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In this paper there are described three different algorithms of Minimum Detectable Activity ( MDA ) calculus, and its use in high resolution gamma spectrometry. In the first part, few introductive theoretical aspects related to the MDA are presented. Further, the theory was applied to real gamma rays spectrometry measurements and the results were compared with the activities reference values. Two different gamma spectrometry systems, both of them using High Purity Germanium (HPGe) detectors, but having different efficiencies, were used. Samples having different geometries and radionuclides content were measured. The measured samples were made by dissolving of some acids containing anthropogenic radionuclides in water, obtaining a density of 1 g/cm 3 . Choosing this type of matrix was done because of its high homogeneity. [ABSTRACT FROM AUTHOR]

In this work, a classical approach was used for calibrating the GESPECOR detector model for computing the full-energy peak efficiency of p-type coaxial HPGe detectors that is based on the use of linear least squares optimization. The key element of the work is the multiplicative model developed for approximating the values of the full-energy peak efficiency provided by GESPECOR code. It was linearized using the logarithmic transformation to allow an easy use of the linear least squares optimization. A procedure was also developed to estimate the optimal values of the parameters, describing the p-type coaxial HPGe detectors. Its application to a Canberra detector GC3018 showed that it is possible to determine accurate values of the full-energy peak efficiency computed by GESPECOR code using the optimized parameter values. • A classical approach for calibrating the GESPECOR model is described. • A multiplicative model approximates the full-energy peak efficiency given by GESPECOR. • Model parameters are optimized using a linear least squares approach. • A simple calibration procedure was developed. • Accurate values of the full-energy peak efficiency are obtained using the optimal parameters. [ABSTRACT FROM AUTHOR]

A novel virtual point detector model was developed for cylindrical high purity germanium detectors that are widely used in gamma-ray spectrometry. According to this model, the full energy peak efficiency response of these detectors can be computed by replacing the detector with a virtual point detector located at the center of the detector crystal. In fact, the novel model makes the transfer of the FEP efficiency response from a reference point source to a given point source, both sources being located on a line that passes through the virtual point detector. The model was tested and provided accurate results. • A novel virtual point detector model is described in this paper. • The FEP efficiency response is approximated by a power function model. • The novel model has a solid theoretical basis. • Two computational ways were developed to apply in practice the model. • This model may provide accurate values of the FEP efficiency response. [ABSTRACT FROM AUTHOR]