[en] This paper discusses sodium vapor deposition on a simulated LMFBR rotating shield plug annular walls, both experimentally and on the basis of numerical calculation. Experiments were carried out to investigate the effects of cover gas natural convection within the annulus to local and average deposition rates. It was found that the generalized average deposition rate, which is similar to Sherwood number, depends on Rayleigh number. Numerical calculation of saturated vapor condensation rate along the wall was also carried out to demonstrate the effect of vapor condensation to be small to real deposition phenomena. The results suggested that deposition process is controlled by the mist transfer and their deposition onto the wall. (author)