Structural material compatibility with high-temperature molten salt environments is a challenge to the deployment of MSRs. To achieve good heat transfer properties and neutron economy in an MSR, the list of candidate salt coolants is restricted to a small number of halides –. Liquid halides, such as fluorides and chlorides, can be corrosive to many structural materials. The oxide layers that are usually relied upon for corrosion protection in aqueous environments are unstable in these liquid salts. This leaves the structural alloy exposed to the salt. In general, components of alloys, such as chromium, are susceptible to selective dissolution by the salt, gradually weakening the material , .
Materials must be selected carefully to achieve good structural integrity and resistance to corrosion over the plant lifetime. To determine an alloys resistance to corrosion samples are exposed to molten salt and investigated with a variety of materials characterization methods. Long-term material exposure experiments are conducted in inert atmosphere gloveboxes to maintain salt quality and repeatability. Samples are exposed at temperatures between 700 °C and 850 °C for periods of up to 3000 hours.
Materials characterization methods commonly used to investigate corroded materials include scanning electron microscopy (SEM), X-Ray dispersive spectroscopy (XRD), transmission electron microscopy (TEM), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and profilometry.
Investigation of depletion of chromium in 316 Stainless Steel after exposure to LiF-BeF2 (66-34 wt.%) at 700 °C for 3000 hours. Scanning electron micrograph of a) the corroded face and b) corroded face in cross section. c) X-Ray dispersive spectroscopy of the corroded face cross section. d) X-Ray dispersive spectroscopy line scan normal to the corroded face .
- Further investigation of commercially available alloys for MSRs such as 316 Stainless Steel and Hastelloy-N
- Evaluation of novel nickel-based alloys in static molten salts.
- Exploration of promising alternative alloy compositions including Molybdenum-based alloys and high entropy alloys (HEAs).
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 G. Zheng, B. Kelleher, G. Cao, M. Anderson, T. Allen, and K. Sridharan, “Corrosion of 316 stainless steel in high temperature molten Li2BeF4 (FLiBe) salt,” J. Nucl. Mater., vol. 461, pp. 143–150, 2015.
 C. W. Forsberg, P. F. Peterson, K. Sridharan, L. Hu, M. Fratoni, and A. K. Prinja, “Integrated FHR technology development: Tritium management, materials testing, salt chemistry control, thermal hydraulics and neutronics, associated benchmarking and commercial basis,” Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Advanced Nuclear Energy Systems (CANES); Univ. of California, Berkeley, CA (United States); Univ. of Wisconsin, Madison, WI (United States); Univ. of New Mexico, Albuquerque, NM (United States), DOE-MIT-0008285, Oct. 2018.