Design and simulation of a hypothetical system for explosives detection based on PGNAA technique

Explosives include elements such as H, C, N and O with specific the amount and ratio. Nitrogen and oxygen are more abundant than others and the amount of nitrogen is an excellent characteristic to detect explosives. The Probability of existing explosives in an environment could be found out by acquiring the amount of nitrogen accumulated in the environment. In this paper, the prompt gamma neutron activation analysis (PGNAA) technique has been used in order to detection and identification of explosives. Using this method, one could detect suspicious packages and bags containing explosives and they are prevented to entry into government agencies, military facilities, airports, ports, embassies, banks, power plants, major organizations and sensitive companies. The nitrogen nucleus emits the thermal neutrons and gamma radiation spectrum 10.83 MeV almost at the same time as it absorbs them. In the designed system, the source and NaI detector has been used as neutron generator and emitted gamma receiver respectively. MCNPX2.6 code has been exploited to simulate neutron - photon transport In this system. To design this system, different thickness of paraffin and lead have been utilized to moderate neutrons and comply with shielding principles and health physics respectively. The designed system is capable of detecting NG explosive with a weight of 323 g and 1023 g for 10 minutes and one minute respectively.