The effect of source chemical composition on the self-attenuation corrections for low-energy gamma-rays in soil samples

To study the influence of the source's chemical composition on the self-attenuation corrections during the activity quantification of low-energy gamma-ray emitters (< 60 keV) in soil samples, we conducted a Monte Carlo-based hypothetical proficiency test in which different analytical laboratories analyze a soil sample, assuming the same density but a different chemical composition. The bias in the activity values was between 4% and 70%, with more than 50% of these results being unacceptable. Our work shows that collecting the detailed chemical composition of the samples is an essential issue to be considered by analytical laboratories that use the Monte Carlo method for the calculation of self-attenuation corrections.