Practical approach of airborne gamma-ray spectrometry using UAVs for evaluating ground-level dose rates

Ji, Y.-Y.*; Ji, W.*; Kim, K.*; Kim, M. J.*; Ochi, Kotaro   ; Morishita, Yuki   ; Sanada, Yukihisa   

UAV-based airborne gamma-ray spectrometry enables rapid radiation mapping, but accurate estimation of ground-level ambient dose rates is difficult because of altitude attenuation, detector field-of-view effects, heterogeneous contamination, and terrain variability. We developed a practical method combining hovering-flight calibration and ground-based validation near the Fukushima Daiichi Nuclear Power Plant. Altitude correction factors were derived using a dual-exponential model and compared with tripod and backpack measurements. Results showed that heterogeneous contamination and terrain introduce systematic biases if correction factors are derived under non-uniform conditions, while calibration at uniform sites improves agreement. The proposed approach demonstrates that UAV airborne surveys can reliably estimate spatial dose-rate distributions when site-dependent corrections are applied.