Alternative core configurations analysis to improve the neutronics performance of modular gas cooled fast reactor

Abstract

This study investigates the neutronics characterization of the Allegro-75 MW_th modular reactor by analyzing three alternative heterogeneous core configurations-axial, radial, axial + radial across three fuel candidates-UPuC, UPuN, and UPuO along with reflector materials namely ZrC, SiC, BeO, and Zr₃Sc₂ to improve neutronics performance, identify the most suitable core configuration and optimal axial reflector thickness. The study revealed that axial + radial heterogeneous core configuration exhibited better performance across each fuel type compared to other heterogeneous models. UPuC with axial + radial heterogeneity was identified as the optimal model as it demonstrated cycle length over ten years, satisfactory neutron spectrum, uniform neutron flux distribution, low radial and axial PPF, high beta effective, and negative Doppler Constant. Analyzing reflector materials with the most suitable fuel model revealed that the optimum axial reflector thickness is 60 cm for all reflector models where BeO emerged as the most favorable reflector due to its superior results in other neutronics parameters.