Numerical analysis of thermomechanical behavior of fuel rod‌ (UO2)in steady state condition using finite element method

Abstract

In designing the fuel rod, having a reliable prediction of fuel performance is of high importance in order to comply with safety principles. Various computer codes have been provided for this purpose. Each of these codes uses different mechanical models, numerical and analytical methods. Accordingly, the purpose of the present work is to develop Fortran computer software for mechanical and thermal analysis of fuel rods using numerical methods, especially applying the principle of virtual work in mechanical analysis of fuel rods in steady-state conditions. The finite element method is used to solve the equations. The mechanical analysis includes phenomena such as swelling and fuel density and clad creep. Through these phenomena and simultaneous performance of mechanical and thermal analysis, fuel-clad interaction, stress and strain rate in fuel and clad, fuel center temperature, oxide layer thickness, fuel, and clad temperature distribution during operation is obtained by the code. The results of the code are compared with the results of the analytical method which are available in other research works. Finally, for the VVER1000 reactor, mechanical and thermal analysis of the fuel rod was performed over a 1600-day interval. According to the simulation, the fuel-clad interaction occurs after 1250 days.

Keywords

• fuel rod
• clad
• fuel pellet
• mechanical analysis
• thermal analysis
• finite element method
• virtual work