The trust of public in the nuclear energy does not necessarily accompany the development of scientific studies and technical methods for radioactive release prevention. Whatever the prevailing attitudes at a certain period of time towards the nuclear and whatever the regulation requirements, Probabilistic Safety Assessment (PSA) stands as the main way to quantify risk and to analyze the safety of a project and of the operational configuration of a nuclear reactor. The nowadays growing extent of safety evaluations for nuclear installations includes PSA for licensing and operation of research reactors. The work describes a wide range of PSA level 1 and level 2 aspects, from component failure data to accident sequences quantification illustrated for a research reactor. Deterministic analyses were also done for calculating the radioactive inventory and release of fission product in cases where accident sequences are leading to fuel damage.