Development and application of vehicle-mounted soil gamma spectrometer

Abstract: In agricultural soil radioactivity research, the specific activities of radionuclides such as U-238, Th-232 and K-40 are mainly analyzed in laboratories after sampling, which is time-consuming and costly, making it unsuitable for large-scale agricultural applications. This paper establishes a mathematical model correlating soil radionuclide specific activity with gamma-ray intensity for on-site rapid detection of soil radioactivity. Based on MCNP simulation calculations, a vehicle-mounted soil gamma spectrometer was developed using a NaI(Tl) detector with dimensions of 5.7×11×40 cm. The instrument, mounted on the rear of an agricultural machine, can detect the content of radioactive elements in the soil during plowing. It features real-time positioning and display of radionuclide specific activity, with the ability to measure up to 88089 centiare per hour. The instrument was applied in a 264267 centiare experimental field, and the distribution maps of the specific activities of U-238, Th-232 and K-40 in the experimental field were obtained. Compared with laboratory analysis results, the relative deviations of the specific activities of U-238, Th-232 and K-40 measured by the vehicle-mounted soil gamma spectrometer were within ±16%, ±15%, and ±10%, respectively. This device can improve the efficiency of measuring soil radionuclide specific activity and reduce the cost of investigating the distribution of agricultural soil radioactivity.