A general methodology to determine natural radionuclides by well-type HPGe detectors

This work aims to determine natural radionuclides (210Pb, 228,226Ra, 234,228Th and 40K) in NORM samples by well-type HPGe detectors because they are of vital importance in studies on environmental samples. For this, a novel methodology has been developed, based on obtaining a general function for the full-energy peak efficiency (FEPE) versus the sample apparent density and composition, keeping the sample height constant. To obtain the general FEPE function, a calibration in efficiency has been accomplished using certified standards provided by IAEA (RGU-1 and RGTh-1), and KCl. Besides, different self-absorption correction functions were compared for cylindrical geometry, where chemical compositions need to be known. Then, a study on using an anti-Compton system was done, getting a lower detection limit and allowing to propose gamma spectrometry as an alternative technique to alpha-particle spectrometry. Finally, the followed methodology to calculate the FEPE was subjected to internal and external validations, checking its validity range.This research was partially funded by a project of the Regional Government of Andalusia “Basic processes regulating the fractionations and enrichments of natural radionuclides under acid mine drainage conditions” (Ref.: UHU-1255876), and a project of the Projects for Novel Principal Investigators “Quantitative study of the variables involved in the radon exhalation rate for granular solids; application to rafts of granular solid phosphogypsum” (Ref.: UHUPJ-00005-632). A.B.L. acknowledges support from funds provided by the Spanish Ministry of Science, Innovation and Universities’ Research Agency and co-financing provided by the European Social Fund (ESF) and the Spanish National Youth Guarantee Implementation Plan under Contract No. PEJ2018-002676-A.Funding for open access charge: Universidad de Huelva / CBU