Efficiency corrections in determining the 137Cs inventory of environmental soil samples by using relative measurement method and GEANT4 simulations. (August 2015)

• Record Type: Journal Article
• Authors: Li, Gang; Liang, Yongfei; Xu, Jiayun; Bai, Lixin
• Is Part Of: Journal of environmental radioactivity. Volume 146(2015:Aug.)
• Page Start: 94
• Page End: 101
• Publication Date: 2015-08
• Subjects: Efficiency correction -- 137Cs inventory -- Relative measurement method -- HPGe gamma spectrometer -- GEANT4 simulation -- Soil erosion; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2015.04.012
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: The determination of 137 Cs inventory is widely used to estimate the soil erosion or deposition rate. The generally used method to determine the activity of volumetric samples is the relative measurement method, which employs a calibration standard sample with accurately known activity. This method has great advantages in accuracy and operation only when there is a small difference in elemental composition, sample density and geometry between measuring samples and the calibration standard. Otherwise it needs additional efficiency corrections in the calculating process. The Monte Carlo simulations can handle these correction problems easily with lower financial cost and higher accuracy. This work presents a detailed description to the simulation and calibration procedure for a conventionally used commercial P-type coaxial HPGe detector with cylindrical sample geometry. The effects of sample elemental composition, density and geometry were discussed in detail and calculated in terms of efficiency correction factors. The effect of sample placement was also analyzed, the results indicate that the radioactive nuclides and sample density are not absolutely uniform distributed along the axial direction. At last, a unified binary quadratic functional relationship of efficiency correction factors as a function of sample density and height was obtained by the least square fitting method. This function covers the sample density and height range of 0.8–1.8 g/cm 3 and 3.0–7.25 cm, respectively. The efficiency correction factors calculated by the fitted function are in good agreement with those obtained by the GEANT4 simulations with the determination coefficient value greater than 0.9999. The results obtained in this paper make the above-mentioned relative measurements more accurate and efficient in the routine radioactive analysis of environmental cylindrical soil samples. Highlights: Determination of 137 Cs inventory in environmental soil samples by using relative measurement method. Activity correction (i.e. efficiency correction) was made by calculating the FEPE values via GEANT4 simulation. The elemental composition, sample density and geometry effect, as well as the effect of sample placement are discussed in detail. A unified binary quadratic function of efficiency correction factors as a function of sample density and height are obtained.