LAUSR

Abstract The fuel bundle in a fast breeder reactor (FBR) is wrapped with wires for guiding the flow of liquid metal. Under operation condition with irradiation and high temperature, the wrapped bundle undergoes complex contact so that the flow channel of liquid will be affected. There are mainly four factors involved: radiation swelling, thermal expansion, radiation creep and thermal creep. In the present study, a full-scale finite element model (FEM) is established to consider the effect of these factors on the complex contact during operation. The established model can capture the contact separation, spacer wire’s dispersion, oval distortion and bowing details of fuel pins. The results show that the local contact dispersion caused by the wire slip can alleviate the severe transverse bending deformation of the bundle. What is more important, we find out that the dispersion of contact points in the peripheral direction of the bundle is another key factor for alleviating the severe deformation of the bundle during operation, this new mechanism – peripheral dispersion of contact – has not been achieved in previous studies.