Drone-based investigations of uranium mining legacies: an airborne gamma spectrometry method to support, inspect, and monitor mine closure processes

Abstract

The rapid technical development of drones (UAV; unmanned aerial vehicle) in combination with improved and miniaturised measurement technology enables a cost-effective and fast deployment in post-mining areas. Drone-based geophysical methods can be used to assess post-mining areas to facilitate remediation planning, and to monitor them as part of long-term institutional control in the post-closure phase. A case study of drone-based gamma spectrometric investigations is presented, using the example of legacies of former uranium mining. This type of legacy poses a direct threat to humans and the environment and is still present in the Central Asian countries of Kyrgyzstan, Kazakhstan, Uzbekistan and Tajikistan. In the DUB-GEM project (Development of a UAV-Based Gamma Spectrometry for the Exploration and Monitoring of Uranium Mining Legacies), a drone-based detector system was developed to investigate and monitor these legacies. Two scintillation detectors (CeBr3, NaI) with different crystal volumes can be used alternately. The drone is a custom-built heavy lift system with a maximum take-off mass of 25 kg. The measurement data can be displayed in real time at a ground station. This allows locating hotspots during the survey and planning subsequent detailed measurements. The use of drone-based systems is particularly advantageous in mining regions that are difficult to access and potentially harmful for human health. This paper shows the results of drone-based gamma spectrometry investigations obtained during a measurement campaign in Central Asia in 2021. The drone prototype developed in the project is also capable of carrying other sensors with a payload of up to 7 kg. In subsequent projects, a new department of the Federal Institute for Geosciences and Natural Resources (BGR) - Research and Development Centre for Post-Mining Areas (FEZB) - will investigate the post-mining areas of former lignite mining in Germany using further geophysical sensor technology.