Materials-engineering challenges for the fusion core and lifetime components of the fusion nuclear science facility

•FNSF provides a fully-integrated fusion environment for materials and component testing.•FNSF phased operational program will span nuclear break-in to DEMO-relevant conditions.•Near term materials R&D issues motivated by current FNSF design activities.•Peak neutron damage levels, helium and hydrogen production rates are identified for the FNSF replaceable and lifetime components. From the perspective of materials research and development (R&D) for the fusion core and near-core lifetime components of deuterium-tritium fusion power systems, the Fusion Neutron Science Facility (FNSF) concept plays a very important function by generating the complete fusion in-service environment and providing a platform for materials component-level testing. The FNSF provides the critical link between the ITER-era and the electricity- producing facilities, DEMO and the commercial power plant. The main features of the FNSF are described and the rationale presented for the selection of structural materials to meet the challenges of the power core components and also for the system lifetime components. The calculated radiation damage parameters and potential operating temperatures requirements for each of the operational phases are presented ranging from nuclear break-in up to DEMO relevant conditions. The interdependence of the FNSF and fusion nuclear materials research are discussed, and examples of near-term materials R&D activities are outlined which could address several current FNSF-related design issues.