Europe and Japan Are Face-to-Face With One of the Major Challenges of Nuclear Fusion: Material Irradiation

One of the biggest challenges facing engineers working on magnetic confinement nuclear fusion reactors, such as the International Thermonuclear Experimental Reactor (ITER), is recreating the conditions necessary for deuterium and tritium nuclei to fuse inside the vacuum chamber of these sophisticated machines.

But that’s not all. When this reaction occurs, the fusion of a deuterium nucleus and a tritium nucleus triggers the production of a helium nucleus and a neutron, released with an energy of about 14 megaelectronvolts (MeV). The problem is that the neutron has no net electric charge, so it cannot stay inside the magnetic field. This field manages to hold the deuterium and tritium nuclei, which have a positive electric charge.

This is why this neutron, when created because of the nuclear fusion reaction, is ejected with enormous energy towards the walls of the vacuum chamber. This particle is fundamental because, in practice, it will be closely linked to producing electrical energy in nuclear fusion reactors. At the same time, it represents a very aggressive form of radiation that can significantly degrade the materials used in the reactor.

Europe and Japan Strengthen Their Alliance

The inner wall of the vacuum chamber and the blanket, a mantle that covers and could regenerate the tritium that acts as fuel in the nuclear fusion reaction, are the components most affected by the direct impact of the high-energy neutrons and the more intense heat flux. Therefore, it's crucial to develop new materials that can withstand the neutron flux and thus ensure a long operating life of the reactor.

This is the purpose of the International Fusion Materials Irradiation Facility DEMO-Oriented Neutron Source (IFMIF-DONES), a laboratory under construction in Escúzar, Spain. This facility will include a linear particle accelerator that will act as a source capable of producing high-energy neutrons. This machine would subject candidate materials for future nuclear fusion reactors, such as ITER or DEMO, to irradiation conditions very similar to those they would have to endure in these machines. The problem is that IFMIF-DONES won’t be ready for irradiation until 2033, and the first data will probably arrive before 2035.

Fortunately, Europe and Japan have realized that it’s possible to shorten the wait. As we’ve seen, one of the major challenges in developing a nuclear fusion reactor with commercial ambitions is finding the materials that allow the mantle to support the interaction of high-energy neutrons. However, these materials must also support the regeneration of tritium, which acts as a fuel in addition to deuterium. The neutrons released in the fusion reaction interact with the lithium in the mantle to produce tritium, which must be processed and injected into the reactor’s vacuum chamber to sustain the response over time.

Europe and Japan have been collaborating in this field of research since 2007 through the International Fusion Energy Research Center (IFERC). The main European contributor is EUROfusion, an institution that coordinates several laboratories that are already providing fundamental data on developing new materials for fusion reactors.

One of these laboratories is the Belgian research center SCK CEN, which has an experimental reactor known as BR2 capable of irradiating materials by exposing them to high-energy neutrons. Another experimental reactor capable of performing these irradiation tests is the WWR-K at the Kazakh Institute of Nuclear Physics. These and other experiments are important because they establish the conditions under which the IFMIF-DONES will conduct the tests.

This article was written by Juan Carlos López and originally published in Spanish on Xataka.

Image | SCK CEN - EUROfusion

More info | EUROfusion

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