Airborne γ-Ray Survey System Developed at LNL.

Measurements of the ground concentrations of potassium, uranium and thorium by γ-ray spectrometry are a well-established technique. At the same time, the request of radioactivity studies is constantly increasing due to more stringent regulations and after the new prospective introduction of nuclear energy in european countries. Whereas the the in situ measurements are requested for samples certification or monitoring of spot area, the airborne gamma spectrometry (AGS) method is highly appropriate for large scale environmental survey. These studies are important both in the case of monitoring the natural ground radioactivity and in the case of potentially contaminated ground areas and they are used in several countries since early 1990s. The AGS method has been found to be a powerful technique with respect to in-situ measurements since it can reduce the time consumption and monitor large areas. This of course put a constraint on the spatial resolution of the method, which averages the signal over the area covered by the time slice (typically of the order of 0.3 km2). A new AGS system has been developed at the LNL and it has been successfully used and tested during a more than 2 hours flight on the Elba Island. All details of the system will be discussed in the next section with a the measured concentration results.