Thermal – hydraulic performance assessment of accident tolerant fuel in a VVER-1000 nuclear reactor via computational fluid dynamics approach and hot channel analysis

Abstract

The integration of accident tolerant fuel technologies into existing reactor designs is a promising approach to enhance nuclear safety and operational reliability. This study presents a comprehensive thermal hydraulic analysis of VVER-1000 reactor core employing various accident tolerant fuel candidates, including uranium dioxide (UO₂) and uranium carbide (UC) fuels with zirconium (Zr) and silicon carbide (SiC) cladding materials. The conventional uranium dioxide–zirconium (UO2 – Zr) combination is used as the reference case for comparison. A full-core neutronic model was developed using Monte Carlo simulations to evaluate essential parameters such as the effective multiplication factor, power peaking factor, delayed neutron fraction, and temperature reactivity coefficients for both fuel and coolant. The hottest channel, identified from the axial power distribution, was modeled in a computational fluid dynamics code to analyze the temperature profiles of the fuel, cladding, and coolant, as well as the convective heat transfer coefficient and the minimum departure from nucleate boiling ratio. Comparative analysis revealed that UC – SiC combination exhibited the most favorable thermal behavior, achieving the lowest peak fuel centerline and cladding surface temperatures, and the largest minimum departure from nucleate boiling ratio which indicates superior safety margins for UC – SiC. This study demonstrates the feasibility and potential safety advantages of accident tolerant fuels implementation in VVER-1000 reactors, offering valuable insights for future fuel design and licensing strategies. © 2026 The Author(s).