Neutron Activator Design for 99Mo Production Yield Estimation via Lead and Water Moderators in Transmutation’s Analysis

Abstract

99Mo/99mTc generator is a remarkable radionuclide choice for imaging in nuclear medicine, thereby a neutron activator including two different neutron moderators was devised in a cyclotron-based technique. Neutron activator was designed for 99Mo production via radiative capture using proton beam of compact cyclotron. Neutron production by a 30 MeV proton beam interacting with tungsten target was considered to drive the activator. Fast neutrons were gradually moderated toward resonance energy range of molybdenum using joint moderators including light and heavy materials. Molybdenum transmutation as a result of neutron absorption was appraised via lead and water moderators, surround the target and a graphite reflector around the moderator region. 98Mo spherical samples with different thicknesses were positioned at radial distances from the target inside the diverse regions of the activator. The neuron flux inside the two moderators was comparable as the water rapidly diminished the flux. The greatest 99Mo production yield occurred inside the lead region at 10 cm distance equal to 430.39 ± 0.05 MBq/g for 0.2 cm radius of the sample. Results indicated using heavy moderator reduces the neutron-adiabatic probability over 98Mo resonance peaks therefore neutron capture improves during transmutation process. In comparison with the reactorbased method, a local method for radioisotope production using small and low-current cyclotrons can decrease the expenditures in nuclear medicine policies due to more safety and commercial usages.