Influence of Neutron Flux on the Interaction of Fuel Assembly Spacers

Abstract

Continuing the study on Fuel Assembly Spacers, the interaction between the cladding and the spacer is analyzed, as it is a key aspect in preserving the structural integrity of the system. At this stage, a neutron flux derived from actual plant data is imposed, considering different burnup histories. This requires recalculating the diametral deformation of the cladding using an anisotropic viscoplastic self-consistent model (VPSC), validated with experimental data. The resulting deformation is used as input for a 1D phenomenological irradiation creep model, where the evolution of the contact is reproduced up to end-of-life. Subsequently, the full cladding–spacer interaction is evaluated using a 3D finite element model with the same self-consistent formulation. Finally, both approaches—phenomenological and viscoplastic —are compared in terms of accuracy, simulation time, and predictive capability.