In the municipality of Escúzar, located near the picturesque Granada in Spain, a crucial moment for the future of European and global energy was recently marked. The laying of the foundation stone initiated the construction of the advanced scientific infrastructure IFMIF-DONES (International Fusion Materials Irradiation Facility – Demo Oriented Neutron Source), a project that represents a turning point in the research and development of fusion energy. This ambitious undertaking, in which Croatia, together with Spain, plays a leading role, is of vital importance for testing and qualifying the materials necessary for the construction of future fusion power plants, including the demonstration power plant DEMO.

Fusion energy: Stellar power for Earth's future

Fusion energy, the process that powers the Sun and stars, has been the focus of scientists for decades as a potentially inexhaustible, safe, and environmentally friendly energy source. Unlike fission, which splits heavy atomic nuclei, fusion combines light nuclei, such as hydrogen isotopes (deuterium and tritium), releasing vast amounts of energy in the process. The fuel for fusion, deuterium, is available in seawater, while tritium can be produced within the fusion power plant itself from lithium, a metal also widely distributed. The advantages of fusion are numerous: it does not produce long-lived high-level radioactive waste like fission power plants, it does not emit greenhouse gases during operation, and it inherently eliminates the risk of an uncontrolled chain reaction that could lead to catastrophic accidents. Achieving controlled fusion on Earth is one of the greatest scientific and technological challenges of the 21st century, but also a promise for a long-term solution to global energy needs and climate change.

European strategy and the key role of DONES

The European Union is committed to achieving fusion energy through a comprehensive strategy based on three fundamental pillars. The first is ITER (International Thermonuclear Experimental Reactor), a huge international experimental reactor being built in Cadarache, France, with the aim of demonstrating the scientific and technological feasibility of fusion as an energy source. After ITER, DEMO will follow, a demonstration fusion power plant that should be the first power plant to produce electricity from fusion and supply it to the grid, confirming its economic viability. The third pillar – IFMIF-DONES – is crucial for DEMO's success. Specifically, one of the biggest challenges in the development of fusion power plants is finding materials that can withstand the extreme conditions inside the reactor, especially intense high-energy neutron irradiation (up to 14 MeV) and high temperatures. Existing materials and knowledge, based mainly on experience from fission reactors, are not sufficient because the operating conditions differ significantly. IFMIF-DONES will be a unique global center for testing, validating, and qualifying advanced materials, simulating the neutron irradiation conditions expected in fusion power plants. Without the data that DONES will provide, the safe and reliable construction of DEMO would not be possible.

The importance of the IFMIF-DONES project has been recognized at the highest European level by its inclusion in the Roadmap of the European Strategic Forum for Research Infrastructures (ESFRI), first in the 2018 Roadmap and then in the updated 2021 Roadmap. This positioned IFMIF-DONES as one of the key strategic research infrastructures for European scientists in the field of energy research and innovation, with the aim of strengthening European competitiveness and technological leadership in this vital sector. The location in Granada was chosen in December 2017 after a positive assessment of the joint Spanish-Croatian proposal by the Fusion for Energy (F4E) agency.

Croatian contribution: Knowledge and innovation at the heart of the project

Croatia has had an extremely important and proactive role in the DONES project from the very beginning. As one of the two leading countries, alongside Spain as the host country, Croatia not only recognized the strategic value of this undertaking early on but is also actively participating in its scientific design, technological development, and preparation for implementation. Croatian scientists, engineers, and institutions, gathered within the DONES.HR consortium coordinated by the Ruđer Bošković Institute (IRB), have been working diligently for years on the development of specific technologies and components for DONES. Their contribution covers a wide range of areas, from research and development of advanced materials, through the design and construction of sophisticated radiation detectors, to the development of complex systems for remote handling and maintenance in a radiation-challenging environment. This early involvement ensures Croatia not only scientific prestige but also the opportunity for technology transfer and strengthening the capacities of domestic industry.

Dr. sc. Tonči Tadić, a prominent physicist from the Ruđer Bošković Institute, head of Croatian fusion activities, and coordinator of the DONES.HR project team, emphasizes the multidisciplinary and far-reaching nature of DONES: "The primary mission of DONES is the irradiation and testing of materials intended for the first wall of future fusion power plants. However, DONES will be much more than that. It will serve as a powerful and versatile neutron source, opening doors for a wide range of research in fundamental and applied science. This includes areas such as non-fusion nuclear physics, medical physics where neutrons can be used for diagnostics and therapy, solid-state physics for studying material structures, fundamental research in biology and medicine, and even the development of new technologies in mechanical engineering and materials science. Any interested scientific institution, research team, or industrial partner will be able to propose and conduct their own research using DONES's capacities." Dr. Tadić also points out that a large amount of highly specialized, and often entirely new, equipment is being developed and produced as part of the project, from advanced detector systems to robotic cranes and manipulators for remote handling of irradiated samples, which represents a significant technological challenge and an opportunity for innovation.

Technical aspects and scientific goals of IFMIF-DONES

At the heart of the IFMIF-DONES facility will be a powerful particle accelerator. This accelerator will produce an intense beam of deuterons (D+), deuterium ions, with a current of 125 milliamperes (mA) and an energy of 40 megaelectronvolts (MeV). This high-energy deuteron beam will be directed at a liquid lithium target. The target will be formed as a thin curtain of liquid lithium, approximately 25 millimeters thick, flowing at a high speed of about 15 meters per second to ensure efficient cooling and stability of the target under intense deuteron bombardment. When deuterons strike lithium nuclei, nuclear reactions will occur that will generate a powerful flux of high-energy neutrons, with a spectrum very similar to that expected in fusion power plants. It is this neutron flux, of sufficient intensity to simulate in an accelerated manner the damage that neutrons would produce during many years of operation of a fusion reactor, that will be used to irradiate samples of various materials. These samples, potential candidates for structural components of fusion power plants, will be placed in specially designed test modules immediately behind the lithium target, in the area of most intense neutron radiation. By precisely measuring changes in the physical, mechanical, and structural properties of the irradiated materials, scientists will be able to create a comprehensive database necessary for the selection and qualification of materials for DEMO and future commercial fusion power plants.

In addition to testing structural materials, DONES will enable research and development of numerous other key technologies for fusion, such as advanced sensors and radiation-resistant electronics, systems for tritium production and handling (one of the fusion fuels), heat transfer technologies using liquid metals (such as lithium), and systems for remote handling and maintenance of components in an activated environment. It is, therefore, a multidisciplinary research center with enormous scientific and industrial potential, which will attract experts from all over the world to Granada.

Japan as a strategic partner and global cooperation

A significant boost to the DONES project occurred during its formal presentation at the EXPO world exhibition in Osaka, when Japan officially confirmed its strategic partnership. On that occasion, on May 21, 2025, at a meeting of the DONES Steering Committee, a Memorandum of Cooperation was signed between the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and the Spanish Ministry of Science, Innovation and Universities. With this act, Japan joined Croatia and Spain as the third key strategic partner in the project, bringing with it vast knowledge, experience, and technological expertise in the field of fusion and advanced materials. Japanese involvement further confirms the global importance of DONES and its role in international efforts to achieve fusion energy.

The Minister of Science, Education and Youth of the Republic of Croatia, Prof. Dr. sc. Radovan Fuchs, welcomed this development, stating: "The Republic of Croatia is extremely proud to actively participate in this monumental European and global undertaking aimed at creating a sustainable, safe, and clean energy source for future generations. The DONES project is not only a scientific challenge but also a geostrategic initiative that brings together states, leading scientific institutions, and advanced industry around a common, noble goal. Cooperation with a technological superpower such as Japan is invaluable in this context and opens new doors for deepening scientific, technological, and economic exchange."

Funding and international participation

The construction and operational costs of such a complex scientific infrastructure require significant financial investments and broad international cooperation. Spain, as the host country, leads with investments: the central government will provide 210 million euros, and an equal amount will be invested by the regional government of Andalusia, recognizing the long-term benefits for the development of the region around Granada. A significant contribution is also expected from the European Commission, in the amount of 202 million euros, through various research and innovation funding programs. Japan has announced funding amounting to 5% of the total construction costs of the facility and 8% of the operational phase costs, which further strengthens the project's financial structure. Italy has also expressed strong interest in participating, having signed a Memorandum of Understanding, and is currently in the final phase of defining its specific contribution. It is estimated that the total value of the DONES project will exceed 700 million euros. Participation from more than 17 countries is expected through various forms of contributions, whether financial, or in equipment, knowledge, or human resources, making DONES a truly global platform for the development of fusion technology.

To manage Spanish contributions, construct and subsequently operate the facility, the Spanish government and the regional government of Andalusia have established a special implementing agency in the form of a public consortium called "IFMIF-DONES España". This consortium will be the formal owner and operator of the facility and the legal entity responsible before national regulatory authorities. It will also be responsible for hosting the international team of experts who will participate in all phases of the project, from design and construction to operation and scientific use of the facility in Escúzar.

A look into the future of energy

With the start of infrastructure construction in Escúzar near Granada, the DONES project enters a new, dynamic phase. The symbolic laying of the foundation stone and the strengthening of international cooperation, especially with Japan, provide a strong impetus to efforts to transform fusion energy from a scientific vision into a practical reality as soon as possible. The challenges are still great, but the potential benefits – clean, safe, and practically inexhaustible energy – justify every effort and resource invested. Croatia, with its scientists and industry, has the opportunity to be at the forefront of this technological wave that will, without a doubt, shape the energy future of our planet.