Although electron energies higher than ۵ MeV are generally required to produce an intense photoneutron flux, an optimized and compact photoneutron source based on a ۵ MeV electron linear accelerator has been designed for boron neutron capture therapy (BNCT) and neutron activation applications using the MCNPX Monte Carlo code in this work. In fact, we investigated a heavy water target, which can be used as a coolant as well as a photoneutron target for the production of high neutron flux based on a ۵ MeV electron linear accelerator and examined different neutron reflectors. Also, Be, BeO, BeD۲, Graphite, ZrH۲, and Pb have been studied as neutron reflector materials. In this study, after a comparison between beryllium and graphite it was obtained that beryllium increase neutron flux a factor of ∼۱۳۰%, thus beryllium was chosen as the best neutron reflector. Finally, we concluded that the use of heavy water as a photoneutron target along with beryllium as a neutron reflector could increase the neutron flux in comparison to previous works that use beryllium and graphite as photoneutron target and neutron reflector, respectively. According to the optimum dimension photoneutron source, a neutron flux of ۳.۶× ۱۰۸ ± ۱.۲% neutrons/cm۲/mA/s is obtained at ۵۰ cm away from the heavy water target. This results with an increase of ∼۳۰۰% in comparison to the other works.