Comparison of Pellet-Cladding Mechanical Interaction for Zircaloy and Silicon Carbide Clad Fuel Rods in Pressurized Water Reactors

Contact between the outer surface of a fuel pellet and the inner surface of the fuel rod cladding can result in several kinds of undesirable behavior. As the pellet swells outward and the cladding creeps down, large stresses are generated in both the pellet and the cladding. This contact may exacerbate chemical degradation of the cladding and the stress may enable rapid propagation of cracks. Because maintaining the cladding as a barrier to fission gas release is necessary for reactor operation, it is important to have accurate models of the pellet-cladding mechanical interaction. This work analyzes the predictions of a standard fuel rod modeling code utilizing a rigid pellet assumption, and compares these results to a model allowing elastic deformation of both the pellet and the cladding. These models are also used to compare two claddings with significantly different mechanical behavior: a traditional Zircaloy metal cladding and a silicon carbide ceramic cladding.