Development and Application of High-Accuracy Metal Fuel Performance Analysis Code Based on Fem Method

Metal fuel is considered to be the future of the Sodium-cooled Fast Reactor due to its advantage. However, the lower melting point is limit for its application, accuracy prediction of the fuel behavior is urgent. In this paper, based on the principle of FEM, the coupled model of thermal conduction and stress-strain analysis is established. The two dimensional model is chosen considering the characteristic of fuel. The heat conduction and mechanical model of fuel rod pellet and cladding, and the fission product behavior model are fully investigated in this paper. Then, the model is analyzed, and the applicable fuel behavior model is obtained. The analysis code SSTFEM is developed and verified using the experimental data. In this paper, the fuel behavior of X425 metal fuel rod under the condition of wire-wrapped constraint is also analyzed. It is found that wire-wrapped has little effect on the temperature distribution and the contact between slug and cladding. However, due to the mechanical constraints at contact points, wrapped wire will have a greater impact on the circumferential stress distribution of cladding. The peak stress appears near the contact point of wrapped wire, which threatens the safety of cladding. The code is used to analyze the effect of the asymmetry deformation which is caused by the asymmetry coolant temperature distribution in adjacent subchannels and the manufacture eccentricity between the slug and the cladding. The effect law of deformation and the stress is obtained after a systematic analysis.