A tokamak is a scientific device that produces energy from nuclear fusion. A huge tokamak is being built in southern France as part of the ITER initiative which has been in development for thirty-five years involving thirty-five different nations. ITER is a nuclear fusion power plant that is designed to investigate using fusion to produce industrial scale carbon-free energy.
ITER is scheduled to go online at the end of 2025. It will be the biggest tokamak ever constructed. It is based on use of toroidal (donut-shaped) magnetic field coils. Tokamaks were originally developed by the Soviet Union in the 1960s. The word tokamak itself is an acronym for “toroidal magnetic confinement” in Russian. ITER’s field coils are the most powerful superconductive magnets ever constructed. The ITER tokamak will utilize eighteen of these magnets which total a weight of six thousand metric tons. It needs them in order to confine the plasma created by the fusion process.
The fusion process consists of atoms of light elements such as helium and hydrogen being fused together to create atoms of heavier elements. A huge amount of energy is released during this process. The walls of the tokamak absorb this heat which is then transferred to a heat exchanger where it is used to boil water to steam. The steam is used to turn a turbine to generate electricity.
A big advantage of fusion is that it does not involve the same risks as energy generation using nuclear fission. During fission, very heavy atoms such as uranium and plutonium are broken apart into atoms of lighter elements. Demonstrating the fusion process on a large scale is one of the reasons for the construction of ITER.
In laboratory conditions, two isotopes of hydrogen, deuterium and tritium, have been found to create the most efficient fusion. Deuterium consists of one electron, one proton and one neutron. It is not radioactive. Tritium consists of one electron, one proton and two neutrons. It is radioactive. In a tokamak, electrons and nuclei are broken apart at temperatures over two hundred thirty-four thousand degrees Fahrenheit. This creates a plasma that can be described as a super-heated gas that is a hundred thousand times less dense that air at sea level.
The volume of the plasma inside the ITER tokamak will be much larger than plasmas generated by previous tokamaks. The temperature of the plasma is so hot that metals cannot be used to confine it. Powerful magnetic fields are used to contain the plasma and enable the fusion reaction. A series of toroidal superconducting magnets is used for this purpose.
The National Institutes of Quantum and Radiological Science and Technology (QST) in Japan is the leader in the development and construction of the toroidal field coils required to contain the plasma in the ITER tokamak. Mitsubishi Heavy Industries (MHI) is delivering five of these huge magnets to France this year.
The biggest five-axis machining equipment in the world is being used to make the coiling equipment. The completed magnets are tested at MHI’s Futami plants with the use of large-scale x-ray and ultrasonic test equipment that were originally developed to inspect nuclear reactor vessels. Each of the field magnets weighs three hundred -and ten metric tons. They are twenty-nine feet wide and fifty-four feet high. This is the size of a five-story building.
Another three of the magnets will be delivered to ITER by 2021. The remainder will be sent in 2022. Three years after all the magnets are in place, the grand launch of ITER will take place. When ITER goes online five years from now, it will be the first fusion reactor in the world to pass breakeven and actually produce more energy that is being input. ITER is expected to produce five hundred megawatts from only fifty megawatts input power.
Many different companies around the world are currently developing different fusion reactor designs in the hope of being the first to create a prototype of small cheap nuclear fusion power reactors.