IFMIF-DONES (Spain)

Overview

The International Fusion Materials Irradiation Facility – Demo Oriented NEutron Source (IFMIF-DONES) is a research infrastructure designed to test, validate, and qualify materials for use in future fusion power plants. Sited in Granada, Spain, it is a key component of the European Fusion Roadmap and is considered essential for the design and construction of a Demonstration Power Plant (DEMO). Fusion reactors, particularly those based on the deuterium-tritium (D-T) fuel cycle, produce high-energy 14.1 MeV neutrons. This intense neutron flux causes significant material degradation, including swelling, embrittlement, and transmutation, which limits the operational lifetime and economic viability of reactor components. IFMIF-DONES will be the first facility capable of generating a sufficiently intense and voluminous flux of fusion-spectrum neutrons to simulate these conditions, allowing scientists and engineers to develop and certify structural materials, such as reduced activation ferritic/martensitic (RAFM) steels and tungsten alloys, for in-vessel components like the first wall and tritium breeding blanket.

Physics / Mechanism

IFMIF-DONES generates its neutron flux not through fusion reactions, but via a particle accelerator-driven process known as the deuteron-lithium (d-Li) stripping reaction. The core of the facility is a high-current linear particle accelerator (linac) designed to produce a continuous-wave beam of deuterons (D+). This beam is accelerated to a final energy of 40 MeV with a total current of 125 mA, resulting in a beam power of 5 MW.

The deuteron beam is directed onto a liquid lithium target. The target consists of a thin film of liquid lithium flowing at high speed (approximately 15 m/s) over a concave backplate. When the high-energy deuterons strike the lithium nuclei, a nuclear stripping reaction occurs. The proton is stripped from the deuteron, and the neutron continues forward, producing a broad spectrum of neutrons with a significant peak energy around 14 MeV, closely mimicking the D-T fusion neutron spectrum. The reaction is represented as:

d + ⁷Li → n + ⁸Be

The flowing liquid lithium serves two purposes: it is the target material for the reaction and the primary coolant, carrying away the 5 MW of heat deposited by the deuteron beam. The high velocity is necessary to prevent the lithium from boiling in the vacuum environment where the beam interacts with it. Behind this lithium target, several test modules are placed. The High Flux Test Module (HFTM) is positioned directly behind the target to receive the highest neutron flux, where small material samples will be irradiated. These samples will be subjected to neutron damage levels of 20-50 displacements per atom (dpa) per full power year, a rate relevant for DEMO's operational lifetime. The facility also includes post-irradiation examination (PIE) hot cells, where the activated samples can be safely handled, tested, and analyzed to characterize changes in their mechanical and physical properties.

Historical development

The concept of a d-Li neutron source for fusion materials testing dates back to the 1970s with the Fusion Materials Irradiation Test (FMIT) facility proposed in the United States, though it was never built. The idea was revived in the 1990s as a broad international collaboration between Europe, Japan, the Russian Federation, and the United States under the International Energy Agency (IEA). This led to the conceptual design of the International Fusion Materials Irradiation Facility (IFMIF).

The original IFMIF design featured two parallel 125 mA accelerators to ensure high availability and a larger irradiation volume. However, due to its high cost (estimated over €1 billion), a staged approach was adopted. The European Fusion Roadmap identified the construction of a fusion-relevant neutron source as a critical-path item for DEMO. In 2017, as part of the "Broader Approach" agreement between Europe and Japan, the decision was made to proceed with a single-accelerator version, named IFMIF-DONES, to be hosted in Europe. This would serve as a demonstrator for the full IFMIF while still providing the necessary irradiation data for DEMO's initial design phase. After a competitive bidding process, Granada, Spain, was selected as the host site in 2017. The Spanish research agency CIEMAT and the European agency Fusion for Energy (F4E) were designated as the primary implementing agencies. The project officially entered its construction phase in the early 2020s.

Current status

As of 2026, IFMIF-DONES is in its construction phase in Escúzar, Granada. Site preparation and civil engineering for the main complex of buildings are well underway. The procurement and manufacturing of key long-lead components for the accelerator, lithium target loop, and test systems are in progress across various European and Japanese institutions. The Linear IFMIF Prototype Accelerator (LIPAc) in Rokkasho, Japan, has served as a crucial validation project, successfully demonstrating the acceleration of a 125 mA deuteron beam to the required intermediate energy of 9 MeV, validating the design of the low-energy section of the DONES accelerator. The project is managed by the IFMIF-DONES España consortium. The current schedule anticipates the start of the commissioning phase in the early 2030s, with the first irradiation experiments planned for the mid-2030s. The project's total construction cost is estimated to be around €700 million, with operating costs projected at €50 million per year.

Notable implementations

IFMIF-DONES is a unique, single-instance facility, not a technology being implemented by multiple companies. The project is a large-scale international collaboration. Key contributors include:

• Spain (Host Country): Through the CIEMAT research center and the IFMIF-DONES España consortium, Spain provides the site, significant funding, and in-kind contributions for construction and operation.
• Fusion for Energy (F4E): The European Union's domestic agency for ITER, F4E manages the European contribution to the project, overseeing procurement and technical integration from member states.
• EUROfusion: This consortium of European fusion research laboratories coordinates the scientific program and the design of the test modules where material samples will be irradiated.
• Japan (via the Broader Approach Agreement): Japan contributes significantly through its expertise developed for the original IFMIF project and the successful operation of the LIPAc prototype accelerator. Contributions include key accelerator components and test facility technologies.
• Other International Partners: Several other countries are expected to join the program as members or partners, contributing to the operational costs in exchange for access to irradiation time.

Open challenges

Despite significant progress, IFMIF-DONES faces substantial scientific and engineering challenges that must be overcome for successful operation.

1. Accelerator Reliability and Availability: The accelerator must operate with extremely high availability (>70%) over long periods (months) to accumulate the required neutron fluence for material damage studies. Achieving this with a high-power, 125 mA continuous-wave beam is a major technological challenge, demanding robust components and sophisticated control systems.
2. Liquid Lithium Target Stability: The free-surface liquid lithium target must remain stable under the intense power deposition of the 5 MW deuteron beam. Issues such as hydrodynamic instabilities, surface evaporation, and erosion of the steel backplate must be managed to ensure a consistent neutron flux and prevent system failures. The highly corrosive nature of liquid lithium at operating temperatures also presents materials compatibility challenges for the entire loop.
3. Remote Handling and Maintenance: All components within the test cell will become highly activated due to neutron bombardment. All maintenance, replacement of test modules, and handling of irradiated samples must be performed entirely by remote handling systems. These systems must be extremely reliable and capable of complex operations in a hazardous environment.
4. Data Correlation and Interpretation: The neutron spectrum from the d-Li source, while similar, is not identical to that of a D-T fusion reactor. It has a high-energy tail extending beyond 14 MeV. Scientists must develop robust models to correlate the material damage data obtained from DONES with the expected performance in an actual fusion environment. This includes accounting for different transmutation rates, particularly helium and hydrogen production, which strongly affect material properties.

Outlook

The successful construction and operation of IFMIF-DONES is considered a prerequisite for licensing and building a commercial fusion power plant. The credible 5-15 year trajectory is as follows:

• 5-Year Outlook (2026-2031): The primary focus will be on completing the civil construction in Granada and the installation of major systems, including the accelerator components, lithium loop, and test cell infrastructure. Manufacturing of the most complex components will be finalized and delivered to the site. The project will transition from a construction focus to an assembly and integration phase.
• 10-Year Outlook (2031-2036): This period will see the beginning of integrated commissioning of the facility, starting with the accelerator and progressing to the lithium target system. The first deuteron beam on target is anticipated in the early 2030s, followed by a gradual ramp-up in power and current. The first irradiation experiments on high-priority materials like EUROFER97 steel will commence, with the goal of achieving initial dpa levels sufficient to inform the final design choices for DEMO.
• 15-Year Outlook (2036-2041): IFMIF-DONES is expected to be in full, routine scientific operation. It will be generating a continuous stream of data on the performance of advanced steels, tungsten alloys, and other candidate structural and functional materials under fusion-relevant conditions. This data will be essential for developing the nuclear design codes and safety cases required for the construction license of the first generation of fusion power plants. The facility will serve as the world's primary resource for fusion materials qualification for decades.

References

1. IFMIF-DONES: The Granada facility for fusion materials — Fusion for Energy (2023)
2. The European roadmap to the realisation of fusion energy — EUROfusion (2018)
3. IFMIF-DONES project: status and main challenges — Journal of Fusion Energy (2021)
4. The role of IFMIF-DONES in the European fusion roadmap — Fusion Engineering and Design (2018)
5. LIPAc, the 125 mA/9 MeV deuteron accelerator prototype for IFMIF: First CW beam operation at high power — Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2020)
6. IFMIF-DONES, a DEMO-Oriented Neutron Source for fusion materials irradiation — Nuclear Fusion (2019)
7. The IFMIF-DONES Test Cell remote handling system: From conceptual to detailed design — Fusion Engineering and Design (2023)
8. IFMIF-DONES España Official Website — IFMIF-DONES España