Assessing radiation levels in the environment by converting total natural gamma radiation into the absorbed dose rate in air:A case study of measured data from Panjia Village,Guiyang County and Tuqiao Village,Yongxing County
China has accumulated massive data on total gamma radiation(γ)from the prolonged extensive surveys of uranium depos-its.However,there is a marked lack of studies on radioactive environment assessment using these data.Based on the measurement principles of total gamma radiation and the absorbed dose rate in air,this study ascertained the relationships of the absorbed dose rate in air with the total natural gamma radiation and nuclide content and,accordingly,established the relationship between total gamma ra-diation and the absorbed dose rate in air.Furthermore,it analyzed the effects of instrument parameters on the measurement error,con-cluding that there existed a strictly linear relationship between the measured total gamma radiation and the absorbed dose rate in the air when bK/bU=2.287 and bTh/bU=0.430.Therefore,the bK/bU and bTh/bU ratios closer to both values correspond to more accurate ab-sorbed dose rates in air converted from the measured total gamma radiation.Using the model of the Hunan Ionizing Radiation Measuring Station,this study calculated the coefficient for converting total gamma radiation into the absorbed dose rate in air,analyzed the error,and deduced the approximate uranium equivalent ranges of potassium and thorium in the instrument parameters.Furthermore,for the rock mass in Panjia Village,Guiyang County,Chenzhou City and the limestone area of Tuqiao Village in Yongxing County of the city,this study measured the total gamma radiation,gamma spectra,and absorbed dose rates in the air at the same stations.The results show that when the average nuclide content ratio CK/CU was less than 1 and CTh/CU ratio was less than 3,the absorbed dose rates in air estimated based on the total gamma radiation(measured using the FD3013 instrument)shared roughly the same error levels with those estimated based on energy spectra using the Beck formula,both yielding root mean square errors below 15%.As inferred from the aver-age CK/CU and CTh/CU ratios of nuclides in China,the absorbed dose rate in air in most areas of China can be estimated using the total gamma radiation measured using an FD3013 instrument(or an instrument with similar performance).Overall,converting the total gamma radiation data from available extensive surveys of uranium deposits into effective absorbed dose rates in the air provides a meth-odological reference for rapid,large-area assessment of the external exposure level of natural radioactivity in the environment.
total gamma radiationgamma spectrumcontent of nuclides(uranium,thorium,and potassium)absorbed dose rate in air
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