The Ups and Downs Toward Practical Fusion Power

Fusion power is highly anticipated as a next-generation energy source.

Among these efforts, an experimental reactor contributing to one of the world's largest projects, ITER (International Thermonuclear Experimental Reactor) is expected to begin operation in Japan this autumn.

In this article, I would like to touch upon the mechanisms and challenges of fusion energy.

As the name suggests, fusion is an idea that aims to utilize the energy generated when multiple atomic nuclei react and fuse into one.

A similar but opposite concept is "nuclear fission." This is also similar in the sense that it utilizes the energy released when a nuclear reaction causes an atom to split.

Incidentally, it is a regrettable historical fact that the hydrogen bomb developed by the United States in the 1950s used the principle of this fusion reaction, and its ignition mechanism was the atomic bomb (fission reaction) that had been developed just prior.

Regarding this fusion reaction, it can be broadly divided into "ultra-high temperature" and "room temperature" types, with the former being relatively mainstream. ITER also falls into this category.

The model for "ultra-high temperature" exists in space; the energy release mechanism of stars that emit their own light is exactly this type.

For example, inside the Sun, one of the stars, hydrogen atoms fuse together to become helium, and we benefit from this as solar energy.

However, in the case of the Sun, the reaction does not occur unless it is at an ultra-high temperature of over 10 million degrees, and the method adopted by ITER also requires generating such an ultra-high temperature state. (It is sometimes called an "artificial sun.")

The difference from the reaction in stars is the type of hydrogen used. Since ITER uses deuterium and tritium, it is called the D-T fusion reaction from their initials.
The technical difficulty lies in the fact that to maintain the reaction, it must be kept at an ultra-high temperature in a state called plasma.

I have previously introduced articles where AI contributed to the control of that plasma.

Another challenge is the procurement of tritium, which is the raw material. While it can be extracted from the Earth's atmosphere, the atmospheric concentration from which it can be collected has already passed its peak and is expected to decrease in the future.
I think this will become a topic of discussion as practical application draws nearer. I will cite just one related article.

ITER, which is the most internationally watched project including this news, is significantly behind its original schedule, and as of now, it is as shown in the table at the beginning of the article.
In any case, the operation of this experimental reactor is an important baton pass to what comes next.

And the other type is the "room temperature" type.

While research is progressing internationally in several areas, in Japan, I often see reports on the initiatives of "Clean Planet."

To explain the principle roughly, it is a mechanism that generates excess heat by adsorbing hydrogen onto nano-scale (one-billionth of a meter) metal particles and applying thermal stimulation.

It was proposed in the 1980s that this could theoretically be achieved at under 1000 degrees, but it was difficult to verify (excess heat could not be confirmed), and verification has become visible since 2010.

The key lies in material technology at the nano-scale (nanomaterials), a field in which Japan is also relatively strong.

However, theoretical research into how to overcome the electrical repulsion between protons at low temperatures to achieve fusion reactions still seems to be halfway there. (There may already be developments in this area in basic research.)

This approach is advantageous in terms of temperature control and raw material procurement. However, it is also said that this method may take even longer than the ultra-high-temperature type, so it is hard to say which is better at this point.

Regardless of which one becomes practical, the energy potential it brings is high, and it is also "clean."

At the same time, however, some people may inevitably feel anxious just hearing the term "nuclear energy."
I would like to first understand the mechanism at a minimum, and then judge it by looking at both the merits and demerits.