ABSTRACT
Objective:To recommend reference composition for sourceless efficiency calibration of food gamma spectrometry by analyzing the composition of common foods based on a combination of sourceless efficiency calibration and active validation.Methods:Thirty common types of food samples in countrywide monitoring of radioactively contaminated foods were analyzed to statistically determine the reference composition of grains and vegetables. Combined with the parameters provided for white quinoa standard source, LabSOCS was applied to carry out the simulation of sourceless efficiency for its different compositions, and to calculate its measured activity, and analyzing its relative deviation to the those given in the certificate.Results:The analytical result of these 30 types of food samples showed that the five elements C, H, O, N and S accounted for 77.0%-93.7% of the food composition, being the main component of these samples. By applying white quinoa′s components and grain-based reference components to the simulation of the sourceless efficiency of white quinoa standard sources, the relative deviations of activity calculations to their certificated activities were in the range of 0.37%-5.86% and 0.38%-5.87% in absolute value, respectively.Conclusions:The white quinoa′s composition and the grain reference composition were applied to the sourceless efficiency simulation of the white quinoa standard source, and the relative deviation of the calculated measured activity to the activity of the standard source certificate was basically identical, so that if the gamma spectrometry-based sourceless efficiency simulation is used to measure the unknown composition of the food samples and it is inconvenient to carry out the analysis of the food samples′ compositions, especially in the case of emergency, it can be referred to the use of the reference compositions obtained in the present study.
ABSTRACT
Objective To further extend the application of coincidence summing correction factor transfer experiments through the analysis of relevant measurements. Methods The passive efficiency was simulated using BE5030 high-purity germanium (HPGe) γ-energy spectrometer equipped with LabSOCS, and the total efficiency was simulated using LabSOCS in GENIE 2000 spectrum analysis software, which was used for calculating the coincidence summing correction factor. The coincidence summing correction factor transfer experiments were performed using the measurements with the point source containing 134Cs, 60Co, and 137Cs as well as the body source to obtain the coincidence summing correction factors of other HPGe γ-energy spectrometers. Results The coincidence summing correction factors for 134Cs and 60Co were obtained using the BE5030 γ-energy spectrum. In verification by certificate activity, the absolute value of the maximum deviation was within 3.53%. Using coincidence summing correction factor transfer experiments, these factors were transferred to other high-purity germanium γ spectrometers. In verification by certificate activity, the absolute value of the maximum deviation was within 5.86%. Conclusion The coincidence summing correction factors calculated using simulated total efficiency by calling LabSOCS in the GENIE 2000 spectrum analysis software are effective in correction, and can be used as correction factors in standard laboratories. Through coincidence summing correction factor transfer experiments, the coincidence summing correction of other high-purity germanium γ-energy spectrometers can be achieved, which broadens the application of coincidence summing correction method.
ABSTRACT
Objective To optimize the Marinelli beaker with the simulation of Laboratory Sourceless Object Calibration Software (LabSOCS), to investigate the detection efficiency of HPGe detector in measuring noble gas, and to provide a reference for the measurement and optimization of noble gas effluent from nuclear power plants. Methods LabSOCS was used to establish a Marinelli beaker model to investigate the relationship of gamma ray detection efficiency of noble gas with gas components, gas density, size and volume of the Marinelli beaker, and the shape of source container. Results The gas components had little effect on the detection efficiency of the noble gas in the Marinelli beaker. The gas density had a relatively great effect on the detection efficiency of low-energy gamma ray. The Marinelli beaker of appropriate height and radius enabled the HPGe detector to get better measurement results. For the BE5030 HPGe detector, the highest detection efficiency of the Marinelli beakers of different volumes were observed at the location where the radius/height ratio was 0.7, and the optimal values of height and radius were given for the Marinelli beakers of different volumes. Conclusion Choosing Marinelli beaker of the appropriate size can improve the detection efficiency of noble gas in the effluent from nuclear power plants.
ABSTRACT
Objective To establish a sourceless efficiency calibration method by coupling Monte Carlo simulation with analytical calculation. Methods Monte Carlo simulation was used to calculate the point-to-point detection efficiency of specific detectors to establish a detection efficiency grid. The detection efficiency of point source, disc, cylindrical, beaker, spherical, U-tube and Marlin cup samples was analyzed using numerical integration method after detection efficiency grid interpolation. Results The above coupling method was used for sourceless efficiency calibration. Within the energy range of 0.2–3 MeV, the relative deviation of calibration between coupling method and Monte Carlo simulation was mostly less than 10%, the maximum relative deviation was 18.06%, and the computation time was reduced by at least 86%. The above coupling method was used for sourceless efficiency calibration of an HPGe detector manufactured by ORTEC for point source detection, which was in good agreement with the experimental calibration, and the relative deviations were less than 10%. Conclusion This method can be generalized and used in the sourceless efficiency calibration of HPGe, LaBr3, and NaI detectors.