Probabilistic Safety Analysis of the International Fusion Materials Irradiation Facility

摘要

Safety assessment of the International Fusion Materials Irradiation Facility (IFMIF) is performed adopting the probabilistic approach: the analysis is oriented towards identifying and quantifying, in terms of expected frequency, the dominant accident sequences occurring to the plant facilities with the potential to hazard the plant, the personnel and, as extreme consequence, the environment and the public. The identification of the initiating events, provided by the Failure Mode and Effect Analysis procedure, is followed by the systems analysis based on Fault Tree technique: finally the accident sequence scenarios are modelled through the Event Tree development and assessed by RISK SPECTRUM software. The study has allowed for the development of all accident sequences resulting from selected initiators relative to IFMIF plant and their grouping within sequence families, denoted as plant damage states, on account of the plant response and accident evolution. The frequency assigned to each family sequence is the sum of the contributors relative to all sequences ending into that particular plant state. The outcome of the analysis shows that IFMIF plant is quite safe and presents no significant hazard to the environment: in fact all the sequences implying potential undesired effects as radioactive release to the outside, show very low frequencies, well below the limit for credible accident (1.0E-6). In addition, due to the novelty of the design and the large spreading assigned to the failure parameter probabilistic distributions (data utilised in the probabilistic analysis of this one of a kind plant are largely of a generic nature), an uncertainty analysis has been performed to add credit to the model quantification and to assess if the sequences have been correctly evaluated on the probability standpoint and finally to verify the fulfilment of the safety requirements.