About Nuclear FusionInstitute Overview
In fusion, two nuclei with small masses collide to form another heavier nucleus, generating enormous energy. Because the total mass after the reaction is slightly smaller than the mass before the fusion reaction, and the difference in mass is converted into energy (E = mc2). The fusion reaction is the universal source of energy in the universe. Inside stars such as the sun, a fusion reaction that produces helium from four hydrogen atoms has been generating energy for over 5 billion years.
Fusion research is underway to harness the universal energy of the universe as an energy source to support our daily lives. To realize a fusion reaction on Earth, deuterium and tritium, isotopes of hydrogen, are considered to be used as fuels. Deuterium and lithium which are necessary to produce tritium, are also found in seawater, making it possible to generate large amounts of energy in tiny quantities. Humans have used fossil fuels such as coal, petroleum, and natural gas as energy sources to build the current advanced scientific and technological industrial society. However, fossil fuel consumption seriously impacts the global environment by producing large amounts of carbon dioxide and nitrogen oxides, and their reserves are limited. Obtaining energy sources with less environmental impact is the most critical issue common to the world, and fusion energy is a possible candidate for a great solution.
To initiate a nuclear fusion reaction, the deuterium and tritium nuclei (ion) must be brought close together, but Coulomb’s repulsive force prevents it. To overcome this repulsive force and bring the nuclei closer together, they must collide at a speed of 1,000 km/s or more. In addition, since the high velocity of the nuclei alone causes them to escape and lose energy, it is necessary to confine the fast-moving nuclei in a certain space, and it is also required to increase the density of the nuclei to increase the number of collisions and obtain more fusion energy. Thus, confining many fast-moving nuclei in a certain space is a condition for a fusion reaction. Such a state is also called a high-temperature plasma.
The sun confines plasma with its enormous gravity, but a magnetic field is used to confine the plasma on the Earth. The motion of the charged particles, such as nuclei and electrons, which constitute the plasma, can be limited around the magnetic field line, and their motion is such that they wrap around the magnetic field lines, confining the high-temperature plasma in a certain space. Plasma research, which aims to understand various complex phenomena occurring in plasmas, is of central importance for developing fusion reactors, provides many research subjects for academic research, and plays an essential role as a basis for understanding cosmic and astronomical phenomena.