An upgraded lab-based method to determine natural γ-ray emitters in NORM samples by using Ge detectors

The regulation existing on NORM activities requires the accurate and quick measurement of natural radionuclides in a wide range of matrices by gamma spectrometry. The aim of this work has been to develop a comprehensive and accurate methodology to determine natural long-lived radionuclides (210Pb, 228,226Ra, 234,228Th and 40K) by gamma spectrometry with Ge detectors in NORM samples. An exhaustive calibration method to obtain the full-energy peak efficiency (FEPE), for each gamma emission energy, as a function of the thickness, apparent density and matrix composition of the cylindrical sample, has been developed. The selected certified calibration standards contain only natural radionuclides belonging to the 238U- and 232Th-series as well as 40K (codes RGU-1, RGTh-1 and RGK-1 from IAEA). Then, the obtained FEPE curves were validated using Genie 2000 simulations and Certified Reference Materials, for which the self-attenuation corrections were considered. Finally, a study on 222Rn losses was done for several samples.Funding for open access charge: Universidad de Huelva / CBU