Development and Verification of an Efficient 3-D Finite Element Analysis Model for Irradiation Deformation of the Fast Reactor Fuel Assembly

The existing performance analysis of the fast reactor fuel assembly faces the challenge of balancing high-fidelity and computational efficiency. This study develops a 3-D irradiation deformation analysis model based on ABAQUS to address this conflict. The model employs shell elements to simulate claddings and the hexagonal duct, beam elements for wrap wires, and simplifies complex mechanical interactions using Tie Constraint, Axial Connector element, and General Contact. User subroutines are implemented to incorporate material irradiation behaviors and the non-uniform operating conditions. A parametric automatic modeling method is also developed to construct simplified structures and mechanical interactions. The analysis model has been verified against out-of-pile compression test for a 127-pin fuel bundle and an irradiation deformation benchmark case for a 169-pin fuel assembly, with verification parameters such as gap variation and ovalization. Results demonstrate good agreement with errors within 20%. Furthermore, compared with the simplified model in BAMBOO, the present model demonstrates higher accuracy in the simulation of mechanical interactions and possesses the capability to capture cladding circumferential effects; compared with the full-scale detailed model, the present model achieves comparable results while improving solution speed by over 100-fold for a 7-pin fuel assembly. This model is reliable, efficient and easily extensible for irradiation deformation analysis and design optimization of fast reactor fuel assemblies.