Mapping the environmental radioactivity in Catalonia using a mobile unit with LaBr3 scintillation detectors.

This study describes the equipment implementation of a mobile gamma spectrometry unit using LaBr₃ detectors and the process followed to obtain a radiological map of Catalonia (Spain). The mobile unit consists of two 2”x2” LaBr₃ scintillation detectors mounted on the top of a 4x4 car. To obtain the preliminary map, the extension of Catalonia was divided in 1425 cells of 5x5 km². Before starting the measurements, we planned a route to ensure a proper distribution and a minimum quantity of spectra within each cell. The car is equipped with a portable computer to control spectra acquisition and a GPS system that associates a position to each spectrum. Each spectrum is stabilised and calibrated. During the acquisition, the computer placed inside the car shows, in real-time, the value of the ambient dose equivalent and the exact location. Therefore, when the software obtains an unexpected high value, the driver of the car can modify the route to acquire more spectra of the area. The first data set of measurements included 70000 spectra obtained during stable weather conditions and represent the preliminary results of the radiological map, as other data campaigns are currently under preparation. In this study, we present the ambient dose equivalent map of Catalonia and isotopic information of interest, such as punctual detections of ¹³⁷Cs and ¹³¹I and other radionuclides. The origin of these detections is analysed and explained in detail.