Characterization of Neutron Field in a Spherical Irradiation Facility

A small-sized dual-hemisphere irradiation facility designed and constructed for using Am-Be isotopic neutron source to study and characterize the neutron field around sample irradiation position for obtaining maximum thermal neutron flux. The foil activation method based on 115In and 197Au was used for monitoring the thermal neutron flux. For field characterization, several combinations of moderation media have been tested (air, sand and water) aiming at the identification of the best combinational setups for sample irradiations using thermal neutrons. To account for epithermal contribution, reaction rates and flux calculations were corrected using tabulated values of Westcott g-factors and resonance integrals for these media. The optimal position for sample irradiation using thermal neutron for both water-water and water-sand setups, inside the irradiation channel, was found at about 6.9 to 10.9 cm from the center of the neutron source.