In this master’s thesis, we studied the efficiency of nuclear fuel utilization in reactors of various sizes based on a consistent core model. The primary goal was to evaluate the efficiency of Small Modular Reactors (SMRs) in comparison to traditional large reactors.
Measure for fuel utilization is total released energy per kilogram of initial uranium fuel content. To assess fuel utilization, we examined fuel cycle length, burnup, and the conversion ratio, as these factors directly influence reactor economics. Even a 1 % improvement in fuel utilization can lead to significant cost savings over a reactor’s lifetime. For example nuclear power plant in Krško (NEK) uses 16.6 metric tonnes of UO2 on a yearly basis. With the cost of 1.6 M€/t, a 1 % improvement would yield more than a quarter of a million euro per year in savings.
Simulations were performed using the OpenMC Monte Carlo neutron transport code. We analyzed twelve reactor configurations for which we calculated: fuel cycle lengths, nuclide compositions, conversion ratio and fission power distribution across space and time. Additionally, we performed parametric analyses, varying both linear power and initial fuel enrichment.
Key findings:
• Smaller reactors exhibit up to 400 % lower fuel utilization efficiency than larger ones.
• Higher fuel enrichment significantly improves efficiency and reduces the gap between small and large reactors.
• For each reactor size, there is an optimal enrichment that maximizes fuel utilization.
• The conversion ratio increases with reactor size and fuel cycle duration, but excessive enrichment can reduce it due to lower availability of fertile material.
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