This paper describes an experimental methodology developed in an Aerosol Test Facility (ATF) for sampling and analysis of sodium aerosol (metal vapour) from the cover gas region of a fast rector, and details of the validation of the methodology in an experimental sodium loop. The methodology involves; (i) sampling of sodium aerosols by drawing them without exposure to the atmosphere, (ii) trapping them in paraffin oil medium, and (iii) analyzing the paraffin oil for the determination of mass concentration by the conductivity method and size distribution by using a Mastersizer. Validation of the methodology is carried out in a sodium loop called the SILVERINA facility. The aerosol size distribution is found to vary from 1 to 12 µm, with the Mass Median Diameter (MMD) around 4.0 µm (σg = 1.5), and the mass concentration is found to be ~9.50 g/m3. The experimental results agree with the values found in the literature.