Europe and Japan walk hand in hand towards nuclear fusion commercial. They have been working together for several years in the JT-60SA experimental reactorthe largest magnetic confinement fusion energy machine that currently exists. However, this is not the only project in which they collaborate. They are also fine-tuning the LIPAc linear particle accelerator (Linear IFMIF Prototype Accelerator or IFMIF Prototype Linear Accelerator).
This machine resides in Rokkasho (Japan). After having undergone a very ambitious update, it is ready to begin the final phase that will conclude with its commissioning in 2027. Its purpose is to test the limits of particle beam physics to pave the way for future fusion reactors. Europe and Japan began developing this 36-meter-long particle accelerator in 2007 with the aim of validating the design of an IFMIF-type machine (International Fusion Materials Irradiation Facility) capable of acting as a neutron source.
To achieve this, this device had to recreate the intense irradiation conditions that occur inside a fusion reactor. One of Europe’s most important contributions is a huge steel cryostat with magnetic shielding and a thermal shield that houses a powerful superconducting radio frequency system. This component serves to accelerate protons and deuterium nuclei until they reach a maximum energy of 9 MeV (megaelectronvolts), which will place them close to the high-energy neutrons that future commercial fusion reactors will produce.
LIPAc is the precursor of IFMIF-DONES, which is already being built in Spain
The knowledge that scientists hope to gain from LIPAc will be used in the development of IFMIF-DONES (International Fusion Materials Irradiation Facility DEMO-Oriented NEutron Source), that is already being built in Escúzar, a town in the province of Granada. The heart of this facility is a linear particle accelerator that will cost approximately 450 million euros, although the Government of Andalusia will provide half of this money. However, this is the cost of the accelerator; The entire IFMIF-DONES project will cost around 700 million euros. Spain will contribute half of this capital.
IFMIF-DONES is one of the three fundamental pillars of the nuclear fusion edifice in whose construction the European Union is involved. The other two are ITER (International Thermonuclear Experimental Reactor) and DEMO. The experimental nuclear fusion reactor that is currently being built in the French town of Cadarache aims to demonstrate that fusion at the scale that man can handle worksand also that it is profitable from an energy point of view.
However, ITER does not aim to produce electricity. That will be the task of DEMO (DEMOnstration Power Plant), a facility that will take the technological advances that have been proven to work correctly at ITER and take them one step further to establish itself as the true precursor of commercial nuclear fusion reactors. However, without IFMIF-DONES there will be no DEMO, so right now Granada is the center of attention.
The IFMIF-DONES linear accelerator will produce high-energy neutrons with the intensity and irradiation volume necessary to test candidate materials
To fully understand the role of the IFMIF-DONES project, it is necessary to briefly review the fundamentals of nuclear fusion. One of the greatest challenges faced by technicians involved in the development of nuclear fusion reactors using magnetic confinement, such as ITER, is to recreate the conditions necessary for them to operate inside the vacuum chamber of these sophisticated machines. deuterium and tritium nuclei fuse.
However, this is by no means all. When this reaction takes place, the fusion of a deuterium nucleus and another tritium nucleus triggers the production of a helium nucleus and a neutron that is ejected with an energy of about 14 MeV. The problem is that the neutron lacks a net electrical charge, so it cannot be confined inside the magnetic field which, however, does manage to retain the deuterium and tritium nuclei, which have a positive electrical charge.
This is the reason why when it originates as a result of the nuclear fusion reaction, this neutron is ejected towards the walls of the vacuum chamber with enormous energy. This particle is very important because in practice it will be closely linked to the production of electrical energy in nuclear fusion reactors, but, at the same time, it represents a very aggressive form of radiation that can significantly degrade the materials used in the reactor.
The components that will be most affected by the direct impact of high-energy neutrons and the most intense heat flow are the internal wall of the vacuum chamber and the blanket.
The components that will be most affected by the direct impact of high-energy neutrons and the most intense heat flow are the inner wall of the vacuum chamber and the blanketwhich is a mantle that covers it and whose purpose is to regenerate the tritium that must be used as fuel in the nuclear fusion reaction. This is why it is crucial to develop new materials that are able to withstand the neutron flux and therefore ensure that the reactor will have a long operational life.
This is, neither more nor less, the purpose of IFMIF-DONES. And to carry it out it is necessary to set up facilities designed to allow the technicians involved in the project evaluate the properties of candidate materials to intervene not only in DEMO, but also in future commercial nuclear fusion reactors.
The mission of this project invites us to intuit what the heart of IFMIF-DONES is: a source capable of producing high-energy neutrons with the intensity and volume of irradiation necessary to test the candidate materials. And this neutron source will be nothing more than a linear particle accelerator that will help IFMIF-DONES scientists to test, validate and qualify the materials that in the medium term should reach future electric energy production plants through fusion.
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