Re-design of 241Am–Be neutron source irradiator facility at NNRI using MCNP-5 code

Evaluation of the flux in various irradiation channels and the absorbed dose rate of radiation by operators 3 cm from the surface of the concrete surrounding the vessel of the 241Am–Be irradiator facility at NNRI, after it had been theoretically modified using MCNP-5 transport code is presented in this work. The 241Am–Be neutron facility at NNRI consist of a single centrally placed neutron source and flanked by two irradiation channels. The theoretical models however had the number of neutron sources increased gradually to five with a fixed number of five irradiation channels of various radii. These were to help assess the viability to increase the irradiator performance and operational capacity. The results indicated an increase in flux in the irradiation channels as well as absorbed dose rates and their dose equivalents as the number of neutron sources increased. The dose equivalent values were all well within the limits set by ICRP and Radiation Protection Board (RPB – Ghana).

► A 241Am–Be neutron source irradiator facility was modelled using MCNP-5 code.
► The number of 241Am–Be neutron sources was varied from two to five.
► The irradiation channels’ flux was determined for each number of neutron sources.
► Neutron flux increased with increasing number of 241Am–Be neutron sources.
► Dose equivalent values far below the allowable limits set by ICRP and RPB-Ghana.