Screening of suitable and testable structural materials for a volumetric neutron source

The construction of a dedicated Volumetric Neutron Source (VNS) has recently been proposed to de-risk the path towards the licensing of EU DEMO and to bring the required technologies, in particular the Breeding Blanket, to the required Technology Readiness Level. The programmatic goals, the operating conditions and the associated requirements of this machine are different from the fusion power machines (ITER, DEMO) considered until now in the European Research Roadmap. A critical analysis and a possible reassessment of the material choices for the Vacuum Vessel (VV) and In-Vessel Components established for ITER and DEMO is therefore a required prepa­ ratory step. Starting from the materials used in the ITER VV and Shielding Blanket, their limits w.r.t. maximum allowable dose are discussed and possible alternatives to maximize the lifetime of the facility are proposed. The materials currently considered for the EU-DEMO Breeding Blanket are recalled and an overview of their present development status is provided. Materials and joining issues for Divertor targets are also discussed. The gaps in materials properties and the needs for additional characterizations are identified. The purpose of this paper is to provide options and information for designers, exploring the operational space of the VNS, the final selection of materials depending on the strategic goals and design choices that will be set for the facility.