Holddown Force Analysis Model Research of Fuel Assembly Leaf Springs with Varied Stiffness

In order to conduct the holddown force analysis of the leaf spring with varied stiffness of PWR fuel assembly, this paper firstly analyzes the loading and unloading processes of the traditional leaf spring, and then comprehensively considers the influence factors such as temperature change, irradiation growth and irradiation relaxation. The holddown force change of the leaf spring with varied stiffness during different loading and unloading processes is further analyzed, and the load-deformation curve of the leaf spring with varied stiffness in the whole process is given. The analysis results show that the irradiated growth of fuel assembly increases the deformation of the leaf spring, but does not change the loading and unloading stiffness curves. The radiation relaxation process of the leaf spring with varied stiffness can be divided into two groups of leaf springs in parallel. Their radiation relaxation amounts are considered separately, and the stiffness curve characteristics remain unchanged. When the radiation growth of fuel assembly is greater than the radiation relaxation of the leaf spring, the plastic deformation of the leaf spring will increase.