Alpha spectrometry system is used to measure the activity concentration of alpha emitting radionuclide such as Po-210, U-234, U-235, U-238, Th-228, Th-230. Th-232 and Pu-239+240. Similar to gamma radionuclide. every alpha radionuclide also has it owns characteristic energy which can be used for its identification. The intensity of the detected alpha particles is used to measure its activity concentration. Since alpha particle energies of many radionuclide differ by as little as 10-20 KeV which is near the resolution of silicon detector such radionuclide must be chemically separated prior to analysis. In order to avoid self-absorption of alpha particles within the sample, a thin-layer sample is prepared by deposition technique onto a metal disc prior to counting in vacuum chamber of an alpha spectrometry system.