Neutronics Study of NIRR-1 Fuelled with 19.75% UO2 Material Using Venture-PC and Scale 6.1 Codes

A comprehensive neutronics analysis using VENTURE-PC and SCALE 6.1 computer codes system has been performed for the core conversion study of Nigeria Research Reactor-1 (NIRR-1). The computed reactor core physics parameters include: group neutron fluxes profiles, power density distributions and neutron flux distributions. The number of active fuel pins used for this analysis is approximate 200 pins, which show that the fuel pins have been reduced to about 58% when compared with the present Highly Enriched Uranium (HEU) fuel (UAl4-Al) of 347 pins. These reductions in the number of fuel pins has given room for more moderators in the core and hence increase the number of hydrogen available to thermalize the neutron in the potential 19.75% UO2 fuelled core for Nigeria Research Reactor-1 (NIRR-1). The diffusion theory based calculated values of thermal flux profiles for the vertical as well as for the horizontal radial directions has been found to agree well with similar calculations using different nuclear analysis tools. The results obtained will qualify uranium dioxide (UO2) fuel as the potential material for future Low Enriched Uranium (LEU) core conversion of Nigeria Miniature Neutron Source Reactors (MNSRs).