The raw intensity of the step size in XANES is directly related with the amount (or concentration) of the element in a sample. Leri et al. described a method to calibrate the raw XANES step size intensity for Cl concentrations in organic samples, and in a continuation of their work, Leri and Ravel then described a similar method using hard X-ray energies. Here, we adapt similar methods to determine the concentration of Ni in molten FLiNaK salt to investigate the corrosion that occurs under MSR operating temperatures.