Development and validation of a UAV-borne NaI(Tl) scintillation system for environmental radiation surveying: a methodological approach

Unmanned aerial vehicles (UAVs) are progressively employed for environmental radiation assessment, providing swift, low-altitude surveillance of regions that are hazardous or inaccessible for ground personnel. This study details the creation and methodological validation of a UAV-mounted gamma-ray spectrometry system utilizing a 2-inch NaI(Tl) scintillation detector incorporated into a multi-rotor platform. The detector underwent calibration at an accredited laboratory utilizing collimated ²⁴¹Am, ¹³⁷Cs, and ⁶⁰Co sources, resulting in a three-point quadratic energy calibration with an energy resolution of 6.19% FWHM at 661.7 keV. Pre-flight bench experiments evaluated detector stability under operational settings by comparing background spectra with motors deactivated, motors activated without propellers (electromagnetic interference), and motors activated with propellers (combined interference and vibration). The detector and propulsion system utilize a single battery via a regulated converter, exemplifying a worst-case scenario. Motor operation resulted in negligible alterations in count rate (<0.4%) or dead time, indicating both electromagnetic and mechanical resilience without the need for supplementary shielding or vibration isolation. The minimum detectable activity for ¹³⁷Cs was assessed in relation to survey altitude, indicating the trade-off between area coverage and sensitivity for mission design. The findings validate that the integrated system satisfies the metrological standards for environmental gamma surveying.