MCNP optimization of fast neutron beam thermalization device based on D-T neutron generator

The 14 MeV neutrons generated by Deuterium-Tritium (D-T) fusion reaction usually need to be moderated for Prompt Gamma Neutron Activation Analysis (PGNAA) applications. A fast neutron beam thermalization device was developed in Northeast Normal University based on a D-T neutron generator (model NG-9). A simple experimental system was set up firstly to validate the feasibility of simulation. The materials and dimensions of moderator and the size of multiplier, reflector and collimator were then optimized through MCNP5 to improve the efficiency of the thermalization device. The thermal, epithermal, fast and total neutron flux across the output surface in final system were increased for a factor of 9.65, 8.70, 5.84 and 6.94 times compared to the initial experimental system, respectively. And the optimized thermalization efficiency is 13.28 times higher than that of the original model of experimental system.