Corrosion of commercial alloys in FLiNaK molten salt containing EuF3 and simulant fission product additives

In liquid–fueled molten salt reactor designs, materials will be exposed to a molten salt containing a multitude of fission products and other corrosive species. Little work has been done to understand the unique corrosion characteristics of materials in fission product-laden liquid–fuel systems. In this study, we conducted corrosion experiments up to 150 h in duration which exposed four commercial alloys (Hastelloy N, Incoloy 800H, 316L stainless steel, and Ni–201) to three molten salt compositions in order to better understand corrosion in liquid–fuel systems and inform reactor design. It was found that the presence of simulant fission product species, at predicted concentrations, in a highly corrosive FLiNaK + EuF3 molten salt does not lead to any detectable increase in corrosion at reactor–relevant conditions. No penetration of simulant fission product species into the samples was detected. The unique corrosion morphology of each of the alloys tested in this work is discussed. In particular, Ni–201 was found to be an ideal salt–facing material in molten fluoride systems, and is essentially immune to corrosion.