Nigerian Research Reactor-1 (NIRR-1) Core Life-time Analysis using Winfrith Improved Multigroup Scheme-Argonne National Lab (WIMS-ANL) and REactor BUrnup System-Argonne National Lab (REBUS-ANL) Computer Code

Abstract The core of the Nigeria Research Reactor-1 has been converted from Highly Enriched Uranium (HEU) fuel to Low Enriched Uranium (LEU); nevertheless, a core lifetime analysis of the converted HEU and current LEU fuel is required. The core lifetime analysis of the NIRR-1 converted HEU and current LEU cores was carried out using the Winfrith Improved Multigroup Scheme-Argonne National Laboratory (WIMS-ANL) and Reactor BUrnup System-Argonne National Laboratory computer codes in this work (REBUS-ANL). One group cross section was generated using the WIMS-ANL. For core lifetime analysis, these group cross sections were employed in the REBUS-ANL programme. A simple reactivity rundown was performed to estimate the core lifetime for HEU and LEU cores at two power levels using the REBUS-ANL code (full and half power). The lifetime of the LEU core was predicted to be approximately 11.91 percent longer than that of the HEU core at full power and 11.81 percent at half power based on the results obtained. This is in good agreement with the value 11 percent reported in the literature, indicating that the selected LEU core can be operated for a longer period of time than the HEU core.