Moderator material efficiency of neutron energy slowing down on D-T reaction neutron generator for SAMOP

We have studied a collimator design setup for the Subcritical Assembly for Mo-99 Production (SAMOP) at the Center for Accelerator Sciences and Technology (CAST), Nuclear Energy Agency of Indonesia (BATAN). The main purpose of the project is for providing sufficient neutrons to produce Mo-99, to be used to produce Tc-99m for nuclear medical applications. The modelling of the collimator is based on Monte Carlo simulation using MCNPX version 5 software to determine the variation of the suitable materials. The collimator consists of moderator, filter, and reflector, where we expected that the output of neutron will be thermal neutron with a sufficient neutron flux of about 10 8 neutron/cm 2 .s. The neutron source used is a D-T reaction neutron generator with a mono-energetic neutron energy of 14.1 MeV. The simulation has been conducted in nine variations, with each experiment uses five types of materials. The best result in terms of neutron flux is seem from the material combination of Al, C 25 H 52 , LiF, and PbF 2 , which produces a thermal neutron flux of 1.24 × 10 7 neutron/cm 2 .s and average energy deposition of 1.88 × 10 6 MeV/g. This research needs to be developed further for subsequent experiments to optimize the combination of materials and geometry systems to be used.