Characterization of Fe and Cr Dissolution and Reaction Product Formation in Molten Chloride Salts With and Without Impurities

ABSTRACT

There is considerable interest in molten chloride salts for several applications including thermal storage and next-generation molten salt reactors (MSRs). Several studies have concluded that Cl salts are highly corrosive to structural materials. Using Oak Ridge National Laboratory’s established methodology, Cl salt compatibility was assessed for candidate Ni-based alloys 230, 600 and 740 H at 600°–800°C in static welded capsules and in flowing thermal convection loop (TCL) salt experiments. Simply drying commercial Cl salt at 550°–650°C and adding~0.05 wt.%Mg was able to produce small specimen mass changes and limited surface attack after 100–1000 h exposures. Intentional additions of H₂O, NiCl₂ and undried salt were used to better understand the role of impurities and achieve the>50 µm levels of attack reported in other studies. Characterisation of Cr depletion and oxide formation in conjunction with pre- and post-test salt chemistry measurements are being used to understand salt compatibility of structural materials.

KEYWORDS:

• Molten salt
• chloride salt
• thermal storage
• nuclear reactors
• Ni-based structural alloys

Acknowledgments

The authors would like to thank A Willoughby, B. Johnston, M. Stephens, T. Lowe, C. Parker, T. Jordan, V. Cox and R. Mayes at ORNL for assistance with the experimental work. J. Jun and J. R. Keiser provided useful comments on the manuscript. This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Solar Energy Technology Office (SETO): CSP award number 33873 and by DOE SBIR research projects with Innoveyda and Liquidmetal Group Holdings, Inc. The input of L. Irwin and M. Bauer as DOE SETO technical project monitors and all of our collaborators is appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the U.S. Department of Energy