Thermonuclear reactors: do they have a future? Who is building a thermonuclear reactor? Why did the creation of thermonuclear installations take so long?

For a long time trudnopisaka asked me to make a post about the thermonuclear reactor under construction. Find out interesting details of the technology, find out why this project is taking so long to be implemented. I've finally collected the material. Let's get acquainted with the details of the project.

How did it all start? The “energy challenge” arose as a result of a combination of the following three factors:

1. Humanity now consumes a huge amount of energy.

Currently, the world's energy consumption is about 15.7 terawatts (TW). Dividing this value by the world population, we get approximately 2400 watts per person, which can be easily estimated and visualized. The energy consumed by every inhabitant of the Earth (including children) corresponds to the round-the-clock operation of 24 hundred-watt electric lamps. However, the consumption of this energy across the planet is very uneven, as it is very large in several countries and negligible in others. Consumption (in terms of one person) is equal to 10.3 kW in the USA (one of the record values), 6.3 kW in the Russian Federation, 5.1 kW in the UK, etc., but, on the other hand, it is equal only 0.21 kW in Bangladesh (only 2% of US energy consumption!).

According to the International Energy Agency (2006), global energy consumption is expected to increase by 50% by 2030. Developed countries could, of course, do just fine without additional energy, but this growth is necessary to lift people out of poverty in developing countries, where 1.5 billion people suffer from severe power shortages.

3. Currently, 80% of the world's energy comes from burning fossil fuels(oil, coal and gas), the use of which:
a) potentially poses a risk of catastrophic environmental changes;
b) inevitably must end someday.

From what has been said, it is clear that now we must prepare for the end of the era of using fossil fuels

Currently, nuclear power plants produce energy released during fission reactions of atomic nuclei on a large scale. The creation and development of such stations should be encouraged in every possible way, but it must be taken into account that the reserves of one of the most important materials for their operation (cheap uranium) can also be completely used up within the next 50 years. The possibilities of nuclear fission-based energy can (and should) be significantly expanded through the use of more efficient energy cycles, allowing the amount of energy produced to almost double. To develop energy in this direction, it is necessary to create thorium reactors (the so-called thorium breeder reactors or breeder reactors), in which the reaction produces more thorium than the original uranium, as a result of which the total amount of energy produced for a given amount of substance increases by 40 times . It also seems promising to create plutonium breeders using fast neutrons, which are much more efficient than uranium reactors and can produce 60 times more energy. It may be that to develop these areas it will be necessary to develop new, non-standard methods for obtaining uranium (for example, from sea water, which seems to be the most accessible).

Fusion power plants

The figure shows a schematic diagram (not to scale) of the device and operating principle of a thermonuclear power plant. In the central part there is a toroidal (donut-shaped) chamber with a volume of ~2000 m3, filled with tritium-deuterium (T-D) plasma heated to a temperature above 100 M°C. The neutrons produced during the fusion reaction (1) leave the “magnetic bottle” and enter the shell shown in the figure with a thickness of about 1 m.

Inside the shell, neutrons collide with lithium atoms, resulting in a reaction that produces tritium:

neutron + lithium → helium + tritium

In addition, competing reactions occur in the system (without the formation of tritium), as well as many reactions with the release of additional neutrons, which then also lead to the formation of tritium (in this case, the release of additional neutrons can be significantly enhanced, for example, by introducing beryllium atoms into the shell and lead). The general conclusion is that this facility could (at least theoretically) undergo a nuclear fusion reaction that would produce tritium. In this case, the amount of tritium produced should not only meet the needs of the installation itself, but also be even somewhat larger, which will make it possible to supply new installations with tritium. It is this operating concept that must be tested and implemented in the ITER reactor described below.

In addition, neutrons must heat the shell in so-called pilot plants (in which relatively “ordinary” construction materials will be used) to approximately 400°C. In the future, it is planned to create improved installations with a shell heating temperature above 1000°C, which can be achieved through the use of the latest high-strength materials (such as silicon carbide composites). The heat generated in the shell, 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 steam is produced and supplied to the turbines.

1985 - The Soviet Union proposed the next generation Tokamak plant, using the experience of four leading countries in creating fusion reactors. The United States of America, together with Japan and the European Community, put forward a proposal for the implementation of the project.

Currently, in France, construction is underway on the international experimental thermonuclear reactor ITER (International Tokamak Experimental Reactor), described below, which will be the first tokamak capable of “igniting” plasma.

The most advanced existing tokamak installations have long reached temperatures of about 150 M°C, close to the values ​​​​required for the operation of a fusion station, but the ITER reactor should be the first large-scale power plant designed for long-term operation. In the future, it will be necessary to significantly improve its operating parameters, which will require, first of all, increasing the pressure in the plasma, since the rate of nuclear fusion at a given temperature is proportional to the square of the pressure. The main scientific problem in this case is related to the fact that when the pressure in the plasma increases, very complex and dangerous instabilities arise, that is, unstable operating modes.

Why do we need this?

The main advantage of nuclear fusion is that it requires only very small amounts of substances that are very common in nature as fuel. The nuclear fusion reaction in the described installations can lead to the release of enormous amounts of energy, ten million times higher than the standard heat released during conventional chemical reactions (such as the combustion of fossil fuels). For comparison, we point out that the amount of coal required to power a thermal power plant with a capacity of 1 gigawatt (GW) is 10,000 tons per day (ten railway cars), and a fusion plant of the same power will consume only about 1 kilogram of the D+T mixture per day .

Deuterium is a stable isotope of hydrogen; In about one out of every 3,350 molecules of ordinary water, one of the hydrogen atoms is replaced by deuterium (a legacy from the Big Bang). This fact makes it easy to organize fairly cheap production of the required amount of deuterium from water. It is more difficult to obtain tritium, which is unstable (half-life is about 12 years, as a result of which its content in nature is negligible), however, as shown above, tritium will appear directly inside the thermonuclear installation during operation, due to the reaction of neutrons with lithium.

Thus, the initial fuel for a fusion reactor is lithium and water. Lithium is a common metal widely used in household appliances (cell phone batteries, etc.). The installation described above, even taking into account non-ideal efficiency, will be able to produce 200,000 kWh of electrical energy, which is equivalent to the energy contained in 70 tons of coal. The amount of lithium required for this is contained in one computer battery, and the amount of deuterium is in 45 liters of water. The above value corresponds to the current electricity consumption (calculated per person) in the EU countries over 30 years. The very fact that such an insignificant amount of lithium can ensure the generation of such an amount of electricity (without CO2 emissions and without the slightest air pollution) is a fairly serious argument for the fastest and most vigorous development of thermonuclear energy (despite all the difficulties and problems) and even without one hundred percent confidence in the success of such research.

Deuterium should last for millions of years, and reserves of easily mined lithium are sufficient to supply needs for hundreds of years. Even if lithium in rocks runs out, we can extract it from water, where it is found in concentrations high enough (100 times the concentration of uranium) to make its extraction economically feasible.

An experimental thermonuclear reactor (International thermonuclear experimental reactor) is being built near the city of Cadarache in France. The main goal of the ITER project is to implement a controlled thermonuclear fusion reaction on an industrial scale.

Per unit weight of thermonuclear fuel, about 10 million times more energy is obtained than when burning the same amount of organic fuel, and about a hundred times more than when splitting uranium nuclei in the reactors of currently operating nuclear power plants. If the calculations of scientists and designers come true, this will give humanity an inexhaustible source of energy.

Therefore, a number of countries (Russia, India, China, Korea, Kazakhstan, USA, Canada, Japan, European Union countries) joined forces in creating the International Thermonuclear Research Reactor - a prototype of new power plants.

ITER is a facility that creates conditions for the synthesis of hydrogen and tritium atoms (an isotope of hydrogen), resulting in the formation of a new atom - a helium atom. This process is accompanied by a huge burst of energy: the temperature of the plasma in which the thermonuclear reaction occurs is about 150 million degrees Celsius (for comparison, the temperature of the Sun’s core is 40 million degrees). In this case, the isotopes burn out, leaving virtually no radioactive waste.
The scheme of participation in the international project provides for the supply of reactor components and financing of its construction. In exchange for this, each of the participating countries receives full access to all technologies for creating a thermonuclear reactor and to the results of all experimental work on this reactor, which will serve as the basis for the design of serial power thermonuclear reactors.

The reactor, based on the principle of thermonuclear fusion, has no radioactive radiation and is completely safe for the environment. It can be located almost anywhere in the world, and the fuel for it is ordinary water. Construction of ITER is expected to last about ten years, after which the reactor is expected to be in use for 20 years.

Clickable 4000 px

Russia's interests in the Council of the International Organization for the Construction of the ITER Thermonuclear Reactor in the coming years will be represented by Corresponding Member of the Russian Academy of Sciences Mikhail Kovalchuk - Director of the Kurchatov Institute, Institute of Crystallography of the Russian Academy of Sciences and Scientific Secretary of the Presidential Council on Science, Technology and Education. Kovalchuk will temporarily replace academician Evgeniy Velikhov in this post, who was elected chairman of the ITER International Council for the next two years and does not have the right to combine this position with the duties of an official representative of a participating country.

The total cost of construction is estimated at 5 billion euros, and the same amount will be required for trial operation of the reactor. The shares of India, China, Korea, Russia, the USA and Japan each account for approximately 10 percent of the total value, 45 percent comes from the countries of the European Union. However, the European states have not yet agreed on how exactly the costs will be distributed between them. Because of this, the start of construction was postponed to April 2010. Despite the latest delay, scientists and officials involved in ITER say they will be able to complete the project by 2018.

The estimated thermonuclear power of ITER is 500 megawatts. Individual magnet parts reach a weight of 200 to 450 tons. To cool ITER, 33 thousand cubic meters of water per day will be required.

In 1998, the United States stopped funding its participation in the project. After the Republicans came to power and rolling blackouts began in California, the Bush administration announced increased investment in energy. The United States did not intend to participate in the international project and was engaged in its own thermonuclear project. In early 2002, President Bush's technology adviser John Marburger III said that the United States had changed its mind and intended to return to the project.

In terms of the number of participants, the project is comparable to another major international scientific project - the International Space Station. The cost of ITER, which previously reached 8 billion dollars, then amounted to less than 4 billion. As a result of the withdrawal of the United States from participation, it was decided to reduce the reactor power from 1.5 GW to 500 MW. Accordingly, the price of the project has also decreased.

In June 2002, the symposium “ITER Days in Moscow” was held in the Russian capital. It discussed the theoretical, practical and organizational problems of reviving the project, the success of which can change the fate of humanity and give it a new type of energy, comparable in efficiency and economy only to the energy of the Sun.

In July 2010, representatives of the countries participating in the ITER international thermonuclear reactor project approved its budget and construction schedule at an extraordinary meeting held in Cadarache, France. .

At the last extraordinary meeting, project participants approved the start date for the first experiments with plasma - 2019. Full experiments are planned for March 2027, although the project management asked technical specialists to try to optimize the process and begin experiments in 2026. The meeting participants also decided on the costs of constructing the reactor, but the amounts planned to be spent on creating the installation were not disclosed. According to information received by the editor of the ScienceNOW portal from an unnamed source, by the time experiments begin, the cost of the ITER project could reach 16 billion euros.

The meeting in Cadarache also marked the first official working day for the new project director, Japanese physicist Osamu Motojima. Before him, the project had been led since 2005 by the Japanese Kaname Ikeda, who wished to leave his post immediately after the budget and construction deadlines were approved.

The ITER fusion reactor is a joint project of the European Union, Switzerland, Japan, USA, Russia, South Korea, China and India. The idea of ​​creating ITER has been under consideration since the 80s of the last century, however, due to financial and technical difficulties, the cost of the project is constantly growing, and the construction start date is constantly being postponed. In 2009, experts expected that work on creating the reactor would begin in 2010. Later, this date was moved, and first 2018 and then 2019 were named as the launch time of the reactor.

Thermonuclear fusion reactions are reactions of fusion of nuclei of light isotopes to form a heavier nucleus, which are accompanied by a huge release of energy. In theory, fusion reactors can produce a lot of energy at low cost, but at the moment scientists spend much more energy and money to start and maintain the fusion reaction.

Thermonuclear fusion is a cheap and environmentally friendly way to produce energy. Uncontrolled thermonuclear fusion has been occurring on the Sun for billions of years - helium is formed from the heavy hydrogen isotope deuterium. This releases a colossal amount of energy. However, people on Earth have not yet learned to control such reactions.

The ITER reactor will use hydrogen isotopes as fuel. During a thermonuclear reaction, energy is released when light atoms combine into heavier ones. To achieve this, the gas must be heated to a temperature of over 100 million degrees - much higher than the temperature at the center of the Sun. Gas at this temperature turns into plasma. At the same time, atoms of hydrogen isotopes merge, turning into helium atoms with the release of a large number of neutrons. A power plant operating on this principle will use the energy of neutrons slowed down by a layer of dense material (lithium).

Why did the creation of thermonuclear installations take so long?

Why have such important and valuable installations, the benefits of which have been discussed for almost half a century, not yet been created? There are three main reasons (discussed below), the first of which can be called external or social, and the other two - internal, that is, determined by the laws and conditions of the development of thermonuclear energy itself.

1. For a long time, it was believed that the problem of the practical use of thermonuclear fusion energy did not require urgent decisions and actions, since back in the 80s of the last century, fossil fuel sources seemed inexhaustible, and environmental problems and climate change did not concern the public. In 1976, the U.S. Department of Energy's Fusion Energy Advisory Committee attempted to estimate the time frame for R&D and a demonstration fusion power plant under various research funding options. At the same time, it was discovered that the volume of annual funding for research in this direction is completely insufficient, and if the existing level of appropriations is maintained, the creation of thermonuclear installations will never be successful, since the allocated funds do not correspond even to the minimum, critical level.

2. A more serious obstacle to the development of research in this area is that a thermonuclear installation of the type under discussion cannot be created and demonstrated on a small scale. From the explanations presented below, it will become clear that thermonuclear fusion requires not only magnetic confinement of the plasma, but also sufficient heating of it. The ratio of expended and received energy increases at least in proportion to the square of the linear dimensions of the installation, as a result of which the scientific and technical capabilities and advantages of thermonuclear installations can be tested and demonstrated only at fairly large stations, such as the mentioned ITER reactor. Society was simply not ready to finance such large projects until there was sufficient confidence in success.

3. The development of thermonuclear energy has been very complex, however (despite insufficient funding and difficulties in selecting centers for the creation of JET and ITER installations), clear progress has been observed in recent years, although an operating station has not yet been created.

The modern world is facing a very serious energy challenge, which can more accurately be called an “uncertain energy crisis.” The problem is related to the fact that reserves of fossil fuels may run out in the second half of this century. Moreover, burning fossil fuels may result in the need to somehow sequester and “store” the carbon dioxide released into the atmosphere (the CCS program mentioned above) to prevent major changes in the planet’s climate.

Currently, almost all the energy consumed by humanity is created by burning fossil fuels, and the solution to the problem may be associated with the use of solar energy or nuclear energy (the creation of fast neutron breeder reactors, etc.). The global problem caused by the growing population of developing countries and their need to improve living standards and increase the amount of energy produced cannot be solved on the basis of these approaches alone, although, of course, any attempts to develop alternative methods of energy production should be encouraged.

Strictly speaking, we have a small choice of behavioral strategies and the development of thermonuclear energy is extremely important, even despite the lack of a guarantee of success. The Financial Times newspaper (dated January 25, 2004) wrote about this:

Let's hope that there will be no major and unexpected surprises on the path to the development of thermonuclear energy. In this case, in about 30 years we will be able to supply electric current from it to energy networks for the first time, and in just over 10 years the first commercial thermonuclear power plant will begin to operate. It is possible that in the second half of this century, nuclear fusion energy will begin to replace fossil fuels and gradually begin to play an increasingly important role in providing energy to humanity on a global scale.

There is no absolute guarantee that the task of creating thermonuclear energy (as an effective and large-scale source of energy for all humanity) will be completed successfully, but the likelihood of success in this direction is quite high. Considering the enormous potential of thermonuclear stations, all costs for projects for their rapid (and even accelerated) development can be considered justified, especially since these investments look very modest against the backdrop of the monstrous global energy market ($4 trillion per year8). Meeting humanity's energy needs is a very serious problem. As fossil fuels become less available (and their use becomes undesirable), the situation is changing, and we simply cannot afford not to develop fusion energy.

To the question “When will thermonuclear energy appear?” Lev Artsimovich (a recognized pioneer and leader of research in this field) once responded that “it will be created when it becomes truly necessary for humanity”

ITER will be the first fusion reactor to produce more energy than it consumes. Scientists measure this characteristic using a simple coefficient they call "Q." If ITER achieves all its scientific goals, it will produce 10 times more energy than it consumes. The last device built, the Joint European Torus in England, is a smaller prototype fusion reactor that, in its final stages of scientific research, achieved a Q value of almost 1. This means that it produced exactly the same amount of energy as it consumed. ITER will go beyond this by demonstrating energy creation from fusion and achieving a Q value of 10. The idea is to generate 500 MW from an energy consumption of approximately 50 MW. Thus, one of the scientific goals of ITER is to prove that a Q value of 10 can be achieved.

Another scientific goal is that ITER will have a very long "burn" time - a pulse of extended duration up to one hour. ITER is a research experimental reactor that cannot produce energy continuously. When ITER starts operating, it will be on for one hour, after which it will need to be turned off. This is important because until now the standard devices we have created have been capable of having a burning time of several seconds or even tenths of a second - this is the maximum. The "Joint European Torus" reached its Q value of 1 with a burn time of approximately two seconds with a pulse length of 20 seconds. But a process that lasts a few seconds is not truly permanent. By analogy with starting a car engine: briefly turning on the engine and then turning it off is not yet real operation of the car. Only when you drive your car for half an hour will it reach a constant operating mode and demonstrate that such a car can really be driven.

That is, from a technical and scientific point of view, ITER will provide a Q value of 10 and an increased burn time.

The thermonuclear fusion program is truly international and broad in nature. People are already counting on the success of ITER and are thinking about the next step - creating a prototype of an industrial thermonuclear reactor called DEMO. To build it, ITER needs to work. We must achieve our scientific goals because this will mean that the ideas we put forward are entirely feasible. However, I agree that you should always think about what comes next. In addition, as ITER operates for 25-30 years, our knowledge will gradually deepen and expand, and we will be able to more accurately outline our next step.

Indeed, there is no debate about whether ITER should be a tokamak. Some scientists pose the question quite differently: should ITER exist? Experts in different countries, developing their own, not so large-scale thermonuclear projects, argue that such a large reactor is not needed at all.

However, their opinion should hardly be considered authoritative. Physicists who have been working with toroidal traps for several decades were involved in the creation of ITER. The design of the experimental thermonuclear reactor in Karadash was based on all the knowledge gained during experiments on dozens of predecessor tokamaks. And these results indicate that the reactor must be a tokamak, and a large one at that.

JET At the moment, the most successful tokamak can be considered JET, built by the EU in the British town of Abingdon. This is the largest tokamak-type reactor created to date, the large radius of the plasma torus is 2.96 meters. The power of the thermonuclear reaction has already reached more than 20 megawatts with a retention time of up to 10 seconds. The reactor returns about 40% of the energy put into the plasma.

It is the physics of plasma that determines the energy balance,” Igor Semenov told Infox.ru. MIPT associate professor described what energy balance is with a simple example: “We have all seen a fire burn. In fact, it is not wood that burns there, but gas. The energy chain there is like this: the gas burns, the wood heats, the wood evaporates, the gas burns again. Therefore, if we throw water on a fire, we will abruptly take energy from the system for the phase transition of liquid water into a vapor state. The balance will become negative and the fire will go out. There is another way - we can simply take the firebrands and spread them in space. The fire will also go out. It’s the same in the thermonuclear reactor we are building. The dimensions are chosen to create an appropriate positive energy balance for this reactor. Sufficient to build a real nuclear power plant in the future, solving at this experimental stage all the problems that currently remain unresolved.”

The dimensions of the reactor were changed once. This happened at the turn of the 20th-21st centuries, when the United States withdrew from the project, and the remaining members realized that the ITER budget (by that time it was estimated at 10 billion US dollars) was too large. Physicists and engineers were required to reduce the cost of installation. And this could only be done due to size. The “redesign” of ITER was led by the French physicist Robert Aymar, who previously worked on the French Tore Supra tokamak in Karadash. The outer radius of the plasma torus has been reduced from 8.2 to 6.3 meters. However, the risks associated with the reduction in size were partly compensated for by several additional superconducting magnets, which made it possible to implement the plasma confinement mode, which was open and studied at that time.

source
http://ehorussia.com
http://oko-planet.su

The second half of the 20th century was a period of rapid development of nuclear physics. It became clear that nuclear reactions could be used to produce enormous energy from tiny amounts of fuel. Only nine years passed from the explosion of the first nuclear bomb to the first nuclear power plant, and when a hydrogen bomb was tested in 1952, there were predictions that thermonuclear power plants would come into operation in the 1960s. Alas, these hopes were not justified.

Thermonuclear reactions Of all the thermonuclear reactions, only four are of interest in the near future: deuterium + deuterium (products - tritium and proton, released energy 4.0 MeV), deuterium + deuterium (helium-3 and neutron, 3.3 MeV), deuterium + tritium (helium-4 and neutron, 17.6 MeV) and deuterium + helium-3 (helium-4 and proton, 18.2 MeV). The first and second reactions occur in parallel with equal probability. The resulting tritium and helium-3 “burn” in the third and fourth reactions

The main source of energy for humanity today is the combustion of coal, oil and gas. But their supplies are limited, and combustion products pollute the environment. A coal power plant produces more radioactive emissions than a nuclear power plant of the same power! So why haven't we switched to nuclear energy sources yet? There are many reasons for this, but the main one recently has been radiophobia. Despite the fact that a coal-fired power plant, even during normal operation, harms the health of many more people than emergency emissions at a nuclear power plant, it does so quietly and unnoticed by the public. Accidents at nuclear power plants immediately become the main news in the media, causing general panic (often completely unfounded). However, this does not mean that nuclear energy does not have objective problems. Radioactive waste causes a lot of trouble: technologies for working with it are still extremely expensive, and the ideal situation when all of it will be completely recycled and used is still far away.

Of all the thermonuclear reactions, only four are of interest in the near future: deuterium + deuterium (products - tritium and proton, released energy 4.0 MeV), deuterium + deuterium (helium-3 and neutron, 3.3 MeV), deuterium + tritium (helium -4 and neutron, 17.6 MeV) and deuterium + helium-3 (helium-4 and proton, 18.2 MeV). The first and second reactions occur in parallel with equal probability. The resulting tritium and helium-3 “burn” in the third and fourth reactions.

From fission to fusion

A potential solution to these problems is the transition from fission reactors to fusion reactors. While a typical fission reactor contains tens of tons of radioactive fuel, which is converted into tens of tons of radioactive waste containing a wide variety of radioactive isotopes, a fusion reactor uses only hundreds of grams, maximum kilograms, of one radioactive isotope of hydrogen, tritium. In addition to the fact that the reaction requires an insignificant amount of this least dangerous radioactive isotope, its production is also planned to be carried out directly at the power plant in order to minimize the risks associated with transportation. The synthesis products are stable (non-radioactive) and non-toxic hydrogen and helium. In addition, unlike a fission reaction, a thermonuclear reaction immediately stops when the installation is destroyed, without creating the danger of a thermal explosion. So why has not a single operational thermonuclear power plant been built yet? The reason is that the listed advantages inevitably entail disadvantages: creating the conditions for synthesis turned out to be much more difficult than initially expected.

Lawson criterion

For a thermonuclear reaction to be energetically favorable, it is necessary to ensure a sufficiently high temperature of the thermonuclear fuel, a sufficiently high density and sufficiently low energy losses. The latter are numerically characterized by the so-called “retention time”, which is equal to the ratio of the thermal energy stored in the plasma to the energy loss power (many people mistakenly believe that the “retention time” is the time during which hot plasma is maintained in the installation, but this is not so) . At a temperature of a mixture of deuterium and tritium equal to 10 keV (approximately 110,000,000 degrees), we need to obtain the product of the number of fuel particles in 1 cm 3 (i.e., plasma concentration) and the retention time (in seconds) of at least 10 14. It does not matter whether we have a plasma with a concentration of 1014 cm -3 and a retention time of 1 s, or a plasma with a concentration of 10 23 and a retention time of 1 ns. This criterion is called the Lawson criterion.
In addition to the Lawson criterion, which is responsible for obtaining an energetically favorable reaction, there is also a plasma ignition criterion, which for the deuterium-tritium reaction is approximately three times greater than the Lawson criterion. “Ignition” means that the fraction of thermonuclear energy that remains in the plasma will be enough to maintain the required temperature, and additional heating of the plasma will no longer be required.

Z-pinch

The first device in which it was planned to obtain a controlled thermonuclear reaction was the so-called Z-pinch. In the simplest case, this installation consists of only two electrodes located in a deuterium (hydrogen-2) environment or a mixture of deuterium and tritium, and a battery of high-voltage pulse capacitors. At first glance, it seems that it makes it possible to obtain compressed plasma heated to enormous temperatures: exactly what is needed for a thermonuclear reaction! However, in life, everything turned out, alas, to be far from so rosy. The plasma rope turned out to be unstable: the slightest bend leads to a strengthening of the magnetic field on one side and a weakening on the other; the resulting forces further increase the bending of the rope - and all the plasma “falls out” onto the side wall of the chamber. The rope is not only unstable to bending, the slightest thinning of it leads to an increase in the magnetic field in this part, which compresses the plasma even more, squeezing it into the remaining volume of the rope until the rope is finally “squeezed out.” The compressed part has a high electrical resistance, so the current is interrupted, the magnetic field disappears, and all the plasma dissipates.

The principle of operation of the Z-pinch is simple: an electric current generates an annular magnetic field, which interacts with the same current and compresses it. As a result, the density and temperature of the plasma through which the current flows increases.

It was possible to stabilize the plasma bundle by applying a powerful external magnetic field to it, parallel to the current, and placing it in a thick conductive casing (as the plasma moves, the magnetic field also moves, which induces an electric current in the casing, tending to return the plasma to its place). The plasma stopped bending and pinching, but it was still far from a thermonuclear reaction on any serious scale: the plasma touches the electrodes and gives off its heat to them.

Modern work in the field of Z-pinch fusion suggests another principle for creating fusion plasma: a current flows through a tungsten plasma tube, which creates powerful X-rays that compress and heat the capsule with fusion fuel located inside the plasma tube, just as it does in a thermonuclear bomb. However, these works are purely research in nature (the mechanisms of operation of nuclear weapons are studied), and the energy release in this process is still millions of times less than consumption.

The smaller the ratio of the large radius of the tokamak torus (the distance from the center of the entire torus to the center of the cross-section of its pipe) to the small one (the cross-section radius of the pipe), the greater the plasma pressure can be under the same magnetic field. By reducing this ratio, scientists moved from a circular cross-section of the plasma and vacuum chamber to a D-shaped one (in this case, the role of the small radius is played by half the height of the cross-section). All modern tokamaks have exactly this cross-sectional shape. The limiting case was the so-called “spherical tokamak”. In such tokamaks, the vacuum chamber and plasma are almost spherical in shape, with the exception of a narrow channel connecting the poles of the sphere. The conductors of magnetic coils pass through the channel. The first spherical tokamak, START, appeared only in 1991, so this is a fairly young direction, but it has already shown the possibility of obtaining the same plasma pressure with a three times lower magnetic field.

Cork chamber, stellarator, tokamak

Another option for creating the conditions necessary for the reaction is the so-called open magnetic traps. The most famous of them is the “cork cell”: a pipe with a longitudinal magnetic field that strengthens at its ends and weakens in the middle. The field increased at the ends creates a “magnetic plug” (hence the Russian name), or “magnetic mirror” (English - mirror machine), which keeps the plasma from leaving the installation through the ends. However, such retention is incomplete; some charged particles moving along certain trajectories are able to pass through these jams. And as a result of collisions, any particle will sooner or later fall on such a trajectory. In addition, the plasma in the mirror chamber also turned out to be unstable: if in some place a small section of the plasma moves away from the axis of the installation, forces arise that eject the plasma onto the chamber wall. Although the basic idea of ​​the mirror cell was significantly improved (which made it possible to reduce both the instability of the plasma and the permeability of the mirrors), in practice it was not even possible to approach the parameters necessary for energetically favorable synthesis.

Is it possible to make sure that the plasma does not escape through the “plugs”? It would seem that the obvious solution is to roll the plasma into a ring. However, then the magnetic field inside the ring is stronger than outside, and the plasma again tends to go to the chamber wall. The way out of this difficult situation also seemed quite obvious: instead of a ring, make a “figure eight”, then in one section the particle will move away from the axis of the installation, and in another it will return back. This is how scientists came up with the idea of ​​the first stellarator. But such a “figure of eight” cannot be made in one plane, so we had to use the third dimension, bending the magnetic field in the second direction, which also led to a gradual movement of the particles from the axis to the chamber wall.

The situation changed dramatically with the creation of tokamak-type installations. The results obtained at the T-3 tokamak in the second half of the 1960s were so stunning for that time that Western scientists came to the USSR with their measuring equipment to verify the plasma parameters themselves. The reality even exceeded their expectations.

These fantastically intertwined tubes are not an art project, but a stellarator chamber bent into a complex three-dimensional curve.

In the hands of inertia

In addition to magnetic confinement, there is a fundamentally different approach to thermonuclear fusion - inertial confinement. If in the first case we try to keep the plasma at a very low concentration for a long time (the concentration of molecules in the air around you is hundreds of thousands of times higher), then in the second case we compress the plasma to a huge density, an order of magnitude higher than the density of the heaviest metals, in the expectation that the reaction will have time to pass in that short time before the plasma has time to scatter to the sides.

Originally, in the 1960s, the plan was to use a small ball of frozen fusion fuel, uniformly irradiated from all sides by multiple laser beams. The surface of the ball should have instantly evaporated and, expanding evenly in all directions, compressed and heated the remaining part of the fuel. However, in practice, the irradiation turned out to be insufficiently uniform. In addition, part of the radiation energy was transferred to the inner layers, causing them to heat up, which made compression more difficult. As a result, the ball compressed unevenly and weakly.

There are a number of modern stellarator configurations, all of which are close to a torus. One of the most common configurations involves the use of coils similar to the poloidal field coils of tokamaks, and four to six conductors twisted around a vacuum chamber with multidirectional current. The complex magnetic field created in this way allows the plasma to be reliably contained without requiring a ring electric current to flow through it. In addition, stellarators can also use toroidal field coils, like tokamaks. And there may be no helical conductors, but then the “toroidal” field coils are installed along a complex three-dimensional curve. Recent developments in the field of stellarators involve the use of magnetic coils and a vacuum chamber of a very complex shape (a very “crumpled” torus), calculated on a computer.

The problem of unevenness was solved by significantly changing the design of the target. Now the ball is placed inside a special small metal chamber (it is called “holraum”, from the German hohlraum - cavity) with holes through which laser beams enter inside. In addition, crystals are used that convert IR laser radiation into ultraviolet. This UV radiation is absorbed by a thin layer of hohlraum material, which is heated to enormous temperatures and emits soft X-rays. In turn, X-ray radiation is absorbed by a thin layer on the surface of the fuel capsule (ball with fuel). This also made it possible to solve the problem of premature heating of the internal layers.

However, the power of the lasers turned out to be insufficient for a noticeable portion of the fuel to react. In addition, the efficiency of the lasers was very low, only about 1%. For fusion to be energetically beneficial at such a low laser efficiency, almost all of the compressed fuel had to react. When trying to replace lasers with beams of light or heavy ions, which can be generated with much greater efficiency, scientists also encountered a lot of problems: light ions repel each other, which prevents them from focusing, and are slowed down when colliding with residual gas in the chamber, and accelerators It was not possible to create heavy ions with the required parameters.

Magnetic prospects

Most of the hope in the field of fusion energy now lies in tokamaks. Especially after they opened a mode with improved retention. A tokamak is both a Z-pinch rolled into a ring (a ring electric current flows through the plasma, creating a magnetic field necessary to contain it), and a sequence of mirror cells assembled into a ring and creating a “corrugated” toroidal magnetic field. In addition, a field perpendicular to the torus plane, created by several individual coils, is superimposed on the toroidal field of the coils and the plasma current field. This additional field, called poloidal, strengthens the magnetic field of the plasma current (also poloidal) on the outside of the torus and weakens it on the inside. Thus, the total magnetic field on all sides of the plasma rope turns out to be the same, and its position remains stable. By changing this additional field, it is possible to move the plasma bundle inside the vacuum chamber within certain limits.

A fundamentally different approach to synthesis is proposed by the concept of muon catalysis. A muon is an unstable elementary particle that has the same charge as an electron, but 207 times more mass. A muon can replace an electron in a hydrogen atom, and the size of the atom decreases by a factor of 207. This allows one hydrogen nucleus to move closer to another without expending energy. But to produce one muon, about 10 GeV of energy is spent, which means that it is necessary to perform several thousand fusion reactions per muon to obtain energy benefits. Due to the possibility of a muon “sticking” to the helium formed in the reaction, more than several hundred reactions have not yet been achieved. The photo shows the assembly of the Wendelstein z-x stellarator at the Max Planck Institute for Plasma Physics.

An important problem of tokamaks for a long time was the need to create a ring current in the plasma. To do this, a magnetic circuit was passed through the central hole of the tokamak torus, the magnetic flux in which was continuously changed. The change in magnetic flux generates a vortex electric field, which ionizes the gas in the vacuum chamber and maintains current in the resulting plasma. However, the current in the plasma must be maintained continuously, which means that the magnetic flux must continuously change in one direction. This, of course, is impossible, so the current in tokamaks could only be maintained for a limited time (from a fraction of a second to several seconds). Fortunately, the so-called bootstrap current was discovered, which occurs in a plasma without an external vortex field. In addition, methods have been developed to heat the plasma, simultaneously inducing the necessary ring current in it. Together, this provided the potential for maintaining hot plasma for as long as desired. In practice, the record currently belongs to the Tore Supra tokamak, where the plasma continuously “burned” for more than six minutes.

The second type of plasma confinement installation, which has great promise, is stellarators. Over the past decades, the design of stellarators has changed dramatically. Almost nothing remained of the original “eight”, and these installations became much closer to tokamaks. Although the confinement time of stellarators is shorter than that of tokamaks (due to the less efficient H-mode), and the cost of their construction is higher, the behavior of the plasma in them is calmer, which means a longer life of the first inner wall of the vacuum chamber. For the commercial development of thermonuclear fusion, this factor is of great importance.

Selecting a reaction

At first glance, it is most logical to use pure deuterium as a thermonuclear fuel: it is relatively cheap and safe. However, deuterium reacts with deuterium a hundred times less readily than with tritium. This means that to operate a reactor on a mixture of deuterium and tritium, a temperature of 10 keV is sufficient, and to operate on pure deuterium, a temperature of more than 50 keV is required. And the higher the temperature, the higher the energy loss. Therefore, at least for the first time, it is planned to build thermonuclear energy using deuterium-tritium fuel. Tritium will be produced in the reactor itself due to irradiation with the fast lithium neutrons produced in it.
"Wrong" neutrons. In the cult film “9 Days of One Year,” the main character, while working at a thermonuclear installation, received a serious dose of neutron radiation. However, it later turned out that these neutrons were not produced as a result of a fusion reaction. This is not the director’s invention, but a real effect observed in Z-pinches. At the moment of interruption of the electric current, the inductance of the plasma leads to the generation of a huge voltage - millions of volts. Individual hydrogen ions, accelerated in this field, are capable of literally knocking neutrons out of the electrodes. At first, this phenomenon was indeed taken as a sure sign of a thermonuclear reaction, but subsequent analysis of the neutron energy spectrum showed that they had a different origin.
Improved retention mode. The H-mode of a tokamak is a mode of its operation when, with a high power of additional heating, plasma energy losses sharply decrease. The accidental discovery of the enhanced confinement mode in 1982 is as significant as the invention of the tokamak itself. There is no generally accepted theory of this phenomenon yet, but this does not prevent it from being used in practice. All modern tokamaks operate in this mode, as it reduces losses by more than half. Subsequently, a similar regime was discovered in stellarators, indicating that this is a general property of toroidal systems, but confinement is only improved by about 30% in them.
Plasma heating. There are three main methods of heating plasma to thermonuclear temperatures. Ohmic heating is the heating of plasma due to the flow of electric current through it. This method is most effective in the first stages, since as the temperature increases, the electrical resistance of the plasma decreases. Electromagnetic heating uses electromagnetic waves with a frequency that matches the frequency of rotation around the magnetic field lines of electrons or ions. By injecting fast neutral atoms, a stream of negative ions is created, which are then neutralized, turning into neutral atoms that can pass through the magnetic field to the center of the plasma to transfer their energy there.
Are these reactors? Tritium is radioactive, and powerful neutron radiation from the D-T reaction creates induced radioactivity in the reactor design elements. We have to use robots, which complicates the work. At the same time, the behavior of a plasma of ordinary hydrogen or deuterium is very close to the behavior of a plasma from a mixture of deuterium and tritium. This led to the fact that throughout history, only two thermonuclear installations fully operated on a mixture of deuterium and tritium: the TFTR and JET tokamaks. At other installations, even deuterium is not always used. So the name “thermonuclear” in the definition of a facility does not mean at all that thermonuclear reactions have ever actually occurred in it (and in those that do occur, pure deuterium is almost always used).
Hybrid reactor. The D-T reaction produces 14 MeV neutrons, which can even fission depleted uranium. The fission of one uranium nucleus is accompanied by the release of approximately 200 MeV of energy, which is more than ten times the energy released during fusion. So existing tokamaks could become energetically beneficial if they were surrounded by a uranium shell. Compared to fission reactors, such hybrid reactors would have the advantage of preventing an uncontrolled chain reaction from developing in them. In addition, extremely intense neutron fluxes should convert long-lived uranium fission products into short-lived ones, which significantly reduces the problem of waste disposal.

Inertial hopes

Inertial fusion is also not standing still. Over the decades of development of laser technology, prospects have emerged to increase the efficiency of lasers by approximately ten times. And in practice, their power has been increased hundreds and thousands of times. Work is also underway on heavy ion accelerators with parameters suitable for thermonuclear use. In addition, the concept of “fast ignition” has been a critical factor in the progress of inertial fusion. It involves the use of two pulses: one compresses the thermonuclear fuel, and the other heats up a small part of it. It is assumed that the reaction that begins in a small part of the fuel will subsequently spread further and cover the entire fuel. This approach can significantly reduce energy costs, and therefore make the reaction profitable with a smaller fraction of reacted fuel.

Tokamak problems

Despite the progress of installations of other types, tokamaks at the moment still remain out of competition: if two tokamaks (TFTR and JET) back in the 1990s actually produced a release of thermonuclear energy approximately equal to the energy consumption for heating the plasma (even though such a mode lasted only about a second), then nothing similar could be achieved with other types of installations. Even a simple increase in the size of tokamaks will lead to the feasibility of energetically favorable fusion in them. The international reactor ITER is currently being built in France, which will have to demonstrate this in practice.

However, tokamaks also have problems. ITER costs billions of dollars, which is unacceptable for future commercial reactors. No reactor has operated continuously for even a few hours, let alone for weeks and months, which again is necessary for industrial applications. There is no certainty yet that the materials of the inner wall of the vacuum chamber will be able to withstand prolonged exposure to plasma.

The concept of a tokamak with a strong field can make the project less expensive. By increasing the field by two to three times, it is planned to obtain the required plasma parameters in a relatively small installation. This concept, in particular, is the basis for the Ignitor reactor, which, together with Italian colleagues, is now beginning to be built at TRINIT (Trinity Institute for Innovation and Thermonuclear Research) near Moscow. If the engineers’ calculations come true, then at a cost many times lower than ITER, it will be possible to ignite plasma in this reactor.

Forward to the stars!

The products of a thermonuclear reaction fly away in different directions at speeds of thousands of kilometers per second. This makes it possible to create ultra-efficient rocket engines. Their specific impulse will be higher than that of the best electric jet engines, and their energy consumption may even be negative (theoretically, it is possible to generate, rather than consume, energy). Moreover, there is every reason to believe that making a thermonuclear rocket engine will be even easier than a ground-based reactor: there is no problem with creating a vacuum, with thermal insulation of superconducting magnets, there are no restrictions on dimensions, etc. In addition, the generation of electricity by the engine is desirable, but It’s not at all necessary, it’s enough that he doesn’t consume too much of it.

Electrostatic confinement

The concept of electrostatic ion confinement is most easily understood through a setup called a fusor. It is based on a spherical mesh electrode, to which a negative potential is applied. Ions accelerated in a separate accelerator or by the field of the central electrode itself fall inside it and are held there by an electrostatic field: if an ion tends to fly out, the electrode field turns it back. Unfortunately, the probability of an ion colliding with a network is many orders of magnitude higher than the probability of entering into a fusion reaction, which makes an energetically favorable reaction impossible. Such installations have found application only as neutron sources.
In an effort to make a sensational discovery, many scientists strive to see synthesis wherever possible. There have been numerous reports in the press regarding various options for so-called “cold fusion.” Synthesis was discovered in metals “impregnated” with deuterium when an electric current flows through them, during the electrolysis of deuterium-saturated liquids, during the formation of cavitation bubbles in them, as well as in other cases. However, most of these experiments have not had satisfactory reproducibility in other laboratories, and their results can almost always be explained without the use of synthesis.
Continuing the “glorious tradition” that began with the “philosopher’s stone” and then turned into a “perpetual motion machine”, many modern scammers are offering to buy from them a “cold fusion generator”, “cavitation reactor” and other “fuel-free generators”: about the philosophical Everyone has already forgotten the stone, they don’t believe in perpetual motion, but nuclear fusion now sounds quite convincing. But, alas, in reality such energy sources do not exist yet (and when they can be created, it will be in all news releases). So be aware: if you are offered to buy a device that generates energy through cold nuclear fusion, then they are simply trying to “cheat” you!

According to preliminary estimates, even with the current level of technology, it is possible to create a thermonuclear rocket engine for flight to the planets of the Solar System (with appropriate funding). Mastering the technology of such engines will increase the speed of manned flights tenfold and will make it possible to have large reserve fuel reserves on board, which will make flying to Mars no more difficult than working on the ISS now. Speeds of 10% of the speed of light will potentially become available for automatic stations, which means it will be possible to send research probes to nearby stars and obtain scientific data during the lifetime of their creators.

The concept of a thermonuclear rocket engine based on inertial fusion is currently considered the most developed. The difference between an engine and a reactor lies in the magnetic field, which directs the charged reaction products in one direction. The second option involves using an open trap, in which one of the plugs is deliberately weakened. The plasma flowing from it will create a reactive force.

Thermonuclear future

Mastering thermonuclear fusion turned out to be many orders of magnitude more difficult than it seemed at first. And although many problems have already been solved, the remaining ones will be enough for the next few decades of hard work of thousands of scientists and engineers. But the prospects that the transformations of hydrogen and helium isotopes open up for us are so great, and the path taken is already so significant that it makes no sense to stop halfway. No matter what numerous skeptics say, the future undoubtedly lies in synthesis.

ITER - International Thermonuclear Reactor (ITER)

Human energy consumption is growing every year, which pushes the energy sector towards active development. Thus, with the emergence of nuclear power plants, the amount of energy generated around the world increased significantly, which made it possible to safely use energy for all the needs of mankind. For example, 72.3% of the electricity generated in France comes from nuclear power plants, in Ukraine - 52.3%, in Sweden - 40.0%, in the UK - 20.4%, in Russia - 17.1%. However, technology does not stand still, and in order to meet the further energy needs of future countries, scientists are working on a number of innovative projects, one of which is ITER (International Thermonuclear Experimental Reactor).

Although the profitability of this installation is still in question, according to the work of many researchers, the creation and subsequent development of controlled thermonuclear fusion technology can result in a powerful and safe source of energy. Let's look at some of the positive aspects of such an installation:

• The main fuel of a thermonuclear reactor is hydrogen, which means practically inexhaustible reserves of nuclear fuel.
• Hydrogen can be produced by processing seawater, which is available to most countries. It follows from this that a monopoly of fuel resources cannot arise.
• The probability of an emergency explosion during the operation of a thermonuclear reactor is much less than during the operation of a nuclear reactor. According to researchers, even in the event of an accident, radiation emissions will not pose a danger to the population, which means there is no need for evacuation.
• Unlike nuclear reactors, fusion reactors produce radioactive waste that has a short half-life, meaning it decays faster. Also, there are no combustion products in thermonuclear reactors.
• A fusion reactor does not require materials that are also used for nuclear weapons. This eliminates the possibility of covering up the production of nuclear weapons by processing materials for the needs of a nuclear reactor.

Thermonuclear reactor - inside view

However, there are also a number of technical shortcomings that researchers constantly encounter.

For example, the current version of the fuel, presented in the form of a mixture of deuterium and tritium, requires the development of new technologies. For example, at the end of the first series of tests at the JET thermonuclear reactor, the largest to date, the reactor became so radioactive that the development of a special robotic maintenance system was further required to complete the experiment. Another disappointing factor in the operation of a thermonuclear reactor is its efficiency - 20%, while the efficiency of a nuclear power plant is 33-34%, and a thermal power plant is 40%.

Creation of the ITER project and launch of the reactor

The ITER project dates back to 1985, when the Soviet Union proposed the joint creation of a tokamak - a toroidal chamber with magnetic coils that can hold plasma using magnets, thereby creating the conditions required for a thermonuclear fusion reaction to occur. In 1992, a quadripartite agreement on the development of ITER was signed, the parties to which were the EU, the USA, Russia and Japan. In 1994, the Republic of Kazakhstan joined the project, in 2001 - Canada, in 2003 - South Korea and China, in 2005 - India. In 2005, the location for the construction of the reactor was determined - the Cadarache Nuclear Energy Research Center, France.

Construction of the reactor began with the preparation of a pit for the foundation. So the parameters of the pit were 130 x 90 x 17 meters. The entire tokamak complex will weigh 360,000 tons, of which 23,000 tons are the tokamak itself.

Various elements of the ITER complex will be developed and delivered to the construction site from all over the world. So in 2016, part of the conductors for poloidal coils was developed in Russia, which were then sent to China, which will produce the coils themselves.

Obviously, such a large-scale work is not at all easy to organize; a number of countries have repeatedly failed to keep up with the project schedule, as a result of which the launch of the reactor was constantly postponed. So, according to last year’s (2016) June message: “receipt of the first plasma is planned for December 2025.”

The operating mechanism of the ITER tokamak

The term "tokamak" comes from a Russian acronym that means "toroidal chamber with magnetic coils."

The heart of a tokamak is its torus-shaped vacuum chamber. Inside, under extreme temperature and pressure, the hydrogen fuel gas becomes plasma—a hot, electrically charged gas. As is known, stellar matter is represented by plasma, and thermonuclear reactions in the solar core occur precisely under conditions of elevated temperature and pressure. Similar conditions for the formation, retention, compression and heating of plasma are created by means of massive magnetic coils that are located around a vacuum vessel. The influence of magnets will limit the hot plasma from the walls of the vessel.

Before the process begins, air and impurities are removed from the vacuum chamber. Magnetic systems that will help control the plasma are then charged and gaseous fuel is introduced. When a powerful electric current is passed through the vessel, the gas is electrically split and becomes ionized (that is, electrons leave the atoms) and forms a plasma.

As the plasma particles are activated and collide, they also begin to heat up. Assisted heating techniques help bring the plasma to melting temperatures (150 to 300 million °C). Particles "excited" to this degree can overcome their natural electromagnetic repulsion upon collision, releasing enormous amounts of energy as a result of such collisions.

The tokamak design consists of the following elements:

Vacuum vessel

(“donut”) is a toroidal chamber made of stainless steel. Its large diameter is 19 m, the small one is 6 m, and its height is 11 m. The volume of the chamber is 1,400 m 3, and its weight is more than 5,000 tons. The walls of the vacuum vessel are double; a coolant will circulate between the walls, which will be distilled water. water. To avoid water contamination, the inner wall of the chamber is protected from radioactive radiation using a blanket.

Blanket

(“blanket”) – consists of 440 fragments covering the inner surface of the chamber. The total banquet area is 700m2. Each fragment is a kind of cassette, the body of which is made of copper, and the front wall is removable and made of beryllium. The parameters of the cassettes are 1x1.5 m, and the mass is no more than 4.6 tons. Such beryllium cassettes will slow down high-energy neutrons formed during the reaction. During neutron moderation, heat will be released and removed by the cooling system. It should be noted that beryllium dust formed as a result of reactor operation can cause a serious disease called beryllium and also has a carcinogenic effect. For this reason, strict security measures are being developed at the complex.

Tokamak in section. Yellow - solenoid, orange - toroidal field (TF) and poloidal field (PF) magnets, blue - blanket, light blue - VV - vacuum vessel, purple - divertor

(“ashtray”) of the poloidal type is a device whose main task is to “cleanse” the plasma of dirt resulting from the heating and interaction of the blanket-covered chamber walls with it. When such contaminants enter the plasma, they begin to radiate intensely, resulting in additional radiation losses. It is located at the bottom of the tokomak and uses magnets to direct the upper layers of plasma (which are the most contaminated) into the cooling chamber. Here the plasma cools and turns into gas, after which it is pumped back out of the chamber. Beryllium dust, after entering the chamber, is practically unable to return back to the plasma. Thus, plasma contamination remains only on the surface and does not penetrate deeper.

Cryostat

- the largest component of the tokomak, which is a stainless steel shell with a volume of 16,000 m 2 (29.3 x 28.6 m) and a mass of 3,850 tons. Other elements of the system will be located inside the cryostat, and it itself serves as a barrier between the tokamak and the outside environment. On its inner walls there will be thermal screens cooled by circulating nitrogen at a temperature of 80 K (-193.15 °C).

Magnetic system

– a set of elements that serve to contain and control plasma inside a vacuum vessel. It is a set of 48 elements:

• Toroidal field coils are located outside the vacuum chamber and inside the cryostat. They are presented in 18 pieces, each measuring 15 x 9 m and weighing approximately 300 tons. Together, these coils generate a magnetic field of 11.8 Tesla around the plasma torus and store energy of 41 GJ.
• Poloidal field coils – located on top of the toroidal field coils and inside the cryostat. These coils are responsible for generating a magnetic field that separates the plasma mass from the walls of the chamber and compresses the plasma for adiabatic heating. The number of such coils is 6. Two of the coils have a diameter of 24 m and a mass of 400 tons. The remaining four are somewhat smaller.
• The central solenoid is located in the inner part of the toroidal chamber, or rather in the “donut hole”. The principle of its operation is similar to a transformer, and the main task is to excite an inductive current in the plasma.
• Correction coils are located inside the vacuum vessel, between the blanket and the chamber wall. Their task is to maintain the shape of the plasma, capable of locally “bulging” and even touching the walls of the vessel. Allows you to reduce the level of interaction of the chamber walls with the plasma, and therefore the level of its contamination, and also reduces the wear of the chamber itself.

Structure of the ITER complex

The tokamak design described above “in a nutshell” is a highly complex innovative mechanism assembled through the efforts of several countries. However, for its full operation, a whole complex of buildings located near the tokamak is required. Among them:

• Control, Data Access and Communication System – CODAC. Located in a number of buildings of the ITER complex.
• Fuel storage and fuel system - serves to deliver fuel to the tokamak.
• Vacuum system - consists of more than four hundred vacuum pumps, the task of which is to pump out thermonuclear reaction products, as well as various contaminants from the vacuum chamber.
• Cryogenic system – represented by a nitrogen and helium circuit. The helium circuit will normalize the temperature in the tokamak, the work (and therefore the temperature) of which does not occur continuously, but in pulses. The nitrogen circuit will cool the cryostat's heat shields and the helium circuit itself. There will also be a water cooling system, which is aimed at lowering the temperature of the blanket walls.
• Power supply. The tokamak will require approximately 110 MW of energy to operate continuously. To achieve this, kilometer-long power lines will be installed and connected to the French industrial network. It is worth recalling that the ITER experimental facility does not provide for energy production, but works only in scientific interests.

ITER funding

The international thermonuclear reactor ITER is a fairly expensive undertaking, which was initially estimated at $12 billion, with Russia, the USA, Korea, China and India accounting for 1/11 of the amount, Japan for 2/11, and the EU for 4/11 . This amount later increased to $15 billion. It is noteworthy that financing occurs through the supply of equipment required for the complex, which is developed in each country. Thus, Russia supplies blankets, plasma heating devices and superconducting magnets.

Project perspective

At the moment, the construction of the ITER complex and the production of all the required components for the tokamak are underway. After the planned launch of the tokamak in 2025, a series of experiments will begin, based on the results of which aspects that require improvement will be noted. After the successful commissioning of ITER, it is planned to build a power plant based on thermonuclear fusion called DEMO (DEMOnstration Power Plant). DEMo's goal is to demonstrate the so-called "commercial appeal" of fusion power. If ITER is capable of generating only 500 MW of energy, then DEMO will be able to continuously generate energy of 2 GW.

However, it should be borne in mind that the ITER experimental facility will not produce energy, and its purpose is to obtain purely scientific benefits. And as you know, this or that physical experiment can not only meet expectations, but also bring new knowledge and experience to humanity.

Lockheed Martin management announced that in February 2018 it received a patent for a compact fusion reactor. Experts call this impossible, although according to The War Zone, “it is possible that the American corporation will make an official statement in the near future.”

FlightGlobal reporter Stephen Trimble tweeted that “a new patent from a Skunk Works engineer shows a compact fusion reactor design with a blueprint for the F-16 as a potential application. A prototype reactor is being tested in Palmdale.”

According to the publication, "The fact that Skunk Works has remained involved in the patent process over the past four years also seems to indicate that they have indeed made progress with the program, at least to some extent." The authors of the material note that four years ago, the project developers released basic information about the basic design of the reactor, the project schedule and the overall goals of the program, which indicates serious work.

Let us recall that Lockheed Martin filed a provisional patent application for “Encapsulating magnetic fields for plasma confinement” on April 4, 2013. At the same time, the official application to the US Patent and Trademark Office was received on April 2, 2014.

Lockheed Martin said the patent was received on February 15, 2018. At one time, Compact Fusion project manager Thomas McGuire said that a pilot plant would be created in 2014, a prototype in 2019, and a working prototype in 2024.

The company reports on its website that the thermonuclear reactor, which its specialists are working on, can be used to provide energy to an aircraft carrier, fighter jet or small city.

In October 2014, the corporation said that preliminary research results indicate the possibility of creating light nuclear fusion reactors with a power of about 100 megawatts and dimensions comparable to a truck (which is about ten times smaller than existing models). In essence, we are talking about an application for the discovery of the century - a radiation-safe reactor capable of providing energy to anything.

For their part, Russian scientists involved in research in the field of controlled thermonuclear fusion called the Lockheed Martin message an unscientific statement aimed at attracting the attention of the general public. However, a photo of a compact thermonuclear reactor, supposedly being created by the American corporation Lockheed Martin, appeared on Twitter.

“This can't happen. The fact is that what is meant by a thermonuclear reactor is very well known from a physical point of view. If it sounds “helium 3? - You must immediately understand that this is a deception. This is a characteristic feature of such quasi-discoveries - where there is one line “how to do it, how to implement it” and ten pages about how it will be good afterwards. This is a very characteristic sign - here, we invented cold thermonuclear fusion, and then they don’t say how to implement it, and then only ten pages later, how great it will be,” Deputy Director of the Laboratory of Nuclear Reactions told Pravda.ru. Flerov JINR in Dubna Andrey Papeko.

“The main question is how to excite a thermonuclear reaction, what to heat it with, what to hold it with - this is also, in general, a question that has not been resolved now. And even, say, laser thermonuclear installations, a normal thermonuclear reaction does not ignite there. And, alas, there is no solution in sight in the foreseeable future,” explained the nuclear physicist.

“Russia is conducting quite a lot of research, this is understandable, it has been published in the entire open press, that is, it is necessary to study the conditions for heating materials for a thermonuclear reaction. In general, this is a mixture with deuterium - there is no science fiction, this physics is all very well known. How to heat it, how to hold it, how to remove energy, if you ignite a very hot plasma, it will eat the walls of the reactor, it will melt them. In large installations, magnetic fields can be used to hold and focus it in the center of the chamber so that it does not melt the walls of the reactor. But in small installations it simply won’t work, it will melt and burn. That is, these, in my opinion, are very premature statements,” he concluded.

“Lockheed Martin has begun developing a compact thermonuclear reactor... The company’s website says that the first prototype will be built within a year. If this turns out to be true, in a year we will live in a completely different world,” this is the beginning of one of “The Attic.” Three years have passed since its publication, and the world has not changed that much since then.

Today, in nuclear power plant reactors, energy is generated by the decay of heavy nuclei. In thermonuclear reactors, energy is obtained during the process of fusion of nuclei, during which nuclei of less mass than the sum of the original ones are formed, and the “residue” is lost in the form of energy. Waste from nuclear reactors is radioactive, and its safe disposal is a big headache. Fusion reactors do not have this drawback, and also use widely available fuel such as hydrogen.

They have only one big problem - industrial designs don't exist yet. The task is not easy: for thermonuclear reactions, the fuel must be compressed and heated to hundreds of millions of degrees - hotter than on the surface of the Sun (where thermonuclear reactions occur naturally). It is difficult to achieve such a high temperature, but it is possible, but such a reactor consumes more energy than it produces.

However, they still have so many potential advantages that, of course, not only Lockheed Martin is involved in development.

ITER

ITER is the largest project in this area. It involves the European Union, India, China, Korea, Russia, the USA and Japan, and the reactor itself has been built on French territory since 2007, although its history goes much deeper into the past: Reagan and Gorbachev agreed on its creation in 1985. The reactor is a toroidal chamber, a “donut”, in which the plasma is held by magnetic fields, which is why it is called a tokamak - That roidal ka measure with ma rotten To atushki. The reactor will generate energy through the fusion of hydrogen isotopes - deuterium and tritium.

It is planned that ITER will receive 10 times more energy than it consumes, but this will not happen soon. It was initially planned that the reactor would begin operating in experimental mode in 2020, but then this date was postponed to 2025. At the same time, industrial energy production will begin no earlier than 2060, and we can only expect the spread of this technology somewhere at the end of the 21st century.

Wendelstein 7-X

Wendelstein 7-X is the largest stellarator-type fusion reactor. The stellarator solves the problem that plagues tokamaks - the “spreading” of plasma from the center of the torus to its walls. What the tokamak tries to cope with due to the power of the magnetic field, the stellarator solves due to its complex shape: the magnetic field holding the plasma bends to stop the advances of charged particles.

Wendelstein 7-X, as its creators hope, will be able to operate for half an hour in 21, which will give a “ticket to life” to the idea of ​​thermonuclear stations of a similar design.

National Ignition Facility

Another type of reactor uses powerful lasers to compress and heat fuel. Alas, the largest laser installation for producing thermonuclear energy, the American NIF, was unable to produce more energy than it consumes.

It is difficult to predict which of all these projects will really take off and which will suffer the same fate as NIF. All we can do is wait, hope and follow the news: the 2020s promise to be an interesting time for nuclear energy.

“Nuclear Technologies” is one of the profiles of the NTI Olympiad for schoolchildren.