The idea of controlled thermonuclear fusion has been on the minds of people for a long time. In theory, such power plants will provide mankind with a reliable and powerful source of energy, like nuclear power plants, but they will be much safer than the latter. However, are our technologies advanced enough to build and operate such a complex device? And can it be commercially justified, or will it cost more money to build and use it than you can earn by selling electricity? Finally, wouldn’t a fusion reactor absorb more energy for its operation than it produces? These questions should be answered by ITER.
Long Haul
In 1985, Soviet leader Mikhail Gorbachev and US leader Ronald Reagan met in Geneva. These talks are considered significant, as the first Cold War began to decline. The parties agreed (albeit formally) on nuclear disarmament. However, Reagan, Gorbachev and French President Francois Mitterrand also signed another agreement — the start of an international project for the design and construction of the ITER fusion reactor (International Experimental Thermonuclear Reactor). Much later, in the 2010s, the name will be rethought and will be interpreted as the Latin word iter — the path.
The designers of the reactor combined the findings of four leading research projects on controlled thermonuclear fusion provided by the Soviet Union, the USA, Japan and the European Community. The design itself took 12 years. During this time, it became clear that the ITER participants would not be able to pull the construction of the reactor according to the original project. So, in 1998 they set a goal of cutting the cost of the reactor by 50%. However, subsequently both the cost and the deadlines for completion of construction were revised more than once. Initially, the reactor was to be built by 2016 for five billion euros. In 2009, the launch was postponed to 2018, then for another year, and in 2015 it was completely shifted by six years until 2025. But the reactor will reach its full capacity only by 2035. At the same time, costs increased to 22 billion euros.
Now seven parties are involved in the construction of ITER: the European Union, India, China, Russia, the USA, South Korea, and Japan. In total, something for the reactor is created by 35 countries (all EU countries are considered as one participant). The construction site itself is in France, in the Cadarache Nuclear Energy Research Center near Marseille.
The European Union assumed 45% of the costs for the construction of ITER (this is logical, because there are many countries there, and the reactor itself will remain on its territory), the other participants invest 9.1% each. However, only 10% of the costs are money. Everything else is building materials, structures, devices, and technologies. The entire reactor is divided into “zones of responsibility” — each participant creates some part of the overall project. This is, perhaps, the most interesting aspect of international cooperation within the framework of ITER. All project participants get full access to all technologies involved in the reactor. In addition, they develop their own science and engineering. For example, in the United States, a new high-strength steel grade was developed specifically for ITER, and in Russia, unique disconnectors for 12 kilovolts and 60,000 amperes.
Thus, after construction is completed, all countries participating in the project will have the technologies and practical experience for designing their own thermonuclear reactors.
Expensive, Difficult, Labor-intensive
ITER is a tokamak. The system of magnets for holding the plasma in it forms a field with an induction of 13 Tesla (this is 200 thousand times greater than the Earth’s magnetic field). For this, conductors made of niobium-tin and niobium-titanium alloys are used, which are in a superconducting state at a temperature of about four kelvins, or – 269 degrees Celsius. To cool to such a temperature, channels are put inside the coils through which liquid helium flows.
The vacuum chamber itself in the form of a torus (a donut, as it is called in ITER) is made of the special stainless steel mentioned above, which can withstand the neutron radiation that occurs during the operation of the tokamak. At 19 meters in diameter and 11 meters high, it weighs more than five thousand tons. The chamber has double walls, between which distilled water splashes – the reactor coolant.
Neutron radiation is the main negative aspect of tokamak operation. To trap high-energy neutrons, the inner wall of the donut is covered with a blanket. This is a system of 440 cassettes made of copper reinforced with stainless steel. The front wall of the cassettes is covered with a beryllium layer 8 to 10 mm thick. As they wear out, the beryllium layers will be replaced. The blanket must slow down the neutrons and remove the heat that is released in the process. Each cassette weighs more than 4.5 tons, and in total they will take 12 tons of beryllium.
At the same time, the blanket is also a tool for experimentation. Three of his TBM (Test Blanket Modules) cassettes contain an isotope of lithium. As a result of the collision of neutrons with this isotope, helium-4 is formed and tritium. Perhaps the use of such cassettes will allow the reactor to thus produce tritium for use as fuel.
Another protective mechanism of ITER is the divertor, which is located at the bottom of the vacuum chamber. Its task is to remove contaminants from the plasma, including beryllium dust, which cause additional radiation that can adversely affect the camera.
ITER uses a mixture of deuterium and tritium as fuel, and this reactor is the first one adapted specifically for it. The fuel will be heated to the state of plasma using a high-frequency heater (in fact, a large microwave oven). You can also use the central electromagnet, providing induction heating of the plasma.
A deuterium-tritium mixture will be introduced into the chamber from which the air is evacuated, with the electromagnets operating. There it will heat up, ionize, and become plasma. To “turn on the gas”, an ice gun will be installed at ITER. It literally freezes the fuel mixture and shoots it into the plasma in small pellets at speeds up to 1000 meters per second. It sounds big, but there will be no more than one gram of fuel in the chamber at any given time.
The largest component of ITER is the cryostat, that is, the reactor shell. It is almost 30 meters high and in diameter and weighs 3850 tons. The cryostat will provide support for all mechanisms of the tokamak and will also become a barrier between it and the external environment. Outside, it will be surrounded by bioprotection — a two-meter layer of concrete.
Of course, the tokamak also has control systems, a fuel system for storing and supplying a deuterium-tritium mixture, a vacuum system for pumping air, a cryogenic and water system for cooling, a remote manipulator for replacing blanket and diverter cassettes, and a waste storage.
ITER is an expensive and complex installation, and it will not supply electricity to the grid – on the contrary, it will actively consume, because it will need 110 megawatts constantly and 620 megawatts during plasma ignition to power it. However, there is a reason for its construction. It is expected that ITER will answer most of the questions regarding the practical use of fusion reactors, will provide an exceptionally large amount of information for improving technology and will subsequently allow the creation of commercially successful power plants. That is, it is an investment for the sake of future profit. However, another option is also possible: ITER will prove that thermonuclear energy is untenable (at least in our time). Well, a negative experience is also an experience.