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S. jr and W. M. Murphey، “Calculation of Thermal Neutron Absorption in Cylindrical and Spherical Neutron Sources”، Metrologia، vol. 7، no. 1، p. 34، 1971. [40] B. Aygün and G. Budak، “A new neutron absorber material: Oil loaded paraffin wax”، Nucl. Sci. Technol.، pp. 33–39، 2012. [‏[41 D. Harder and K.-P.Hermann، “Tissue-Equivalent Materials and the ICRU Sphere”، Radiat. Prot. Dosimetry، vol. 12، no. 2، pp. 125–128، Aug. 1985. Abstract The neutron is an unstable particle with a short half-life of about eleven minutes and should be artificially produced for use in industry, medicine, and research. Nuclear reactors are known as the most important neutron source, but their huge dimensions and the high technology involved, the safety and security concerns, and the costly maintenance and repair, have made it impossible to use in many ways. (α,n) sources are an approporiate alternative to fission nuclear reactors. In this study, the most commonly used neutron source, Am-Be, has been used. The neutrons produced from this source have different energies in the 0-11 MeV range. In order to slow down non-thermal neutrons and increase the flux of thermal neutrons, a moderator is used around the source. In this study, Am-Be neutron source in different moderators was simulated by use of MCNP Monte Carlo code and the best moderator and its optimized thickness for using thermal neutrons has been proposed. Then the effect of adding a reflector and neutron multiplier material to the source has been investigated. finally, appropriate sheilding for the final configuration was studied in order to minimize biological damage when working with the neutron source. The performed simulations indicated that using a spherical moderator instead of common cylindrical moderators can lead to an increase in thermal neutron flux. Among the different moderators, paraffin produced the highest flux of thermal neutrons. Moreover, beryllium was established as the best neutron reflector and multiplier to increase the thermal flux of an Am- Be neutrons source. After all, the most suitable shield to have the minimum equivalent dose in an ICRU sphere was proposed. The final proposed configuration includes a paraffin sphere of radius 7 cm, beryllium with the thickness of 23 cm and again paraffin with a thickness of 31 cm and Kennetium alloy with a thickness of 7 cm. The thermal neutron flux in a distance between 4 to 7 cm is maximum.