon surface is observed by a high-resolution scanning electron microscope and the corresponding energy-dispersive X-ray spectroscopy line-scan analysis is also performed.