Corrosion of structural materials presents a critical challenge in the use of lead-bismuth eutectic (LBE) asa nuclear coolant in an accelerator-driven system. By forming a protective layer on the steel surfaces,corrosion of steels in LBE cooled reactors can be mitigated. The amount of oxygen concentration requiredto create a continuous and stable oxide layer on steel surfaces is related to the oxidation process. So far,there is no oxidation experiment in fuel assemblies (FA), let alone specific oxidation detail information. This information can be, however, obtained by numerical simulation. In the present study, a newcoupling method is developed to implement a coupling between the oxygen mass transfer model and thecommercial computational fluid dynamics (CFD) software ANSYS-CFX. The coupling approach is verified. Using the coupling tool, we study the oxidation process of the FA and investigate the effects of differentinlet parameters, such as temperature, flow rate on the mass transfer process.