Numerical simulation of impurity particles migration and deposition within the 5 × 5 fuel assembly under nucleate boiling conditions

Deposition of corrosion products on the cladding surface can cause many problems in PWRs, such as CRUD-induced power shift, localized corrosion, and increased radioactive risk. To gain a deeper understanding of fouling behavior within the fuel assembly, the migration and deposition of impurity particles were investigated with CFD method, where the Eulerian two-fluid model, species transport model, and fouling deposition model are considered. The relationship between fouling deposition rate and thermal–hydraulic parameters was investigated, and the distribution of fouling thickness along both the axial and circumferential directions was analyzed. The results show that the maximum fouling thickness reaches 44 µm in a refueling cycle. Compared with the inner rods, the corner rods have a higher fouling thickness in single-phase region and a lower fouling thickness in nucleate boiling region. The results obtained in this study could provide a reference for the investigation of deposition behavior within the reactor core.