Mechanistic assessment of aerosol transport in an SFR cover gas space under operating condition

The cover gas space is an inert isolation layer provided for sodium systems in sodium-cooled fast reactors. During normal reactor operation, sodium aerosols are generated continuously in the cover gas space. Understanding the complex dynamics of the evolution and transport of the aerosol is essential from the perspective of the reactor operation. Such assessments provide vital insights into deposition patterns of aerosols to the components mounted on the roof slab. In the present manuscript, the evolution and transport of aerosol in the cover gas space as well as in roof-slab annular gaps are studied in detail with the help of computational fluid dynamics tool. The present model is validated against the experimental data from the literature. There is good agreement between temperature variation, aerosol number and mass concentration across the cover gas height. Post validation, the study of thermal and aerosol transport in the full-scale reactor cover gas for a medium-sized reference reactor is carried out. It is observed that aerosol sizes greater than ∼31 μm are mostly concentrated near either the sodium pool surface, component wall or near the vessel boundary. It is found that the average mass concentration in the cover gas space is uniform (∼ 29 g/m3). However, the annular regions are found to have a non-uniform distribution of aerosols with heavier particles confined to the lower annular regions in wavy like patterns having the same Count Mean Diameter (CMD) as in the bulk cover gas space. The CMD in the top annular regions is ∼ 2 μm.