THREE-DIMENSIONAL PCI MODELLING IN DIONISIO 3.0

GOLDBERG, EZEQUIEL; A. SOBA

Paris

Workshop; Progress on Pellet?Cladding Interaction and Stress Corrosion Cracking; 2019

IAEA

A recently developed three-dimensional finite element model for pellet-cladding interaction (PCI) based in the CohesiveZone Method, originally developed to treat discontinuities that progress in the continuum, in the 3.0 version of the DIONISIOcode is presented. Given that the numerical technique used in DIONISIO is based on the finite element method to solvedifferential equations over defined domains, the development of a cohesive zone method provides a very robust formulation tomanage the gap between pellet and cladding treated as a discontinuity. The approach resulted in a natural mode to tackle PCIconsidering specifically the cylindrical geometry of pellet and cladding, being innocuous when contact surfaces are apart, andpresenting the expected behaviour through the entirety of contact and in the case that the surfaces were to disjoin any numberof times during the simulation. Selected results of the model compared to special experiments designed to simulate the pelletcladdingthermomechanical interaction and under irradiation experiments taken from the IAEA database as well as a deepdiscussion about the advantages and shortcomings of this methodology are presented. Additionally, allowing the use of threedimensionalgeometries, this model offers the possibility of performing simulations of asymmetric scenarios such as certainoblations or eccentricity of the pellet or the cladding, heating conditions regarding the position of the rod in a reactor core,pellet superficial defects as a result of fuel element assembly and ballooning of the cladding in LOCA cases, among others.