"Pure" thermonuclear energy will not be

At a recent meeting in Sarov, President Medvedev formulated a program for the development of nuclear energy in the country: in the near future-to optimize the water-inflated energy reactor, in the medium term-to form energy based on a closed cycle with fast neutron reactors, in the long term-the practical development of controlled thermal synthesis as the basis of energy future. The last paragraph is commented by Dmitry Dyakonov , Doctor Fiz.-Mat. sciences, deputy head of the department of the St. Petersburg Institute of Nuclear Physics of the Russian Academy of Sciences.

The extraction of nuclear energy is based on the fundamental fact that the nucleus of chemical elements from the middle of the Mendeleev table is packed tightly, and along the edges of the table, i.e. The lightest and most heavy nuclei are less densely. The most densely packed the kernels of iron and its neighbors according to the periodic system. Therefore, we win energy in two cases: when we divide the 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 of dividing heavy elements - uranium, plutonium, thorium - or in nuclear reactions of the synthesis (sticking) of light elements - hydrogen, lithium, berylia, and their isotopes. In nature, in natural conditions, both types of reactions are realized. The synthesis reactions are in all stars, including the Colnz, and are almost the only initial source of energy on Earth - if not directly through sunlight, then indirectly - through oil, coal, gas, water and wind. The natural reaction of division took place on Earth about two billion years ago on the territory of the current Gabon in Africa: a lot of uranium in one place accidentally accumulated there and a natural nuclear reactor worked for 100 million years! Then the concentration of uranium decreased, and the natural reactor stalled.

In the middle of the XX century. Humanity has begun the artificial development of gigantic energy enclosed in nuclei. The atomic bomb (uranium, plutonium) “works” on the reactions of division, a hydrogen bomb (which is not at all from hydrogen, but is called this) - to the synthesis reactions. In a bomb, reaction goes one moment and are explosive. You can reduce the intensity of nuclear reactions, stretch them in time and use them reasonably as a controlled source of energy. Many hundreds of nuclear reactors of various types have been built in the world where division reactions are underway and heavy elements are “burned” - uranium, thorium or plutonium. The task also arose to make a controlled synthesis reaction so that it also serves as a source of energy.

It took only a few years to carry out a controlled reaction of division of division. However, the controlled synthesis reaction was a much more difficult task, which has not yet been fully dealt with. The fact is that in order for two light cores, such as deater and tritium, they can merge, they need to overcome a large potential barrier. The most straightforward way to achieve this is to disperse two light nuclei to high energy, so that they themselves slip through the barrier. This implies that the mixture of deater and tritium should be heated to a very high temperature - about 100 million degrees! At this temperature, the mixture, of course, is ionized, i.e. It is plasma. The plasma is kept in a vessel in the form of a bagel, a magnetic field of a complex configuration and warmed up. This attitude, the invention of I.E. Tamma, A.D. Sakharov, L.A. Arzimovich and others, is called “Tokamak”. The main problem here is to achieve the stability of very hot plasma so that it does not “land on the walls” of the vessel. This requires large installation sizes and, accordingly, very strong magnetic fields in large volume. There are almost no fundamental difficulties here, but there are many technical problems that have not yet been resolved.

Recently, they began to build an international installation of ITER in the area of ​​ex-en-province in France. Russia is actively involved in the project, introducing 1/11 financing. By 2018, the international Tokamak should earn and demonstrate the fundamental possibility of generating energy due to the thermonuclear reaction of the synthesis of helium from a mixture of deater and tritium. This energy in terms of a mass of fuel is tens of millions of times more than one that is released in chemical reactions, for example, during the burning of organic fuel.

Here, the “fuel”, as we see, is a mixture of deater and tritium. Deuterium (“heavy water”) is contained in the form of a small impurity in any water, and it is not difficult to single out it technically. Its reserves are indeed not limited. Triytius is not found in nature, since it is radioactive and decays in 12 years. The standard way to get a tritium is from lithium, by bombardment of it with neutrons. It is assumed that in ITER we need only a small “seeding” of tritium to launch the reaction, and then it will be developed by itself due to the bombing of neutrons formed during the reaction of the lithium “blanket”, i.e. "Blankets", the shell of the current. Therefore, in fact, lithium serves fuel. There is also a lot of it in the earth's crust, but it cannot be said that lithium is an unlimited quantity: if all the energy in the world was produced in this way, the explored deposits of the lithium necessary for this would be enough for 1000 years. About the same amount of the same year, explored uranium and thorium will be enough if we produce energy in ordinary nuclear boilers [1] .

One way or another, the self-supporting thermonuclear reaction of the “burning” of hydrogen isotopes at the modern level of science and technology, apparently, can be realized that this will be successfully demonstrated in ten years, at the installation of ITER. This is a very interesting project both in scientific and technologically, and it is good that our country is involved in it. Moreover, this is not a very frequent case when Russia is not only at the world level, but in many ways this world level sets.

The question is different: can the “thermal” serve as the basis for the industrial receipt of “pure” and “unlimited” energy, according to the enthusiasts of the project. The answer is apparently negative, and that's why.

The fact is that neutrons formed during the synthesis are much more valuable in itself than the energy that is allocated.

Indeed, if you overlay the surface of the Tokamak with a thick “blank” from the most ordinary natural uranium-238, then under the influence of a quick neutron from the synthesis of the nucleus of uranium, it breaks down with the release of additional energy about 200 MeV. Let us pay attention to the numbers:

- the synthesis reaction (1) gives energy of 17.6 MeV in Tokamak plus neutron;

- The subsequent reaction of division in a uranium form gives about 200 MeV.

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

It is noteworthy that Uranus-238 in the form must not be very clean or enriched; On the contrary, there is also the impoverished uranium, which remains a lot in the dumps after enrichment, and even the spent nuclear fuel from ordinary thermal atomic stations. Instead of burying the spent fuel, you can use it with great benefit in a uranium form.

In fact, the effectiveness increases even more, given that the fast neutron, getting into uranium form, causes many diverse reactions, as a result of which, in addition to the release of 200, the energy of energy forms several more cores of plutonium. Thus, uranium form also serves as a powerful manufacturer of new nuclear fuel. Plutonium can then be “burned” at an ordinary thermal nuclear power plant with an effective release of about 340 more for each core of Plutonium.

Even taking into account the fact that one of the additional neutrons should be used for the reproduction of the fuel tritium, the addition of uranium blanket to the Tokamak and several ordinary nuclear power plants that “eat” by plutonium from this form, allows you to increase the energy efficiency of Tokamak at least twenty -five [2] , and according to some estimates, fifty times! This is all a relatively simple and worked out technology. It is clear that not a single sane person, not a single government, not a single commercial organization will miss such an opportunity to repeatedly increase the efficiency of energy production.

If it comes to industrial production, then the thermonuclear synthesis on the Tokomak will essentially be just a “cost”, just a source

Precious neutrons, and 96% of energy will still be produced in division reactions, and Uranus-238, respectively, will respectively. Thus, there will never be a “pure” thermal unit.

Moreover, if the most complex, expensive and least worked out part of this chain - thermonuclear synthesis - produces less than 4% of the final power, then a natural question arises: is this a link is needed? Maybe there are cheaper and effective sources of neutrons?

It is possible that in the near future something completely new will be invented, but now there are achievements, how to use other sources of neutrons instead of a thermal unit to freely “burn” natural uranium-238 or thorium. I mean:

-Rapor-dampers (brider) on fast neutrons (2nd point of the recent Sarov program);

- Electric -core briding;

- Nuclear synthesis at low temperature using muon catalysis.

Each method has its own difficulties and its advantages, and each worthy of a separate story. A nuclear cycle based on thorium also deserves a separate conversation, which is especially relevant for us, since in Russia there is more thorium than Uranus. India, where a similar situation, has already chosen Toria as the basis of her future energy. Many people in our country are inclined to the fact that the thorium cycle is the most economical and safe method of energy production in almost unlimited quantities.

Now Russia is at a crossroads: you need to choose a strategy for the development of energy for many decades ahead. To select the optimal strategy, an open and critical discussion by the scientific and engineering community of all aspects of the program is necessary.

* * *

This article is dedicated to the memory of Yuri Viktorovich Petrov (1928-2007), a wonderful scientist and man, Doctor Fiz.-Mat. sciences, head of the Sector of the St. Petersburg Institute of Nuclear Physics of the Russian Academy of Sciences, which taught the author what is written here.

[1] Yu.V. Petrov, hybrid nuclear reactors and moon catalysis, in the collection “Nuclear and thermonuclear Energy of the Future”, M., Energoatomizdat (1987), p. 172.

[2] S.S. Gershtein, Yu.V. Petrov and L.I. Ponomarev, municipal catalysis and nuclear briding, successes of physical sciences, v. 160, p. 3 (1990).

The article was first published in the Application Environmental Appendix to the Gatchinskaya Pravda newspaper dated 01.09.2009.