Application of the spatial efficiency e(~r) of a HpGe detector to determine the speci activity of radioactive material in cylindrical extended sources

In the present work, the intrinsic efficiency for a high-resolution spectroscopy gamma system as a function of the source-detector position, i.e. (r), and the specific activity for a radioactive homogeneous extended source in cylindrical geometry, for an energy of 661.65 keV (137Cs), were determined. Mathematical expressions for the intrinsic spatial efficiency and the spe ci activity of a volumetric cylindrical sample were obtained from basic concepts of solid angle and gamma attenuation. In order to determine the intrinsic spatial e iency, a 137Cs source of known activity was positioned at difference source-detector position. This efficiency was used to establish the specific activity for different reference materials.This methodology allows us to determine the spe ci activity of radioactive species present in volumetric samples, such as soil, water and construction materials samples, without the direct use of reference materials for qu anti ation of radiation levels. The reference material was only used to validate the method. The advantage of this method is that allows specific activity determination without the need of making matrix effect corrections (shape and size of the sample, sample density, self-attenuation and moisture), which are the principal error sources in this type of measurement