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Recently, nuclear fusion-related experiments and dedicated facilities worldwide relying on the usage of liquid metals are experiencing a renewed interest. This is the case of the International Fusion Materials Irradiation Facility – DEMO-Oriented Neutron Source (IFMIF-DONES), a radioactive facility which will use several cubic meters of pure liquid lithium as a target for deuterons to produce high neutron fluxes having an energy spectrum as effective as the expected fusion reactors. The primary mission of IFMIF-DONES will be to irradiate selected candidate structural materials for building a comprehensive database on fusion material properties. Generally, alkali metals, such as lithium, exhibit safety issues related to their chemical reactive nature and material compatibility. Due to the wide uncertainty regarding the lithium behavior confirmed by an extensive literature review, a dedicated experimental facility has been conceived to primarily study lithium ignition conditions in support of the licensing process of IFMIF-DONES. The ultimate purpose of the LiFIRE facility will be to demonstrate by means of experimental evidences the set of requirements on lithium fire protection to be applied to the final engineering design of IFMIF-DONES. This work describes the final design, construction and experimental campaign of the LiFIRE facility currently under development at CIEMAT's premises. [ABSTRACT FROM AUTHOR]

• Lithium natural reactivity and potential flammability are critical for its safe handling. • A reliable lithium fire protection methodology has been outlined for IFMIF-DONES facility. • Lithium fire prevention, detection and mitigation measures have been defined. Several experimental facilities, mainly focused on nuclear fusion applications, propose lithium as main coolant and/or tritium breeder material, limiter or divertor for its advantageous properties. Lithium fire hazard represents a critical risk for the production of an important population of reactive, corrosive and toxic aerosols, and for the potential mobilization, transport and release of radioactive species, initially retained in the molten metal, as in experimental facilities like the IFMIF-DONES accelerator neutron source. Consequently, a specific methodology should be developed for managing possible lithium fire scenarios that could occur during the lifetime of these unique facilities. Applying the Defense-in-Depth principle to minimize the fire risk in the particular case of the IFMIF-DONES plant, this work describes a set of passive and active measures for lithium fire prevention, detection and mitigation in compliance with main international and national standards on fire protection. According to the present safety analyses, active measures, including the use of fixed extinguishing systems employing chemical agents, do not seem to be entirely reliable in case of large lithium fires, for which more preferable passive fire protection measures are also being considered to be implemented in the final design of IFMIF-DONES, such as room inertization, catch pans and drain systems, constituting together a main line of defense to safely manage potential lithium fire scenarios. [ABSTRACT FROM AUTHOR]

Integration of safety aspects in IFMIF-DONES design is a main objective of EUROfusion and European Commission projects. IFMIF-DONES will be a radioactive facility of the first category, and stringent safety objectives must be achieved and demonstrated. A very low acceptable risk for the worker, the public and the environment is the main principle in the design phase. The progress of safety activities is performed iteratively as detailed engineering develops, taking into account the uniqueness of the facility: a high-power deuterons accelerator (125 mA, 40 MeV), a target of flowing liquid lithium, traps for activation products, a dedicated-design module for irradiated samples, a massive shielding cooled room with confinement function, and a number of conventional systems with safety functions. Several phases are developed: (i) identification of sources and materials at risk, radioactive and nonradioactive, subject to potential mobilization, (ii) failure mode analysis and effects of systems, starting at the functional level, and support with probabilistic analysis, (iii) identification of scenarios leading to unacceptable risk if unmitigated, (iv) proposal of layers of defense by means of safety-credited components and design features, (v) deterministic analysis of scenarios in support of requirements, and (vi) definition and demonstration of safety requirements charged to components. [ABSTRACT FROM AUTHOR]