Development and Flight Trial of a UAV-based Gamma Ray and Neutron Detection System for Large-Area Radioactivity Mapping and Source Activity Estimation

TL;DR

This paper presents a UAV-mounted gamma ray and neutron detection system using SiPM-based scintillation detectors, along with an analytic model for estimating ground radioactivity, validated through indoor tests with successful source localization and activity estimation.

Contribution

It introduces a novel UAV-compatible detection payload and an analytic efficiency model for accurate radioactivity estimation from aerial measurements.

Findings

Successful localization of Cs-137 and Co-60 sources within 0.5 m

Radioactivity estimation errors within 10%

Detection efficiency model agrees within 10% of experimental data

Abstract

Advances in scintillation crystal and Silicon PhotoMultiplier (SiPM) technologies have enabled the development of compact, lightweight, and low-power radiation detectors that are suitable for integration with Unmanned Aerial Vehicles (UAVs). This integration enables efficient and cost-effective large-area radiation monitoring while minimising occupational exposure. In this work, a SiPM-based NaIL scintillation detection payload was developed, characterised, and mounted on a multirotor UAV for gamma ray and neutron source localisation and activity estimation applications. To support these capabilities, an analytic radionuclide detection efficiency model was developed and used to estimate radioactivity on the ground from aerial energy spectrum measurements. The analytic expression for the detection efficiency incorporated physical phenomena, including the branching ratio, detector solid angle, air attenuation, and intrinsic peak efficiency, leading to agreement within 10% of experimental radionuclide detection efficiencies. The UAV-based radiation detection system was physically validated through a controlled indoor live radioactive source demonstration at 1.5 m, 3 m, and 4.5 m flight heights. Using the developed ground-level radioactivity estimation method, Cs-137 and Co-60 sources were successfully localised within 0.5 m, and their activities were estimated with errors on the order of 10% or less.