There are many regulations related to the radiological control of NORMs (Naturally Occurring Radioactive Materials) in activities such as mining, industry, etc. Consequently, it is necessary to
apply fast and accurate methods to measure the activity concentrations of long-lived natural radionuclides (e.g., 238U, 234,232,230,228Th, 228,226Ra, 210Pb, 210Po, and 40K) in samples characterized by a wide
variety of compositions and densities, such as mining samples (wastes, minerals, and scales). Thus, it
is relevant to calculate the radioactive index (RI), which summarizes for all radionuclides the ratio
between the activity concentration and its respective threshold activity concentration as established
by regulations, in order to classify a material as a NORM. To proceed with the determinations of
these radionuclides, two spectrometric techniques based on both alpha-particle and gamma-ray
detections should be employed. In the case of gamma-ray spectrometry, it is necessary to correct
the full-energy peak efficiency (FEPE) obtained for the calibration sample, εc, due to self-attenuation
and true coincidence summing (TCS) effects. The correction is especially significant at low gamma
emission energies, that is, Eγ < 150 keV, such as 46 keV (210Pb) and 63 keV (234Th). On the other hand,
in samples which contain radionuclides that are in secular disequilibrium with others belonging to
the same series (238U or 232Th series), like wastes or intermediate products, it is necessary to measure
some pure-alpha emitters (232Th, 230Th, 210Po) by employing alpha-particle spectrometry. A practical
and general validated procedure based on both alpha and gamma spectrometric techniques and
using semiconductor detectors is presented in this study
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