An innovative multi-layer shell model for in-pile thermo-mechanical behavior analysis of plate-type fuel assemblies

Abstract

In this study, an innovative large-deformation multi-layer shell model is developed. In order to improve the efficiency of simulating the thermo-mechanical coupling behavior in complex plate-type fuel assemblies, the fuel plates are simulated by 2D shell element, with the irradiation swelling and creep effects involved. The specific theoretical frame for the kinematic models and three-dimensional constitutive models is presented, together with the generalized force update algorithm. The application of the developed shell model in the thermal–mechanical behavior simulation of a monolithic U-Mo/Al fuel assembly indicates that (1) the out-of-plane displacements of the side plates can be precisely calculated, with the calculation time ∼92% shorter than that of a full 3D simulation of 308-day irradiation behavior; (2) the out-of-plane displacements of the fuel plates excluding the peripheral ones can also be well obtained, with small relative deviations to the full 3D simulation results; (3) using 3D solid models for the peripheral fuel plates, a fuel assembly finite element (FE) model with 2D&3D geometric models for the fuel plates is proposed with a total computation time decrease of 64%, and the precise of deformation simulation results can be improved comprehensively. This research provides important theoretical models and algorithms for the irradiation-induced deformation analysis of complex plate-type fuel assemblies.