Semyon Semyonov
The breakthrough in the Chinese nuclear program - a successful trial of a thermo-nuclear reactor, is another step in humanity's attempts to find a cheap and clean energy substitute. Agent Saimon, the writer on the blog "Target: Space" extensively reviews the significance of the experiment.
The Chinese news agency Xinhua reports that yesterday Chinese scientists conducted the first test of an innovative thermonuclear reactor. The experiment, which lasted 3 seconds, was successful, and an electric current of 200 kiloamperes was produced.
what's the matter
It is about an advanced experimental facility called "Tokamak" with the use of superconductivity" (EAST in English). This is basically a nuclear fusion reactor for research purposes. Its mode of operation is different from the mode of operation of normal nuclear reactors, in which a controlled process of nuclear fission takes place. In the process of nuclear fission, an atom of a heavy and unstable element, usually uranium or plutonium (actually only certain isotopes of these elements, i.e. the element's nuclei with a certain number of neutrons), disintegrates into several smaller nuclei and as a result a lot of energy is emitted. If it is a nuclear weapon, the process is not controlled and a chain reaction is created.
Nuclear fusion process works differently. It is based on the principle that two small, lightweight nuclei can unite into the nucleus of a heavier element. In fusion, much more energy is emitted than in fission processes, but for this nuclear reaction to occur, several conditions must be met. One of the most famous conditions is the Lawson criterion. Without going into the physics behind the processes, it follows that in order for the reaction to be stable, very high temperature and pressure must be achieved. For example, in the above experiment, deuterium and tritium atoms (isotopes of hydrogen, which can be obtained from "heavy water" and lithium) turned into helium-4 atoms at a temperature of one hundred million degrees Celsius.
A good example of a natural nuclear fusion reactor is our sun. The stars get their energy from nuclear fusion processes that take place in them (the aforementioned process where hydrogen turns into helium). Also a thermonuclear explosive charge, known by its more popular name - a hydrogen bomb, receives its energy from a process of nuclear fusion. But in both cases the high pressure and temperature are easily achieved. In stars there is the pressure of the gas that causes the reactions to occur in the nucleus, and in a hydrogen bomb a normal nuclear charge is used as an explosive.
And here actually lies the problem of using nuclear fusion to get the energy. Unlike nuclear reactors that are based on fission, in fusion there is no radioactive waste. The fuel for the processes can be obtained in a relatively simple way - for example, deuterium can be obtained from water. But the reaction requires a temperature and pressure that no substance can bear. The solution to this is to hold the materials with a strong magnetic field. The materials, by the way, are, because of the conditions, in a state of plasma accumulation (ionized gas).
The solution and its implementation
The solution is applied by a large device in the shape of a torus - a shape reminiscent of a round pretzel (it can also be described as a cylinder whose ends are joined, and it forms a closed shape). Extremely strong magnets are installed on it that hold the hot plasma inside, in a vacuum chamber. The torus is mounted on heavy metal posts. To build strong magnets it is possible to use the phenomenon of superconductivity which enables the creation of electromagnets with a stronger magnetic field.
Such a device is called a Tokamak - Russian for a toroidal cell (in the shape of a torus) inside magnetic coils. The concept was born in the 50s when Russian scientists presented the concept to their Western colleagues. The first tokamak was activated in the USSR towards the seventies of the last century. In 1982, Tokamak-7 was built, a unique facility based on superconductivity that practically shaped all those that followed it.
EAST is located in the city of Hefei, the capital of Anhui province, and operates under the auspices of the Institute of Plasma Physics of the Chinese Academy of Sciences. The facility is an upgrade of the first Chinese tokamak - HT-7 (the successor of Hefei Tokamak-7). The number 7 is not chosen randomly, the Chinese tokamak was built in close cooperation with Russia in 1994, and is based on the aforementioned tokamak-7. The ambitious project of the Chinese Academy of Sciences, released in 1998, included the comprehensive upgrade of the HT-7 tokamak, which was named HT-7U. The construction, which reportedly cost 25 million dollars, was completed this year, and the first operational test was held yesterday. [More about EAST in this professional article. Pictures of HT-7 can be seen here].
Xinhua reports that the director of the institute that manages EAST, Li Jiangang, said that he is very satisfied with the results of the experiment, which he says is a breakthrough in the research of controlled nuclear fusion processes. "The results of the experiment indicate that we are ahead of our competitors by at least a decade," Lee said. "Our achievements will advance the vision of clean and available energy for all humanity." Another achievement of China is the facility itself, which it claims is cheaper and simpler to build than the competition.
The ITER in France. Photo: the official website
Not only in China
The Chinese project is not unique - dozens of tokamaks have been built all over the world - but only a small part of them have the strength and power needed to support a nuclear fusion reaction that could generate electricity even for a few consecutive seconds. The Japanese tokamak JT-60 holds the record, which managed to hold the plasma for 28.6 seconds. Smaller tokamaks are used for more modest research. In 1994, even Iran bought a Russian-made tokamak (and they bought another one from China). But both facilities are not of high power and are used only for research purposes and cannot ignite a thermonuclear reaction. Although a few months ago the Iranians announced that they had achieved nuclear fusion, it was either a misunderstanding or a deliberate deception.
These days, the tokamak ITER (International Thermonuclear Experimental Reactor) is being built in northern France, the purpose of which is to try and prove that it is indeed possible to build a thermonuclear power plant that can provide electricity continuously. When built, it will be the most powerful tokamak ever. This international project has, as of today, 7 participants: Russia, China, the European Union, Japan, India, South Korea and the USA, which left it in 1999 but returned four years later. The first ITER experiment is planned for 2016.
Sir John Cockcroft, Nobel laureate in physics and director of the British Tokamak, was once asked - when will the first fusion reactor appear that can supply electricity industrially? Cockroft answered "in 20 years". When asked the same question seven years later, he again answered "in 20 years." Of course, the journalists couldn't help but remind him of his previous answer, to which Croft responded: "As you can see, I'm not changing my mind."
Expectations today are that tokamaks that will provide electricity regularly will appear within 30 to 50 years. But some of the senior Russian scientists, such as Georgi A. Eliseev, who runs the Russian scientific center "Kurchetov Institute", are sure that from a technical and scientific point of view this could be achieved already nowadays and everything depends only on the degree of desire and investment. Until then, available and clean energy will remain a dream for humanity.
Semyon Semyonov writes on the "Target: Space" blog on a focused coverage website
