Molten Salt Reactors (MSRs) are an advanced reactor design of interest to the nuclear power industry, as their design allows for operation at lower pressures and higher temperatures compared to Light Water Reactors (LWRs). MSRs also have passive safety features such as large negative reactivity coefficients. Moreover, there is potential to produce less waste with shorter lifetimes than current reactor designs, in addition to breeding of fuel for better utilization of uranium and thorium resources. However, MSR designs currently face challenges associated with the corrosion of structural materials, limiting the possibility of MSR viability. The mechanisms corrosion behavior in these systems are not well understood and require study. The objective of this work is to study mechanisms of salt infiltration and de-alloying in structural materials. Laser-induced breakdown spectroscopy (LIBS) was used to investigate alloy surfaces after exposure to molten salt. A binary nickel – chromium alloy with a 16 % weight percent Cr composition was tested, as Ni-Cr alloys and their derivatives are of primary interest for structural use in molten salt systems. Samples were exposed to a KCl-MgCl2 eutectic salt at a temperature of 700°C for 1000, 2000, and 2500 hours. These static tests were conducted in molybdenum capsules to control external impact on the corrosion. Salt preparation along with test conditions were tightly controlled to limit impurities in the salt and inhibit any additional corrosion processes that could cause fluctuation or high error in results. A commercially available LIBS instrument outfitted with a high-resolution echelle spectrometer was used to collect the optical emission spectra of the LIBS plasmas. This talk will report new insights into the behavior of nickel alloy interfaces in contact with molten chloride salts. LIBS data will be used to show how salt infiltrates into the alloys and interacts with alloy constituents.

Measurement of molten KCl-MgCl2 salt penetration depth in nickel alloys using LIBS

2019 Fall National Meeting

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