Probabilistic safety analysis of a Greek Research Reactor

This paper presents the work and the results of a Level 1 Probabilistic Safety Assessment performed for the Greek Research Reactor of the National Center for Scientific Research “Demokritos”. Event trees have been used to study the response of the installation to various initiating events whereas fault trees have been used in the modelling of safety system failures. Using generic data, the probability of an accident leading to severe core damage ( 10% of core melted) from internal initiating events has been estimated to be 3×10−6 per year of reactor operation. The largest contributions to the probability of small damage are made by accidents initiated by loss of cooling and excess reactivity. Large releases of radioactivity are expected with a negligibly low frequency of about 1×10−11/year.