Neutron-gamma survey system for decommissioning and dismantling activities

The nuclear plant decommissioning and dismantling (D&D) operations will amount to €200 billion in costs over decades around the world, with three-fourths coming from Europe. Decommissioning includes activities such as planning, physical and radiological characterization, facility and site decontamination, dismantling, and materials management. This work is focused on the development of a compact, light and low-power consumption neutron-gamma survey system which could be easily mounted on an remotely operated vehicle. It is made up of a 4”x4”x2” NaIL (NaI:Tl + 1% 6Li [95% enriched]) neutron/gamma scintillation detector coupled to a SiPM array. Digital pulse processing techniques were implemented to acquire and process the signals, by means of a CAEN DT5780 unit. A comprehensive characterization of this system, based on experiments and Monte Carlo simulations, is reported. The system can be used as a secondary inspection tool, useful for identifying radioactive and special nuclear materials in hotspots.