HYPOTHESES, FACTS, REASONINGS

Lunar Helium-3 is the thermonuclear fuel of the future.

Comment by the author of the site: With the activation of the American Lunar space program, one hears more and more often that, along with the presence of water, the Moon has huge reserves of the helium-3 isotope - the fuel of the nuclear energy of the future. Is this so, what prospects does this promise to humanity, do we need to explore the Moon at all and how can this be done - this is just a small list of questions, the answers to which you will learn in this article, which is the chapter "Helium-3" from the book of Academician of the Russian Academy of Sciences Eric Mikhailovich Galimov "Concepts and miscalculations: Fundamental space research in Russia in the last twenty years. Twenty years of fruitless efforts."

The fact that the Moon is enriched with helium-3 has been known since lunar matter was first brought to Earth. In samples of lunar soil brought by American astronauts during the Apollo expeditions and delivered by Soviet automatic vehicles Luna, the relative concentration of the helium isotope 3He (3He/4He ratio) turned out to be a thousand times higher than in terrestrial helium. This is the result of the irradiation of the surface of the Moon by the corpuscular radiation of the Sun, which is not protected by the atmosphere. Over the course of billions of years, atoms of elements emitted by the Sun, most of all hydrogen and helium in the isotopic ratio inherent in the Sun, are introduced into the surface dusty layer (regolith) of the Moon. Another fact - that 3 He is an effective thermonuclear fuel - was known to physicists even earlier. However, no practical conclusion was drawn from these facts in those years. Terrestrial energy was provided due to the rapidly developing oil and gas production. Nuclear power was based on available uranium raw materials. Controlled thermonuclear fusion was not carried out even on the simpler reaction of deuterium with tritium. On Earth, helium-3 is not available in commercial quantities.

In the late 80s - early 90s. there were publications about the possible use of the moon as a source of energy for the earth. For example, projects were proposed for transmitting solar energy collected on the surface of the Moon to the Earth in the form of a focused high-frequency beam. The idea of ​​extraction and delivery of lunar helium-3 was also expressed. An enthusiast for this idea, in particular, was the American astronaut Harold Schmidt, who had been on the moon. He wrote a serious book on the possibility of using helium-3.

Calling for a return to lunar exploration, in addition to the specific and urgent task of studying the internal structure of the moon, I constantly mentioned the development of lunar helium-3 resources as a task that must be kept in mind as a distant prospect.

I think that today we do not fully foresee what the conquest of the Moon will give us, and therefore we are embarking on this uncertainly, timidly and with a delay. More than once I had to write about the fact that the study of the Moon is of great importance for fundamental geology. Reconstruction of the early history of the Earth, the origin of the atmosphere, oceans and life on it, is impossible without studying the Moon. If only simply because the traces of the first 500-600 million years of the history of the Earth are completely erased in its geological record, and they are preserved on the Moon. And because the Moon and Earth represent a genetically unified system.

It has two protons and two neutrons.

Encyclopedic YouTube

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✪ Helium - SUPERFLUID AND THE COLDEST ELEMENT!

✪ Superfluid helium. University of Stuttgart

✪ Prospects for thermonuclear energy (says physicist Anton Tyulusov)

✪ Operation "Helium"

✪ Operation "Helium". 3rd series

Subtitles

I want to recommend you the channel of Andrey of the degree on he shoots a video course in organic chemistry for grade 10 now more than 40 videos on 12 topics are available on his channel subscribe to the channel of Andrey to publish and play for 100 points and so today I will tell you about the most common noble gas in the foreseeable universe, which, moreover, can still acquire unique superfluid properties at extremely low temperatures, meet helium in the periodic table, this element is in the upper right corner, it is very easy to find at number 2, I think that today people get acquainted with this inert gas since childhood because of its lightness relative to air, helium is great for inflating holiday balloons that children like so much, this is all due to the fact that the molar mass of helium is about seven times less than the molar masses of air, but nevertheless, in terms of prevalence, gels on earth are extremely rare in the air, it is only only one part per million, the main share of the resulting helium for the same balls is natural gas, in which the concentration of helium can reach up to seven percent by weight, all because as a result of the radioactive decay of uranium or thorium in the earth's crust, helium can accumulate in underground voids with natural gas and not volatilize into the atmosphere, however, if you take it on a larger scale, then in the entire observable universe or it will take the honorable second place in terms of prevalence among all elements, yielding only to hydrogen and forming about a quarter of all atoms, just imagine that all atoms heavier than the gel forms only two percent of the mass of the entire mass of matter, here you can feel how small we are on the scale of the universe; space was formed during the big bang about 14 billion years ago, let's now return from heaven to earth and consider the properties of this gas in a more tangible experiment. has colors besides that it still has no taste or smell you could find out if you ever tried to breathe this gas however such experiments are extremely dangerous because our cells do not breathe helium they need oxygen for this it even forced the current sellers of balloon gel balloons adding up to 20 percent of oxygen to them that you hung at parties has become safer if a high-frequency high-voltage discharge is passed through the oculus with gel, it will begin to glow in a dull orange color, the brightness of which will depend on the voltage and on the diameter of the ampoule, I used the dpla generator as a voltage source knew about and what made it possible for me to hold the ampoule right in my hand and for the presence of an electric capacitance in my body, in principle, like any other, unlike it on or xenon, helium ignites already at a distance from the generator wire, since it has less ionization energy, unfortunately with chemical from the point of view, in fact, it does not shine with interesting properties at all; it does not react with practically any substance, although, nevertheless, in the form of a plasma, it looks like what you see in an ampoule; gels can form an extremely unstable compound with hydrogen, deuterium, or some metals, and at high pressure that thousands of atmospheres even special substances are formed from clart and helios nitrogen, which in the form of crystals can be grown on diamond substrates, it’s a pity that all these substances are very unstable and it’s almost impossible to see them under normal conditions, but you don’t need to be upset because the gel has the most interesting and unique physical properties of all gases. in that when cooled to a temperature of 42 kelvin, it actually becomes the lightest and also the coldest liquid, the density of which is almost 10 times less than the density of water in degrees Celsius, liquid helium is obtained at crazy minus two hundred and sixty-eight degrees, which is very cold, so cold that some metals at such temperature becomes superconductors, for example, mercury or niobium, in order to maintain such a low temperature, liquid helium is located in a double Dewar vessel, which is still cooled with liquid nitrogen from the outside. The same technology for cooling liquid helium is used in modern devices to create nuclear magnetic resonance in them. which, due to the high cost, in turn, is cooled with cheaper liquid nitrogen, in this way the liquid gel serves medicine and also for the research of scientists, but the most interesting thing is yet to come before that, I told you about the first form of liquid helium, the so-called helium 1, if you start to cool it by lowering the pressure in the vessel, the liquid helium will eventually pass the so-called

Prevalence

Opening

The existence of helium-3 was suggested by the Australian scientist Mark Oliphant while working at the University of Cambridge at. This isotope was finally discovered by Luis Alvarez and Robert Kornog in .

Physical properties

Receipt

Currently, helium-3 is not extracted from natural sources (on Earth, small amounts of helium-3 are available, which are extremely difficult to extract), but is created by the decay of artificially obtained tritium.

Price

The average price of helium-3 in 2009 was, according to some estimates, about 930 USD per liter.

Helium-3 mining plans on the Moon

Helium-3 is a by-product of reactions occurring on the Sun and is present in some quantity in the solar wind and the interplanetary medium. Helium-3 entering the Earth's atmosphere from interplanetary space quickly dissipates back, its concentration in the atmosphere is extremely low

Hypothetically, during thermonuclear fusion, when 1 ton of helium-3 reacts with 0.67 tons of deuterium, energy is released that is equivalent to the combustion of 15 million tons of oil (however, the technical feasibility of this reaction has not yet been studied). Consequently, the population of our planet of the lunar resource of helium-3 (according to the maximum estimates) could be enough for about five millennia. The main problem remains the reality of extracting helium from the lunar regolith. As mentioned above, the content of helium-3 in regolith is ~1 g per 100 tons. Therefore, to extract a ton of this isotope, at least 100 million tons of soil should be processed on site.

Usage

Neutron counters

Gas counters filled with helium-3 are used for neutron detection. This is the most common method for measuring the neutron flux. They react

n+ 3 He → 3 H + 1 H + 0.764 MeV.

The charged reaction products - triton and proton - are registered by a gas counter operating in the mode of a proportional counter or a Geiger-Muller counter.

Obtaining ultra-low temperatures

By dissolving liquid helium-3 in helium-4, millikelvin temperatures are reached.

Medicine

Helium-3 as nuclear fuel

The reaction 3 He + D → 4 He + p has a number of advantages over the most achievable deuterium-tritium reaction T + D → 4 He + n under terrestrial conditions. These benefits include:

1. Tens of times lower neutron flux from the reaction zone, which dramatically reduces the induced radioactivity and degradation of the reactor structural materials;
2. The resulting protons, unlike neutrons, are easily captured and can be used to generate additional electricity, for example, in an MHD generator;
3. Synthesis starting materials are inactive and their storage does not require special precautions;
4. In a reactor accident with depressurization of the core, the radioactivity of the release is close to zero.

The disadvantages of the helium-deuterium reaction include a significantly higher temperature threshold. It is necessary to reach a temperature of approximately 10 9 K due to the Coulomb barrier in order for it to start. And at a lower temperature, the thermonuclear reaction of fusion of deuterium nuclei with each other proceeds much more readily, and the reaction between deuterium and helium-3 does not occur.

In art

In science fiction works (games, films, anime), helium-3 sometimes acts as the main fuel and as a valuable resource, including that mined on the moon.

The plot of the 2009 British science fiction film Luna 2112 is based on the operation of the Lunar mining complex. The complex ensures the extraction of the helium-3 isotope, with the help of which it was possible to stop the catastrophic energy crisis on Earth.

In the political comedy Iron Sky, lunar helium-3 is the cause of an international nuclear conflict over mining rights.

In the anime " planetes» Helium-3 is used as fuel for rocket engines, etc.

Literature

• Dobbs E.R. Helium Three. - Oxford University press, 2000. ISBN 0-19-850640-6
• Galimov E.M. If you have energy, you can extract everything - Rare earths. 2014. No. 2. S. 6-12.
• The Helium-3 Shortage: Supply, Demand, and Options for Congress // FAS, December 22, 2010 (English)

Notes

1. Audi G., Wapstra A. H., Thibault C.

Probably few things in the field of thermonuclear energy are surrounded by myths like Helium 3. In the 80s-90s it was actively popularized as a fuel that would solve all the problems of controlled thermonuclear fusion, as well as one of the reasons to get off the Earth (because on its earth is literally a few hundreds of kilograms, and on the moon a billion tons) and finally start exploring the solar system. All this is based on very strange ideas about the possibilities, problems and needs of thermonuclear energy that does not exist today, which we will talk about.

The machine for mining helium3 on the moon is already ready, the only thing left to do is to find a use for it.

When they talk about helium3, they mean thermonuclear fusion reactions He3 + D -> He4 + H or He3 + He3 -> 2He4 + 2H. Compared to classical D + T -> He4 +n there are no neutrons in the reaction products, which means that there is no activation of the construction of a thermonuclear reactor by superenergetic neutrons. In addition, the fact that neutrons from the “classics” carry away 80% of the energy from the plasma is considered a problem, so the self-heating balance occurs at a higher temperature. Another noteworthy advantage of the helium version is that electricity can be removed directly from the charged particles of the reaction, and not by heating water with neutrons - as in old coal-fired power plants.

So, all this is not true, or rather a very small part of the truth.

Let's start with the fact that at the same plasma density and optimal temperature, the reaction He3 + D will give in 40 times less energy release per cubic meter of working plasma. In this case, the temperature required for at least a 40-fold rupture will be 10 times higher - 100 keV (or one billion degrees) versus 10 for D +T. By itself, such a temperature is quite achievable (the record for tokamaks today is 50 keV, only two times worse), but in order to establish an energy balance (cooling rate VS heating rate, including self-heating), we need to increase the energy release by 50 times from cubic meters of He3 + D reaction, which can only be done by raising the density by the same 50 times. In combination with a tenfold increase in temperature, this gives increase in plasma pressure by 500 times- from 3-5 atm to 1500-2500 atm, and the same increase in back pressure to keep this plasma.

But the pictures are inspiring.

Remember, I wrote that the magnets of the ITER toroidal field, which create counterpressure to the plasma, are absolutely record-breaking products, the only ones in the world in terms of parameters? So, He3 fans suggest making magnets 500 times more powerful.

Ok, forget about the difficulties, maybe the advantages of this reaction pay them off?

Various thermonuclear reactions that are applicable for CTS. He3 + D gives slightly more energy than D + T, but a lot of energy is spent on overcoming the Coulomb repulsion (charge 3 and not 2), so the reaction is slow.

Let's start with neutrons. Neutrons in an industrial reactor will be a serious problem, damaging the vessel materials, heating all the elements facing the plasma so much that they have to be cooled with a decent amount of water. And most importantly, the activation of materials by neutrons will lead to the fact that even 10 years after the shutdown of a thermonuclear reactor, it will have thousands of tons of radioactive structures that cannot be disassembled by hand, and which will be aged in storage for hundreds and thousands of years. Getting rid of neutrons would obviously make it easier to create a thermonuclear power plant.

Fraction of energy carried away by neutrons. If you add more He3 to the reactor, you can reduce it to 1%, but this will further tighten the ignition conditions.

OK, but what about the direct conversion of the energy of charged particles into electricity? Experiments show that the flow of ions with an energy of 100 keV can be converted into electricity with 80% efficiency. We don't have neutrons here... I mean, they don't take away all the energy that we can only get in the form of heat - let's get rid of steam turbines and put in ion collectors?

Yes, there are technologies for direct conversion of plasma energy into electricity, they were actively studied in the 60s-70s, and showed an efficiency in the region of 50-60% (not 80, it should be noted). However, this idea is poorly applicable both in D + T reactors and in He3 + D. Why this is so, this picture helps to understand.

It shows the heat loss of the plasma through different channels. Compare D+T and D + He3. Transport is what can be used to directly convert plasma energy into electricity. If in the D + T variant, everything is taken away from us by nasty neutrons, then in the case of He3 + D, everything is taken away by the electromagnetic radiation of the plasma, mainly synchrotron and X-ray bremsstrahlung (in the picture Bremsstrahlung). The situation is almost symmetrical, all the same, it is necessary to remove heat from the walls and still by direct conversion we can't pull out more than 10-15% the energy of thermonuclear combustion, and the rest - the old fashioned way, through a steam engine.

Illustration in a study on direct plasma energy conversion at the largest open trap Gamma-10 in Japan.

In addition to theoretical limitations, there are also engineering ones - in the world (including the USSR) gigantic efforts were spent on creating installations for the direct conversion of plasma energy into electricity for conventional power plants, which made it possible to increase the efficiency from 35% to 55%. Mainly based on MHD generators. 30 years of work of large teams ended in zilch - the resource of the installation was hundreds of hours, when power engineers need thousands and tens of thousands. The gigantic amount of resources spent on this technology has led, in particular, to the fact that our country has lagged behind in the production of power gas turbines and steam-gas turbine cycle plants (which give exactly the same increase in efficiency - from 35 to 55%!).

By the way, powerful superconducting magnets are also needed for MHD generators. Shown here are the SP magnets for a 30 MW MHD generator.

In recent months, the media have been talking a lot about the existence of a number of states (primarily the United States, Russia and China) of projects for the production of helium-3 for controlled thermonuclear reactions. These projects are seen by many as literally the solution to all of humanity's problems. So what is helium-3?

Of all the helium atoms that exist on Earth, 99.999862% of the atoms have a mass 4 times that of a hydrogen atom. This is helium-4. Its atomic nuclei are alpha particles that are formed during radioactive decay. And the remaining 0.000138% of helium atoms are only 3 times heavier than a hydrogen atom. This is helium-3.

The ratio of helium-3 and helium-4 on the scale of the Universe is significantly different - there the number of these isotopes differs by about one order of magnitude. In meteorite matter and in lunar rocks, the content of helium-3 varies from 17 to 32% of the total amount of helium. Billions of years ago, the ratio of helium-4 to helium-3 on Earth was the same as in the entire universe. However, during the time that has passed since then, the helium formed during the primary nucleosynthesis has completely evaporated from the earth's atmosphere. And all the helium that is on Earth today was formed as a result of radioactive decay. That is, on Earth there is practically only helium-4. And helium-3 is formed only on the Sun as a result of thermonuclear reactions occurring there (mainly helium-4 is formed on the Sun, but a lot of helium-3 is also formed there). From the Sun, these elements scatter into space in the form of the so-called "solar wind" (a special type of cosmic rays). The "solar wind" does not hit the Earth and other planets: the atmosphere and the magnetic field interfere. But, say, on the Moon, devoid of an atmosphere, particles of the "solar wind" fall and "get stuck" in the surface layer of the soil.

Until some time, these facts were of purely theoretical interest. On a practical level, they started talking about helium-3 when it became clear that oil would run out in the coming decades. Coal and gas will last a little longer, but also not for long. Obviously, the only way to solve the energy problem is to use the energy of the atomic nucleus. However, the reserves of uranium are also not infinite ... Therefore, the idea of ​​using thermonuclear fusion has been invariably popular for half a century.

In thermonuclear reactions taking place on the Sun, four atoms of the light isotope of hydrogen are combined into one helium atom with the release of energy. However, for thermonuclear reactions produced on Earth, the light hydrogen isotope (constituting 99.985% of all hydrogen) will not work, because the fusion reaction of light hydrogen isotopes has an extremely small cross section (reaction probability). It is this low cross section of the reaction that ensures the stability of the Sun - otherwise it would not be a stable thermonuclear reaction, but a thermonuclear explosion.

For thermonuclear reactions produced on Earth, "heavy hydrogen" - deuterium - is needed. Of the hydrogen that exists on Earth (mostly in the form of water), deuterium makes up 0.015%. It can be obtained by electrolysis of ordinary water, in which deuterium is 0.0017% by weight. However, in addition to deuterium, a thermonuclear reaction requires a second component, the atom of which must be 3 times heavier than hydrogen. It can be either "superheavy hydrogen", which is called tritium, or the same helium-3. Tritium does not exist on Earth, in addition, it is very highly radioactive and unstable. Tritium is suitable for hydrogen bombs and experimental facilities, but not for "industrial" reactors (in hydrogen bombs, tritium is formed when lithium is irradiated with neutrons as a result of the reaction: 6 Li + n -> 3 H + 4 He). A thermonuclear reaction involving tritium is described by the following equation: 2 H + 3 H -> 4 He + n + 17.6 MeV. It is this reaction that is considered as the main one in the planned projects, in particular, in the international ITER project being created.

However, the disadvantage of such a reaction is, firstly, the need for highly radioactive tritium for it, and, secondly, the fact that strong neutron radiation occurs during such a reaction. Therefore, projects of a “neutronless” thermonuclear reaction have been created recently, for which helium-3, a light isotope of helium, serves as fuel. The equations for "neutronless" reactions are as follows:

3 He + 3 He -> 4 He + 2p + 12.8 MeV,
3 He + D -> 4 He + p + 8.35 MeV.

The advantage of reactions on helium-3 in comparison with the deuterium-tritium reaction is that, firstly, it does not require radioactive isotopes as fuel, and, secondly, the resulting energy is carried away not with neutrons, but with protons, from which it will be easier to extract energy.

The only problem is the virtual absence of helium-3 on Earth. But, as mentioned above, helium-3 is in the lunar soil. Therefore, in order to have sources of energy after the end of fossil fuels, the space agencies of different countries are developing plans to build a base on the moon, which will process lunar soil (called regolith), extract helium-3 from it and in liquefied form to deliver it to thermonuclear power plants on Earth. One ton of helium-3 is enough to provide the energy needs of all mankind for several years, which will pay off all the costs of creating a lunar base. Bush has already set a goal: to create an American lunar base in 2015-2020.

And what is being done in Russia today? Here is a selection of reports from news agencies

"Russia can resume the lunar program within a few years
January 15, 2004

Russia is discussing the issue of resuming programs for the exploration of the Moon and Mars, Nikolai Moiseev, First Deputy Head of Rosaviakosmos, told ITAR-TASS. "By the end of the year, the Federal Space Program until 2015 will be developed, which may include these projects," he said. According to Moiseev, "scientists come up with many initiatives to organize expeditions to the Moon and Mars, but it is not yet known which of them will be included in the federal program."

Russia can revive the lunar program within a few years, says Roald Kremnev, First Deputy Director General of the Lavochkin Research and Production Association.
"After the curtailment of the Soviet program for the exploration of the Earth's satellite in the late 70s of the last century, we have been supporting scientific and technical developments on this topic at the modern level for more than three decades," Kremnev says. According to him, at the present time at the enterprise where the legendary "Lunokhod" was created, "there is a serious backlog on lunar automata." The creation and launch of such a device, according to Kremnev, will cost 600 million rubles.

Lunar energy sources can save the Earth from a global energy crisis, academician Eric Galimov, a member of the Bureau of the Space Council of the Russian Academy of Sciences, believes. Tritium mined on the Moon and delivered to Earth can be used for thermonuclear fusion, the scientist claims.
Source: NEWSru.com

Russian scientist proposes to rake miracle fuel from the moon with bulldozers
January 23, 2004

Academician of the Russian Academy of Sciences, member of the bureau of the Space Council of the Russian Academy of Sciences Eric Galimov believes that it is necessary to immediately begin preparations for the extraction of lunar fuel, ITAR-TASS reports. Production of helium-3 on the Moon and its removal from there by spacecraft, in his opinion, can be started in 30-40 years.

“In order to provide all of humanity with energy for a year, only two or three flights of spacecraft with a carrying capacity of 10 tons are needed, which will deliver helium-3 from the Moon ... The cost of interplanetary delivery will be ten times less than the cost of electricity generated now at nuclear power plants ", - said Galimov.

According to the scientist, the delivery of the substance can begin in 30-40 years, but it is necessary to start work in this area now. According to him, the development of the project "will require only 25-30 million dollars." The scientist proposes to collect helium-3 from the lunar surface with special bulldozers.
Source: Lenta.Ru

Last week, in his speech on the new US space program, President Bush announced that a permanent base should be established on the Moon as the first step towards further human space exploration. He also said that lunar soil could be recycled to produce rocket fuel and breathable air.

Bush cited two ways of processing lunar soil as an example, but, in fact, the list of lunar minerals is quite long ... Silicon available in lunar soil can be used to make solar panels, iron - for various metal structures, aluminum, titanium and magnesium - to create a ship that will go into space away from the Earth.
And, of course, they are going to extract the helium-3 isotope on the Moon, which is very rare on Earth, and its production under terrestrial conditions is very expensive.

(adapted from SiliconValley.com)

In March 2003, the leadership of the Chinese space program officially announced the start of work on sending a research probe to the moon. Recently, the scientific director of this project, Academician of the Chinese Academy of Sciences Ouyang Ziyuan, announced that already at this first stage of lunar exploration, China expects to make a great contribution to science and to the development of space technologies. So the Chinese lunar project promises to quickly pay for itself.

The first phase of China's lunar exploration program will, among other things, measure the thickness of the lunar soil, estimate the age of the surface, and determine the amount of helium-3 available there (a very rare helium isotope on Earth that can be used as fuel for a fusion reactor)
(based on SpaceDaily materials)

Interesting arguments about space programs needed to obtain helium-3 reserves are given in the article by Candidate of Technical Sciences, Corresponding Member of the Academy of Cosmonautics. K. E. Tsiolkovsky Yuri Eskov “For clean fuel - to Uranus”, published in Rossiyskaya Gazeta, April 11, 2002. The author writes that it is even more efficient than on the Moon to search for helium-3 in the atmospheres of distant giant planets, for example, Uranus, where helium-3 is 1:3000 (which is a thousand times more than in lunar soil). At the suggestion of the author, “The production of helium-3 and its delivery to the Earth should be carried out by unmanned disposable space vehicles (“tankers”), the electronuclear engine of which with a power of 100,000 kW operates throughout the entire two-way flight. In 10 years, the device will overcome the unimaginable distance of 6 billion km. Note that an engine capable of covering such a gigantic distance in an acceptable time (10 years) can only operate on nuclear energy using the same fuel as current nuclear power plants (in principle, you can fly on solar batteries, but then the device will weigh hundreds thousand tons); moreover, the said engine is environmentally very “dirty”. The trick, however, is that it is launched from a high near-Earth orbit and its entire life passes in space, so it does not create any environmental problems for the population of the Earth.

The system of uninterrupted supply of ground-based TNPPs with a total capacity of 3 billion kW will consist of "tankers" launched periodically (four times a year) from near-Earth orbit. The vehicle will only have enough fuel for one way: it will fly to the target with empty tanks. Having flown to Uranus and entering an orbit within the planet's atmosphere, the “tanker” will start operating in the plant mode for dividing the surrounding atmosphere into components: it will separate commercial helium-3 and hydrogen from liquefied gas, which is used as fuel for the return flight; most of the hydrogen and all of the ordinary helium will be dumped overboard. Thus, return refueling (without which the task of returning is unrealizable) turns out to be in fact free. As a result of the flight, 70 tons of liquid helium-3 will be delivered to near-Earth orbit; there will be about 40 "tankers" on the Earth-Uranus route at any given time.

A natural question arises: to what extent can the technologies existing today ensure the functioning of such a system? Answer: most of these elements are, as they say, “in hardware”, the rest are at the level of far advanced design developments, partially brought to the experimental stage. The main problem here is the onboard power plant. To date, a huge positive experience has been accumulated in the creation and operation of ground-based nuclear power plant reactors with a capacity of 4 million kW with a resource of up to 30 years; the power of nuclear submarine reactors reaches 100,000 kW with a resource of tens of years, there is also domestic experience in the creation and operation of unique small-sized nuclear installations for spacecraft with a power of up to 100 kW high-temperature reactors for space nuclear engines were tested both in the USA and in the USSR. As for the size of the launched unmanned vehicle (450 tons, including 200 tons of fuel), it corresponds in order of magnitude to the mass of the ISS (and in the final project, the mass of the ISS is planned to be even larger); the total annual cargo flow into orbit (1900 tons) is less than that planned for standard programs (space communications, television broadcasting, etc.). The vast majority of the elements of such an orbital helium-hydrogen plant already exist today and are successfully operating in the cryogenic industry.” The author says that even with the current level of technological development, such a project would be quite economically viable: “The selling price of electricity in the world is from 5 to 10 cents per kW. h. From the simplest arithmetic it is clear that the delivery of helium-3 from Uranus will remain profitable even at a price of 1 ton of 10 billion dollars. The cost of launching one such plant into orbit is 10 million dollars per ton (by the way, this is the current price of gold), and in the short term reusable carriers will reduce this price to 1 million dollars per ton of output cargo.”

It has become commonplace to say that knowledge-intensive industries (nuclear, space, etc.) are the locomotive of the economy. The case with helium-3 is the same case. This method, which will allow solving the energy problem for a sufficiently long time, if there are opportunities to find funds for its implementation, can become a chance for the progress of Russian science-intensive industries: both cosmonautics (which is a subject for a separate discussion) and thermonuclear technology.
At the moment, there are two main directions in thermonuclear fusion: tokamaks and laser fusion. The first of these options is currently being implemented in the project of the international experimental thermonuclear reactor ITER. This reactor is designed according to the “tokamak” scheme (which means an abbreviation for the phrase “Toroidal Chamber with Magnetic Coils”). The principle of operation of a tokamak is as follows: an electric current is created in a plasma bunch, and at the same time, like any current, it has its own magnetic field - the plasma bunch, as it were, becomes a magnet itself. And then, with the help of an external magnetic field of a certain configuration, a plasma cloud was suspended in the center of the chamber, not allowing it to come into contact with the walls. There are always free ions and electrons in the gas, which begin to move in a circle in the chamber. This current heats the gas, the number of ionized atoms grows, the current strength increases and the plasma temperature rises simultaneously. This means that the number of hydrogen nuclei that have merged into a helium nucleus and released energy is increasing. However, experiments begun almost fifty years ago at the Moscow Institute of Atomic Energy showed that the plasma suspended in a magnetic field turned out to be unstable - the plasma clot "decayed" very quickly and fell out onto the walls of the chamber. It turned out that a combination of a number of complex physical processes leads to instability. In addition, it turned out that the time of stable plasma confinement increases with the size of the setup. The largest domestic machine TOKAMAK-15 already has a toroidal vacuum chamber with an outer "donut" diameter of more than five meters. Large research tokamaks were built in Russia, Japan, the USA, France, and England. A few years ago, experts came to the conclusion that the remaining unsolved problems should be investigated at a facility as close as possible to a real power thermonuclear reactor. This understanding led to the creation of ITER. This variant of conducting a controlled thermonuclear reaction differs from all other installations and methods primarily in that it has basically gone beyond the realm of doubts and searches. Thanks to the vast database of physical and engineering data accumulated over fifty years of research, he came close to the stage of an experimental reactor. This, apparently, inspired the international community to create ITER - scientists decided that even a rich country does not make any sense to build a thermonuclear reactor alone - the result will be knowledge and experience that will still become common property and will not immediately contribute anything to the national economy. At the same time, by joining forces, you can dramatically accelerate the progress towards your working fusion and reduce your own costs. Therefore, in 1992, an agreement was signed on the joint technical design of the ITER reactor under the auspices of the IAEA. And its conceptual design at the initiative of our country began four years earlier. The ITER design team included specialists from the European Union, Russia, the USA and Japan.
Another direction on the way to a controlled thermonuclear reaction is laser thermonuclear fusion (LTF). It lies in the fact that the target of the "raw material" for a thermonuclear reaction is irradiated from all sides by laser beams, and thus conditions are created there that are sufficient for the implementation of a thermonuclear reaction. The difficulty is how to implement it technically. My dissertation work consists in carrying out computer simulation of the phenomenon of optical resonance in spherical targets under laser irradiation. Calculations show that, under certain conditions, an energy concentration occurs in an optical target, at which the conditions necessary for a thermonuclear reaction may arise.

The state that masters the technology of thermonuclear fusion, this technology before others, will receive huge advantages over others. In order for Russia not to remain on the outskirts of civilization and take part in the development of these projects, the political will of the state leadership is needed, much like it was with Soviet nuclear and space projects in the middle of the 20th century.

This isotope is planned to be mined on the Moon for the needs of thermonuclear energy. However, this is a matter of the distant future. Nevertheless, helium-3 is extremely in demand today, in particular, in medicine.

Vladimir Teslenko

The total amount of helium-3 in the Earth's atmosphere is estimated at only 35,000 tons. Its flow from the mantle into the atmosphere (through volcanoes and faults in the crust) is several kilograms per year. In the lunar regolith, helium-3 gradually accumulated over hundreds of millions of years of exposure to the solar wind. As a result, a ton of lunar soil contains 0.01 g of helium-3 and 28 g of helium-4; this isotopic ratio (~0.04%) is much higher than in the Earth's atmosphere.

The ambitious plans for the extraction of helium-3 on the Moon, which are seriously considered not only by space leaders (Russia and the United States), but also by newcomers (China and India), are connected with the hopes placed on this isotope by the energy industry. The nuclear reaction 3He+D→4He+p has a number of advantages over the most achievable deuterium-tritium reaction T+D→4He+n under terrestrial conditions.

These advantages include a dozen times lower neutron flux from the reaction zone, which dramatically reduces the induced radioactivity and degradation of the reactor structural materials. In addition, one of the reaction products, protons, unlike neutrons, are easily captured and can be used to generate additional electricity. At the same time, both helium-3 and deuterium are inactive, their storage does not require special precautions, and in the event of a reactor accident with depressurization of the core, the radioactivity of the release is close to zero. The helium-deuterium reaction also has a serious drawback - a significantly higher temperature threshold (a temperature of the order of a billion degrees is required to start the reaction).

Although all this is a matter of the future, helium-3 is extremely in demand even now. True, not for energy, but for nuclear physics, the cryogenic industry and medicine.

Magnetic resonance imaging

Since its inception in medicine, magnetic resonance imaging (MRI) has become one of the main diagnostic methods that allow you to look "inside" various organs without any harm.

Approximately 70% of the mass of the human body falls on hydrogen, the nucleus of which, the proton, has a certain spin and an associated magnetic moment. If a proton is placed in an external constant magnetic field, the spin and magnetic moment are oriented either along the field or towards it, and the energy of the proton in the first case will be less than in the second. A proton can be transferred from the first state to the second by transferring to it a strictly defined energy equal to the difference between these energy levels, for example, by irradiating it with electromagnetic field quanta at a certain frequency.

How to magnetize helium-3

The simplest and most direct way to magnetize helium-3 is to cool it in a strong magnetic field. However, the efficiency of this method is very low, moreover, it requires strong magnetic fields and low temperatures. Therefore, in practice, the method of optical pumping is used - the transfer of spin to helium atoms from polarized pump photons. In the case of helium-3, this occurs in two stages: optical pumping in the metastable state and spin exchange between helium atoms in the ground and metastable states. Technically, this is realized by irradiating a cell with helium-3, transferred to a metastable state by a weak high-frequency electric discharge, with circular polarization laser radiation in the presence of a weak magnetic field. Polarized helium can be stored in a vessel lined with cesium at a pressure of 10 atmospheres for about 100 hours.

This is exactly how an MRI scanner works, only it does not detect individual protons. If we place a sample containing a large number of protons in a powerful magnetic field, then the numbers of protons with a magnetic moment directed along and opposite to the field will be approximately equal. If we begin to irradiate this sample with electromagnetic radiation of a strictly defined frequency, all protons with a magnetic moment (and spin) “along the field” will turn over, taking the position “towards the field”. In this case, there is a resonant absorption of energy, and during the process of returning to the initial state, called relaxation, there is a re-emission of the received energy, which can be detected. This phenomenon is called nuclear magnetic resonance, NMR. The average polarization of a substance, on which the useful signal depends in NMR, is directly proportional to the strength of the external magnetic field. To obtain a signal that can be detected and separated from noise, a superconducting magnet is required - only it can create a magnetic field with an induction of the order of 1-3 T.

magnetic gas

An MRI scanner "sees" proton clusters, therefore it is excellent for studying and diagnosing soft tissues and organs containing large amounts of hydrogen (mainly in the form of water), and also makes it possible to distinguish the magnetic properties of molecules. In this way, you can, say, distinguish arterial blood containing hemoglobin (the main oxygen carrier in the blood) from venous blood containing paramagnetic deoxyhemoglobin - this is the basis of fMRI (functional MRI), which allows you to track the activity of brain neurons.

But, alas, such a wonderful technique as MRI is completely unsuitable for studying air-filled lungs (even if you fill them with hydrogen, the signal from a gaseous medium with a low density will be too weak against the noise background). And the soft tissues of the lungs are not very well visible with the help of MRI, because they are "porous" and contain little hydrogen.

Is it possible to bypass this limitation? It is possible if you use a "magnetized" gas - in this case, the average polarization will not be determined by an external field, because all (or almost all) magnetic moments will be oriented in one direction. And this is not fiction at all: in 1966, the French physicist Alfred Kastler received the Nobel Prize with the wording "For the discovery and development of optical methods for studying Hertzian resonances in atoms." He dealt with the issues of optical polarization of spin systems - that is, just the "magnetization" of gases (in particular, helium-3) using optical pumping during resonant absorption of photons with circular polarization.

Nuclear magnetic resonance uses the magnetic properties of hydrogen nuclei - protons. Without an external magnetic field, the magnetic moments of the protons are arbitrarily oriented (as in the first image). When a powerful magnetic field is applied, the magnetic moments of the protons are oriented parallel to the field, either "along" or "towards". These two positions have different energies (2). A radiofrequency pulse with a resonant frequency corresponding to the energy difference "turns" the magnetic moments of the protons "towards" the field (3). After the end of the radio frequency pulse, a reverse "flip" occurs, and the protons emit at the resonant frequency. This signal is received by the radiofrequency system of the tomograph and used by the computer to build the image (4).

Breathe deep

The use of polarized gases in medicine was pioneered by a group of researchers from Princeton and New York University at Stony Brook. In 1994, scientists published an article in the journal Nature showing the first MRI image of a mouse lung.

True, MRI is not quite standard - the technique was based on the response not of hydrogen nuclei (protons), but of xenon-129 nuclei. In addition, the gas was not quite ordinary, but hyperpolarized, that is, “magnetized” in advance. Thus, a new diagnostic method was born, which soon began to be used in human medicine.

Hyperpolarized gas (usually mixed with oxygen) enters the furthest corners of the lungs, which makes it possible to obtain an MRI image with a resolution that is an order of magnitude higher than the best x-rays. It is even possible to build a detailed map of the partial pressure of oxygen in each area of ​​the lungs and then draw conclusions about the quality of the blood flow and the diffusion of oxygen in the capillaries. This technique makes it possible to study the nature of lung ventilation in asthmatics and to control the breathing process of critical patients at the level of the alveoli.

How MRI works. An MRI scanner detects clusters of protons - the nuclei of hydrogen atoms. Therefore, MR imaging shows differences in the content of hydrogen (mainly water) in different tissues. There are other ways to distinguish one tissue from another (say, differences in magnetic properties), which are used in specialized studies.

The advantages of MRI using hyperpolarized gases are not limited to this. Since the gas is hyperpolarized, the useful signal level is much higher (about 10,000 times). This means that there is no need for super-strong magnetic fields, and leads to the design of so-called low-field MRI scanners - they are cheaper, more mobile and much more spacious. In such installations, electromagnets are used that create a field of the order of 0.005 T, which is hundreds of times weaker than standard MRI scanners.

small obstacle

Although the first experiments in this area were carried out with hyperpolarized xenon-129, it was soon replaced by helium-3. It is harmless, produces sharper images than xenon-129, and has three times the magnetic moment, resulting in a stronger NMR signal. In addition, the enrichment of xenon-129 due to the proximity of the mass with other xenon isotopes is an expensive process, and the achievable gas polarization is significantly lower than that of helium-3. In addition, xenon-129 has a sedative effect.

But if low-field tomographs are simple and cheap, why isn't hyperpolarized helium MRI being used in every clinic now? There is one obstacle. But what!

Cold War Legacy

The only way to get helium-3 is by the decay of tritium. Much of the stock of 3He owes its origin to the decay of tritium produced during the nuclear arms race during the Cold War. In the United States, by 2003, approximately 260,000 liters of "raw" (unpurified) helium-3 had been accumulated, and by 2010 only 12,000 liters of unused gas remained. In connection with the growing demand for this scarce gas, the production of limited quantities of tritium was even restored in 2007, and by 2015 it is planned to receive an additional 8,000 liters of helium-3 annually. At the same time, the annual demand for it is already at least 40,000 liters (of which only 5% is used in medicine). In April 2010, the US Committee on Science and Technology concluded that a shortage of helium-3 would lead to real negative consequences for many areas. Even scientists working in the US nuclear industry have difficulty acquiring helium-3 from the state's stockpiles.

Mixing cooling

Another industry that cannot do without helium-3 is the cryogenic industry. To achieve ultra-low temperatures, the so-called. dilution refrigerator that uses the effect of dissolving helium-3 into helium-4. At temperatures below 0.87 K, the mixture separates into two phases, rich in helium-3 and helium-4. The transition between these phases requires energy, and this allows cooling to very low temperatures - down to 0.02 K. The simplest such device has a sufficient supply of helium-3, which gradually moves through the interface into the phase rich in helium-4 with absorption of energy . When the supply of helium-3 runs out, the device will not be able to work further - it is "disposable".
It is this method of cooling, in particular, that was used in the Planck orbital observatory of the European Space Agency. Planck's task was to record the anisotropy of the CMB (with a temperature of about 2.7 K) with high resolution using 48 HFI (High Frequency Instrument) bolometric detectors cooled to 0.1 K. Before the supply of helium-3 in the cooling system was exhausted, Planck managed to take 5 pictures of the sky in the microwave range.

The auction price of helium-3 fluctuates around $2,000 per liter, and no downward trend is observed. The shortage of this gas is due to the fact that the bulk of helium-3 is used to make neutron detectors, which are used in devices for detecting nuclear materials. Such detectors register neutrons according to the (n, p) reaction - the capture of a neutron and the emission of a proton. And in order to detect attempts to import nuclear materials, a lot of such detectors are required - hundreds of thousands of pieces. It is for this reason that helium-3 has become fantastically expensive and inaccessible to mass medicine.

However, there are hopes. True, they are not assigned to lunar helium-3 (its production remains a distant prospect), but to tritium, which is formed in heavy-water reactors of the CANDU type, which are operated in Canada, Argentina, Romania, China and South Korea.