Thermal analysis at target for neutron generation in fissile assay

A target was designed to produce intense neutrons of 1012 neutrons/sec in order to analyze the fissile content by interrogation in the Lead Slowing Down Spectrometer (LSDS) system. A high energy and current electron linear accelerator was used in neutron production by bremsstrahlung radiation. However, the interaction by electron and radiation in the target generates large amounts of heat. Several coolants were simulated in the target and the heat removal capacity was performed. The thermal property of coolant in the target was calculated using the CFX code. The heat distribution by the cooling method was simulated and the forced convection method was used to calculate the temperature distribution on the different coolants and flow rate. Helium shows a good cooling property, but it needs high flow rate with high pressure. Air may be a good candidate coolant if the limit of neutron activation is satisfied in the circulating system. When the coolants were used in the target, each metal plate of the target was kept under the melting temperature. For the estimation of the coolant performance, the neutron influence by the coolant was examined as well. The material property was also evaluated for various target cases. The displacement per atom (DPA) analysis of the target was performed for a life time operation of the LSDS system. For the target container material (HT-9), the optimum thickness was obtained from the sensitivity simulation.