Hot-spots finding with modular gamma-ray system for sort and segregate activities

Abstract

In the framework of the PI3SO project (Proximity Imaging System for Sort and Segregate Operations) funded by INFN-Energy project, aimed at the low and intermediate level radioactive waste (radwaste) classification, conditioning and characterization, a scanning system based on a set of 128 gamma-ray detectors based on CsI(Tl) crystal scintillators readout by a silicon photomultiplier have been built and characterized. These are arranged in linear arrays grouped in modules, each one being made of sixteen detection elements compose a sensitive unit, named module, and eight modules define the full-scintillators scanning system. The combination of four modules, arranged in a linear configuration, defines a sliding linear array named detection unit. Placed one above a scanning table and the other parallel to it underneath the table, the two co-moving detection units detect gamma-rays from sparse objects on table improving the detection of partially gamma sources and they will identify the hot-spot. The described modules are suitable for the sorting of nuclear materials and can be used as scanner of radioactive objects placed on a large area surface. Each unit was tested with point-like laboratory gamma-ray 137Cs and 22Na source: the results are promising in view of the integration with the mechanical system which will move the detection units scanning the radwaste. Next step are planned tests in a real environment.