Investigating the Neutronics Parameters of NIRR-1 Core Using Venture-PC and Scale 6.1 Codes in the 19.75% Enriched UO2-Zircaloy-4 Material

This study is an investigation on neutronics parameters for Nigeria Research Reactor-1 (NIRR-1)
core, a low power Miniature Neutron Source Reactors (MNSRs) using VENTURE-PC and SCALE 6.1
codes in the 19.75% enriched uranium dioxide (UO2)-Zircaloy-4 material. The number of active fuel
pins used for this analysis is approximate 200 pins, which shows that the fuel pins have been reduced
to about 58% when compared with the present Highly Enriched Uranium (HEU) fuel (UAl4-Al alloy
clad in aluminum) of 347 pins. These reductions in the number of fuel pins have 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 NIRR-1. The value of the total control rod worth,
reactivity worth, and shutdown margin were 7.23 mk, 4.04 mk, and 3.19 mk, respectively. Moreover,
the thermal neutrons flux level, peak power density, and maximum neutron density were 1.24 x 1012
ncm-2s-1, 4.31033 W/cc and 6.94535 x 10-6 neutron/cc, respectively. These results are in good
agreement when compared to the experimental result of the HEU core. The diffusion theory based
calculated values of thermal flux profiles for the vertical as well as for the horizontal radial directions
have been found to agree well with similar calculations using various nuclear analysis tools. These
studies indicate that LEU (19.75%) results are conservative and can be applied to ascertain the
reliability of VENTURE-PC code, SCALE 6.1 code, and UO2-zircaloy-4 as the potential material for
future calculation of NIRR-1 core neutronics parameters.