Conceptual design of a PWR microreactor core without enriched uranium

Nuclear microreactors, owing to their compact architecture and high operational efficiency, represent a promising alternative for clean and safe energy generation, particularly in remote regions or emergency scenarios. A key challenge in the development of such systems is the diversification of nuclear fuels beyond conventional uranium dioxide, with the goal of improving fuel utilization, reducing plutonium inventories, and minimizing proliferation risks. In this context, this study proposes and compares different configurations of a PWR-type microreactor operating exclusively with MOX fuel produced from natural uranium, without enrichment. Six initial PuO 2 concentrations were evaluated, ranging from 5% to 30%. The SCALE computational system was employed to model the fuel element and assess the core burnup behavior. The results indicate that compact cores, with volumes as small as approximately 445 L, can achieve fuel cycles exceeding 10 years while delivering an electrical output of around 12 MWt. These findings provide a solid technical basis for evaluating the feasibility of natural-uranium MOX as an alternative fuel in long-life microreactors. • Design of a PWR microreactor core using MOX fuel without uranium enrichment. • Compact core geometry with reduced dimensions and a total volume of 445 L. • Long-term operation exceeding 10 years, delivering approximately 4 MWe.