Tritium is the great “but” of nuclear fusion, and this promising project has the formula to do without it

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The recipe for nuclear fusion proposed by ITER has two fundamental ingredients: deuterium and tritium. In order for the nuclei of these two isotopes of hydrogen to overcome their natural electrical repulsion and fuse in order to release a large amount of energy, the plasma confined inside the reactors must reach a temperature of at least 150 million degrees Celsius. .

Interestingly, the Sun has it easier. Inside, the nuclei of protium, which is the most abundant isotope of hydrogen in nature, fuse at a temperature much lower than the 150 million degrees Celsius that we need to reach on Earth. And they do it because the strong gravitational field of the star that gives us its energy subjects the protium nuclei to a pressure that we cannot recreate on our planet at the moment.

After all, the fusion reaction between two nuclei is the result of the balance between temperature, which determines their kinetic energy, and the pressure to which they are being subjected. If the pressure is very high the temperature can be lower. And if the pressure is moderate, the temperature will necessarily have to be higher. Otherwise the nuclei will not acquire kinetic energy they need to overcome their natural electrical repulsion and merge.

However, beyond the need to get the plasma to reach a very high temperature, nuclear fusion by magnetic confinement faces another challenge: the need to use tritium. And it is that this isotope of hydrogen is radioactive, and, in addition, it is very scarce.

In fact, on Earth there are currently only about 25 kg of tritium, and in all likelihood ITER will need to use them when it begins testing with plasma. Even so, the plan of the engineers working on this reactor is that this chemical element is ultimately regenerated by coating the interior of the walls of the vacuum chamber with lithium.

TAE has a plan to dispense with tritium in nuclear fusion

Let’s recap. As we have seen, tritium is one of the two ingredients of nuclear fusion, but it is radioactive. And very scarce. Well, let’s change it for another chemical element. Yes, it is possible, and precisely this is the plan TAE Technologiesan American company that was born in the relatively distant 1998 with a purpose: to make possible the generation of electricity through a nuclear fusion reaction that did not involve the participation of radioactive elements.

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What TAE proposes is, simply, replace tritium with boron. In this way, the nuclei of hydrogen and boron would be involved in the fusion, and the product of the reaction would be a large amount of energy and helium, which is an inert chemical element. Sounds good. Really good. But it is not a bargain. And it is that in practice for the hydrogen and boron nuclei to fuse it is essential that the plasma reaches a temperature much higher than that of ITER, which is already overwhelming.

taereactor

This recreation of the ‘Norman’ nuclear fusion reactor developed by TAE Technologies clearly reflects how different their proposal is from the ‘tokamak’ reactor used by ITER. In fact, this one looks much more like a linear particle accelerator.

As we have seen, for the fusion of deuterium and tritium nuclei in ITER to take place, it is necessary to heat the plasma to 150 million degrees Celsius. However, for the TAE reactor to be able to fuse the hydrogen and boron nuclei, the temperature must be increased to an intimidating figure: no less than 1 billion degrees Celsius.

To fuse the hydrogen and boron nuclei, the temperature must be increased to an intimidating figure: 1 billion degrees Celsius.

This increase in temperature is due to the fact that boron is a heavier chemical element than tritium, so that the presence of a greater number of positively charged particles in its nucleus requires that the particles involved in the reaction gain more kinetic energy in order to overcome its natural electrical repulsion.

In any case, the TAE engineers have come to the conclusion that for the plasma to reach such a high temperature, its reactor must be more like a linear particle accelerator than to the enclosure tokamak used by experimental nuclear fusion reactors, such as JET or ITER. In fact, they have already built several prototypes, and with each of them they have managed to significantly increase the temperature of the plasma that they have reached with their predecessor.

They have called their fourth prototype ‘Norman’, they finished it in 2017, and using it they demonstrated that they were capable of holding the plasma at a temperature of 75 million degrees Celsius. Not bad at all, but there is still a long way to go before the plasma reaches the 1 billion degrees Celsius needed to fuse the hydrogen and boron nuclei.

In any case, they are on it. In fact, with the ‘Copernicus’ reactor they hope to reach the 150 million degrees Celsius needed to fuse deuterium and tritium by 2025. And by the middle of the next decade they plan to have a prototype of commercial fusion reactor. It sounds too ambitious, but hopefully they get it. For the good of all.

Images: TAE Technologies

More information: TAE Technologies | New Atlas

The recipe for nuclear fusion proposed by ITER has two fundamental ingredients: deuterium and tritium. In order for the nuclei…

The recipe for nuclear fusion proposed by ITER has two fundamental ingredients: deuterium and tritium. In order for the nuclei…

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