地面放射性测量模型γ剂量率值空间分布规律研究

Study on Spatial Distribution of Dose Rate of Ground Radioactivity Calibration Pads

地面模型是根据IAEA174号报告研建的用于校准便携式γ能谱仪、γ辐射仪的计量标准装置,最初主要用于地质勘查。2016年至2018年,新研建了钾含量30%(YK3)和铀含量1%(YU4)的两个模型,并确定了模型量值。远离模型表面中心位置的剂量率较低,随着中心点的接近,剂量率逐渐上升,YK3和YU4的剂量率坪区分别为模型中心点及周围半径约40 cm和50 cm范围内,在坪区内剂量率变化均不大于0.6%;在参考点3.0 cm上的剂量率分别为320.8 nGy·h^(-1)和4.3×10^(4)nGy·h^(-1);超过3.0 cm时,剂量率随高度呈非线性变化;根据不同高度上的理论计算和实测结果比对,在40 cm高度实测范围以内,YK3实测结果与理论计算结果相对偏差在3%范围以内,120 cm高度实测范围内,YU4实测结果与理论计算结果相对偏差在2%范围以内。

The calibration pad is constructed according to IAEA Technical Reports Series No.174 for the calibration of portable gamma spectrometer,gamma radiometer metering device,initially mainly used in geological exploration.From 2016 to 2018,two new pads with potassium concentration of 30%(YK3)and uranium concentration of 1%(YU4)were developed and determined.The dose rate at the location far away from the center of the pad surface was low,and increased gradually as the center point approached.The dose rate plateau zones of YK3 and YU4 were within the radius of about 40 cm and 50 cm around the pad center point,respectively,and the change of dose rate within the plateau zone was no more than 0.6%;The dose rates at the 3.0 cm height of the central point were 320.8 nGy·h^(-1)and 4.3×10^(4)nGy·h^(-1),respectively.When the height exceeded 3.0 cm,the dose rate changed non⁃linearly with height.According to the comparison between the theoretical calculation and the measured results at different heights,within the height of 40 cm,the relative deviation between the measured results of YK3 and the theoretical calculation results is within 3%;within the height of 120 cm,the relative deviation between the measured results of YU4 and the theoretical calculation results is within 2%.