Abstract
The longevity of structural materials in the implementation of molten salt reactor (MSR) systems requires an elevated degree of consideration due to extreme environments inherent to the MSR. Evaluating the suitability of materials is partially determined by their corrosion rate, however, there is a gap in the methodology of redox control during the operation of an MSR system. Likely due to carbide precipitation, two out of three spark plasma sintered nickel alloys showed weight gain after corrosion testing (-0.075 & -0.027 mm/year) and the third demonstrating a corrosion rate of 0.0358 mm/year. The performance of the AM-SS316L during corrosion testing was influenced by a manufacturing parameter (slower contour scan speeds), in which the corrosion rates range between 0.35 – 0.73 mm/year. Optimized manufacturing processes of AM-SS316L should be put into consideration when fabricating structural materials for MSR applications to maximize the longevity of the system. This work provides foundational electrochemical parameters and manufacturing strategies essential for MSR structural design.
In this study, cyclic voltammetry was performed on various masses (40 to 0.1g) of molten FLiNaK salt (LiF 46.5- NaF 11.5- KF 42.0 mol%) to measure the redox potential of the salt constituent, the K+/K reaction couple, at 650°C and 600°C at scanning rates of 50, 100, and 200 mV/s. Additionally, additively manufactured stainless steel 316L (AM-SS316L) and spark plasma sintered (SPS) nickel alloys were immersed in molten FLiNaK salt at 700°C for extended durations of time (100-500 hours) to assess corrosion resistance. K+/K redox potentials were measured using a three-electrode nickel system, which measured to be -1.217 to -1.788 V (vs. Ni), demonstrating electrochemical behavior consistent with literature studies of K+/K redox potentials in FLiNaK salt.