Comparison of airborne radiation detectors carried by rotary-wing unmanned aerial systems

Abstract

The Universitat Politecnica de Catalunya (UPC), the Physikalisch-Technische Bundesanstalt (PTB) and the German Federal Office of Radiation Protection (BfS) have analysed the response of a 2”x2” (diameter x height) NaI and a 1.5”x1.5” CeBr3 scintillators, and a 1500 mm3 CZT semiconductor airborne spectrometric detectors mounted on Unmanned Aerial Vehicles (UAV) in a comparison campaign carried out in the aerial site of Mollerussa (Spain). The background count rates and H*(10) rates measured by the airborne detectors at the aerial site and with a 137Cs point source of 345 MBq have been compared at altitudes of 1.5 m, 10 m, 20 m, 40 m, 60 m and 100 m a.g.l. (above ground level). Furthermore, natural activity concentrations in soil have been calculated with different methodologies using the spectra acquired in the background flights. The airborne detectors together with the implemented calculation methodologies show in general a good agreement. The CZT detector has a significant lower efficiency than both scintillators due to the smaller size and, therefore shows poorer results. Finally, parallel flights over the 137Cs point source at 10 m, 20 m and 40 m were carried to evaluate the methods implemented by the three teams to localize point sources. The three systems were able to locate properly the source.