Abstract
In response to the Fukushima Daiichi Nuclear Power Plant accident, there has occurred the unabated growth in the number of airborne platforms developed to perform radiation mapping—each utilising various designs of a low-altitude uncrewed aerial vehicle. Alongside the associated advancements in the airborne system transporting the radiation detection payload, from the earliest radiological analyses performed using gas-filled Geiger-Muller tube detectors, modern radiation detection and mapping platforms are now based near-exclusively on solid-state scintillator detectors. With numerous varieties of such light-emitting crystalline materials now in existence, this combined desk and computational modelling study sought to evaluate the best-available detector material compatible with the requirements for low-altitude autonomous radiation detection, localisation and subsequent high spatial-resolution mapping of both naturally occurring and anthropogenically-derived radionuclides. The ideal geometry of such detector materials is also evaluated. While NaI and CsI (both elementally doped) are (and will likely remain) the mainstays of radiation detection, LaBr3 scintillation detectors were determined to possess not only a greater sensitivity to incident gamma-ray radiation, but also a far superior spectral (energy) resolution over existing and other potentially deployable detector materials. Combined with their current competitive cost, an array of three such composition cylindrical detectors were determined to provide the best means of detecting and discriminating the various incident gamma-rays.
Highlights
As a consequence of the graphic and globally significant severe reactor accidents at both the Chernobyl Nuclear Power Plant (ChNPP—1986), and the Fukushima Daiichi Nuclear Power Plant (FDNPP—2011), some of the greatest levels of environmental radioactivity are associated with accidents that occurred at power-generating nuclear sites
Regarded by the public as the largest contributor to environmental radioactivity, with significant levels of contamination released by both incidents [1], the greatest anthropogenic source and contributor to environmental radioactivity is associated with historic weapons testing [2]
An approximate doubling of the peak intensity is apparent between the 25 mm and 50 mm thick detectors—a consequence of the increased gamma-ray photon absorption by the greater volume of detector material, resulting in fewer undetected photons escaping from the detector volume having not been fully absorbed
Summary
As a consequence of the graphic and globally significant severe reactor accidents at both the Chernobyl Nuclear Power Plant (ChNPP—1986), and the Fukushima Daiichi Nuclear Power Plant (FDNPP—2011), some of the greatest levels of environmental radioactivity are associated with accidents that occurred at power-generating nuclear sites. Unlike the aforementioned reactor releases, this material was distributed globally in contrast to the less spatial-extensive (but higher total activity) plumes that were dispersed into the surrounding regions from both the Chernobyl and Fukushima accidents. Such highly localised and elevated activity anomalies are associated with localities around the world where reprocessing, fuel generation and defence facilities formerly existed [3]. Despite these significant contributors to environmental radioactivity, the incident radiation typically encountered during routine radiation surveys is a consequence of naturally occurring radioactive materials (NORM); ore and deposits; either concentrated on, or just below, the surface.
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