Last week, the European Union approved a €202 million investment in IFMIF-DONES, the International Fusion Materials Irradiation Facility currently under construction in Granada, Spain.
This milestone cements IFMIF-DONES as a cornerstone of Europe’s fusion roadmap and reflects a growing recognition that fusion’s commercial viability depends not just on plasma physics, but on materials that can survive reactor-grade conditions over years of operation.
The Materials Bottleneck
Fusion reactors generate extreme heat and bombard internal walls with high-energy (~14 MeV) neutrons. Over time, these neutrons degrade structural components, making them brittle, distorting their shape, and altering their atomic structure. This cumulative damage is a primary constraint on reactor longevity and uptime.
To date, most material testing has taken place in fission reactors or low-energy neutron sources. But those environments fail to replicate the high-flux, high-energy neutron loads of D-T fusion. That leaves a critical blind spot: we still don’t know how candidate materials behave under sustained fusion-level neutron bombardment.
IFMIF-DONES is designed to close that gap. The facility uses a 125 mA deuteron beam, accelerated to 40 MeV, and directed into a flowing lithium target. This generates a continuous stream of high-energy neutrons via nuclear stripping reactions. Small capsules of candidate materials are exposed just behind the lithium curtain to mimic the damage expected in a fusion reactor’s first wall.
Initial test campaigns will focus on reduced-activation ferritic-martensitic steels like EUROFER, alongside tungsten composites, next-gen alloys, and potentially liquid metal systems. These materials will form the foundation of future blankets, divertors, and structural components.
Cross-section of the IFMIF-DONES facility. Picture courtesy of IFMIF-DONES.
Role in Europe’s Fusion Roadmap
Europe’s fusion program now rests on three interlocking pillars:
ITER (France): Focused on demonstrating the scientific and engineering feasibility of large-scale fusion power.
IFMIF-DONES (Spain): Provides crucial data on how candidate materials hold up under fusion-relevant conditions.
DEMO: Aims to take ITER’s findings and actually generate electricity, operating as a pilot plant.
These three pillars work together. ITER proves the physics, IFMIF-DONES validates the materials, and DEMO integrates both into a functional power plant.
IFMIF-DONES is expected to take ~10 years to build, with initial operations targeted for the mid-2030s. That aligns with other critical inflection points across the fusion ecosystem:
DEMO plans to finalize its engineering design by the late 2030s, with construction expected to begin soon after.
Private fusion startups are projecting pilot operations throughout the 2030s.
Global regulators are beginning to develop qualification standards and licensing pathways.
If all goes to plan, IFMIF-DONES will be producing data on the commercial viability of fusion materials by the mid-2030s. That data will underpin engineering design lifetimes and maintenance intervals, as well as regulatory licensing decisions. It could also influence insurance and risk underwriting for commercial deployments.
Implications for Private European Startups
It’s been expressly stated that the IFMIF-DONES project will prioritize European SMEs and industrial partners, a move aimed at strengthening domestic supply chains and supporting the continent’s technological sovereignty in fusion.
Two European startups are particularly well-positioned to benefit here:
Proxima Fusion (Germany) is tightly integrated with the Max Planck Institute for Plasma Physics, a core EUROfusion partner. While Proxima is building out internal test capability, access to IFMIF-DONES could accelerate validation and redirect capital toward stellarator design and HTS optimization.
Renaissance Fusion (France) collaborates closely with the French Alternative Energies and Atomic Energy Commission (CEA) and is deeply embedded in EU fusion research. For Renaissance, neutron data will be crucial to understanding corrosion rates, activation profiles, and MHD behavior under sustained D-T loads.
If they can offload some of the burden of irradiation testing to IFMIF-DONES, startups like Renaissance and Proxima can redirect capital and talent toward system integration and design. The result could be faster iteration cycles, de-risked materials choices, and early influence over the standards that will govern commercial fusion deployment.