Since fall 2025, Fraunhofer IWS has been one of the leading partners in Saxony’s fusion research network “SAXFUSION”. The network supports researchers and companies in developing expertise and unlocking value creation opportunities at an early stage for the emerging fusion energy market. Through targeted support for early-career talent, it also strengthens Saxony as a hub for innovation.

With its expertise, Fraunhofer IWS is currently focusing on barrier coatings against tritium diffusion, additive manufacturing processes for heavy-duty heat exchangers and other components, and specialty alloys for reactor design.

Thin Coatings to Block Volatile Tritium

One of the major challenges is the limited availability of tritium. As a key component of the fusion fuel mixture, it is extremely rare worldwide. According to estimates, there are only 3.5 kilograms of natural tritium on earth. Therefore, future reactors will use some of the neutrons produced during fusion to breed sufficient tritium from lithium-6 in the reactor itself. As a hydrogen isotope, tritium diffuses easily through almost any material. Because valuable fusion fuel can escape as a result and the process can lead to material embrittlement, designers require high-performance diffusion barriers. This is where “TritiumStopp” comes in, a joint research project of Fraunhofer IWS and the Max Planck Institute for Plasma Physics (IPP) in Garching. “This involves considerable engineering challenges,” emphasizes Head of Research Management Dr. Jens Möller. “We must ensure that the tritium remains in the closed cycle and that the steel in the reactor is not damaged.” In addition, tritium emits beta radiation. The barrier must not only be impermeable and radiation-resistant, but also particularly robust in order to withstand the extreme temperatures involved in nuclear fusion.

The partners in the TritiumStopp project are pursuing an approach that involves coating the reactor piping with thin layers produced using physical vapor deposition (PVD). Two potentially suitable layer types were identified: hard nitride coatings, e.g. titanium nitride, and diamond-like amorphous carbon. Fraunhofer IWS helped develop some of the coating technologies used for this purpose. “We have a great deal of transfer experience in this field,” says Dr. Volker Weihnacht, Acting Head of Thin-film Technology. As extremely hard and wear-resistant protective coatings, they have already proven themselves on tools and components in vehicle and mechanical engineering. Although such properties are of secondary importance in a fusion reactor, the particularly dense layer structures significantly impede tritium diffusion. They are also known to be extremely robust and are already established in large-scale technology. “We have the technologies in principle, but we need to further develop and test them for the new application,” explaines Dr. Weihnacht.

For example, whereas previous applications tended to involve coating small 3D parts in large quantities, the fusion application requires uniform and large-area deposition on pipes or pipe segments. “Developing a concept for a largescale, practical process is a key issue not only for us, but also for our network partners,” adds Anne-Katrin Leopold, SAXFUSION Coordinator at Fraunhofer IWS.

Additively Manufactured Parts for Extreme Conditions

In another subproject, the Fraunhofer teams in Dresden are investigating how to manufacture heat exchangers, radiation shields and heat shields (“blankets”) that can withstand the intense neutron flux inside the reactor while remaining resistant to neutron activation. This requires highly unusual and complex geometries, using sophisticated materials and material combinations. To achieve this, materials scientists and engineers at Fraunhofer IWS are relying on additive manufacturing processes. Copper chromium zirconium, for example, is on the shortlist for the internal heat exchangers. “This material conducts heat just as well as copper, but has greater mechanical strength,” explains Samira Gruber. For the first wall, the fusion community has already largely settled on high-temperature-resistant tungsten, which can withstand neutron erosion for a comparatively long time before the parts need to be replaced on a regular basis. However, there are still some problems to be solved here as well. The additive processing of tungsten requires a high energy input, for example.

High-performance Materials with Unique Properties

High-entropy Alloys consisting of several elements in similar proportions – are also in the running for the fusion reactor materials of the future. This class of materials offers many unusual properties: Some of these materials are particularly difficult to activate, others are more resistant to high temperatures, and still others are highly resilient to mechanical stress. If these and other properties can be combined in a designed material that can be easily processed additively in industrial plants, many design problems, such as those relating to blanket supports in reactors, would be easier to solve. As part of the Fusion 2040 program initiated by the German Federal Ministry of Research, Technology and Space, Martina Zimmermann at Fraunhofer IWS is working on such High-entropy Alloys (HEAs) in collaboration with the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), laser and powder manufacturers, and other small and medium-sized enterprises.

Foreseeable Impact on Energy, Medical, Home, and Laser Technology

Since the time frame for the construction of the first commercial fusion reactor in Germany is still undetermined, the teams at Fraunhofer IWS always keep medium-term applications for other application areas in mind when conducting their fusion research. Efficient and heat-resistant tritium barriers could, for example, reduce fatigue of steel components in high-temperature electrolyzers, fuel cells, and hydrogen pipes. The teams also expect significant progress in the secondary use of this technology for turbine construction and rocket engines. Potential applications include more powerful heat exchangers for power plants and households, laser optics for welding and cutting systems, and medical technology.

”SAXFUSION”: Hope for New Regional Value Chains

The SAXFUSION network, founded at the end of 2025, also offers enormous potential for new jobs, impetus, and regional value creation in Saxony and beyond. In view of the nationwide upswing in fusion research, Dr. Jens Möller from Fraunhofer IWS Dresden and Dr. Michael Bussmann from HZDR initiated this network, which now consists of eight Saxon universities and institutes. Coordination has been taken on by the HZDR and Fraunhofer IWS, which are responsible for application-oriented material and manufacturing process innovations on the one hand, and basic research, high-performance laser, and complex supercomputer simulations of fusion processes on the other. Dresden University of Technology contributes its expertise in nuclear reactor safety. The participating universities also educate the next generation of fusion technology professionals. The Leipzig-based Leibniz Institute of Surface Engineering (IOM) contributes expertise in precision optics. But that’s not all: “There is considerable interest in SAXFUSION from industry,” according to Anne-Katrin Leopold. “I am sure that more partners will join, especially from the business community.” She compares the ambitious project of building and operating a fusion reactor with the USA’s Apollo program, which at the time led to social change, technological advances, and new business start-ups. “Maybe that’s exactly what we need right now: a visionary idea that inspires us to overcome even the greatest challenges together.”