The current work presents a numerical simulation of ballooning and burst behavior of Zircaloy type nuclear fuel cladding during a Loss of Coolant Accident (LOCA). The work is based on the commercial numerical simulation software SIMULIA ABAQUS©. The algorithm for the material thermo-mechanical behavior relies on several external sources for material properties and constitutive behaviors. The implementation into ABAQUS© is done through the use of FORTRAN programmed user subroutines. The Abaqus/Explicit solver is chosen to better facilitate the fast ballooning near cladding burst, and relies on the VUMAT subroutine along with several other utility and secondary routines to provide the Elasto-Viscoplastic/CREEP Thermo-Mechanical relations and boundary conditions. The code requires various user inputs which enable the implementation of several different constitutive behaviors and material related properties. The thermo mechanical behavior includes the transient effects of Material anisotropy, Cold Work and Annealing, Irradiation damages, Oxidation, Phase Transformation and of course Temperature and rate dependent properties. Preliminary validation included comparison with the HALDEN IFA650.2 calibration LOCA experiment, performed with as-received cladding, and the FRAPTRAN1.4 code predictions. Ballooning shape, rupture temperature and max diametric expansion of the cladding at failure displayed good agreement with the benchmark experiment under the current assumptions. A moderate azimuthal temperature variation in 3D was also modeled, and its results emphasized the significance of 3D modelling as opposed to the commonly employed axisymmetric variations. The goal is to eventually calibrate and validate the model with coupled thermo-hydraulics and fuel performance codes during the upcoming LORELEI single rod LOCA experiments in the French JHR reactor.
