Probabilistic safety evaluation of the gas-cooled breeder reactor

The paper presents results of a preliminary reliability and fault tree analysis related to the Gas-cooled Breeder Reactor (GBR). This analysis was performed in the frame of a GBR safety assessment carried out under the sponsorship of the Commission of the European Communities. The study dealt with possible and credible sequences of events following initiating accidents. The paper concentrates on the so-called ''worst credible'' accident--the fast depressurisation of the reactor--which has the highest probability of leading to a gross melt-out, and quantifies the probability and magnitude of possible radioactive releases. The consequences to the public are assessed and an overall evaluation of the risks is given. The conclusion is that it is possible with the Gas-cooled Breeder Reactor to reduce the risks to the environment to levels equal or smaller than those already accepted for other reactor systems