Abstract
Advancements in the development of gamma-ray spectrometers (GRS) have led to small and lightweight spectrometers that can be used under unmanned aerial vehicles (UAVs). Airborne GRS measurements are used to determine radionuclide concentrations in the ground, among which the natural occurring radionuclides 40K, 238U, and 232Th. For successful applications of these GRS sensors, it is important that absolute values of concentrations can be measured. To extract these absolute radionuclide concentrations, airborne gamma-ray data has to be corrected for measurement height. However, the current analysis models are only valid for the height range of 50–250 m. The purpose of this study is to develop a procedure that correctly predicts the true radionuclide concentration in the ground when measuring in the UAV operating range of 0–40 m. An analytical model is developed to predict the radiation footprint as a function of height. This model is used as a tool to properly determine a source-detector geometry to be used in Monte-Carlo simulations of detector response at various elevations between 0 and 40 m. The analytical model predicts that the smallest achievable footprint at 10 m height lies between 22 and 91 m and between 40 and 140 m at 20 m height. By using Monte-Carlo simulations it is shown that the analytical model correctly predicts the reduction in full energy peak gamma-rays, but does not predict the Compton continuum of a spectrum as a function of height. Therefore, Monte-Carlo simulations should be used to predict the shape and intensity of gamma-ray spectra as a function of height. A finite set of Monte-Carlo simulations at intervals of 5 m were used for the analysis of GRS measurements at heights up to 35 m. The resulting radionuclide concentrations at every height agree with the radionuclide concentration measured on the ground.
Highlights
Technological advancements in the development of unmanned aerial vehicles (UAVs) have led to the availability of affordable drones that can be used for geophysical gamma-ray spectrometry surveys
As described in (Nicolet and Erdi-Krausz, 2003), the International Atomic Energy Agency (IAEA) model is valid for the 50–250 m range and this figure clearly shows that there is a difference in the predicted signal decrease between the IAEA and the model presented in equation (2) in the height range from 0 to 40 m
Height corrections for gamma-ray spectra are applied by using the exponential integral
Summary
Technological advancements in the development of unmanned aerial vehicles (UAVs) have led to the availability of affordable drones that can be used for geophysical gamma-ray spectrometry surveys. These UAVs can carry payloads in the order of kilograms, which is roughly the weight of a gamma-ray spectrometer needed to efficiently map radio nuclide activities in an area (Nicolet and Erdi-Krausz, 2003). Ground-based surveys are typically used to map an area with a high spatial resolution, but are limited by the accessibility of the terrain Airborne surveys overcome this limitation and can conveniently be used to cover rocky, wet, and densely vegetated terrain. Manned airborne surveys have the inherent drawback that they are expensive and have to follow the aircraft safety rules, which impose a minimum flying height and airborne surveys cannot obtain the high standard of spatial resolution which the land-borne surveys can
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
