Critical mineral supply chain readiness for commercial fusion energy: A framework with applications to the ARC and EU-DEMO tokamaks

Private fusion energy companies are targeting commercial electricity generation within the next two decades, yet the material supply chains required to build and operate these reactors have received limited systematic assessment. This paper develops and applies a Supply Chain Readiness Level (SCRL) framework to evaluate 13 materials for the ARC compact tokamak, arguably the most detailed publicly documented commercial fusion design. The framework assesses each material across three dimensions: demand (bottom-up engineering estimates from published design parameters), supply chain maturity (geographic concentration, volume adequacy, and specification gap), and timeline criticality (investment lead times measured against deployment scenarios). The analysis uses the Hillesheim et al. (2026) Version 3A engineering baseline as the primary reference case, the Sorbom et al. (2015) original concept as a historical comparator, and the published EU-DEMO material assessment as a cross-design benchmark. Five materials essential to the ARC design score Critical. Four share a single failure mode, fusion-grade production that has not yet been established at any scale: enriched lithium-6 for tritium breeding, REBCO superconducting tape, FLiBe molten salt, and vanadium alloy V-4Cr-4Ti. The fifth, beryllium, is Critical on volume grounds, with single-reactor demand approaching 40% of global annual production. The specification gap between the commodity form and the fusion-grade product, rather than raw material scarcity or geographic concentration, is the dominant constraint across the material set. Under deployment timelines stated by leading private developers, decision windows for several critical materials are already closed or closing. Industry survey evidence from the Fusion Industry Association's 2026 supply chain report independently confirms both rising materials concern among developers and the coordination failure between developers and suppliers that prevents timely investment. The SCRL framework provides the quantified, material-specific demand signals needed to bridge this gap.