Design-Phase Probabilistic Risk Assessment for the International Fusion Materials Irradiation Facility

This paper briefly presents Probabilistic Risk Assessment (PRA) developed for the International Fusion Materials Irradiation Facility – DEMO Oriented Neutron Energy Source (IFMIF-DONES) at the design-phase of the facility. The IFMIF-DONES facility is used to test the suitability of certain materials for fusion power plant (DEMO plant) conditions. The neutron flux for the irradiation of the materials is produced by directing a deuteron beam through a lithium target. In this process, radioactive tritium and activation products are also produced, and there is a risk for a radioactive release to environment. Based on the safety analyses performed in the design-phase of the facility, the main risks of the facility are that either the deuteron beam damages the structures behind the lithium target or lithium reacts with oxygen. The accident scenarios with potential for significant radioactive releases have been modelled by eight event trees in the PRA model. Failures of safety functions, such as beam shutdown, inerting functions and isolation functions, have been modelled using fault trees. Preliminary quantification of the PRA model has been performed based on component reliability data collected from fusion applications as well as nuclear power plant domain.