VOLUME 19 (Supplement)

Comparative neutronic performance of UO₂ ceramic and UO₂-silumin fuels in a VVER-1200 reactor using GETERA code

Interest in the development of accident-tolerant fuels (ATFs) has intensified significantly, driven by the need to mitigate the high-temperature vulnerabilities of traditional uranium dioxide (UO₂) fuel systems during severe accident scenarios. The objective of this study is to examine the viability of an alternative UO₂-silumin matrix dispersion fuel, inspired by small modular marine reactors, for deployment in a large-scale commercial VVER-1200 pressurized water reactor. To evaluate this advanced fuel system, steady-state core thermal-hydraulic calculations were coupled with neutronic depletion analyses using the deterministic GETERA-93 code. Key operational metrics, including axial temperature profiles, core criticality variations, and spent fuel nuclide evolution, were evaluated relative to a standard UO₂ baseline. The thermal-hydraulic findings revealed that the high thermal conductivity of the UO₂-silumin matrix fuel reduced the peak centerline fuel temperature from 1819.7°C to 526.9°C under nominal full-power conditions, significantly expanding thermal safety margins during severe-accident scenarios. Neutronic optimization results indicated that a matrix fuel enrichment to 6.2% combined with uniform dispersion of 0.011 wt.% gadolinia (Gd₂O₃) as an integral burnable absorber (IBA) within the silumin matrix successfully matched the baseline operating lifetime of 846 effective full-power days (EFPD). Furthermore, the alternative fuel supported nonproliferation objectives by yielding a 3.1% reduction in total fissile content at end of cycle. The study demonstrates that the proposed UO2-silumin cermet fuel delivers excellent heat-removal capabilities and equivalent fuel-cycle length performance, establishing it as a promising candidate for enhanced accident tolerance and fuel-element optimization in existing light water reactors.