The appearance of a thermonuclear reactor has been expected for more than half a century. Expectations are so overheated that a very popular conspiracy theory has arisen, as if in fact it was invented a long time ago, but the oil magnates hide the invention from the masses so as not to lose superprofits. Like any conspiracy theories, such a theory does not stand up to criticism and remains a topic for detective prose. However, understanding this does not negate the main question: when will we master thermonuclear energy?
SUNNY BOSTER
A thermonuclear reaction (or nuclear fusion reaction), in which lighter nuclei are fused into heavier ones, was described by physicists back in the 1910s. And for the first time it was observed by the English scientist Ernst Rutherford. In 1919, he pushed helium with nitrogen at high speed to produce hydrogen and heavy oxygen. Five years later, Rutherford successfully completed the synthesis of superheavy hydrogen tritium from heavy hydrogen nuclei of deuterium. Around the same time, astrophysicist Arthur Eddington put forward a bold hypothesis that stars burn due to the course of thermonuclear reactions in their bowels. In 1937, the American scientist Hans Bethe was able to prove the occurrence of thermonuclear reactions in the Sun - therefore, Eddington was right.
The idea of reproducing a "solar fire" on Earth belonged to the Japanese physicist Tokutaro Hagiwara, who in 1941 suggested the possibility of initiating a thermonuclear reaction between hydrogen nuclei using an explosive chain reaction of uranium fission - that is, an atomic explosion should create conditions (ultra-high temperature and pressure) to start thermonuclear fusion. A little later, Enrico Fermi, who participated in the creation of the American atomic bomb, came to the same idea. In 1946, under the leadership of Edward Teller, a research project on the use of thermonuclear energy was launched at the Los Alamos Laboratory.
The first thermonuclear device was detonated by the US military on November 1, 1952, at Enewetok Atoll in the Pacific Ocean. We conducted a similar experiment in 1953. Thus, humanity has been using thermonuclear fusion for over sixty years, but only for destructive purposes. Why can't you use it more rationally?
PLASMA MASTERS
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From the point of view of energy, the optimal plasma temperature for a thermonuclear reaction is 100 million degrees. This is several times higher than the temperature in the interior of the Sun. How to be?
Physicists have proposed keeping the plasma inside a "magnetic trap." In the early 1950s, Andrei Sakharov and Igor Tamm calculated the configuration of magnetic fields capable of compressing plasma into a thin filament and preventing it from falling onto the chamber walls. It was on the basis of the scheme they proposed that numerous tokamaks were created.
It is believed that the term "TOKAMAK" originated as an abbreviation for the phrase "TOroidal CAMERA with Magnetic Coils". The main design element is indeed the coils that create a powerful magnetic field. The working chamber of the tokamak is filled with gas. As a result of the breakdown under the action of the vortex field, enhanced ionization of the gas in the chamber occurs, which turns it into plasma. A plasma filament is formed that moves along the toroidal chamber and is heated by a longitudinal electric current. Magnetic fields keep the cord in balance and give it a shape that prevents it from touching the walls and burning them.
To date, the plasma temperature at tokamaks has reached 520 million degrees. However, warming up is the very beginning of the journey. A tokamak is not a power plant - on the contrary, it consumes energy without giving anything in return. A thermonuclear power plant should be built on different principles.
First of all, the physicists decided on the fuel. Almost ideal for a power reactor is a reaction based on the fusion of nuclei of hydrogen isotopes - deuterium and tritium (D + T), as a result of which a helium-4 nucleus and a neutron are formed. Ordinary water will serve as a source of deuterium, and tritium will be obtained from lithium irradiated with neutrons.
Then the plasma must be heated to 100 million degrees and strongly compressed, keeping in this state for a long time. From the point of view of engineering design, this is an incredibly complex and expensive task. It is the complexity and high cost that have held back the development of this direction of energy for a long time. The company was not ready to finance such a large project until there was confidence in its success.
THE ROAD TO THE FUTURE
The Soviet Union, where unique tokamaks were built, ceased to exist, but the idea of mastering thermonuclear energy did not die, and the leading countries realized that the problem could only be solved together.
And now the first experimental thermonuclear reactor for power engineering is being built today in the village of Cadarache, in southeast France, near the city of Aix-en-Provence. Russia, the USA, the European Union, Japan, China, South Korea, India and Kazakhstan are taking part in the implementation of this great project.
Strictly speaking, the facility to be built in Cadarache will still not be able to operate as a thermonuclear power plant, but it may bring its time closer. It is no coincidence that it was called ITER - this abbreviation stands for International Thermonuclear Experimental Reactor, but it also has a symbolic meaning: in Latin iter is a road, a path. Thus, the Cadarash reactor should pave the way for the thermonuclear power of the future, which will ensure the survival of humanity after the depletion of fossil fuels.
ITER will be structured as follows. In its central part, there is a toroidal chamber with a volume of about 2000 m3, filled with tritium-deuterium plasma heated to temperatures above 100 million degrees. The neutrons formed during the fusion reaction leave the "magnetic bottle" and through the "first wall" enter the blanket free space about a meter thick. Inside the blanket, neutrons collide with lithium atoms, resulting in a reaction with the formation of tritium, which will be produced not only for ITER, but also for other reactors if they are built. In this case, the "first wall" is heated by neutrons to 400 ºC. The released heat, as in conventional stations, is taken by the primary cooling circuit with a coolant (containing, for example, water or helium) and transferred to the secondary circuit, where water vapor is produced,going to turbines that generate electricity.
The ITER installation is truly a mega-machine. Its weight is 19,000 tons, the inner radius of the toroidal chamber is 2 meters, the outer radius is more than 6 meters. Construction is already in full swing, but no one can say for sure when the first positive energy output will be received at the installation. However, ITER plans to produce 200,000 kWh, which is equivalent to the energy contained in 70 tons of coal. The required amount of lithium is contained in one mini-battery for a computer, and the amount of deuterium is contained in 45 liters of water. And it will be absolutely clean energy.
At the same time, deuterium should be enough for millions of years, and the reserves of easily extracted lithium are quite sufficient to meet the need for it for hundreds of years. Even if the reserves of lithium in the rocks run out, physicists will be able to extract it from seawater.
ITER will definitely be built. And, of course, I am glad that our country is taking part in this project of the future. Only Russian specialists have many years of experience in creating large superconducting magnets, without which it is impossible to keep the plasma in the filament: thanks to tokamaks!
Anton Pervushin