Humanity is going through a turbulent period, driven by the pressing need to act in the face of such major challenges as the climate and water crisis, the growing global demand for energy, the depletion of carbon and actinide-based fuel reserves and the harmful effects on health and the environment resulting from the use of these fuels.

Certainly, the progress made in the field of renewable energies makes achieving a sustainable energy model a well-founded hope. However, the most promising strategy with the greatest potential to be the energy source of the future is based on thermonuclear fusion. Once we have this inherently safe technology, whose fuel is virtually inexhaustible (deuterium and lithium reserves are colossal and easily extracted from seawater) and with minimal environmental impact (no carbon dioxide emissions and without long life radioactive waste), humanity’s progress will gain new momentum.

Where to look for fusion energy?

In other issues of this series, it has been discussed in some detail why fusion energy is the stellar engine. It is the energy that heats the furnace of the stars. In the Sun, at pressures of 25 PPa (25 × 10¹⁵ Pa) and temperatures of 15 MK (15 × 10⁶ K), the nuclei of the lightest atom (hydrogen) collide with each other and undergo nuclear fusion reactions that cause the emission of an enormous amount of energy, responsible for the creation and maintenance of life on our planet[1].

Our goal, then, is to master and manage this energy. It would be like bringing the power of the Sun and the stars to our planet.

[1] Every second 700 million metric tonnes of hydrogen are transformed by nuclear fusion into helium ash. In this process, five million metric tonnes of matter are converted into energy. How to achieve this energy?

Getting two light nuclei to fusion, as we have seen in previous articles, requires overcoming enormous Coulombic repulsive forces. For decades, two different strategies have been used to solve this problem on Earth: magnetic confinement and inertial confinement:

• With magnetic confinement, nuclei are heated to very high temperatures to form plasma that is “bottled” by colossal magnetic fields to give them time to undergo fusion reactions due to thermal agitation.

Basic components of the tokamak device for magnetic confinement

Inertial confinement involves compressing small spheres containing light atoms by powerful pulsed laser (or ion) beams to suddenly increase extremely their density and temperature until their fusion.

Schematic inertial confinement reactor

Both strategies must overcome technological challenges at the frontier of knowledge.

Towards magnetic confinement fusion

We have also seen in previous issues that the first promising fruits in the magnetic confinement field were harvested in the 1990s. This was done with the help of a machine with tokamak technology called JET (Joint European Torus), located in the United Kingdom. Its satisfactory results suggested that the scientific community should embark on a larger project in which, in addition to the reactor, other ancillary systems could be tested. This led to ITER (International Thermonuclear Experimental Reactor), which is being built in Cadarache (France). Its objective is to confirm the technical feasibility of nuclear fusion by magnetic confinement. ITER, the world’s largest tokamak, is expected to start operations in 2025 and to be fully operational in 2035. Thirty-five countries have joined forces to tackle this major challenge, with Fusion for Energy (based in Barcelona) as the agency linking the European contribution. The next step on the nuclear fusion agenda is to design a plant to test the commercial feasibility of producing electricity through nuclear fusion by magnetic confinement. The goals of this project, dubbed DEMO (Demonstration Power Station), are to prove that electricity can be produced cost-effectively and continuously, and that both thermal capture and tritium regeneration systems are efficient. DEMO, therefore, in addition to a device that will be able to feed electricity into the grid, will serve as a model for future commercial reactors.

Magnetic confinement fusion technology research roadmap

IFMIF. A necessary facility

The huge technological gap between ITER and DEMO requires the establishment of multiple complementary lines of scientific and technological research. IFMIF (International Fusion Irradiation Facility) is one of them.

Indeed, the vessel of this first generation of high-power reactors, needed to imprison this “sun” on Earth, will be hammered by an intense flux of neutrons and other energetic particles. Therefore, very robust materials, able to withstand this harsh operating environment, have to be developed and characterised[1]. While ITER will be a huge experiment being operated in relatively short operation campaigns, DEMO will be operated continuously, the materials being irradiated, and damaged, up to 100 times more.

IFMIF is a research programme, which began in 1994, in the first phase, as collaboration between Japan, the European Union, the United States and Russia. This initial phase was followed by several other ones becoming closer and closer to its main objective: to build a neutron source with intensity and energy similar to those of a fusion reactor in order to test and qualify materials that will be candidates for the construction of these devices. Currently, there is no neutron source whose power is analogous to that of a working fusion reactor!

[1] In fact, the neutron flux produced by the deuterium-tritium reactions (with an order of magnitude of about 10¹⁸ m^-2·s^-1 and a maximum energy of 14.1 MeV) will bombard the reactor materials, causing damage that may exceed 10 dpa-NRTs per year of operation. In addition, the materials must exhibit not only low presence of isotopes that activate with long half-lives, but also moderate decay heat values.

Schematic overview of the IFMIF installation

Are we technologically ready?

The path to the current maturity of a high-power neutron source has been a long and tortuous one. Since 2007, IFMIF activities have been developed in the framework of the IFMIF-EVEDA project, which is part of the Europe-Japan Broader Approach Agreement. The objective of IFMIF-EVEDA is to validate the engineering design of three facilities at the frontier of technological knowledge:

• A prototype high-flux test module, at KIT (Germany).
• An experimental lithium target loop, at Oarai (Japan), integrating all elements of the final IFMIF facility related to the lithium circuit.
• A prototype high-power accelerator (LIPAc), at Rokkasho (Japan).

Comparison between one of the IFMIF accelerators (top) and the LIPAc prototype (bottom)

The next step is to integrate these facilities into a single system.

Urgent need to supply fusion power to the electric grid

The design and construction of IFMIF, which integrates, as discussed in other articles in this series, deuteron accelerators and delicate subsidiary systems, requires complex and innovative technologies, with high costs and long lead times. However, the fusion schedule commits to supplying electricity to the grid by the middle of this century. Therefore, the design, construction and licensing of DEMO is becoming increasingly urgent. This made advisable to accelerate the initial IFMIF project and, in 2014, the IFMIF-DONES (DEMO Oriented Neutron Source) initiative was born. This decision places Europe and Spain at the forefront of scientific and technological powers in this field.

IFMIF-DONES. A unique facility in the world

IFMIF-DONES is an unavoidable intermediate step in the early data compilation on candidate materials for the construction of DEMO. Nevertheless, the simplifications introduced in DONES will in no way hinder, on the contrary, the future extension to IFMIF.

The IFMIF-DONES concept thus adopts a gradual approach towards IFMIF construction, with better distribution of investments over time and less demanding initial requirements. However:

• DONES shall build as much as possible on the IFMIF design.
• The design of DONES should allow for future expansion into IFMIF.
• The cost of DONES should be reduced as much as possible.
• DONES will only integrate one accelerator.
• Remote control operations should be minimised.

IFMIF-DONES will be a device without equal in the world, where a 125 mA, 40 MeV deuteron beam will impinge on a liquid lithium target (flowing at about 15 m/s), producing a suitable neutron irradiation field in the area of the test modules. It thus involves the combination of the three key facilities described above.

In sum, IFMIF-DONES will be a machine emulating the neutron bombardment that occurs in first generation fusion reactors.

IFMIF-DONES and its additional benefits

The scientific, technological and industrial research carried out in the IFMIF-DONES project will bring enormous benefits to future generations.

The primary objective is undoubtedly to immediately provide the materials database to make nuclear fusion (a safe, inexhaustible and clean source of energy) a reality.

But, let us not forget, IFMIF-DONES is an unprecedented source of neutrons in the world, which, in addition to the fusion community, will be able to benefit other scientific, technological and industrial fields. In other words, IFMIF-DONES will open the doors to a new generation of high power accelerators for multidisciplinary R&D.

A decisive step in Granada towards fusion energy

In brief, IFMIF-DONES, which will crown another fundamental step towards managing this star energy on our planet, following the agreement between Croatia and Spain, and with the support of Fusion for Energy and EUROfusion, will be built in Escúzar, a small town near the beautiful and historic city of Granada, located in Spain, in the south of Europe.

Geographical location of the IFMIF-DONES facility in Spain

Schematic 2D drawing with the IFMIF-DONES main facilities in Escúzar

3D view of the future IFMIF-DONES facility management building

Through a better understanding of the materials, we continue to deepen the foundations for producing safe, inexhaustible and clean fusion energy.

Our goal is to provide a bright future for all generations to come.

Our great challenge has just begun!