In this blog post, we’ll explore the principles and advantages of nuclear fusion power, its technical challenges, and its potential as a future energy source.
Broadly speaking, all the energy we use can be considered nuclear energy. This is because nearly all energy on Earth fundamentally originates from the heat and light generated by the Sun’s nuclear fusion process. The uneven heating of the Earth’s surface caused by sunlight drives atmospheric circulation, which we harness for wind power. Furthermore, solar heat triggers the water cycle through evaporation and condensation, a process utilized in hydroelectric power generation. Plants and photosynthetic bacteria use sunlight directly as an energy source for their life processes, while other animals and microorganisms obtain energy by consuming them. Thermal power generation also utilizes the energy stored in coal and oil, which originated from ancient organisms. Ultimately, the very fact that we can read, write, and move can be seen as stemming from energy derived from the Sun—that is, the product of nuclear fusion.
The term “nuclear energy,” as commonly used, refers to the energy released when atomic nuclei split, or nuclear fission energy. Nuclear fission directly converts part of a substance’s mass into energy, resulting in a very high energy density. Thanks to this characteristic, it has long been used as a major method of power generation; however, following the Chernobyl and Fukushima nuclear accidents, concerns about safety and radioactive waste have grown, leading to increased interest in new alternatives.
On the other hand, conventional fossil fuels are finite resources, and despite the rapid expansion of various renewable energy sources—such as hydro, wind, tidal, and biomass—several challenges remain in meeting both electricity demand and grid stability. Consequently, research continues into new energy sources that offer both high energy efficiency and the potential to reduce carbon emissions, with nuclear fusion energy at the center of this effort. Nuclear fusion is a future energy technology expected to offer higher potential energy efficiency than nuclear fission while significantly reducing long-lived high-level radioactive waste.
Nuclear fusion technology utilizes Einstein’s mass-energy equivalence principle (E=mc²) to convert the mass deficit generated during the fusion of atomic nuclei into energy. This principle is essentially the same as that by which energy is generated in the Sun and is sometimes likened to creating a “miniature Sun” on Earth. Although various fusion methods are being researched, one of the most promising approaches currently is D-T fusion. This method uses deuterium (D) and tritium (T)—isotopes of hydrogen—as fuel. When the two atomic nuclei fuse at ultra-high temperatures, they produce a helium (He) nucleus, a neutron (n), and a massive amount of energy.
Fortunately, deuterium can be obtained relatively easily from seawater, and tritium can be produced by bombarding lithium with neutrons. In particular, since the neutrons generated during the fusion process can be used to produce more tritium, the concept of self-sustaining fuel breeding is feasible in the long term. Compared to nuclear fission using uranium, this approach has the advantage of being far more abundant and sustainable in terms of fuel resources.
The problem is that an ultra-high-temperature environment is required to initiate a nuclear fusion reaction. To bring atomic nuclei close enough to fuse, one must overcome extremely strong electrostatic repulsion.
While nuclear fusion occurs naturally in the Sun’s core due to temperatures of approximately 15 million degrees and immense pressure, it is difficult to replicate such pressure on Earth. Therefore, it is necessary to create an ultra-high-temperature plasma of over 100 million degrees and cause atomic nuclei to collide at extremely high speeds. No matter how efficient nuclear fusion is as a power generation method, the process of creating such an extreme environment is, in itself, a very difficult technical challenge.
Even if hydrogen plasma reaching 100 million degrees is generated, controlling it stably presents yet another major challenge. Since ordinary materials as we know them cannot withstand such temperatures, it is impossible to create a container to directly hold the plasma. The tokamak is a representative device designed to solve this problem. A tokamak uses powerful magnetic fields to confine charged plasma in mid-air. Charged particles experience the Lorentz force within the magnetic field, causing them to move in a spiral path; the tokamak utilizes this principle to stably circulate and heat the plasma inside a doughnut-shaped magnetic field. However, the extremely strong magnetic field must be precisely controlled, and developing technology to suppress plasma instabilities remains a critical challenge that must be addressed.
There are still many challenges to overcome before humanity can fully master the technology to freely induce and stably control nuclear fusion. Nevertheless, nuclear fusion power is regarded as a future energy technology with advantages such as abundant fuel resources, high energy efficiency, the potential to reduce carbon emissions, and the ability to provide a long-term energy supply. For these reasons, nuclear fusion power is often referred to as a “dream technology” that must eventually be realized.
