Identification of shielded sources using a CZT detector and an unmanned ground vehicle

Abstract

This work is dedicated to ability of a coplanar cadmium zinc telluride (CZT) detector to identify lost/orphan radioactive sources hidden inside soil layers. Considering point-like sources placed in soil and the CZT detector fixed on an unmanned ground vehicle (UGV), relevant measurement geometries were proposed. Full-energy peak efficiency (FEPE) calibrations of the CZT detector were prepared using the MCNP6.1 radiation transport code. In order to check the simulation set-up, control measurements were performed and compared with the Monte Carlo simulations.FEPEs obtained were used for estimations of minimum detectable activities (MDA) and their dependencies on the source depth in soil. Thereafter, field tests of the CZT detector were performed. Within field measurements, radioactive sources with known activities slightly above the MDA values were placed in upper layers of soil of a grassed meadow. The meadow surface was scanned by the CZT detector mounted on a mobile ground robotic platform remotely controlled by an operator. Results of the radiation mapping with the CZT detector were depicted as maps of count rates. On the basis of the maps created, positions of shielded sources were clearly revealed.