Thread Content
Considering the background related to uniform corrosion of highly burned nuclear fuel discussed earlier, its main influencing factors can be classified into the following categories: the inherent properties of the material itself; the burnup level of the fuel core directly affects irradiation defects and the distribution of fission products, while the composition and microstructure of the zirconium alloy cladding determine the density of the oxide film, thereby influencing its corrosion resistance. Temperature and heat flux conditions: The higher the temperature at the interface between the cladding and the coolant, the faster the oxidation rate of the zirconium alloy ； An increase in heat flux raises the thermal resistance of the oxide film, further increasing the interfacial temperature and accelerating the corrosion process. Primary loop water chemistry conditions – the concentrations of impurities such as LiOH and H₃BO₃ in the coolant, as well as dissolved oxygen and fluoride ions – have a direct impact on the stability of the oxide film on zirconium alloys. An excessively high Li⁺ concentration can significantly accelerate the corrosion rate. Irradiation-related effects: Irradiation inside the reactor alters the chemical composition of water, while also disrupting the crystal structure of the cladding oxide film, resulting in an increase in corrosion rate by 1.2 to 4.4 times; this increase continues as the irradiation dose rises. Operating condition parameters: At high fuel consumption, the fuel stays in the reactor for a longer period of time, causing the oxide layer to continue thickening. Meanwhile, the interactions between the fuel pellets and the cladding resulting from power fluctuations also contribute to accelerating the corrosion process indirectly.