In the early days of nuclear energy in Brazil, a reactor named Argonaut, designed at Argonne National Laboratory, reached criticality at the Institute of Nuclear Engineering (IEN). The presence of a nuclear research facility at the campus of Federal University of Rio de Janeiro is still a cause of concern with regard to the radiological safety of the surrounding community, even though this facility has been securely operating for more than 50 years. In addition, the risk premium paid to IEN workers has also been disputed by the National Office of Account Control. Thus, the aim of this study is to assess the radiological impact and potential risk from Argonaut reactor accidental releases. A recent accident scenario reassessment concluded that severe physical damage of the core after reactor shutdown should be the emergency situation with the greatest potential risk among feasible postulated accidents. The damage caused by failure of a handling crane dropping concrete shielding covers (each weighing 2.5 tons) on the core would lead to breaking of the aluminum coating and the nuclear fuel plates with their release to the reactor hall. This paper evaluates the short-term effective dose rates by inhalation and plume immersion for workers and members of the public, which would be induced by inventory partial release to the atmosphere. The conclusion is that potential risk remains above 1/10 of the limit of annual dose for workers while it stays below the transient levels for members of the public in unrestricted areas.