Search

Abstract: In-situ gamma-ray spectrometry is widely used for monitoring of natural as well as man-made radionuclides and corresponding gamma fields in the environment or working places. It finds effective application in the operational and accidental monitoring of nuclear facilities and their vicinity, waste depositories, radioactive contamination measurements and environmental mapping or geological prospecting. In order to determine accurate radionuclide concentrations in these research fields, Monte Carlo codes have recently been used to obtain the efficiency calibration of in-situ gamma-ray detectors. This work presents an inter-comparison between two Monte Carlo codes applied to in-situ gamma-ray spectrometry. On the commercial market, Canberra has its LABSOCS/ISOCS software which is relatively inexpensive. The ISOCS mathematical efficiency calibration software uses a combination of Monte Carlo calculations and discrete ordinate attenuation computations. Efficiencies can be generated in a few minutes in the field and can be modified easily if needed. However, it has been reported in the literature that ISOCS computation method is accurate on average only within 5%, and additionally in order to use LABSOCS/ISOCS it is necessary a previous characterization of the detector by Canberra, which is an expensive process. On the other hand, the multipurpose and open source GEANT4 takes significant computer time and presents a non-friendly but powerful toolkit, independent of the manufacturer of the detector. Different experimental measurements of calibrated sources were performed with a Canberra portable HPGe detector and compared to the results obtained using both Monte Carlo codes. Furthermore, a variety of efficiency calibrations for different radioactive source distributions were calculated and tested, like plane shapes or containers filled with different materials such as soil, water, etc. LabSOCS simulated efficiencies for medium and high energies were given within an accuracy of below 5% for point sources and 10% maximum accuracy for more complicated geometries. Accuracy for LabSOCS decreased for low energy emissions. Finally an analysis and discussion of the results and the main differences found between LabSOCS and GEANT4 were performed. [Copyright &y& Elsevier]

In this paper coincidence summing corrections in gamma-ray spectrometry have been analyzed in depth. Experimental setup included a n-type germanium detector and two efficient geometries of measurement (Marinelli beaker and air filter) calibrated with multi gamma radionuclides in the energy range of 40-1500 keV. Monte Carlo simulations were carried out using the GEANT4 code in order to develop this work. Firstly an optimization of the detector dimensions was performed to obtain the full-energy peak efficiency curve. Next, the simulation of the decay schemes for involved multi gamma radionuclides were appended to the GEANT4 code including beta, alpha, EC decay, together with the subsequent relaxation process consisting of a cascade of fluorescent X-rays and Auger electrons. In order to test the simulations an comparison between an experimental and a calculated spectra of 133Ba point source was carried out. Finally coincidence summing effects for gamma-ray emission and X-ray, Auger electron, beta and EC electron were studied in detail. [ABSTRACT FROM AUTHOR]

In this paper, we will expose the work performed for the adaptation and refinement of the GEANT4 simulation toolkit (originally designed for Monte Carlo simulations in High-Energy Physics) in order to simulate Ge detectors in low-level gamma spectrometry. Special emphasis will be given to show and validate our own algorithms implemented in GEANT4 code for variance reduction and data analysis, that have been used for a quicker and precise efficiency calibration at different source-detector configurations of one of the low-level germanium gamma systems available in our laboratory. [Copyright &y& Elsevier]

The GEANT4 software was developed by RD44, a world-wide collaboration of national institutes, laboratories and large High-Energy Physics experiments. GEANT4 is a public software package composed of tools which can be used to accurately simulate the passage of particles through matter. In this article, the first attempt to use GEANT4 to model a reverse electrode germanium detector (REGe), and to improve also its efficiency calibration procedure, is presented. A variance reduction algorithm based on a directional bias scheme is implemented into GEANT4 in order to accelerate the efficiency computations. A fast optimisation method to model the detector geometry using standard point sources is also presented and validated for point, Marinelli and air filter sources. The simulated full-energy peak efficiencies agreed with the measured values to within 1% between 36 and 1460 keV for these three counting geometries. [Copyright &y& Elsevier]

The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage. • Examples of the use of Monte Carlo simulation to calculate coincidence summing corrections. • Simple cases with two types of germanium detectors and four kinds of sources were investigated. • Calculation of coincidence summing correction factors for 60Co, 134Cs, 133Ba and 22Na is presented. • Input files, correction factors and recommendations are available on a dedicated webpage. [ABSTRACT FROM AUTHOR]

Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage. • Examples of the use of Monte Carlo simulation using different software. • Simple cases with two types of germanium detectors and four kinds of sources. • Calculation of full-energy peak and total efficiencies for 5 energies. • Input files and efficiency calculation results available on a dedicated webpage. [ABSTRACT FROM AUTHOR]