A new technique has been developed to effectively slow down runaway electrons by introducing "heavy" ions, such as neon or argon, into the reactor.
A functional fusion reactor is still a dream, but it could eventually come true thanks to the many studies and experiments with the goal of unlocking an unlimited supply of clean energy. The problems that scientists face in obtaining nuclear fusion are undoubtedly serious and indeed difficult, but everything is surmountable. And it seems that one of the main problems is solved.
Nuclear fusion is not a process invented by mankind, but originally existing in nature, the process feeds our Sun. Deep inside our home star, hydrogen atoms sit together to form helium, which kickstarts the process. Fusion releases a huge amount of energy, but it costs a lot to create extremely high pressure and temperature, which is difficult to reproduce on Earth in a controlled manner.
Last year, researchers at MIT brought us closer to fusion by placing plasmas at just the right pressure, now two researchers at Chalmers University have discovered another piece of the puzzle.
One problem that engineers have encountered is runaway electrons. These extremely high-energy electrons can suddenly and unexpectedly accelerate to very high speeds, which can destroy the reactor wall without warning.
Doctoral students Linnea Heshlow and Ole Amberose have developed a new technique to effectively slow down these runaway electrons by introducing "heavy" ions such as neon or argon into the reactor. As a result, electrons, colliding with a high charge in the nuclei of these ions, slow down and become much more controllable.
“When we can effectively slow down the runaway electrons, we will be one step closer to a functional fusion reactor,” says Linnea Heshlov.
The researchers have created a model that can effectively predict electron energy and behavior. Using Mathematical Plasma Modeling, physicists can now effectively control the escape velocity of electrons without interrupting the fusion process.
“Many people believe that this will work, but it is easier to go to Mars than to achieve a merger,” says Linnea Heshlov: “You could say that we are trying to collect stars here on earth, and this may take some time. It takes incredibly high temperatures, hotter than the center of the sun, for us to successfully merge here on earth. So I hope it's all a matter of time."
based on newatlas.com, translation
July 9, 2016Innovative projects using modern superconductors will soon allow controlled thermonuclear fusion, some optimists say. Experts, however, predict that practical application 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? To begin with, we need to understand the difference between classical nuclear fission and thermonuclear fusion.
The fission of the atom consists in the fact that radioactive isotopes - uranium or plutonium - are split and converted into other highly radioactive isotopes, which then must be buried or recycled.
The 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 face a daunting task - how to control this process at a power plant?
This is something scientists have been working on since the 1960s. Another experimental fusion reactor called Wendelstein 7-X has started operation 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 (a stellarator instead of a tokamak).
high energy plasma
All thermonuclear installations have a common feature - an annular shape. It is based on the idea of using powerful electromagnets to create a strong electromagnetic field shaped like 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 must appear in the very center of the ring. It is then ignited so that thermonuclear fusion can begin.
Demonstration of possibilities
Two such experiments are currently underway in Europe. One of them is the Wendelstein 7-X, which recently generated its first helium plasma. The other is ITER, a huge experimental fusion facility in the south of France that is still under construction and will be ready to go live in 2023.
Real nuclear reactions are expected to take place at ITER, albeit only for a short period of time and certainly no longer than 60 minutes. This reactor is just one of many steps on the way to making nuclear fusion a reality.
Fusion reactor: smaller and more powerful
Recently, several designers have announced a new reactor design. According to a group of students from the Massachusetts Institute of Technology, as well as representatives of the weapons company Lockheed Martin, fusion can be carried out in facilities that are much more powerful and smaller than ITER, and they are ready to do it within ten years.
The idea of the new design is to use modern high-temperature superconductors in electromagnets, which exhibit their properties when cooled with liquid nitrogen, rather than conventional ones, which require liquid helium. The new, more flexible technology will make it possible to completely change the design of the reactor.
Klaus Hesch, who is in charge of nuclear fusion technology at the Karlsruhe Institute of Technology in southwest Germany, is skeptical. It supports the use of new high-temperature superconductors for new reactor designs. But, according to him, to develop something on a computer, taking into account the laws of physics, is not enough. It is necessary to take into account the challenges that arise when putting an idea into practice.
Science fiction
According to Hesh, the MIT student model only shows the possibility of a project. But it's actually a lot of science fiction. The project assumes that serious technical problems of thermonuclear fusion are solved. But modern science has no idea how to solve them.
One such problem is the idea of collapsible coils. Electromagnets can be dismantled in order to get inside the ring that holds the plasma in the MIT design model.
This would be very useful because one would be able to access objects in the internal system and replace them. 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 here there are more fundamental difficulties: the connections between them are not as simple as the connections of copper cables. No one has even thought of concepts that would help solve such problems.
too hot
High temperature is also a problem. At the core of the fusion plasma, the temperature will reach about 150 million degrees Celsius. This extreme heat remains 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 pipe in which the tritium necessary for nuclear fusion to occur will "reproduce".
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 the hot gas enters are called the "divertor". It can heat up to over 2000°C.
Diverter problem
In order for the installation to withstand such temperatures, engineers are trying to use the metal tungsten used in old-fashioned incandescent lamps. The melting point of tungsten is about 3000 degrees. But there are other limitations as well.
In ITER, this can be done, because heating in it does not occur constantly. It is assumed that the reactor will operate only 1-3% of the time. But that's not an option for a power plant that needs to run 24/7. And, if someone claims to be able to build a smaller reactor with the same power as ITER, it is safe to say that he does not have a 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 fusion can actually produce more energy than would be spent on heating the plasma. The next step is to build a brand 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 scheduled 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 middle of the 21st century.
Cold Fusion Rossi
In 2014, an independent test of the E-Cat reactor concluded that the device averaged 2,800 watts of power output over a 32-day period with a consumption of 900 watts. This is more than any chemical reaction is capable of isolating. The result speaks either of a breakthrough in thermonuclear fusion, or of outright fraud. The report disappointed skeptics, who doubt whether the test was truly independent and suggest possible falsification of the test results. Others have been busy figuring out the "secret ingredients" that enable Rossi's fusion to replicate the technology.
Rossi is a scammer?
Andrea is imposing. He publishes proclamations to the world in unique English in the comments section of his website, pretentiously called the Journal of Nuclear Physics. But his previous failed attempts have included an Italian waste-to-fuel project and a thermoelectric generator. Petroldragon, a waste-to-energy project, failed in part because the illegal dumping of waste is controlled by Italian organized crime, which has filed criminal charges against it for violating waste management 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 Rossi, and the editor-in-chief of the New Energy Times bluntly called him a criminal with a string of failed energy projects behind him.
Independent Verification
Rossi signed a contract with the American company Industrial Heat to conduct a year-long secret test of a 1-MW cold fusion plant. The device was a shipping container packed with dozens of E-Cats. The experiment had to be controlled by a third party who could confirm that heat generation was indeed taking place. Rossi claims to have spent much of the past year practically living in a container and overseeing operations for more than 16 hours a day to prove the commercial viability of the E-Cat.
The test ended in March. Rossi's supporters eagerly awaited the observers' report, hoping for an acquittal for their hero. But in the end they got sued.
Trial
In a Florida court filing, Rossi claims the test was successful and an independent arbitrator confirmed that the E-Cat reactor produces six times more energy than it consumes. He also claimed that Industrial Heat agreed to pay him $100 million - $11.5 million upfront after the 24-hour trial (ostensibly for licensing rights so the company could sell the technology in the US) and another $89 million after the successful completion of the extended trial. within 350 days. Rossi accused IH of running a "fraudulent scheme" to steal his intellectual property. He also accused the company of misappropriating E-Cat reactors, illegally copying innovative technologies and products, functionality and designs, and abusing a patent on his intellectual property.
Goldmine
Elsewhere, Rossi claims that in 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 is at stake. Industrial Heat has dismissed these claims as baseless and is going to actively defend itself. More importantly, she claims that she "worked for more than three years to confirm the results that Rossi allegedly achieved with his E-Cat technology, all without success."
IH doesn't believe in the E-Cat, 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 reported his serious concerns about the method of measuring thermal power. 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 scam.
Experimental confirmation
Nevertheless, a number of researchers - Alexander Parkhomov of the Peoples' Friendship University of Russia and the Martin Fleishman Memorial Project (MFPM) - have succeeded in replicating Russia's cold fusion. The MFPM report was titled "The End of the Carbon Era Is Near". The reason for such admiration was the discovery of a burst of gamma radiation, which cannot be explained otherwise than by a thermonuclear reaction. According to the researchers, Rossi has exactly what he is talking about.
A viable open recipe for cold fusion could spark an energy gold rush. Alternative methods may be found to bypass Rossi's patents and keep him out of the multi-billion dollar energy business.
So perhaps Rossi would prefer to avoid this confirmation.
3. Problems of controlled thermonuclear fusion
Researchers in all developed countries pin their hopes on overcoming the coming energy crisis with a controlled thermonuclear reaction. Such a reaction - the synthesis of helium from deuterium and tritium - has been taking place on the Sun for millions of years, and under terrestrial conditions for fifty years now they have been trying to carry it out in giant and very expensive laser facilities, tokamaks (a device for carrying out a thermonuclear fusion reaction in hot plasma) and stellarators ( closed magnetic trap to contain high-temperature plasma). However, there are other ways to solve this difficult problem, and instead of huge tokamaks, it will probably be possible to use a rather compact and inexpensive collider - an accelerator on colliding beams - for the implementation of thermonuclear fusion.
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. If we assume that all thermonuclear power plants will produce 10 trillion. kW / h of electricity per year, that is, as much as all the power plants of the Earth produce today, then the world 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 fusion is possible when two deuterium atoms are combined. If this reaction is mastered, energy problems will be solved immediately and forever.
In any of the known versions of controlled thermonuclear fusion (CTF), thermonuclear reactions cannot enter the mode of uncontrolled increase in power, therefore, such reactors are not intrinsically safe.
From a physical point of view, the problem is formulated simply. For a self-sustaining nuclear fusion reaction to occur, it is necessary and sufficient to satisfy 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 radius of which is 10-12-10-13 s.cm. However, atomic nuclei have a positive electric charge, and like charges repel each other. At the boundary of the action of nuclear forces, the energy of the Coulomb repulsion is about 10 keV. To overcome this barrier, the nuclei in the collision must have a kinetic energy of at least not less than this value.
2. The product of the concentration of reacting nuclei and the retention time during which they retain the indicated 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 at least cover the energy costs of initiating the reaction, atomic nuclei must undergo many collisions. In each collision in which a fusion reaction occurs between deuterium (D) and tritium (T), 17.6 MeV of energy is released, i.e. approximately 3.10-12 J. If, for example, 10 MJ energy is spent on ignition, then the reaction will break even if at least 3.1018 D-T pairs take part 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 fractions 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 - a cold fusion. What is a cold fusion - this 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 on 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 achievement of ultra-high temperature to split the nucleus of the atom. The thermal method gives an uncontrolled nuclear reaction. The energy of a cold fusion is the energy of the transition state. One of the main conditions for the design of a reactor for carrying out a cold fusion reaction 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 Taleiarkhan from the Oak Ridge National Laboratory, Richard Leikhi from the Polytechnic University. Renssilira and Academician Robert Nigmatulin - recorded a cold thermonuclear reaction in the laboratory.
The group used a beaker of liquid acetone the size of two to three glasses. Sound waves were intensely transmitted through the liquid, producing an effect known in physics as acoustic cavitation, the consequence of which is sonoluminescence. During cavitation, small bubbles appeared in the liquid, which increased to two millimeters in diameter and exploded. Explosions were accompanied by flashes of light and release of energy i.e. the temperature inside the bubbles at the time of the explosion reached 10 million degrees Kelvin, and the energy released, according to the experimenters, is enough to carry out thermonuclear fusion.
"Technically" the essence of the reaction lies in the fact that as a result of the combination of two atoms of deuterium, a third is formed - an isotope of hydrogen, known as tritium, and a neutron, characterized by an enormous amount of energy.
The current in the superconducting state is zero, and, therefore, the minimum amount of electricity will be spent on maintaining the magnetic field. 8. Superfast systems. Controlled thermonuclear fusion with inertial confinement The difficulties associated with the magnetic confinement of plasma can, in principle, be circumvented if nuclear fuel is burned in extremely short times, when ...
For 2004 . The next negotiations on this project will be held in May 2004 in Vienna. The reactor will be built in 2006 and is scheduled to be launched in 2014. How it works Fusion* is a cheap and environmentally friendly way to produce energy. For billions of years, uncontrolled thermonuclear fusion has been taking place on the Sun - helium is formed from the heavy isotope of hydrogen deuterium. Wherein...
The experimental thermonuclear reactor is headed by E.P. Velikhov. The United States, having spent 15 billion dollars, withdrew from this project, the remaining 15 billion has already been spent by international scientific organizations. 2. Technical, environmental and medical problems. During the operation of controlled thermonuclear fusion (UTF) installations. neutron beams and gamma radiation occur, as well as...
Energy and what quality will be needed in order for the released energy to be sufficient to cover the costs of starting the energy release process. We will discuss this question below in connection with the problems of thermonuclear fusion. On the energy quality of lasers In the simplest cases, the limitations on the conversion of low-quality energy into high-quality energy are obvious. Here are some examples from...
1. Introduction
3. Problems of thermonuclear fusion control
3.1 Economic problems
3.2 Medical problems
4. Conclusion
5. References
1. Introduction
The problem of controlled thermonuclear fusion is one of the most important tasks facing mankind.
Human civilization cannot exist, let alone develop, without energy. Everyone is well aware that the developed sources of energy, unfortunately, may soon be depleted. According to the World Energy Council, the explored 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, suitable for development oil fields left, and already our grandchildren may face a very serious problem of lack of energy.
Nuclear power plants, which are best supplied with fuel, could, of course, supply humanity with electricity for more than one hundred years.
Object of study: Problems of controlled thermonuclear fusion.
Subject of study: Thermonuclear fusion.
Purpose of the study: Solve the problem of thermonuclear fusion control;
Research objectives:
· To study types of thermonuclear reactions.
· Consider all possible options for bringing the energy released during a thermonuclear reaction to a person.
· Put forward a theory about the conversion of 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 do work, radiate heat or radiation. Energy in any system is always conserved, but it can be transferred to another system or changed in form.
Achievement conditions of controlled thermonuclear fusion are hindered 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.
· Thirdly, the amount of energy released must be greater than was expended for heating and limiting the density of the gas.
The next problem is the accumulation of this energy and converting it into electricity
2. Thermonuclear reactions on the Sun
What is the source of solar energy? What is the nature of the processes during which a huge amount of energy is produced? How long will the sun continue to shine?
The first attempts to answer these questions were made by astronomers in the middle of the 19th century, after the physicists formulated the law of conservation of energy.
Robert Mayer suggested that the Sun shines due to the constant bombardment of the surface by meteorites and meteor 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∙10 15 kg of meteoric matter fall on it every second. For a year it will be 6∙10 22 kg, and for the lifetime of the Sun, for 5 billion years - 3∙10 32 kg. Sun mass M
= 2∙10 30 kg, therefore, in five billion years, matter 150 times more than the mass of the Sun should have fallen on the Sun.The second hypothesis was also put forward by Helmholtz and Kelvin in the middle of the 19th century. They suggested that the Sun radiates by contracting 60–70 meters annually. The reason for the contraction is the mutual attraction of the particles of the Sun, which is why this hypothesis is called contraction. 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 Moon's soil.
The third hypothesis about the possible sources of solar energy was put forward 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 transformation of uranium into thorium and then into lead is accompanied by the release of energy. Subsequent analysis of this hypothesis also showed its failure; a star composed of only uranium would not release enough energy to provide the observed luminosity of the Sun. In addition, there are stars that are many times more luminous than our star. It is unlikely that those stars would also contain more radioactive material.
The most probable hypothesis turned out to be 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 thermonuclear reaction of converting hydrogen into helium could be the source of solar energy. It was 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. Approximately 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 "burning" 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 is the proton-proton cycle - a very slow reaction (characteristic time 7.9∙10 9 years), as it is due to weak interaction. Its essence lies in the fact that from four protons a helium nucleus is obtained. In this case, a pair of positrons and a pair of neutrinos are released, as well as 26.7 MeV of energy. The number of neutrinos emitted by the Sun per second is determined only by the luminosity of the Sun. Since when 26.7 MeV is released, 2 neutrinos are born, the neutrino emission rate is: 1.8∙10 38 neutrinos/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 compared to the theoretical value for the standard solar model. Low-energy neutrinos that arise 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 rest mass other than zero, oscillations (transformations) of various types of neutrinos are possible (the Mikheev-Smirnov-Wolfenstein effect) (there are three types of neutrinos: electron, muon and tauon neutrinos). Because other neutrinos have much smaller interaction cross sections with matter than electrons, 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.
Every second, the Sun recycles about 600 million tons of hydrogen. Stocks of nuclear fuel will last another five billion years, after which it will gradually turn into a white dwarf.
The central parts of the Sun will shrink, heating up, and the heat transferred to the outer shell will lead to its expansion to sizes monstrous compared to modern ones: the Sun will expand so much that it will absorb Mercury, Venus and will spend "fuel" a hundred times faster, than at present. 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!
Of course, we 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 also begin to burn, turning into heavy elements, and the Sun will enter a 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 large 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.
3. Problems of controlled thermonuclear fusion
Researchers in all developed countries pin their hopes on overcoming the coming energy crisis with a controlled thermonuclear reaction. Such a reaction - the synthesis of helium from deuterium and tritium - has been taking place on the Sun for millions of years, and under terrestrial conditions for fifty years now they have been trying to carry it out in giant and very expensive laser facilities, tokamaks (a device for carrying out a thermonuclear fusion reaction in hot plasma) and stellarators ( closed magnetic trap to contain high-temperature plasma). However, there are other ways to solve this difficult problem, and instead of huge tokamaks, it will probably be possible to use a rather compact and inexpensive collider - an accelerator on colliding beams - for the implementation of thermonuclear fusion.
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. If we assume that all thermonuclear power plants will produce 10 trillion. kW / h of electricity per year, that is, as much as all the power plants of the Earth produce today, then the world 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 fusion is possible when two deuterium atoms are combined. If this reaction is mastered, energy problems will be solved immediately and forever.
In any of the known versions of controlled thermonuclear fusion (CTF), thermonuclear reactions cannot enter the mode of uncontrolled increase in power, therefore, such reactors are not intrinsically safe.
MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION
Federal Agency for Education
SEI HPE "Blagoveshchensk State Pedagogical University"
Faculty of Physics and Mathematics
Department of General Physics
Course work
on the topic: Problems of thermonuclear fusion
discipline: Physics
Artist: V.S. Kletchenko
Head: V.A. Evdokimova
Blagoveshchensk 2010
Introduction
Thermonuclear reactions and their energy efficiency
Conditions for the occurrence of thermonuclear reactions
Realization of thermonuclear reactions in terrestrial conditions
The main problems associated with the implementation of thermonuclear reactions
Implementation of controlled thermonuclear reactions in TOKAMAK-type facilities
ITER project
Modern studies of plasma and thermonuclear reactions
Conclusion
Literature
Introduction
At present, 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 station or a nuclear power plant reactor, it immediately becomes clear why. Scientists in the 20th century, in the face of an energy crisis, found a way to generate electricity from matter, the amount of which is not limited. Thermonuclear reactions take place during the decay of deuterium and tritium. One liter of water contains so much deuterium that thermonuclear fusion can release as much energy 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 with the help of thermonuclear fusion would be as simple as with the help of hydroelectric power stations, then humanity would never experience a crisis in the energy sector. To obtain energy in this way, a temperature equivalent to the temperature at the center of the sun is needed. Where to get such a temperature, how expensive the installations will cost, how profitable is such energy production and is such a installation safe? These questions will be answered in the present work.
Purpose of work: study of properties and problems of thermonuclear fusion.
Thermonuclear reactions and their energy efficiency
Thermonuclear reaction - the synthesis of heavier atomic nuclei from lighter ones in order to obtain energy, which is controlled.
It is known that the nucleus of the 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 isotopes of hydrogen. 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 р, two neutrons n and is called tritherium (tritium) Т. the energy released during the fission of heavy nuclei. In the fusion reaction, energy is released, which, per 1 kg of substance, is much greater than the energy released in the uranium fission reaction. (Here, the released energy refers to the kinetic energy of the particles formed as a result of the reaction.) For example, in the reaction of the 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.
In the synthesis of a helium nucleus from four protons:
4 1 1 p→ 2 4 Not + 2 +1 1 e,
even more energy is released, equal to 6.7 MeV per particle. The energy 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 occurrence of thermonuclear reactions
For the fusion of light nuclei, it is necessary to overcome the potential barrier caused by the Coulomb repulsion of protons in like positively charged nuclei. For the fusion of hydrogen nuclei 1 2 Dx, it is necessary to bring them closer to a distance r, equal to approximately r ≈ 3 10 -15 m. To do this, you need to do work equal to the electrostatic potential energy of repulsion P \u003d e 2: (4πε 0 r) ≈ 0.1 MeV. The deuteron nuclei will be able to overcome such a barrier if their average kinetic energy 3/2 kT is equal to 0.1 MeV during the collision. This is possible at T = 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 about 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 in the Sun and stars and are the source of energy that provides their radiation. Every second, the Sun radiates 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 in one 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 process of metabolism. The radiation power of the Sun has not changed much over the many billions of years of the existence of the solar system.
One of the ways for thermonuclear reactions to proceed 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 carbon 6 12 C nuclei that play the role of catalysts. At the beginning of the cycle, a fast proton penetrates into the nucleus of the carbon atom 6 12 C and forms an unstable nucleus of the nitrogen isotope 7 13 N with γ-quantum radiation:
6 12 С + 1 1 p → 7 13 N + γ.
With a half-life of 14 minutes, the transformation 1 1 p→ 0 1 n + +1 0 e + 0 0 ν e occurs in the 7 13 N nucleus and the nucleus of the 6 13 C isotope is formed:
7 13 N → 6 13 С + +1 0 e + 0 0 ν e.
approximately every 32 million years, the 7 14 N nucleus captures a proton and turns into an oxygen nucleus 8 15 O:
7 14 N+ 1 1 p→ 8 15 O + γ.
An unstable 8 15 O nucleus with a half-life of 3 minutes emits a positron and a neutrino and turns into a 7 15 N nucleus:
8 15 О→ 7 15 N+ +1 0 e+ 0 0 ν e.
The cycle ends with the reaction of absorption of a proton by the 7 15 N nucleus with its decay into a carbon 6 12 С nucleus and an α-particle. This happens after about 100 thousand years:
7 15 N+ 1 1 p → 6 12 С + 2 4 He.
A new cycle begins again with the absorption of a 6 12 C proton by carbon, which comes out on average after 13 million years. The individual reactions of the cycle are separated in time by intervals that are prohibitively large on earthly time scales. However, the cycle is closed and occurs continuously. Therefore, various reactions of the cycle occur on the Sun simultaneously, 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. The formation of one helium gamma atom releases 700 thousand kWh of energy. 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 support thermonuclear reactions and solar radiation for billions of years.
Realization of thermonuclear reactions in terrestrial conditions
The implementation of thermonuclear reactions in terrestrial conditions will create huge opportunities for obtaining energy. For example, when using the deuterium contained in one liter of water, the same amount of energy will be released in a fusion reaction as will be released when burning about 350 liters of gasoline. But if the thermonuclear reaction proceeds spontaneously, then a colossal explosion will occur, since the energy released in this case is very large.
Conditions close to those that are realized in the bowels of the Sun were realized in a hydrogen bomb. There is a self-sustaining thermonuclear reaction of an explosive nature. The explosive is a mixture of deuterium 1 2 D with tritium 1 3 T. The high temperature necessary for the reaction to proceed is obtained by the explosion of a conventional atomic bomb placed inside a thermonuclear one.
The main problems associated with the implementation of thermonuclear reactions
In a fusion reactor, the fusion reaction must be slow, and 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 to obtain a self-sustaining thermonuclear reaction. For such a reaction, it is necessary that the rate of energy release in the system where the reaction occurs is not less than the rate of energy removal from the system. At temperatures of the order of 10 8 K, thermonuclear reactions in a deuterium plasma have a noticeable intensity and are accompanied by the release of large energy. In a unit of plasma volume, 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 .
