To use the calibration curves of known concentrations (Fig. ) to quantify corrosion measurements, the spectra need to be transformed into the same shape and intensity. To accomplish this, the background signals (pure FLiNaK) from the corrosion and calibration measurements were fitted. Each background measurement was fitted with a 4 th degree polynomial to capture the shape in the entire energy range and avoid the noise in each signal (dashed lines in Fig. ). The fitting functions were divided by one another to create a conversion function between the signal shapes.