Sivkova Olga Dmitrievna

This work took 3rd place at the regional NOU

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Municipal educational institution

Secondary school № 175

Leninsky district of N. Novgorod

Problems of thermonuclear fusion

Completed by: Sivkova Olga Dmitrievna

Pupil 11 "A" class, school №175

Supervisor:

Kirzhaeva D.G.

Nizhny Novgorod

year 2013.

Introduction 3

2. Controlled thermonuclear fusion 8

3. Advantages of thermonuclear fusion 10

4. Problems of thermonuclear fusion 12

4.1 Environmental issues 15

4.2 Medical problems 16

5. Fusion installations 18

6. Prospects for the development of thermonuclear fusion 23

Conclusion 26

Literature 27

Introduction

According to various forecasts, the main sources of electricity on the planet will end in 50-100 years. Mankind will run out of oil reserves in 40 years, gas - in a maximum of 80, and uranium - in 80-100 years. Coal reserves may last for 400 years. But the use of this fossil fuel, moreover, as the main one, puts the planet on the brink of an ecological catastrophe. If today such merciless pollution of the atmosphere is not stopped, there can be no talk of any centuries. This means that we need an alternative source of energy in the foreseeable future.

And there is such a source. This is thermonuclear power engineering, which uses absolutely non-radioactive deuterium and radioactive tritium, but in volumes that are thousands of times smaller than in nuclear power. And this source is practically inexhaustible, it is based on the collision of hydrogen nuclei, and hydrogen is the most widespread substance in the Universe.

One of the most important tasks facing humanity in this area isthe problem of controlled thermonuclear fusion.

Human civilization cannot exist, much less develop, without energy. Everyone understands well that the mastered energy sources, unfortunately, may soon be exhausted. According to the World Energy Council, the proven reserves of hydrocarbon fuels on Earth remain for 30 years.

Today the main sources of energy are oil, gas and coal.

According to experts, the reserves of these minerals are running out. There are almost no explored and exploitable oil fields left, and our grandchildren may already face a very serious problem of energy shortages.

The most fuel-provided nuclear power plants could, of course, supply mankind with electricity for more than one hundred years.

Object of study:Problems controlled thermonuclear fusion.

Subject of study:Thermonuclear fusion.

Purpose of the study:Solve the problem of thermonuclear fusion control;

Research objectives:

• Study the types of thermonuclear reactions.
• Consider all possible options for delivering the energy released during a thermonuclear reaction to a person.
• Put forward the theory of converting energy into electricity.

Initial fact:

Nuclear energy is released during the decay or fusion of atomic nuclei. Any energy - physical, chemical, or nuclear - is manifested by its ability to perform work, emit heat or radiation. Energy in any system is always conserved, but it can be transferred to another system or changed in form.

Achievement the conditions of controlled thermonuclear fusion are hampered by several main problems:

• First, you need to heat the gas to a very high temperature.
• Secondly, it is necessary to control the number of reacting nuclei for a sufficiently long time.
• Third, the amount of energy released must be greater than was expended to heat and limit the density of the gas.
• The next problem is storing this energy and converting it into electricity.

1. Thermonuclear reactions in the Sun

What is the source of solar energy? What is the nature of the processes that generate enormous amounts of energy? How long will the sun still shine?

The first attempts to answer these questions were made by astronomers in the middle of the 19th century, after physicists formulated the law of conservation of energy.

Robert Meyer suggested that the sun shines by constantly bombarding the surface with meteorites and meteoric particles. This hypothesis was rejected, since a simple calculation shows that in order to maintain the luminosity of the Sun at the current level, it is necessary that 2 ∙ 1015 kg of meteoric matter. This will amount to 6 ∙ 10 per year.22 kg, and during the existence of the Sun, for 5 billion years - 3 ∙ 1032 kg. Mass of the Sun M = 2∙10 30 kg, therefore, for five billion years on the Sun, matter should have fallen 150 times the mass of the Sun.

The second hypothesis was put forward by Helmholtz and Kelvin also in the middle of the 19th century. They hypothesized that the sun radiates by compressing 60–70 meters annually. The reason for the compression is the mutual attraction of the Sun's particles, which is why this hypothesis was calledcontraction ... If we make a calculation according to this hypothesis, then the age of the Sun will be no more than 20 million years, which contradicts modern data obtained from the analysis of the radioactive decay of elements in geological samples of the earth's soil and the soil of the Moon.

The third hypothesis about possible sources of solar energy was expressed by James Jeans at the beginning of the 20th century. He suggested that the depths of the sun contain heavy radioactive elements that spontaneously decay, while energy is emitted. For example, the conversion of uranium to thorium and then to lead is accompanied by the release of energy. Subsequent analysis of this hypothesis also showed its inconsistency; a star made of uranium alone would not emit enough energy to provide the Sun's apparent luminosity. In addition, there are stars whose luminosity is many times greater than the luminosity of our star. It is unlikely that those stars will also contain more radioactive material.

The most likely hypothesis was the hypothesis of the synthesis of elements as a result of nuclear reactions in the interiors of stars.

In 1935, Hans Bethe hypothesized that the source of solar energy could be a thermonuclear reaction that converts hydrogen into helium. It is for this that Bethe received the Nobel Prize in 1967.

The chemical composition of the Sun is about the same as that of most other stars. About 75% is hydrogen, 25% is helium and less than 1% is all other chemical elements (mainly carbon, oxygen, nitrogen, etc.). Immediately after the birth of the Universe, there were no "heavy" elements at all. All of them, i.e. elements heavier than helium and even many alpha particles were formed during the "combustion" of hydrogen in stars during thermonuclear fusion. The characteristic lifetime of a star like the Sun is ten billion years.

The main source of energy isproton-proton cycle - very slow reaction (characteristic time 7.9 ∙ 109 years), since it is due to weak interaction. Its essence lies in the fact that four protons produce a helium nucleus. In this case, a pair of positrons and a pair of neutrinos are released, as well as 26.7 MeV energy. The number of neutrinos emitted by the Sun per second is determined only by the luminosity of the Sun. Since the release of 26.7 MeV produces 2 neutrinos, the rate of neutrino emission is 1.8 ∙ 1038 neutrino / s. A direct test of this theory is the observation of solar neutrinos. High-energy neutrinos (boron) are recorded in chlorine-argon experiments (Davis experiments) and consistently show a lack of neutrinos in comparison with the theoretical value for the standard model of the Sun. Low-energy neutrinos arising directly in the pp-reaction are recorded in gallium-germanium experiments (GALLEX at Gran Sasso (Italy - Germany) and SAGE at Baksan (Russia - USA)); they are also "missing".

According to some assumptions, if neutrinos have a nonzero rest mass, oscillations (transformations) of various types of neutrinos (the Mikheev - Smirnov - Wolfenstein effect) are possible (there are three types of neutrinos: electron, muon and tauon neutrinos). Because other neutrinos have much smaller cross sections for interaction with matter than electron neutrinos, the observed deficit can be explained without changing the standard model of the sun, built on the basis of the entire set of astronomical data.

The Sun processes about 600 million tons of hydrogen every second. The reserves of nuclear fuel will last for another five billion years, after which it will gradually turn into a white dwarf.

The central parts of the Sun will shrink, warming up, and the heat transferred with this outer shell will lead to its expansion to a size monstrous in comparison with modern ones: the Sun will expand so much that it will swallow Mercury, Venus and spend "fuel" a hundred times faster, than currently. This will increase the size of the sun; our star will become a red giant, the size of which is comparable to the distance from the Earth to the Sun!

We, of course, will be notified in advance of such an event, since the transition to a new stage will take approximately 100-200 million years. When the temperature of the central part of the Sun reaches 100,000,000 K, helium will begin to burn, turning into heavy elements, and the Sun will enter the stage of complex cycles of contraction and expansion. At the last stage, our star will lose its outer shell, the central core will have an incredibly high density and size, like that of the Earth. A few more billion years will pass, and the Sun will cool down, turning into a white dwarf.

2. Controlled thermonuclear fusion.

Controlled thermonuclear fusion (CTF) is the synthesis of heavier atomic nuclei from lighter ones in order to obtain energy, which, unlike explosive thermonuclear fusion (used in thermonuclear weapons) is manageable. Controlled thermonuclear fusion differs from traditional nuclear energy in that the latter uses a decay reaction, during which lighter nuclei are obtained from heavy nuclei. Deuterium will be used in the main nuclear reactions that are planned to be used in order to carry out controlled thermonuclear fusion (2 H) and tritium (3 H), and in the more distant future, helium-3 (3 He) and boron-11 (11 B).

Controlled thermonuclear fusion can use different types of thermonuclear reactions, depending on the type of fuel used.

Thermonuclear fuel includes deuterium.2 D 1, tritium 3 T 1 and 6 Li 3 ... The primary nuclear fuel of this type is deuterium.6 Li 3 serves as a raw material for the production of secondary thermonuclear fuel -tritium.

Tritium 3 T 1 - superheavy hydrogen3 H 1 - obtained by irradiation of natural Li (7.52% 6 Li 3 ) neutrons and alpha particles (4 α 2 - helium nuclei4 not 2 ). Deuterium mixed with tritium is used as a thermonuclear fuel.6 Li 3 (in the form of LiD and LiТ ). During the implementation of nuclear fusion reactions in fuel, reactions of fusion of helium nuclei occur (at temperatures of tens to hundreds of millions of degrees). Emitted neutrons are absorbed by nuclei6 Li 3 , while an additional amount of tritium is formed by the reaction:6 Li 3 + 1 p 0 \u003d 3 T 1 + 4 He 2 ( in the reaction the sum of the mass numbers 6 + 1 \u003d 3 + 4 and the sum of charges 3 + 0 \u003d 1 + 2 should be the same on both sides of the equation). Two deuterium nuclei (heavy hydrogen) give as a result of the fusion reaction one tritium nucleus (superheavy hydrogen) and a proton (the nucleus of a normal hydrogen atom): 2 D 1 + 2 D 1 \u003d 3 T 1 + 1 P 1; The reaction can go in a different way, with the formation of a helium isotope nucleus3 He 2 and neutron 1 n 0: 2 D 1 + 2 D 1 \u003d 3 He 2 + 1 n 0. Tritium reacts with deuterium, neutrons reappear that can interact with6 Li 3: 2 D 1 + 3 T 1 \u003d 4 He 2 + 1 n 0 etc. The calorific value of thermonuclear fuel is 5-6 times higher than that of fissile materials. Deuterium reserves in the hydrosphere are about10 13 t ... However, at present, only uncontrolled reactions (explosion) are practically carried out, and the search for methods of carrying out a controlled thermonuclear reaction is being carried out, which, in principle, makes it possible to provide humanity with energy for an almost unlimited period.

3.Advantages of fusion

What are the advantages of thermonuclear fusion over nuclear fission reactions, which make it possible to hope for a large-scale development of thermonuclear energy? The main and fundamental difference is the absence of long-lived radioactive waste, which is characteristic of nuclear fission reactors. And although during the operation of a thermonuclear reactor the first wall is activated by neutrons, the choice of suitable low-activated structural materials opens up the fundamental possibility of creating a thermonuclear reactor in which the induced activity of the first wall will decrease to a completely safe level within thirty years after the reactor is shut down. This means that an exhausted reactor will need to be mothballed for only 30 years, after which the materials can be recycled and used in a new synthesis reactor. This situation is fundamentally different from fission reactors, which generate radioactive waste that require processing and storage for tens of thousands of years. In addition to low radioactivity, thermonuclear power engineering has huge, practically inexhaustible reserves of fuel and other necessary materials, sufficient to produce energy for many hundreds, if not thousands of years.

It was these advantages that prompted the main nuclear countries to begin large-scale research on controlled thermonuclear fusion in the mid-1950s. The first successful tests of hydrogen bombs had already been carried out in the Soviet Union and the United States by this time, which confirmed the fundamental possibility of using nuclear fusion energy under terrestrial conditions. From the very beginning it became clear that controlled thermonuclear fusion has no military application. In 1956, the research was declassified and since then has been carried out in the framework of broad international cooperation. The hydrogen bomb was created in just a few years, and at that time it seemed that the goal was close, and that the first large experimental installations, built in the late 1950s, would receive thermonuclear plasma. However, it took more than 40 years of research to create conditions under which the release of thermonuclear power is comparable to the heating power of the reacting mixture. In 1997, the largest thermonuclear installation, the European TOKAMAK (JET), received 16 MW of thermonuclear power and came close to this threshold.

What caused this delay? It turned out that in order to achieve the goal, physicists and engineers had to solve a lot of problems that they did not even know about at the beginning. During these 40 years, the science was created - plasma physics, which made it possible to understand and describe the complex physical processes occurring in the reacting mixture. Engineers had to solve equally complex problems, including how to create a deep vacuum in large volumes, select and test suitable structural materials, develop large superconducting magnets, powerful lasers and X-ray sources, develop pulsed power systems capable of creating powerful beams of particles. to develop methods for high-frequency heating of the mixture and much more.

4. Problems of controlled thermonuclear fusion

Researchers from all developed countries pin their hopes for overcoming the coming energy crisis with a controlled thermonuclear reaction. Such a reaction - the synthesis of helium from deuterium and tritium - has been going on on the Sun for millions of years, and under terrestrial conditions they have been trying to implement it for fifty years in giant and very expensive laser installations, tokamaks (a device for carrying out a thermonuclear fusion reaction in hot plasma) and stellarators ( closed magnetic trap for confining high-temperature plasma). However, there are other ways to solve this difficult problem, and instead of huge tokamaks for the implementation of thermonuclear fusion, it will probably be possible to use a rather compact and inexpensive collider - an accelerator on colliding beams.

The Tokamak requires very small amounts of lithium and deuterium to operate. For example, a reactor with an electrical power of 1 GW burns about 100 kg of deuterium and 300 kg of lithium per year. Assuming that all thermonuclear power plants will produce 10 trillion. kWh of electricity per year, that is, as much as all the power plants of the Earth produce today, then the world's reserves of deuterium and lithium will be enough to supply humanity with energy for many millions of years.

In addition to the fusion of deuterium and lithium, a purely solar thermonuclear is possible when two deuterium atoms combine. In the case of mastering this reaction, energy problems will be solved immediately and forever.

In any of the known variants of controlled thermonuclear fusion (CTF), thermonuclear reactions cannot enter the mode of uncontrolled increase in power, therefore, such reactors are not inherent in internal safety.

From a physical point of view, the problem is not difficult to formulate. To carry out a self-sustaining nuclear fusion reaction, it is necessary and sufficient to observe two conditions.

1. The energy of the nuclei participating in the reaction must be at least 10 keV. For nuclear fusion to start, the nuclei participating in the reaction must fall into the field of nuclear forces, the range of which is 10-12-10-13 cm. However, atomic nuclei have a positive electric charge, and like charges repel. At the turn of the action of nuclear forces, the energy of the Coulomb repulsion is about 10 keV. To overcome this barrier, nuclei in collision must have kinetic energy, at least not less than this value.
2. The product of the concentration of reacting nuclei by the retention time during which they retain the specified energy must be at least 1014 s.cm-3. This condition - the so-called Lawson criterion - determines the limit of the energy profitability of the reaction. In order for the energy released in the fusion reaction to even cover the energy consumption for the initiation of the reaction, atomic nuclei must undergo many collisions. In each collision, in which the fusion reaction between deuterium (D) and tritium (T) occurs, 17.6 MeV of energy is released, i.e., approximately 3.10-12 J. If, for example, an energy of 10 MJ is spent on ignition, then the reaction will be non-loss if at least 3.1018 DT pairs participate in it. And for this, a rather dense high-energy plasma must be kept in the reactor for a long time. This condition is expressed by the Lawson criterion.

If both requirements can be met simultaneously, the problem of controlled thermonuclear fusion will be solved.

However, the technical implementation of this physical problem faces enormous difficulties. After all, an energy of 10 keV is a temperature of 100 million degrees. A substance at such a temperature can be kept for even a fraction of a second only in a vacuum, by isolating it from the walls of the installation.

But there is another method for solving this problem - cold fusion. What is a cold thermonuclear? It is an analogue of a "hot" thermonuclear reaction taking place at room temperature.

In nature, there are at least two ways of changing matter within one dimension of the continuum. You can boil water over a fire, i.e. thermally, or in a microwave oven, i.e. frequency. The result is the same - the water boils, the only difference is that the frequency method is faster. It also uses the reach of ultra-high temperature to split the nucleus of the atom. The thermal method gives an uncontrolled nuclear reaction. The energy of the cold fusion is the energy of the transition state. One of the main conditions for the design of the reactor for the reaction of cold fusion is the condition of its pyramidal - crystalline form. Another important condition is the presence of rotating magnetic and torsion fields. The intersection of the fields occurs at the point of unstable equilibrium of the hydrogen nucleus.

Scientists Ruzi Taleyarkhan of Oak Ridge National Laboratory, Richard Lehi of Polytechnic University. Rensilira and academician Robert Nigmatulin - recorded a cold thermonuclear reaction in laboratory conditions.

The group used a beaker of liquid acetone about the size of two to three glasses. Sound waves were intensely passed through the liquid, producing an effect known in physics as acoustic cavitation, which results in sonoluminescence. During cavitation, small bubbles appeared in the liquid, which increased to two millimeters in diameter and exploded. The explosions were accompanied by flashes of light and the release of energy, i.e. the temperature inside the bubbles at the time of the explosion reached 10 million degrees Kelvin, and the released energy, according to the experimenters, is sufficient to carry out thermonuclear fusion.

The "technical" essence of the reaction is that as a result of the combination of two deuterium atoms, a third is formed - an isotope of hydrogen, known as tritium, and a neutron, characterized by a colossal amount of energy.

4.1 Economic problems

When creating the TCB, it is assumed that it will be a large installation equipped with powerful computers. It will be a whole small city. But in the event of an accident or equipment breakdown, the work of the station will be disrupted.

This is not foreseen, for example, in modern NPP projects. It is believed that the main thing is to build them, and what will be later is not important.

But in case of failure of 1 station, many cities will be left without electricity. This can be seen in the example of a nuclear power plant in Armenia. Removing radioactive waste has become very expensive. At the request of the green NPP was closed. The population was left without electricity, the equipment of the power plant was worn out, and the money allocated by international organizations for restoration was wasted.

A serious economic problem is the decontamination of abandoned facilities where uranium was processed. For example, "in the city of Aktau, there is its own small" Chernobyl ". It is located on the territory of the chemical and hydrometallurgical plant (KHGMZ). The radiation of gamma background in the uranium processing shop (UMC) in some places reaches 11,000 micro-roentgens per hour, the average background level is 200 micro-roentgens ( The usual natural background is from 10 to 25 micro-roentgens per hour.) After the plant was shut down, no decontamination was carried out at all. A significant part of the equipment, about fifteen thousand tons, has already irreparable radioactivity. At the same time, such dangerous items are stored under the open sky, are poorly guarded and are constantly taken away from the territory of KhGMZ.

Therefore, since there are no eternal productions, due to the emergence of new technologies, the TCB may be closed and then objects, metals from the enterprise will enter the market and the local population will suffer.

The UTS cooling system will use water. But according to environmentalists, if we take statistics on nuclear power plants, the water from these reservoirs is not suitable for drinking.

According to experts, the reservoir is full of heavy metals (in particular, thorium-232), and in some places the level of gamma radiation reaches 50 - 60 micro-roentgens per hour.

That is, now, during the construction of a nuclear power plant, funds are not provided that would return the area to its original state. And after the closure of the enterprise, no one knows how to bury the accumulated waste and clean up the former enterprise.

4.2 Medical problems

The harmful effects of TCF include the production of mutants of viruses and bacteria that produce harmful substances. This is especially true of viruses and bacteria in the human body. The emergence of malignant tumors and cancer will most likely be a common disease of the residents of the villages living near the TCB. Residents always suffer more because they have no means of protection. Dosimeters are expensive and medicines are not available. Waste from the TCB will be dumped into rivers, released into the air or pumped into underground layers, which is currently happening at the nuclear power plant.

In addition to damage that appears soon after exposure to high doses, ionizing radiation has long-term consequences. Basically, carcinogenesis and genetic disorders that can occur at any dose and nature of radiation (single, chronic, local).

According to reports from doctors who registered the diseases of the NPP workers, cardiovascular diseases (heart attacks) followed first, followed by cancer. The heart muscle becomes thinner under the influence of radiation, becomes flabby, less durable. There are completely incomprehensible diseases. For example, liver failure. But why this is happening, none of the doctors still knows. If radioactive substances enter the respiratory tract during an accident, doctors cut out the damaged tissue of the lung and trachea and the disabled person walks with a portable device for breathing

5. Fusion installations

Scientists in our country and most of the developed countries of the world have been dealing with the problem of using thermonuclear reactions for energy purposes for many years. Unique thermonuclear installations have been created - the most sophisticated technical devices designed to study the possibility of obtaining colossal energy, which is released so far only during the explosion of a hydrogen bomb. Scientists want to learn how to control the course of a thermonuclear reaction - the reaction of combining heavy hydrogen nuclei (deuterium and tritium) with the formation of helium nuclei at high temperatures - in order to use the energy released during this for peaceful purposes, for the benefit of people.

There is very little deuterium in a liter of tap water. But if this deuterium is collected and used as fuel in a thermonuclear installation, then you can get as much energy as from burning almost 300 kilograms of oil. And to provide the energy that is now obtained by burning conventional fuel produced in a year, it would be necessary to extract deuterium from the water contained in a cube with a side of only 160 meters. One Volga River annually carries about 60,000 such cubic meters of water to the Caspian Sea.

For a thermonuclear reaction to occur, several conditions must be met. So, the temperature in the zone where heavy hydrogen nuclei are combined should be about 100 million degrees. At such an enormous temperature, we are no longer talking about a gas, but about a plasma. Plasma is a state of matter when, at high gas temperatures, neutral atoms lose their electrons and turn into positive ions. In other words, plasma is a mixture of freely moving positive ions and electrons. The second condition is the need to maintain a plasma density in the reaction zone of at least 100 thousand billion particles per cubic centimeter. And, finally, the main and most difficult thing is to keep the course of the thermonuclear reaction for at least one second.

The working chamber of a thermonuclear installation is toroidal, similar to a huge hollow donut. It is filled with a mixture of deuterium and tritium. A plasma loop is created inside the chamber itself - a conductor through which an electric current of about 20 million amperes is passed.
Electric current serves three important functions. First, it creates plasma. Secondly, it heats it up to one hundred million degrees. And, finally, the current creates a magnetic field around itself, that is, it surrounds the plasma with magnetic lines of force. In principle, the lines of force around the plasma should have kept it suspended and prevented the plasma from touching the chamber walls. However, keeping the plasma suspended is not so easy. Electrical forces deform a plasma conductor, which does not have the strength of a metal conductor. It bends, hits the wall of the chamber and gives off its thermal energy to it. To prevent this, coils are also put on over the toroidal chamber, creating a longitudinal magnetic field in the chamber, pushing the plasma conductor away from the walls. Only this is not enough, since the plasma conductor with current tends to stretch, to increase its diameter. The magnetic field, which is created automatically, without extraneous external forces, is also called upon to keep the plasma conductor from expanding. The plasma conductor is placed with the toroidal chamber in another larger chamber made of a non-magnetic material, usually copper. As soon as the plasma conductor makes an attempt to deviate from the equilibrium position, an induction current arises in the copper shell according to the law of electromagnetic induction, which is opposite in the direction of the current in the plasma. As a result, an opposing force appears that repels the plasma from the chamber walls.
To keep the plasma from contacting the chamber walls with a magnetic field was proposed in 1949 by A.D. Sakharov, and a little later the American J. Spitzer.

In physics, it is customary to give names to each new type of experimental setup. A structure with such a winding system is called a tokamak - short for "toroidal chamber and magnetic coil".

In the 1970s, a thermonuclear installation named "Tokamak-10" was built in the USSR. It was developed at the Institute of Atomic Energy. I.V. Kurchatov. On this installation, the temperature of the plasma conductor was 10 million degrees, the plasma density was not lower than 100 thousand billion particles per cubic centimeter, and the plasma confinement time was close to 0.5 seconds. Tokamak-15, the largest installation in our country today, has also been built at the Moscow scientific center Kurchatov Institute.

All created thermonuclear installations so far only consume energy to heat up the plasma and create magnetic fields. The thermonuclear installation of the future should, on the contrary, release so much energy that a small part of it can be used to maintain a thermonuclear reaction, that is, to heat the plasma, create magnetic fields and power many auxiliary devices and devices, and give the main part for consumption in the electrical network.

In 1997, in the UK at the JET tokamak, the input and output energy were matched. Although this, of course, is not enough for self-sustaining the process: up to 80 percent of the energy received is lost. In order for the reactor to work, it is necessary to produce five times more energy than is spent on heating the plasma and creating magnetic fields.
In 1986, the countries of the European Union, together with the USSR, the USA and Japan, decided to jointly develop and build by 2010 a sufficiently large tokamak capable of producing energy not only to maintain thermonuclear fusion in plasma, but also to obtain useful electrical power. This reactor was named ITER, an abbreviation for International Thermonuclear Experimental Reactor. By 1998, it was possible to complete the design calculations, but due to the refusal of the Americans, changes in the design of the reactor had to be made in order to reduce its cost.

You can let the particles move naturally, and the camera can be shaped to follow their path. The camera then looks rather bizarre. It repeats the shape of a plasma filament that appears in the magnetic field of external coils of complex configuration. The magnetic field is created by external coils of a much more complex configuration than in a tokamak. Devices of this kind are called stellarators. The Uragan-3M torsatron has been built in our country. This experimental stellarator is designed to contain plasma heated to ten million degrees.

Currently, tokamaks have other serious competitors using inertial thermonuclear fusion. In this case, several milligrams of the deuterium-tritium mixture are enclosed in a capsule with a diameter of 1–2 millimeters. Pulsed radiation of several dozen high-power lasers is focused on the capsule. As a result, the capsule instantly evaporates. It is necessary to invest 2 MJ of energy into radiation in 5-10 nanoseconds. Then the light pressure will compress the mixture to such an extent that a thermonuclear fusion reaction can take place. The energy released during the explosion, which is equivalent in power to an explosion of one hundred kilograms of TNT, will be converted into a more convenient form for use - for example, into an electrical one. However, the construction of stellarators and inertial synthesis facilities also runs into serious technical difficulties. Probably, the practical use of thermonuclear energy is not a question for the near future.

6. Prospects for the development of thermonuclear fusion

As an important task for the nuclear industry, in the long term, is the development of technologies for controlled thermonuclear fusion as the basis for the energy of the future. At present, strategic decisions on the development and development of new energy sources are being taken all over the world. The need to develop such sources is associated with the expected shortage of energy production and limited fuel resources. Controlled thermonuclear fusion (CTF) is one of the most promising innovative energy sources. The fusion energy is released during the fusion of the nuclei of heavy hydrogen isotopes. The fuel for the fusion reactor is water and lithium, the reserves of which are practically unlimited. Under terrestrial conditions, the implementation of CCF is a complex scientific and technological problem associated with obtaining a substance temperature of more than 100 million degrees and thermal insulation of the synthesis region from the walls of the reactor.

Fusion is a long-term project, with a commercial facility expected to be built by 2040-2050. The most likely scenario for mastering thermonuclear energy involves the implementation of three stages:
- mastering the regimes of long-term combustion of a thermonuclear reaction;
- demonstration of electricity production;
- creation of industrial thermonuclear stations.

Within the framework of the international project ITER (International Thermonuclear Experimental Reactor), it is planned to demonstrate the technical feasibility of confining plasma and obtaining energy.The main programmatic goal of the ITER project is to demonstrate the scientific and technical feasibility of obtaining energy through the reactions of fusion (fusion) of hydrogen isotopes - deuterium and tritium. The design thermonuclear power of the ITER reactor will be about 500 MW at a plasma temperature of 100 million degrees.
In November 2006, all the participants of the ITER project - the European Union, Russia, Japan, the USA, China, Korea and India signed the Agreements on the establishment of the International ITER Organization for Thermonuclear Energy for the joint implementation of the ITER project. The construction phase of the reactor began in 2007.

Russia's participation in the ITER project consists in the development, manufacture and delivery of the main technological equipment to the reactor construction site (Cadarache, France) and making a monetary contribution, which in total amounts to about 10% of the total cost of the reactor construction. The USA, China, India, Korea and Japan have the same share of the contribution.
A roadmap for mastering the energy of controlled thermonuclear fusion

2000 (current level):
Challenges: achieving equity in cost and energy production
The latest generation of tokamaks has made it possible to come close to the implementation of controlled thermonuclear combustion with a large release of energy.
The power of the thermonuclear fusion reactions has reached the level of 17 MW (JET unit, EC), which is comparable to the power put into the plasma.
2020 year:

Tasks solved in the ITER project: long-term reaction, mastering and integration of thermonuclear technologies.

The goal of the ITER project is to achieve controlled ignition of a thermonuclear reaction and its long-term combustion with a tenfold excess of the thermonuclear power over the power for initiating the Q³10 fusion reaction.

2030:
Problem to be solved: construction of a demonstration station DEMO (OTE)
The choice of optimal materials and technologies for the OTE, the design, construction and start-up tests of an experimental thermonuclear power plant within the DEMO project were completed, the conceptual design of the PTE was completed.
2050 year
Tasks to be solved: design and construction of PTE, completion of tests of electric power generation technologies at DEMO.
Creation of an industrial power plant with a high safety margin and acceptable economic indicators of energy cost.
Humanity will get its hands on an inexhaustible, environmentally and economically acceptable source of energy.The fusion reactor project is based on the "Tokamak" type magnetic plasma confinement systems, first developed and implemented in the USSR. In 1968, a plasma temperature of 10 million degrees was reached at the T-3 tokamak. Since that time, the Tokamak installations have become the leading direction in research on thermonuclear fusion in all countries.

Currently, Russia operates tokamaks T-10 and T-15 (RRC "Kurchatov Institute"), T-11M (FSUE GNTs RF TRINITI, Troitsk, Moscow region), Globus-M, FT-2, Tuman-3 (Physics Ioffe Technical Institute, St. Petersburg, RAS) and stellarator L-2 (General Physics Institute, Moscow, RAS).

Conclusion

Based on the research carried out, the following conclusions can be drawn:

Thermonuclear fusion is the most rational, environmentally friendly and cheap way of generating energy, in terms of the amount of heat received, incomparable with natural sources used by humans at the moment. Of course, the process of mastering thermonuclear fusion would solve many problems of mankind, both in the present and in the future.

In the future, thermonuclear fusion will make it possible to overcome another "crisis of humanity", namely, the overpopulation of the Earth. It is no secret that the development of earthly civilization provides for a constant and steady growth of the planet's population, therefore the question of the development of "new territories", in other words, the colonization of neighboring planets of the solar system for the creation of permanent settlements is a matter of the very near future.

Literature

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6. http://www.college.ru./astronomy- Astronomy
7. http://n-t.ru/tp/ie/ts.htm Thermonuclear fusion in the Sun - new version Vladimir Vlasov

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Slide captions:

THERMONUCLEAR FUSION

DEFINITION This is a kind of nuclear reaction in which light atomic nuclei combine into heavier ones due to the kinetic energy of their thermal motion.

GETTING ENERGY

REACTION EQUATION WITH FORMATION HE ⁴

THERMONUCLEAR REACTION ON THE SUN

CONTROLLED FUEL SYNTHESIS

TOROIDAL CHAMBER WITH MAGNETIC COILS (TOKAMAK)

THE NECESSITY OF DEVELOPING THERMONUCLEAR SYNTHESIS

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

Federal Agency for Education

GOU VPO "Blagoveshchensk State Pedagogical University"

Faculty of Physics and Mathematics

Department of General Physics

Course work

on the topic: Problems of thermonuclear fusion

by discipline: Physics

Executor: V.S. Kletchenko

Leader: V.A. Evdokimova

Blagoveshchensk 2010

Introduction

Thermonuclear reactions and their energy benefits

Conditions for the course of thermonuclear reactions

Implementation of thermonuclear reactions in terrestrial conditions

The main problems associated with the implementation of thermonuclear reactions

Implementation of controlled thermonuclear reactions in installations of the "TOKAMAK" type

ITER project

Modern research of plasma and thermonuclear reactions

Conclusion

Literature

Introduction

Currently, humanity cannot imagine its life without electricity. She is everywhere. But traditional methods of generating electricity are not cheap: just imagine the construction of a hydroelectric power plant or a nuclear power plant reactor, it immediately becomes clear why. Scientists of the 20th century, in the face of an energy crisis, have found a way to generate electricity from a substance, the amount of which is not limited. Thermonuclear reactions occur during the decay of deuterium and tritium. One liter of water contains so much deuterium that as much energy can be released during thermonuclear fusion as is obtained by burning 350 liters of gasoline. That is, we can conclude that water is an unlimited source of energy.

If obtaining energy using thermonuclear fusion were as simple as using hydroelectric power plants, then humanity would never experience a crisis in the energy sector. To generate energy in this way, you need a temperature equivalent to that at the center of the sun. Where to get such a temperature, how expensive will the installation cost, how profitable is such energy production and is such an installation safe? These questions will be answered in this work.

Purpose of work: studying the properties and problems of thermonuclear fusion.

Thermonuclear reactions and their energy benefits

A thermonuclear reaction is the synthesis of heavier atomic nuclei from lighter ones in order to obtain energy, which is of a controlled nature.

It is known that the nucleus of a hydrogen atom is a proton p. There is a lot of such hydrogen in nature - in air and in water. In addition, there are heavier hydrogen isotopes. The nucleus of one of them contains, in addition to the proton p, also the neutron n. This isotope is called deuterium D. The nucleus of another isotope contains, in addition to the proton p, two neutrons n and is called tritium (tritium) T. Thermonuclear reactions occur most efficiently at ultrahigh temperatures of the order of 10 7 - 10 9 K. the energy that is released during the fission of heavy nuclei. In the fusion reaction, energy is released, which, per 1 kg of substance, is much more than the energy released in the fission reaction of uranium. (Here, the released energy refers to the kinetic energy of particles formed as a result of the reaction.) For example, in the reaction of fusion of deuterium 1 2 D and tritium 1 3 T nuclei into a helium nucleus 2 4 He:

1 2 D + 1 3 T → 2 4 He + 0 1 n,

The energy released is approximately equal to 3.5 MeV per nucleon. In fission reactions, the energy per nucleon is about 1 MeV.

When fusing a helium nucleus from four protons:

4 1 1 p → 2 4 He + 2 +1 1 e,

even more energy is released, equal to 6.7 MeV per particle. The energetic advantage of thermonuclear reactions is explained by the fact that the specific binding energy in the nucleus of a helium atom significantly exceeds the specific binding energy of the nuclei of hydrogen isotopes. Thus, with the successful implementation of controlled thermonuclear reactions, humanity will receive a new powerful source of energy.

Conditions for the course of thermonuclear reactions

For the fusion of light nuclei, it is necessary to overcome the potential barrier due to the Coulomb repulsion of protons in positively charged nuclei of the same name. For the fusion of hydrogen nuclei 1 2 D, it is necessary to bring them closer to a distance r equal to approximately r ≈ 3 10 -15 m. For this, it is necessary to perform work equal to the electrostatic potential repulsive energy P \u003d e 2: (4πε 0 r) ≈ 0.1 MeV. Deuteron nuclei will be able to overcome such a barrier if their average kinetic energy 3/2 kT will be 0.1 MeV upon collision. This is possible at T \u003d 2 10 9 K. In practice, the temperature required for the occurrence of thermonuclear reactions decreases by two orders of magnitude and amounts to 10 7 K.

A temperature of the order of 10 7 K is typical for the central part of the Sun. Spectral analysis showed that the matter of the Sun, like many other stars, contains up to 80% hydrogen and about 20% helium. Carbon, nitrogen and oxygen make up no more than 1% of the mass of stars. With a huge mass of the Sun (≈ 2 10 27 kg), the amount of these gases is quite large.

Thermonuclear reactions occur on the Sun and stars and are the source of energy that provides their radiation. Every second the Sun emits an energy of 3.8 10 26 J, which corresponds to a decrease in its mass by 4.3 million tons. Specific release of solar energy, i.e. the release of energy per unit mass of the Sun per second is equal to 1.9 10 -4 J / s kg. It is very small and amounts to about 10 -3% of the specific energy release in a living organism in the course of metabolism. The power of the Sun's radiation has practically not changed over the many billions of years of the existence of the solar system.

One of the ways of thermonuclear reactions on the Sun is the carbon-nitrogen cycle, in which the combination of hydrogen nuclei into a helium nucleus is facilitated in the presence of 6 12 C carbon nuclei acting as catalysts. At the beginning of the cycle, a fast proton penetrates into the nucleus of a carbon atom 6 12 C and forms an unstable nucleus of the nitrogen isotope 7 13 N with emission of a γ-quantum:

6 12 С + 1 1 p → 7 13 N + γ.

With a half-life of 14 minutes in the 7 13 N nucleus, the transformation 1 1 p → 0 1 n + +1 0 е + 0 0 ν е occurs and the nucleus of the 6 13 С isotope is formed:

7 13 N → 6 13 С + +1 0 е + 0 0 ν е.

approximately every 32 million years, the 7 14 N nucleus captures a proton and turns into the 8 15 O oxygen nucleus:

7 14 N + 1 1 p → 8 15 O + γ.

The unstable 8 15 O nucleus with a half-life of 3 minutes emits a positron and neutrino and turns into a 7 15 N nucleus:

8 15 О → 7 15 N + +1 0 е + 0 0 ν е.

The cycle ends with the reaction of absorption by the 7 15 N nucleus of a proton with its decay into a 6 12 C carbon nucleus and an α-particle. This happens about 100 thousand years later:

7 15 N + 1 1 p → 6 12 C + 2 4 He.

A new cycle begins again with the absorption of a proton by carbon 6 12 C, emanating on average after 13 million years. Individual reactions of the cycle are distant in time by intervals that are prohibitively large on earthly time scales. However, the cycle is closed and occurs continuously. Therefore, different reactions of the cycle occur on the Sun at the same time, starting at different times.

As a result of this cycle, four protons merge into a helium nucleus with the appearance of two positrons and γ-radiation. To this must be added the radiation arising from the fusion of positrons with plasma electrons. When one helium gammatome is formed, 700 thousand kWh of energy are released. This amount of energy compensates for the loss of solar energy for radiation. Calculations show that the amount of hydrogen available in the Sun will be enough to sustain thermonuclear reactions and solar radiation for billions of years.

Implementation of thermonuclear reactions in terrestrial conditions

The implementation of thermonuclear reactions in terrestrial conditions will create tremendous opportunities for energy production. For example, when using deuterium contained in one liter of water, the same amount of energy will be released in the fusion reaction as when about 350 liters of gasoline are burned. But if the thermonuclear reaction proceeds spontaneously, then a colossal explosion will occur, since the energy released during this is very large.

Conditions close to those that are realized in the interior of the Sun were realized in a hydrogen bomb. There a self-sustaining thermonuclear reaction of an explosive nature takes place. The explosive is a mixture of deuterium 1 2 D with tritium 1 3 T. The high temperature required for the reaction to proceed is obtained by the explosion of an ordinary atomic bomb placed inside a thermonuclear bomb.

The main problems associated with the implementation of thermonuclear reactions

In a thermonuclear reactor, the fusion reaction must proceed slowly, it must be possible to control it. The study of reactions occurring in high-temperature deuterium plasma is the theoretical basis for obtaining artificial controlled thermonuclear reactions. The main difficulty is maintaining the conditions necessary for obtaining a self-sustaining thermonuclear reaction. For such a reaction, it is necessary that the rate of energy release in the system where the reaction takes place is not less than the rate of energy removal from the system. At temperatures of the order of 10 8 K, thermonuclear reactions in deuterium plasma have a noticeable intensity and are accompanied by the release of high energy. In a unit volume of plasma, when deuterium nuclei are combined, a power of 3 kW / m 3 is released. At temperatures of the order of 10 6 K, the power is only 10 -17 W / m 3.

Innovative projects using modern superconductors in the near future will make it possible to carry out controlled thermonuclear fusion, some optimists say. Experts, however, predict that practical implementation will take several decades.

Why is it so difficult?

Fusion energy is considered a potential source of energy for the future. This is the pure energy of the atom. But what is it and why is it so difficult to achieve? First, you need to understand the difference between classical nuclear fission and thermonuclear fusion.

Atomic fission means that radioactive isotopes - uranium or plutonium - are fissioned and converted into other highly radioactive isotopes, which must then be buried or reprocessed.

The thermonuclear fusion reaction consists in the fact that two isotopes of hydrogen - deuterium and tritium - merge into a single whole, forming non-toxic helium and a single neutron, without producing radioactive waste.

Control problem

The reactions that take place on the sun or in a hydrogen bomb are thermonuclear fusion, and engineers are faced with the daunting task of how to control this process at a power plant?

This is what scientists have been working on since the 1960s. Another experimental thermonuclear fusion reactor called Wendelstein 7-X began work in the northern German city of Greifswald. It is not yet designed to create a reaction - it is just a special design that is being tested (stellarator instead of tokamak).

High energy plasma

All thermonuclear installations have a common feature - a ring-like shape. It is based on the idea of \u200b\u200busing powerful electromagnets to create a strong electromagnetic field in the shape of a torus - an inflated bicycle tube.

This electromagnetic field must be so dense that when it is heated in a microwave oven to one million degrees Celsius, a plasma should appear in the very center of the ring. It is then ignited so that fusion can begin.

Demonstration of possibilities

There are two similar experiments currently underway in Europe. One of them is Wendelstein 7-X, which recently generated its first helium plasma. The other is ITER, a huge experimental fusion plant in the south of France that is still under construction and will be ready to go live in 2023.

It is assumed that real nuclear reactions will take place on ITER, albeit only for a short period of time and certainly no longer than 60 minutes. This reactor is just one of many steps towards putting nuclear fusion into practice.

Fusion reactor: smaller and more powerful

Several designers recently announced a new design for the reactor. According to a group of MIT students and representatives of the arms manufacturer Lockheed Martin, thermonuclear fusion can be carried out in installations that are much more powerful and smaller than ITER, and they are ready to do it within ten years.

The idea of \u200b\u200bthe new design is to use modern high-temperature superconductors in electromagnets, which show their properties when cooled with liquid nitrogen, rather than conventional ones, which require liquid helium. The new, more flexible technology will allow a complete redesign of the reactor.

Klaus Hesch, in charge of nuclear fusion technology at the Karlsruhe Institute of Technology in southwestern Germany, is skeptical. It supports the use of new high temperature superconductors for new reactor designs. But, according to him, it is not enough to develop something on a computer, taking into account the laws of physics. It is necessary to take into account the challenges that arise when translating an idea into practice.

Science fiction

According to Hesh, the MIT student model shows only the possibility of a project. But it's actually a lot of science fiction. The project assumes that serious technical problems of thermonuclear fusion have been solved. But modern science has no idea how to solve them.

One such problem is the idea of \u200b\u200bcollapsible coils. In the MIT design model, the electromagnets can be disassembled to get inside the plasma-holding ring.

This would be very useful, because one could access and replace objects in the internal system. But in reality, superconductors are made of ceramic material. Hundreds of them must be intertwined in a sophisticated way to form the correct magnetic field. And this is where more fundamental difficulties arise: the connections between them are not as simple as those of copper cables. Nobody has even thought about concepts that would help solve such problems.

Too hot

High temperatures are also a problem. In the core of the fusion plasma, the temperature will reach about 150 million degrees Celsius. This extreme heat stays in place - right in the center of the ionized gas. But even around it, it is still very hot - from 500 to 700 degrees in the reactor zone, which is the inner layer of a metal tube, in which tritium, which is necessary for nuclear fusion to take place, will be "reproduced".

The fusion reactor has an even bigger problem - the so-called power release. This is the part of the system that receives used fuel from the fusion process, mainly helium. The first metal components that get hot gas are called the "divertor". It can heat up to over 2000 ° C.

Divertor problem

In order for the installation to withstand such temperatures, engineers are trying to use the metallic tungsten used in old-fashioned incandescent bulbs. The melting point of tungsten is about 3000 degrees. But there are other limitations as well.

In ITER, this can be done, because heating does not occur constantly in it. The reactor is expected to operate only 1-3% of the time. But this is not an option for a power plant that needs to operate 24/7. And, if someone claims to be able to build a smaller reactor with the same capacity as ITER, it is safe to say that they have no solution to the divertor problem.

Power plant in a few decades

Nevertheless, scientists are optimistic about the development of thermonuclear reactors, although it will not be as fast as some enthusiasts predict.

ITER should show that controlled thermonuclear fusion can actually produce more energy than would be expended to heat the plasma. The next step will be the construction of an entirely new hybrid demonstration power plant that actually generates electricity.

Engineers are already working on its design. They will have to learn from ITER, which is slated to launch in 2023. Given the time required for design, planning and construction, it seems unlikely that the first fusion power plant will be launched much earlier than the mid-21st century.

Rossi's cold fusion

In 2014, an independent test of the E-Cat reactor concluded that the device produced an average of 2800 watts of output power over a period of 32 days while consuming 900 watts. This is more than any chemical reaction can produce. The result speaks either of a breakthrough in thermonuclear fusion, or of outright fraud. The report has disappointed skeptics who question whether the test was truly independent and speculate that the test results could be falsified. Others set out to figure out the "secret ingredients" that allow Rossi's fusion to replicate the technology.

Is Rossi a crook?

Andrea is imposing. He publishes proclamations to the world in unique English in the comments section of his website, the pretentiously titled Journal of Nuclear Physics. But his previous unsuccessful attempts included an Italian project for converting garbage into fuel and a thermoelectric generator. Petroldragon, a waste-to-energy project, has failed in part because the illegal disposal of waste is controlled by Italian organized crime, which has filed criminal charges against him for violating waste regulations. He also created a thermoelectric device for the US Army Corps of Engineers, but during testing, the gadget produced only a fraction of the declared power.

Many do not trust Russia, and the editor-in-chief of the New Energy Times called him a felon with a series of unsuccessful energy projects behind him.

Independent verification

Rossi signed a contract with the American company Industrial Heat to conduct a year-long secret testing of a 1-MW cold fusion plant. The device was a shipping container packed with dozens of E-Cats. The experiment had to be monitored by a third party who could confirm that there was indeed heat generation. Rossi claims to have spent most of the past year practically living in a container and overseeing operations for over 16 hours a day to prove the commercial viability of the E-Cat.

The test ended in March. Rossi's supporters anxiously awaited the observer's report, hoping for an acquittal of their hero. But in the end they got a lawsuit.

Trial

In a statement to a Florida court, Rossi claims the test was successful and an independent arbiter confirmed that the E-Cat reactor produces six times more energy than it consumes. He also claimed that Industrial Heat had agreed to pay him $ 100 million - $ 11.5 million upfront after a 24-hour trial (ostensibly for licensing rights so the company could sell the technology in the US) and another $ 89 million after successfully completing an extended trial. within 350 days. Rossi accused IH of carrying out a "fraudulent scheme" aimed at stealing his intellectual property. He also accused the company of misappropriating E-Cat reactors, illegally copying innovative technologies and products, functionality and designs, and improperly seeking a patent for its intellectual property.

Goldmine

Elsewhere, Rossi claims that, amid one of his demonstrations, IH received $ 50-60 million from investors and another $ 200 million from China after a replay involving top Chinese officials. If this is true, then a lot more than a hundred million dollars are at stake. Industrial Heat dismissed these claims as unfounded and will actively defend itself. More importantly, she claims that "for more than three years, she has been working to validate the results that Rossi allegedly achieved with his E-Cat technology, and all to no avail."

IH does not believe the E-Cat will work, and the New Energy Times sees no reason to doubt it. In June 2011, a representative of the publication visited Italy, interviewed Rossi and filmed a demonstration of his E-Cat. A day later, he announced his serious concerns about the method of measuring heat output. After 6 days, the journalist posted his video on YouTube. Experts from all over the world sent him analyzes, which were published in July. It became clear that this was a hoax.

Experimental confirmation

Nevertheless, a number of researchers - Alexander Parkhomov from Russian University Friendship of Peoples and the Martin Fleischman Memory Project (MFPM) - managed to reproduce the cold fusion of Russia. The MFPM report was titled "The End of the Carbon Era is Near." The reason for this admiration was the discovery of a burst of gamma radiation, which cannot be explained otherwise than as a thermonuclear reaction. According to the researchers, Rossi has exactly what he is talking about.

A viable open recipe for cold fusion has the potential to trigger an energetic gold rush. Alternative methods could be found to circumvent Rossi's patents and leave him out of the multibillion-dollar energy business.

So perhaps Rossi would have preferred to avoid this confirmation.

The article discusses the reasons why controlled thermonuclear fusion has not found industrial application so far.

When in the fifties of the last century the Earth was shaken by powerful explosions thermonuclear bombsit seemed that before peaceful use fusion energies very little is left: one or two decades. There were also grounds for such optimism: only 10 years had elapsed from the moment the atomic bomb was used to the creation of a reactor that produced electricity.

But the task of curbing thermonuclear fusion turned out to be extraordinarily difficult. Decades passed one after another, and access to unlimited supplies of energy was never obtained. During this time, humanity, burning fossil resources, polluted the atmosphere with emissions and overheated it with greenhouse gases. The disasters at Chernobyl and Fukushima-1 have discredited nuclear power.

What prevented the mastery of such a promising and safe process of thermonuclear fusion, which could forever remove the problem of providing mankind with energy?

Initially, it was clear that for the reaction to proceed, it is necessary to bring the hydrogen nuclei closer together so that the nuclear forces could form the nucleus of a new element - helium with the release of a significant amount of energy. But hydrogen nuclei are repelled from each other by electrical forces. An assessment of the temperatures and pressures at which a controlled thermonuclear reaction begins has shown that no material can withstand such temperatures.

For the same reasons, pure deuterium, an isotope of hydrogen, was rejected. After spending billions of dollars and decades of time, scientists were finally able to ignite a thermonuclear flame for a very short time. It remains to learn how to hold the fusion plasma for a long time. It was necessary to move from computer modeling to the construction of a real reactor.

At this stage, it became clear that the efforts and funds of a separate state would not be enough for the construction and operation of experimental and experimental industrial installations. Within the framework of international cooperation, it was decided to implement a project of an experimental thermonuclear reactor worth more than $ 14 billion.

But in 1996, the United States ceased its participation and, accordingly, funding for the project. For some time, the implementation went on at the expense of Canada, Japan and Europe, but it never came to the construction of the reactor.

The second project, also international, is being implemented in France. Long-term retention of plasma occurs due to a special form of the magnetic field - in the form of a bottle. The basis of this method was laid by Soviet physicists. The first installation of the "Tokamak" type should give at the output more energy than is spent on igniting and holding the plasma.

By 2012, the installation of the reactor should have been completed, but there is still no information on successful operation. Perhaps the economic upheavals of recent years have made adjustments to the plans of scientists.

Difficulties in achieving controlled thermonuclear fusion gave rise to a lot of speculation and false reports about the so-called "Cold" thermonuclear nuclear fusion reaction. Despite the fact that no physical capabilities or laws have yet been found, many researchers argue about its existence. After all, the stakes are too high: from Nobel Prizes for scientists to the geopolitical domination of a state that has mastered this technology and gained access to energy abundance.

But every such message turns out to be exaggerated or downright false. Serious scientists are skeptical about the existence of such a reaction.

The real possibilities of mastering fusion and starting commercial operation of thermonuclear reactors are postponed to the middle of the 21st century. By this time, it will be possible to select the necessary materials and work out its safe operation. Since such reactors will operate with very low density plasma, safety of fusion power plants will be much higher than nuclear power plants.

Any violation in the reaction zone will immediately "extinguish" the thermonuclear flame. But you should not neglect safety measures: the unit power of the reactors will be so great that an accident even in the heat extraction circuits can lead to both casualties and pollution. environment... The only thing left to do is to wait 30-40 years and see the era of energy abundance. If we live, of course.

The extraction of nuclear energy is based on the fundamental fact that the nuclei of chemical elements from the middle of the periodic table are packed tightly, and at the edges of the table, i.e. the lightest and heaviest kernels are less dense. The most densely packed iron nuclei and its neighbors in the periodic table. Therefore, we win energy in two cases: when we divide heavy nuclei into smaller fragments, and when we glue light nuclei into larger ones.

Accordingly, energy can be extracted in two ways: in nuclear reactions division heavy elements - uranium, plutonium, thorium or in nuclear reactions synthesis (sticking together) of light elements - hydrogen, lithium, beryllium and their isotopes. In nature, in natural conditions, both types of reactions are realized. Fusion reactions take place in all stars, including the sun, and are practically the only source of energy on Earth - if not directly through sunlight, then indirectly - through oil, coal, gas, water and wind. A natural fission reaction took place on Earth about 2 billion years ago on the territory of present-day Gabon in Africa: there accidentally accumulated a lot of uranium in one place, and a natural nuclear reactor worked for 100 million years! Then the uranium concentration decreased, and the natural reactor stalled.

In the middle of the 20th century, mankind began to artificially master the gigantic energy contained in the nuclei. An atomic bomb (uranium, plutonium) "works" on fission reactions, a hydrogen bomb (which is not at all made of hydrogen, but so called) - on fusion reactions. In a bomb, reactions take place in an instant and are explosive. You can reduce the intensity of nuclear reactions, stretch them over time and use them intelligently as a controlled source of energy. Many hundreds of nuclear reactors of various types have been built in the world, where fission reactions take place, and heavy elements - uranium, thorium or plutonium - are "burned". The task also arose to make the fusion reaction controlled so that it could serve as a source of energy.

It took humanity only a few years to realize a controlled fission reaction. However, the controlled fusion reaction turned out to be a much more difficult task, which has not yet been fully mastered. The point is that in order for two light nuclei, for example, deuterium and tritium, to merge, they need to overcome a large potential barrier.

The most straightforward way to do this is to overclock two light nuclei to high energies so that they can pass the barrier themselves. This implies that the mixture of deuterium and tritium must be heated to a very high temperature - about 100 million degrees! At this temperature, the mixture is, of course, ionized, i.e. is plasma. The plasma is held in a donut-shaped vessel by a magnetic field of a complex configuration and heated. This installation, the invention of IE Tamm, AD Sakharov, LA Artsimovich and others, is called "tokamak". The main problem here is to achieve the stability of a very hot plasma so that it does not "land on the walls" of the vessel. This requires a large installation and, accordingly, very strong magnetic fields in a large volume. There are almost no fundamental difficulties here, but there are many technical problems that have not yet been resolved.

Construction of an international ITER facility has recently begun in the Aix-en-Provence region of France. Russia also actively participates in the project, contributing 1/11 of the funding. By 2018, the international tokamak should be operational and demonstrate the fundamental possibility of generating energy through a thermonuclear fusion reaction

where d - deuterium nucleus (one proton and one neutron), t - tritium nucleus (one proton and two neutrons), He - helium nucleus (two protons and two neutrons), n Is a neutron produced as a result of a reaction, and "17.6 MeV" is the energy in mega-electron-volts released in a single reaction. This energy is tens of millions of times higher than that which is released during chemical reactions, for example, when burning fossil fuel.

Here the "fuel", as we see, is a mixture of deuterium and tritium. Deuterium ("heavy water") is contained as a small impurity in any water, and it is not difficult to isolate it technically. Its reserves are really not limited. Tritium, on the other hand, does not occur in nature, since it is radioactive and decays in 12 years. The standard way to obtain tritium is from lithium by bombarding it with neutrons. It is assumed that only a small "seed" of tritium will be needed in ITER to start the reaction, and then it will be produced by itself due to neutron bombardment from reaction (1) of a lithium "blanket", i.e. "Blankets", tokamak shells. Therefore, the actual fuel is lithium. There is also a lot of it in the earth's crust, but it cannot be said that lithium is unlimited: if all the energy in the world was produced today due to reaction (1), the explored deposits of lithium necessary for this would be enough for 1000 years. Explored uranium and thorium will be enough for about the same number of years if energy is produced in conventional nuclear boilers.

One way or another, the self-sustaining thermonuclear fusion reaction (1) at the modern level of science and technology is apparently possible to be realized, and there is hope that this will be successfully demonstrated in ten years at the ITER facility. This is a very interesting project both scientifically and technologically, and it is good that our country participates in it. Moreover, this is not a very frequent case when Russia is not only at the world level, but in many ways also sets this world level.

The question is different - can "fusion" serve as a basis for industrial production of "clean" and "unlimited" energy, as the project's enthusiasts claim. The answer seems to be no, and here's why.

The fact is that the neutrons formed during the synthesis (1) are in themselves much more valuable than the energy that is released during this process.

But to warm teapots on neutrons is a robbery,

And here we give the prodigals a fight:

We will cover the active zone

Uranium blanket - won!

(from "Ballad about muon catalysis", Y. Dokshitser and D. Dyakonov, 1978)

Indeed, if the surface of the tokamak is overlaid with a thick "blanket" of the most ordinary natural uranium-238, then under the action of a fast neutron from reaction (1), the uranium nucleus splits with the release of additional energy of about 200 MeV. Let's pay attention to the numbers:

The fusion reaction (1) gives an energy of 17.6 MeV in a tokomak, plus a neutron

The subsequent fission reaction in the uranium blanket gives about 200 MeV.

Thus, if we have already built a complex thermonuclear installation, then a relatively simple addition to it in the form of a uranium blanket allows us to increase energy production 12 times!

It is noteworthy that uranium-238 in the blanket does not have to be very pure or enriched: on the contrary, depleted uranium, of which a lot remains in dumps after enrichment, and even spent nuclear fuel from conventional thermal nuclear power plants, are also suitable. Instead of burying the spent fuel, it can usefully be used in a uranium blanket.

In fact, the efficiency increases even more if we take into account that a fast neutron, falling into a uranium blanket, causes many different reactions, as a result of which, in addition to the release of 200 MeV energy, several more plutonium nuclei are formed. Thus, the uranium blanket also serves as a powerful producer of new nuclear fuel. Plutonium can then be "burned" at a conventional thermal nuclear power plant, with an effective release of about 340 MeV for each plutonium nucleus.

Even taking into account the fact that one of the additional neutrons must be used to reproduce fuel tritium, the addition of a uranium blanket to the tokamak and several conventional nuclear power plants that "feed" plutonium from this blanket makes it possible to increase the energy efficiency of the tokamak at least once every twenty five , and by some estimates - fifty times! All this is a relatively simple and proven technology. It is clear that no sane person, no government, no commercial organization will miss this opportunity to dramatically increase the efficiency of energy production.

If it comes to industrial production, then thermonuclear fusion at the tokomak will essentially be just a "seed", just a source of precious neutrons, and 96% of the energy will still be produced in fission reactions, and uranium-238 will be the main fuel, respectively. Thus, there will never be a "pure" fusion.

Moreover, if the most complex, expensive and least developed part of this chain - thermonuclear fusion - produces less than 4% of the final power, then a natural question arises, is this link even necessary? Maybe there are cheaper and more efficient sources of neutrons?

It is possible that in the near future something completely new will be invented, but already now there are developments how to use other sources of neutrons instead of thermonuclear in order to freely "burn" natural uranium-238 or thorium. Means

Fast breeder reactors (breeders)

(2nd point of the recent Sarov program)

Electronuclear breeding

Nuclear fusion at a low temperature using muon catalysis.

Each method has its own difficulties and advantages, and each deserves a separate story. The thorium-based nuclear cycle also deserves a separate discussion, which is especially important for us, since there is more thorium in Russia than uranium. India, where the situation is similar, has already chosen thorium as the basis for its future energy. Many people in our country are inclined to believe that the thorium cycle is the most economical and safe method of producing energy in almost unlimited quantities.

Now Russia is at a crossroads: it is necessary to choose a strategy for the development of the energy sector for many decades to come. Choosing the optimal strategy requires open and critical discussion by the scientific and engineering community of all aspects of the program.

This note is dedicated to the memory of Yuri Viktorovich Petrov (1928-2007), a remarkable scientist and man, Doctor of Phys.-Math. Sciences, head of the sector of the St. Petersburg Institute of Nuclear Physics of the Russian Academy of Sciences, who taught the author what is written here.

Yu.V. Petrov, Hybrid nuclear reactors and muon catalysis, in the collection "Nuclear and thermonuclear energy of the future", M., Energoatomizdat (1987), p. 172.

S. S. Gershtein, Yu. V. Petrov and L. I. Ponomarev, Muon catalysis and nuclear breeding, Advances in Physical Sciences, vol. 160, p. 3 (1990).

In the photo: Yu.V. Petrov (right) and Nobel Prize laureate in physics J. ‘T Hooft, photo by D. Dyakonov (1998).