Mrdja Dusan, Bikit Kristina, Forkapic Sofija, Bikit Istvan, Slivka Jaroslav, Hansman Jan
Department of Physics, Faculty of Sciences, University of Novi Sad, Serbia.
Department of Physics, Faculty of Sciences, University of Novi Sad, Serbia.
J Environ Radioact. 2018 Aug;188:23-29. doi: 10.1016/j.jenvrad.2017.11.005. Epub 2017 Nov 10.
Performing in-situ measurements of gamma radiation originating from soil requires adequate detection efficiency curves, which can be obtained by Monte-Carlo simulations. In simulations, soil density of 1.046 g/cm was used, with the following elemental composition of soil in which gamma radiation was generated: O - 47%, Si -35%, Al - 8%, Fe - 3.9%, C - 2.1%, Ca - 1.4%, K - 1.3%, N - 0.6%, Mg - 0.6%, N - 0.1%. Soil matrix was represented by cylindrical volume of 1.5 m diameter and 0.5m thickness, while germanium detector was placed at 1 m height above the soil. The simulated gamma spectrum, originated from K-40, as well as from members of Th-232 chain, and daughters of Ra-226, was obtained. Homogeneous distribution of various radionuclides (Ra-226, Th-232, K-40) in soil matrix is considered in this work. Gamma spectra obtained in simulations were analyzed, and together with simulated detection efficiency data they provide comparison with real experimental measurements and practical application of results derived by Monte-Carlo simulations. As a result of this work, the corresponding detection efficiency curve for HPGe detector was obtained, which can be applied for in-situ measurements of radionuclide concentration in soil, assuming uniform radionuclide distribution. In order to validate our simulation results regarding detection efficiency, we performed in-situ measurements of soil radioactivity and compared the obtained activity concentrations with laboratory measurements. We found a good agreement, within activity concentration uncertainty, between in-situ measurement results and average values of activity concentrations obtained by laboratory measurements.
对源自土壤的伽马辐射进行现场测量需要足够的探测效率曲线，这可以通过蒙特卡罗模拟获得。在模拟中，使用的土壤密度为1.046 g/cm³，产生伽马辐射的土壤具有以下元素组成：氧 - 47%，硅 - 35%，铝 - 8%，铁 - 3.9%，碳 - 2.1%，钙 - 1.4%，钾 - 1.3%，氮 - 0.6%，镁 - 0.6%，钠 - 0.1%。土壤基质由直径1.5米、厚度0.5米的圆柱形体积表示，而锗探测器放置在土壤上方1米高度处。获得了源自钾 - 40以及钍 - 232链成员和镭 - 226子体的模拟伽马谱。这项工作考虑了土壤基质中各种放射性核素（镭 - 226、钍 - 232、钾 - 40）的均匀分布。对模拟中获得的伽马谱进行了分析，并将其与模拟探测效率数据一起用于与实际实验测量进行比较以及蒙特卡罗模拟结果的实际应用。作为这项工作的结果，获得了HPGe探测器相应的探测效率曲线，假设放射性核素分布均匀，该曲线可用于土壤中放射性核素浓度的现场测量。为了验证我们关于探测效率的模拟结果，我们对土壤放射性进行了现场测量，并将获得的活度浓度与实验室测量结果进行了比较。我们发现在活度浓度不确定度范围内，现场测量结果与实验室测量获得的活度浓度平均值之间具有良好的一致性。
