Compatibility of Inconel 617 alloy with eutectic fluoride salts at high temperatures

Thermal Energy Storage (TES) capsules made of Inconel 617 alloy were filled with high purity eutectic fluoride salts and thermally cycled at eutectic temperature ±100 K for a period of up to 50,000 hours. The containment life performance characteristics with fluoride salts were examined. The depletion of Al and Cr near the inner edges was found. Atomic Absorption Spectroscopy revealed that both Al and Cr were dissolved in the fluoride salts at high temperatures. The changes in melting temperature and heat of fusion of fluoride salts during thermal cycling were measured with Thermal Differential Analysis. A modified diffusion equation for a one‐dimensional semi‐infinite bar was applied to the depletion of Al on the interior surfaces of the containers. Good agreement was obtained between the analysis and the measured concentration profiles. The present study suggests that the corrosion was a diffusion controlled process and an expected lifetime of 5–7 years is reasonable and predictable based upon the limit...