Research activities of Vinca Institite have been based on two heavy water research reactors: 10 MW one, RA and zero power RB. Reactor RA was operational from 1962 to 1982. In 2010, spent fuel have been sent to the country of origin, and reactor now is in decommissioning. During operational phase of the reactor there were no recorded accidental releases into the environment just operational ones. Results of the environmental impact assessment, of the assumed emission of radionuclides, from the ventilation of nuclear reactor "RA" in Vinca, to the atmospheric boundary layer are presented in this paper. Evaluation was done by using the Gaussian straight-line diffusion model and taking into account characteristics of the reactor ventilation system, the assumed emission release of radioactivity (from the literature), site-specific meteorological data for six-year period and local topography around nuclear reactor, and corresponding dose factors for inventory of radionuclides. Based on the described approach, and assuming that the range of appropriate meteorological data for six year period for the application of described mathematical model is enough for this kind of analysis, it can be concluded that the nuclear reactor "RA", in the course of its work from 1962 to 1982, had no influence on the surrounding environment through the air above regulatory limits. [Projekat Ministarstva nauke Republike Srbije, br. III 45003]