Three-Dimensional Pellet-Cladding Mechanical Interaction through Cohesive Model in DIONISIO 3.0

Abstract

In order to extend the capabilities of the DIONISIO code to three-dimensional domains, we have included a new algorithm to simulate the contact between pellet and cladding and between pellets based in Cohesive Finite Elements. In addition to dividing the rod in a user-defined number of segments, the user can now choose the dimensionality of the domain in which a representative pellet-gap-cladding system is solved. This new model can determine the moment in which two surfaces begin to experience contact and define the evolution of the contact force, including separation of the surfaces and successive contacts. Moreover, it could provide a solution to simulate asymmetric problems concerning the eccentricity of the pellet and cladding, asymmetries in temperature distribution due to the position of a rod in a bundle, especially in accident conditions, or the presence of a defect in the pellet, among others. We present our results testing this kind of contact element, showing improvements over the previous two-dimensional axisymmetric model using Lagrange multipliers and comparing our results with experiments displaying a high correlation so as to validate the concept.