Unavailability analysis of a lithium target system for a test facility

For an experimental facility like the International Fusion Materials Irradiation Facility, safety, performance and reliability are outstanding attributes. The results of an analysis aimed at estimating the unavailability figure of the target system and evaluating the expected performance of the plant, in terms of safe and reliable operation, are presented in this article. Starting points of the analysis have been the identification of relevant plant functions and relationships between plant systems and functions and the definition of relationships among the systems themselves. Fault tree technique has been adopted to address the topic: with regard to the reference configuration, systems boundaries and interfaces have been identified as well as the dependent failures between systems and components. Due to the novelty of the plant and its prototypical character, reliability data introduced in the numerical simulation underwent an accurate screening process among the current available databases, sometimes requiring the expert judgment assessment. Finally an uncertainty, importance and sensitivity analysis has been performed in order to add credit to the model and to highlight reliability-critical systems and components: results are analyzed to assess the compliance with the plant availability requirements and design criteria. Risk Spectrum code has been utilized for the system unavailability quantification.