Modeling of Formation and Evolution of Cracks in Zirconium-Based Claddings of Nuclear Fuel Rods Within DIONISIO 3.0

Various numerical models are developed that seek to reproduce, in a simulation instance, the formation and evolution of cracks in the claddings of nuclear fuel elements. The algorithms are based on the cohesive zone method within the finite element framework. When applied to simulations involving fracture mechanics, cohesive elements have various advantages, such as not needing to know the stress state in advance, representing the nucleation of the crack, and being able to reproduce the contact between the crack surfaces after fracture, with numerous application examples for ductile materials, including metals. The models developed were included in the DIONISIO 3.0 nuclear fuel code and compared with analytical test cases, controlled tests of nuclear materials, and a large set of experimental exercises with rods subjected to steep power ramps where breakages are caused due to contact with the pellets. Similarly, these new models were used in controlled experiments where the conditions of an accident type such as a loss-of-coolant accident are reproduced, analyzing the variation of the thermohydraulic, thermomechanical, and structural parameters of a rod.