Post-corrosion XANES spectra collected along the vertical direction of the BN cell were measured to determine the spatial distribution of the corroded Ni ions within the molten salt. The spectra as a function of distance from the foil are shown in Fig. . To avoid time-dependence changes in concentration during measurements, the spatial scans were done at room temperature after high-temperature corrosion experiments were completed. The Ni 2+ valence state is apparent from the XANES measurements at the distances away from the foil location, and the spectrum at 0 mm is purely metallic as expected. A concentration distribution within the salt is apparent on a log-linear scale. We found that the spatial profiles of both Ni 2+ and Ni 0 concentrations cannot be fitted by a simple dif-fusion equation. We note that in Fig. , the concentration of Ni 2+ at 3 mm distance from the foil is much larger that in Fig. . This is a result of (inadvertent) shifting of the BN cell horizontally between measurements that were separated by several hours. This first corrosion experiment demonstrated that the custom BN cells were sufficiently transparent for XAS measurements to capture the valence state and concentration of corroded Ni ions while containing the salt at elevated temperatures. The BN cells withstood both the extreme temperatures within the furnace and held the salt without leakage. XAS captured the Ni concentration with enough temporal resolution to precisely track the corrosion process.