Structural Integrity Analysis of Fuel Element Cladding Based on Fluid-Solid-Heat Coupling

When a transient condition occurs in the reactor system, the transient and great change of the coolant will impact the structural integrity of the fuel element cladding and endanger the safety of the reactor. In this paper, taking the 3×3 fuel assembly of a PWR as the object, 3D refined simulation of the flow and heat transfer characteristics of fuel assembly and temperature, deformation and stress of fuel element cladding under cold water accident is carried out with the fluid-solid-thermal coupling method. The results show that the spacer grid can enhance the convective heat transfer intensity on the fuel rod surface; When the cladding is deformed, it bends to the side in contact with the rigid convex and bulges to the side in contact with the spring; the temperature and the maximum equivalent stress of the contact part between the cladding and the spacer grid increase with the accident time, and the maximum equivalent stress exceeds the yield strength of the cladding material, which will cause strength failure and affect its structural integrity. The research in this paper can provide reference for the integrity evaluation of reactor fuel element cladding under transient condition.