Analysis of nuclear fuel rod temperature distribution using CFD calculation and analytical solution

Abstract

Analysis of temperature distribution within a nuclear fuel rod is needed to be performed for safety purpose. The maximum fuel temperature must be ensured to be not exceeding the fuel integrity limit to prevent the release of hazardous fission products to the environment. The fuel temperature distribution is obtained through the calculation of the heat transfer process within the fuel rod. The multiple heat transfer processes with various heat transfer modes involved in transporting the fission heat generation in the fuel meat to the coolant are interesting and important to be studied in detail to verify the safety aspect of nuclear fuel. This paper aims to show the applicability of CFD FLUENT and analytical solution in calculating the temperature distribution within a nuclear fuel rod. The CFD FLUENT simulation was performed using the two-dimensional axisymmetric model and the three-dimensional model, while the analytical solution was performed using the one-dimensional heat conduction equation and an energy balance equation. The calculations were performed in both laminar and turbulent coolant flow regime cases. A sensitivity analysis was also conducted to investigate the fuel properties which has a significant contribution to the fuel meat temperature. The results show that the two-dimensional and three-dimensional CFD FLUENT simulations and the analytical solution give similar results in calculating the fuel rod temperature distribution in laminar and turbulent coolant flow cases. Both CFD FLUENT and analytical solution can show the distribution profiles of coolant average temperature, cladding outer surface temperature, cladding inner surface temperature, fuel meat surface temperature, and fuel meat centerline temperature. The distribution of coolant temperature near the cladding surface was only provided by CFD calculation. Unfortunately, the results of CFD FLUENT simulation and analytical solution do not agree with the experimental result available in the literature due to the limitation of CFD FLUENT. Another result of this work reveals that fuel meat conductivity, gap conductivity and heat generation distribution have a significant role in predicting the fuel rod temperature accurately. Finally, this work concludes that the CFD FLUENT simulation and a simple analytical solution are capable in predicting the fuel temperature distribution by calculating the heat transfer within a fuel rod and the heat removal from the fuel to the coolant. Further work is still needed to conduct the verification and validation of the CFD FLUENT and analytical solution results.