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Fast neutron nuclear power plant. The energy of the future turns green with fast neutron reactors

Accompanied by the release of temperature, depending on the design features, two types are distinguished - a reactor on fast neutrons and slow, sometimes called thermal.

The neutrons released during the reaction have a very high initial speed, theoretically covering thousands of kilometers per second. These are fast neutrons. In the process of moving, due to collisions with atoms of surrounding matter, their speed slows down. One of the simplest and available ways To artificially reduce speed is to place water or graphite in their path. Thus, having learned to regulate the level of these particles, man was able to create two types of reactors. “Thermal” neutrons got their name due to the fact that the speed of their movement after slowing down practically corresponds to the natural speed of intra-atomic thermal movement. In numerical equivalent, it is up to 10 km per second. For the microcosm, this value is relatively low, so the capture of particles by nuclei occurs very often, causing new rounds of fission (chain reaction). The consequence of this is the need for much less fissile material, which fast neutron reactors cannot boast of. In addition, some others are reduced. This point explains why most operating nuclear stations use slow neutrons.

It would seem that if everything is calculated, then why do we need a fast neutron reactor? It turns out that not everything is so simple. The most important advantage of such installations is the ability to supply other reactors, as well as create an increased fission cycle. Let's look at this in more detail.

A fast neutron reactor makes more complete use of the fuel loaded into the core. Let's start in order. Theoretically, only two elements can be used as fuel: plutonium-239 and uranium (isotopes 233 and 235). Only the U-235 isotope is found in nature, but there is very little of it to talk about the prospects of such a choice. The specified uranium and plutonium are derivatives of thorium-232 and uranium-238, which are formed as a result of exposure to a neutron flux. But these two are much more common in their natural form. Thus, if it were possible to launch a self-sustaining chain reaction of fission of U-238 (or plutonium-232), then its result would be the emergence of new portions of fissile material - uranium-233 or plutonium-239. When neutrons are slowed down to thermal speed (classical reactors), such a process is impossible: the fuel in them is U-233 and Pu-239, but a fast neutron reactor allows such an additional transformation.

The process is as follows: we load uranium-235 or thorium-232 (raw materials), as well as a portion of uranium-233 or plutonium-239 (fuel). The latter (any of them) provide the neutron flux necessary to “ignite” the reaction in the first elements. During the decay process, the station's generators convert it into electricity. Fast neutrons affect raw materials, converting these elements into... new portions of fuel. Typically, the amounts of burned and generated fuel are equal, but if more raw materials are loaded, then the generation of new portions of fissile material occurs even faster than consumption. Hence the second name for such reactors - breeders. Excess fuel can be used in classic slow types of reactors.

The disadvantage of fast neutron models is that uranium-235 must be enriched before loading, which requires additional financial investments. In addition, the design of the core itself is more complex.

After the launch and successful operation of the world's first nuclear power plant in 1955, on the initiative of I. Kurchatov, a decision was made to build an industrial nuclear power plant with a channel-type pressurized water reactor in the Urals. Features of this type of reactor include superheating of steam to high parameters directly in the core, which opened up the possibility of using serial turbine equipment.

In 1958, in the center of Russia, in one of the most picturesque corners of the Ural nature, the construction of the Beloyarsk Nuclear Power Plant began. For installers, this station began back in 1957, and since the topic of nuclear power plants was closed in those days, in correspondence and life it was called the Beloyarsk State District Power Plant. This station was started by employees of the Uralenergomontazh trust. Through their efforts, in 1959, a base with a workshop for the production of water and steam pipelines (1 circuit of the reactor) was created, three residential buildings were built in the village of Zarechny, and construction of the main building began.

In 1959, workers from the Tsentroenergomontazh trust appeared at the construction site and were tasked with installing the reactor. At the end of 1959, a site from Dorogobuzh, Smolensk region, and installation work headed by V. Nevsky, future director of the Beloyarsk NPP. All work on the installation of thermal mechanical equipment was completely transferred to the Tsentroenergomontazh trust.

The intensive period of construction of the Beloyarsk NPP began in 1960. At this time, the installers had to, along with conducting construction work master new technologies for the installation of stainless pipelines, linings of special rooms and radioactive waste storage facilities, installation of reactor structures, graphite masonry, automatic welding, etc. We learned on the fly from specialists who had already taken part in the construction of nuclear facilities. Having moved from the technology of installation of thermal power plants to the installation of equipment for nuclear power plants, the workers of Tsentroenergomontazh successfully completed their tasks, and on April 26, 1964, the first power unit of the Beloyarsk NPP with the AMB-100 reactor supplied the first current to the Sverdlovsk energy system. This event, along with the commissioning of the 1st power unit of the Novovoronezh NPP, meant the birth of the country's large nuclear power industry.

The AMB-100 reactor was a further improvement in the reactor design of the World's First Nuclear Power Plant in Obninsk. It was a channel-type reactor with higher thermal characteristics of the core. Obtaining steam of high parameters due to nuclear overheating directly in the reactor was a big step forward in the development of nuclear energy. the reactor operated in one unit with a 100 MW turbogenerator.

Structurally, the reactor of the first power unit of the Beloyarsk NPP turned out to be interesting in that it was created virtually without a frame, i.e., the reactor did not have a heavy, multi-ton, durable body, like, say, a water-cooled water-cooled VVER reactor of similar power with a body 11-12 m long , with a diameter of 3-3.5 m, wall and bottom thickness of 100-150 mm or more. The possibility of constructing nuclear power plants with open-channel reactors turned out to be very tempting, since it freed heavy engineering plants from the need to manufacture steel products weighing 200-500 tons. But the implementation of nuclear overheating directly in the reactor turned out to be associated with well-known difficulties in regulating the process, especially in terms of monitoring its progress , with the requirement for precision operation of many instruments, the presence of a large number of pipes of various sizes under high pressure, etc.

The first unit of the Beloyarsk NPP reached its full design capacity, however, due to the relatively small installed capacity of the unit (100 MW), the complexity of its technological channels and, therefore, high cost, the cost of 1 kWh of electricity turned out to be significantly higher than that of thermal stations in the Urals.

The second unit of the Beloyarsk NPP with the AMB-200 reactor was built faster, without great stress in the work, since the construction and installation team was already prepared. The reactor installation has been significantly improved. It had a single-circuit cooling circuit, which simplified the technological design of the entire nuclear power plant. Just like in the first power unit, main feature AMB-200 reactor produces high-parameter steam directly into the turbine. On December 31, 1967, power unit No. 2 was connected to the network - this completed the construction of the 1st stage of the station.

A significant part of the history of operation of the 1st stage of the BNPP was filled with romance and drama, characteristic of everything new. This was especially true during the period of block development. It was believed that there should be no problems with this - there were prototypes from the AM “First in the World” reactor to industrial reactors for plutonium production, on which basic concepts, technologies, design solutions, many types of equipment and systems, and even a significant part of the technological regimes were tested . However, it turned out that the difference between the industrial nuclear power plant and its predecessors is so great and unique that new, previously unknown problems arose.

The largest and most obvious of them was the unsatisfactory reliability of the evaporation and superheating channels. After a short period of their operation, gas depressurization of fuel elements or coolant leaks appeared with unacceptable consequences for the graphite masonry of reactors, technological operating and repair modes, radiation exposure on personnel and environment. According to the scientific canons and calculation standards of that time, this should not have happened. In-depth studies of this new phenomenon forced us to reconsider the established ideas about the fundamental laws of boiling water in pipes, since even with a low heat flux density, a previously unknown type of heat transfer crisis arose, which was discovered in 1979 by V.E. Doroshchuk (VTI) and subsequently called the “heat transfer crisis of the second kind.”

In 1968, a decision was made to build a third power unit with a fast neutron reactor at the Beloyarsk NPP - BN-600. The scientific supervision of the creation of BN-600 was carried out by the Institute of Physics and Power Engineering, the design of the reactor plant was carried out by the Experimental Mechanical Engineering Design Bureau, and the general design of the unit was carried out by the Leningrad branch of Atomelectroproekt. The block was built by a general contractor - the Uralenergostroy trust.

When designing it, the operating experience of the BN-350 reactors in Shevchenko and the BOR-60 reactor was taken into account. For the BN-600, a more economical and structurally successful integral layout of the primary circuit was adopted, according to which the reactor core, pumps and intermediate heat exchangers are located in one housing. The reactor vessel, having a diameter of 12.8 m and a height of 12.5 m, was installed on roller supports fixed to the base plate of the reactor shaft. The mass of the assembled reactor was 3900 tons, and the total amount of sodium in the installation exceeded 1900 tons. Biological protection was made of steel cylindrical screens, steel blanks and pipes with graphite filler.

The quality requirements for installation and welding work for the BN-600 turned out to be an order of magnitude higher than those achieved previously, and the installation team had to urgently retrain personnel and master new technologies. So in 1972, when assembling a reactor vessel from austenitic steels, a betatron was used for the first time to control the transmission of large welds.

In addition, during the installation of internal devices of the BN-600 reactor, special requirements for cleanliness were imposed, and all parts brought in and removed from the intra-reactor space were recorded. This was due to the impossibility of further flushing the reactor and pipelines with sodium coolant.

Nikolai Muravyov played a major role in the development of reactor installation technology, who was invited to work from Nizhny Novgorod, where he previously worked in a design bureau. He was one of the developers of the BN-600 reactor project, and by that time he was already retired.

The installation team successfully completed the assigned tasks of installing the fast neutron unit. Filling the reactor with sodium showed that the cleanliness of the circuit was maintained even higher than required, since the pour point of sodium, which depends in the liquid metal on the presence of foreign contaminants and oxides, turned out to be lower than those achieved during the installation of the BN-350, BOR-60 reactors in the USSR and nuclear power plants " Phoenix" in France.

The success of the installation teams at the construction of the Beloyarsk NPP largely depended on the managers. First it was Pavel Ryabukha, then the young energetic Vladimir Nevsky came, then he was replaced by Vazgen Kazarov. V. Nevsky did a lot for the formation of a team of installers. In 1963, he was appointed director of the Beloyarsk Nuclear Power Plant, and later he headed Glavatomenergo, where he worked hard to develop the country’s nuclear power industry.

Finally, on April 8, 1980, the power start-up of power unit No. 3 of the Beloyarsk NPP with the BN-600 fast neutron reactor took place. Some design characteristics of the BN-600:

  • electrical power – 600 MW;
  • thermal power – 1470 MW;
  • steam temperature – 505 o C;
  • steam pressure – 13.7 MPa;
  • gross thermodynamic efficiency – 40.59%.

Special attention should be paid to the experience of handling sodium as a coolant. It has good thermophysical and satisfactory nuclear physical properties, and is well compatible with stainless steels, uranium and plutonium dioxide. Finally, it is not scarce and relatively inexpensive. However, it is very chemically active, which is why its use required the solution of at least two serious problems: minimizing the likelihood of sodium leakage from circulation circuits and inter-circuit leaks in steam generators and ensuring effective localization and termination of sodium combustion in the event of a leak.

The first task was generally quite successfully solved at the stage of developing equipment and pipeline projects. The integral layout of the reactor turned out to be very successful, in which all the main equipment and pipelines of the 1st circuit with radioactive sodium were “hidden” inside the reactor vessel, and therefore its leakage, in principle, was possible only from a few auxiliary systems.

And although BN-600 is today the largest power unit with a fast neutron reactor in the world, Beloyarsk NPP is not one of the nuclear power plants with large installed capacity. Its differences and advantages are determined by the novelty and uniqueness of production, its goals, technology and equipment. All reactor installations of the BelNPP were intended for pilot industrial confirmation or denial of technical ideas and solutions laid down by designers and constructors, research of technological regimes, structural materials, fuel elements, control and protective systems.

All three power units have no direct analogues either in our country or abroad. They embodied many of the ideas for the future development of nuclear energy:

  • power units with industrial-scale channel water-graphite reactors were built and commissioned;
  • serial turbo units with high parameters with thermal power cycle efficiency from 36 to 42% were used, which no nuclear power plant in the world has;
  • fuel assemblies were used, the design of which excludes the possibility of fragmentation activity entering the coolant even when the fuel rods are destroyed;
  • carbon steel is used in the primary circuit of the reactor of the 2nd unit;
  • the technology for using and handling liquid metal coolant has been largely mastered;

The Beloyarsk NPP was the first nuclear power plant in Russia to face in practice the need to solve the problem of decommissioning spent reactor plants. The development of this area of ​​activity, which is very relevant for the entire nuclear energy industry, had a long incubation period due to the lack of an organizational and regulatory document base and the unresolved issue of financial support.

The more than 50-year period of operation of the Beloyarsk NPP has three fairly distinct stages, each of which had its own areas of activity, specific difficulties in its implementation, successes and disappointments.

The first stage (from 1964 to the mid-70s) was entirely associated with the launch, development and achievement of the design level of power of the 1st stage power units, a lot of reconstruction work and problem solving associated with imperfect designs of units, technological modes and ensuring stable operation of fuel channels. All this required enormous physical and intellectual efforts from the station staff, which, unfortunately, were not crowned with confidence in the correctness and prospects of choosing uranium-graphite reactors with nuclear superheated steam for the further development of nuclear energy. However, the most significant part of the accumulated operating experience of the 1st stage was taken into account by designers and constructors when creating uranium-graphite reactors according to next generation.

The beginning of the 70s was associated with the choice of a new direction for the further development of the country's nuclear energy - fast neutron reactor plants with the subsequent prospect of building several power units with breeder reactors using mixed uranium-plutonium fuel. When determining the location for the construction of the first pilot industrial unit using fast neutrons, the choice fell on the Beloyarsk NPP. This choice was significantly influenced by the recognition of the ability of the construction teams, installers and plant personnel to properly build this unique power unit and subsequently ensure its reliable operation.

This decision marked the second stage in the development of the Beloyarsk NPP, which for the most part was completed with the decision of the State Commission to accept the completed construction of the power unit with the BN-600 reactor with an “excellent” rating, rarely used in practice.

Ensuring the quality of work at this stage was entrusted to the best specialists both from construction and installation contractors and from the station operating personnel. The plant personnel acquired extensive experience in setting up and mastering nuclear power plant equipment, which was actively and fruitfully used during commissioning work at the Chernobyl and Kursk nuclear power plants. Special mention should be made of the Bilibino NPP, where, in addition to commissioning work, an in-depth analysis of the project was carried out, on the basis of which a number of significant improvements were made.

With the commissioning of the third block, the third stage of the station’s existence began, which has been going on for more than 35 years. The goals of this stage were to achieve the design parameters of the unit, confirm in practice the viability of design solutions and gain operating experience for subsequent consideration in the design of a serial unit with a breeder reactor. All these goals have now been successfully achieved.

The safety concepts laid down in the unit design were generally confirmed. Since the boiling point of sodium is almost 300 o C higher than operating temperature, the BN-600 reactor operates almost without pressure in the reactor vessel, which can be made of highly plastic steel. This virtually eliminates the possibility of rapidly developing cracks. And the three-circuit scheme of heat transfer from the reactor core with an increase in pressure in each subsequent circuit completely eliminates the possibility of radioactive sodium from the 1st circuit getting into the second (non-radioactive) circuit, and even more so into the steam-water third circuit.

Confirmation of the achieved high level of safety and reliability of the BN-600 is carried out after the accident on Chernobyl nuclear power plant safety analysis, which did not identify any immediate need for technical improvements. Statistics on the activation of emergency protections, emergency shutdowns, unplanned reductions in operating power and other failures show that the BN-6OO reactor is at least among the 25% of the best nuclear units in the world.

According to the results of the annual competition, Beloyarsk NPP in 1994, 1995, 1997 and 2001. was awarded the title “Best NPP in Russia”.

Power unit No. 4 with the fast neutron reactor BN-800 is in the pre-startup stage. The new 4th power unit with the BN-800 reactor with a capacity of 880 MW was brought to the minimum controlled power level on June 27, 2014. The power unit is designed to significantly expand the fuel base of nuclear power and minimize radioactive waste through the organization of a closed nuclear fuel cycle.

The possibility of further expansion of the Beloyarsk NPP with power unit No. 5 with a fast reactor with a capacity of 1200 MW is being considered - the main commercial power unit for serial construction.

When we are told, for example, that “a power plant on solar panels with a capacity of 1200 MW has been built,” this does not mean at all that this solar power plant will provide the same amount of electricity as the VVER-1200 nuclear reactor provides. Solar panels cannot work at night - therefore, if averaged over the seasons, they are idle for half of the day, and this already reduces the capacity factor by half. Solar panels, even the newest varieties, work much worse in cloudy weather, and the average values ​​here are also not encouraging - clouds with rain and snow, fogs reduce the capacity factor by another half. “SPP with a capacity of 1200 MW” sounds ringing, but we must keep in mind the figure of 25% - technologically, this capacity can only be used by ¼.

Solar panels, unlike nuclear power plants, operate not for 60-80 years, but for 3-4 years, losing the possibility of conversion sunlight V electric current. You can, of course, talk about some kind of “cheaper generation”, but this is outright deceit. Solar power plants require large areas of territory, problems with disposal of waste solar panels So far no one has really done anything. Recycling will require the development of quite serious technologies, which are unlikely to please the environment. If we talk about power plants using wind, then the words will have to be used almost the same, since in this case the capacity factor is about a quarter of the installed capacity. Sometimes instead of wind there is calm, sometimes the wind is so strong that it forces the “mills” to stop, as it threatens the integrity of their structure.

Weather vagaries of renewable energy sources

There is no escape from the second “Achilles heel” of renewable energy sources. Power plants based on them operate not when the electricity they generate is needed by consumers, but when the weather outside is sunny or the wind is of suitable strength. Yes, such power plants can generate electricity, but what if the power transmission networks are not able to receive it? The wind blew at night, you can turn on wind power plants (power plants), but at night you and I sleep, and the enterprises do not work. Yes, such traditional power plants based on renewable resources, such as hydroelectric power stations, are able to cope with this problem by increasing the idle discharge of water (“past the turbine”) or simply accumulating a supply of water in their reservoirs, but in the event of floods, it is not so easy for them. And for solar and wind power plants, energy storage technologies are not so developed as to “store” the generated electricity for the moment when grid consumption increases.

There is also the other side of the coin. Will an investor invest in the construction of, say, a gas power plant in a region where solar panels are installed in large quantities? How can you recoup the money invested if “your” power plant doesn’t work half the time? Payback period, bank interest... “Oh, why do I need such a headache!”- declares the cautious capitalist and builds nothing. And here we have a weather anomaly, it rained for a week with complete calm. And the cries of outraged consumers forced to run diesel generators on their front lawns fade into a rumble. You cannot force investors to build thermal power plants; without benefits and subsidies from the state, they will not take risks. And this in any case becomes an additional burden on state budgets, as well as in the case if the state, having not found accommodating investors, builds thermal power plants on its own.

We hear a lot about how many solar panels are used in Germany, right? But at the same time, the number of power plants operating on local brown coal in the country is growing, mercilessly emitting into the atmosphere the same “e-two” that must be combated while fulfilling the terms of the 2015 Paris Agreement. “Brown power plants” are forced to build the federal government of Germany, the governing bodies of the federal states - they have no other choice, otherwise those same fans of “green energy” will take to the streets with protests due to the fact that there is no current in their sockets, which in the evenings you have to sit by a torch.

We exaggerate, of course, but only to make the absurdity of the situation more obvious. If the generation of electricity literally depends on the weather, then it turns out that it is technically impossible to satisfy basic electricity needs using the sun and wind. Yes, theoretically, it is possible to entangle the whole of Europe with Africa with additional power lines (power lines) so that the current from the sunny Sahara comes to houses standing on the gloomy coast of the North Sea, but this costs absolutely incredible money, the payback period of which is close to infinity. Should there be a coal or gas powered one next to each solar power plant? Let us repeat, but the combustion of hydrocarbon energy resources at power plants does not make it possible to fully implement the provisions of the Paris Agreement on reducing CO 2 emissions.

Nuclear power plant as the basis of “green energy”

Dead end? For those countries that have decided to get rid of nuclear energy, this is it. Of course, they are looking for a way out of it. They are improving coal and gas combustion systems, abandoning fuel oil power plants, making efforts to increase the efficiency of furnaces, steam generators, and boilers, and increasing efforts to use energy-saving technologies. This is good, this is useful, this must be done. But Russia and its Rosatom They propose a much more radical option - to build a nuclear power plant.

Construction of a nuclear power plant, Photo: rusatom-overseas.com

Does this method seem paradoxical to you? Let's look at it from a logical point of view. Firstly, there are no CO 2 emissions from nuclear reactors as such - there are no chemical reactions, the flame does not roar wildly in them. Consequently, the fulfillment of the terms of the Paris Agreement “takes place.” The second point is the scale of electricity generation at nuclear power plants. In most cases, nuclear power plant sites have at least two, or even all four, reactors; their total installed capacity is enormous, and the capacity factor consistently exceeds 80%. This “breakthrough” of electricity is sufficient to satisfy the needs of not just one city, but an entire region. But nuclear reactors “don’t like” when their power is changed. Sorry, it's going to be a little bit now technical details to make it clearer what we mean.

Control and protection systems for nuclear reactors

The principle of operation of a power reactor is not so complicated schematically. Energy atomic nuclei is converted into thermal energy of the coolant, thermal energy is converted into mechanical energy of the electric generator rotor, which, in turn, is converted into electrical energy.

Atomic – thermal – mechanical – electrical, this is a kind of energy cycle.

Ultimately, the electrical power of the reactor depends on the power of the controlled, controlled nuclear chain reaction fission of nuclear fuel. We emphasize – controlled and manageable. Unfortunately, we have known well since 1986 what happens if a chain reaction gets out of control and management.

How is the course of a chain reaction monitored and controlled, what needs to be done to ensure that the reaction does not immediately spread to the entire volume of uranium contained in the “nuclear cauldron”? Let us recall the school truisms without going into the scientific details of nuclear physics - this will be quite enough.

What is a chain reaction “on fingers”, if someone has forgotten: one neutron arrived, knocked out two neutrons, two neutrons knocked out four, and so on. If the number of these very free neutrons becomes too large, the fission reaction will spread throughout the entire volume of uranium, threatening to develop into a “big bang.” Yes, of course, a nuclear explosion will not take place; for it it is necessary that the content of the uranium-235 isotope in the fuel exceeds 60%, and in power reactors the fuel enrichment does not exceed 5%. But even without an atomic explosion, the problems will be overwhelming. The coolant will overheat, its pressure in the pipelines will increase supercritically, after their rupture, the integrity of the fuel assemblies may be damaged and all radioactive substances will escape outside the reactor, insanely polluting the surrounding areas and burst into the atmosphere. However, the details of the Chernobyl nuclear power plant disaster are known to everyone, we will not repeat them.

Accident at the Chernobyl nuclear power plant, Photo: meduza.io

One of the main components of any nuclear reactor is the control and protection system. There should not be more free neutrons than the strictly calculated value, but they should not be less than this value - this will lead to the attenuation of the chain reaction, the nuclear power plant will simply “stop”. Inside the reactor there must be a substance that absorbs excess neutrons, but in an amount that allows the chain reaction to continue. Nuclear physicists have long figured out which substance does this best - the boron-10 isotope, so the control and protection system is also simply called “boron”.

Rods with boron are included in the design of reactors with graphite and water moderator; for them there are the same technological channels as for fuel rods and fuel elements. Neutron counters in the reactor operate continuously, automatically giving commands to the system that controls the boron rods, which moves the rods, immersing them in or removing them from the reactor. At the beginning of the fuel session, there is a lot of uranium in the reactor - the boron rods are immersed deeper. Time passes, the uranium burns out, and the boron rods begin to be gradually removed - the number of free neutrons must remain constant. Yes, we note that there are also “emergency” boron rods “hanging” above the reactor. In case of violations that could potentially send the chain reaction out of control, they are plunged into the reactor instantly, killing the chain reaction in the bud. A pipeline has burst, a coolant leak has occurred - this is a risk of overheating, emergency boron rods are triggered instantly. Let's stop the reaction and slowly figure out what exactly happened and how to fix the problem, and the risk should be reduced to zero.

There are different neutrons, but we have the same boron

Simple logic, as you can see, shows that increasing and decreasing the energy power of a nuclear reactor—“power maneuver,” as the power engineers say—is a very difficult job, which is based on nuclear physics and quantum mechanics. A little more “deep into the process”, not too far, don’t be afraid. In any fission reaction of uranium fuel, secondary free neutrons are formed - the same ones that in the school formula “knocked out two neutrons.” In a power reactor, two secondary neutrons are too many; for controllability and controllability of the reaction, a coefficient of 1.02 is needed. 100 neutrons arrived, 200 neutrons were knocked out, and out of these 200 secondary neutrons, 98 should “eat”, absorb that same boron-10. Boron suppresses excessive activity, we tell you that for sure.

But remember what happens if you feed a child a bucket of ice cream - he will happily eat the first 5-6 servings, and then go away because he “can’t fit in any more.” Humans are made of atoms, and therefore the character of atoms is no different from ours. Boron-10 can eat neutrons, but not an infinite number, the same “can’t fit anymore” will definitely come. The bearded men in white coats at the nuclear power plant suspect that many people realize that at heart nuclear scientists remain curious children, so they try to use as “mature” vocabulary as possible. Boron in their vocabulary is not “eaten by neutrons”, but “burned out” - this sounds much more respectable, you will agree. One way or another, every demand from the power grid to “turn down the reactor” leads to more intense burnout of the boron protection and control system and causes additional difficulties.

Model of a fast neutron reactor, Photo: topwar.ru

With a coefficient of 1.02, everything is also not so simple, since in addition to prompt secondary neutrons that appear immediately after the fission reaction, there are also delayed ones. After fission, a uranium atom falls apart, and neutrons also fly out of these fragments, but after a few microseconds. There are few of them compared to instant ones, only about 1%, but with a coefficient of 1.02 they are very important, because 1.02 is an increase of only 2%. Therefore, the calculation of the amount of boron must be performed with pinpoint accuracy, constantly balancing on fine line“the reaction getting out of control means an unscheduled shutdown of the reactor.” Therefore, in response to every demand, “turn on the gas!” or “Slow down, why are you so fired up!” a chain reaction of the nuclear power plant duty shift begins, when each nuclear worker on its staff offers a larger number of idiomatic expressions...

And once again about nuclear power plants as the basis of “green energy”

Now let's return to where we left off - high power generation capacity, over a large territory served by nuclear power plants. How larger territory– the more opportunities there are to place ES powered by RES on it. The more such ES, the higher the likelihood that peak consumption will coincide with the period of their greatest generation. This is where the electricity from solar panels will come from, this is where the wind energy will come from, this is where the tidal wave will successfully hit the side, and all together they will smooth out the peak load, allowing nuclear workers at the nuclear power plant to calmly drink tea, looking at the monotonously, without interruption, working neutron counters.

Renewable Energy, hsto.org

The calmer the situation at the nuclear power plant, the fatter the burghers can become, since they can continue to heat their sausages on the grill without any problems. As you can see, there is nothing paradoxical in the combination of renewable energy sources and nuclear generation as a base, everything is exactly the opposite - such a combination, if the world has seriously decided to fight CO 2 emissions, is the optimal way out of the situation, without in any way crossing out all the options modernizations and improvements of thermal power plants that we talked about.

Continuing the “kangaroo style”, we suggest “jumping” to the very first sentence of this article – about the finiteness of any traditional energy resources on planet Earth. Because of this, the main, strategic direction of energy development is the conquest of the thermonuclear reaction, but its technology is incredibly complex and requires coordinated, joint efforts of scientists and designers from all countries, serious investments and many years of hard work. How long it will take can now be guessed using coffee grounds or bird entrails, but one must, of course, plan for the most pessimistic scenario. We need to look for fuel that can provide that same basic generation for as long as possible. long term. There seems to be plenty of oil and gas, but the planet’s population is also growing, and more and more kingdom-states are striving for the same level of consumption as in the countries of the “golden billion”. According to geologists, there are 100-150 years of fossil hydrocarbon fuel left on Earth, unless consumption grows at a faster rate than at the present time. And it seems that this will happen, since the population of developing countries craves an increase in the level of comfort...

Fast reactors

Proposed Russian nuclear project The way out of this situation is known, this is the closure of the nuclear fuel cycle by involving nuclear breeder reactors and fast neutron reactors in the process. A breeder is a reactor in which, as a result of a fuel session, the output of nuclear fuel is more than what was initially loaded, a breeder reactor. Those who have not yet completely forgotten the school physics course may well ask the question: excuse me, but what about the law of conservation of mass? The answer is simple - no way, since in a nuclear reactor the processes are nuclear, and the law of conservation of mass does not apply in its classical form.

More than a hundred years ago, Albert Einstein linked mass and energy together in his special theory of relativity, and in nuclear reactors this theory is strictly practical. The total amount of energy is conserved, and about conservation total number mass in in this case there is no question. A huge reserve of energy “sleeps” in the atoms of nuclear fuel, released as a result of the fission reaction; we use part of this reserve for our own benefit, and the other part miraculously transforms uranium-238 atoms into a mixture of atoms of plutonium isotopes. Fast neutron reactors, and only they, make it possible to convert the main component of uranium ore - uranium-238 - into a fuel resource. The reserves of uranium-235, depleted in content and not used in thermal nuclear reactors, accumulated during the operation of thermal neutron nuclear power plants amount to hundreds of thousands of tons, which no longer need to be extracted from mines, which no longer need to be “exfoliated” from waste rock - its there is an incredible amount of uranium at enrichment plants.

MOX fuel at your fingertips

Theoretically it’s understandable, but not completely, so let’s try it again “on our fingers”. The very name “MOX fuel” is just an English abbreviation written in letters of the Slavic alphabet, which is written as MOX. Explanation – Mixed-Oxide fuel, free translation – “fuel from mixed oxides”. Basically, this term refers to a mixture of plutonium oxide and uranium oxide, but this is only basically. Since our respected American partners were unable to master the technology for producing MOX fuel from weapons-grade plutonium, Russia also abandoned this option. But the plant we built was designed in advance to be universal - it is capable of producing MOX fuel from spent fuel from thermal reactors. If anyone has read the articles Geoenergetics.ru in this regard, he remembers that the isotopes of plutonium 239, 240 and 241 in spent fuel are already “mixed” - there are 1/3 of them each, so in MOX fuel created from spent fuel there is a mix of plutonium, a kind of mix inside a mix .

The second part of the main mix is ​​depleted uranium. To exaggerate: we take a mix of plutonium oxide extracted from spent nuclear fuel using the PUREX process, add ownerless uranium-238 and get MOX fuel. In this case, uranium-238 does not participate in the chain reaction; only the mixed plutonium isotopes “burn.” But uranium-238 is not just “present” - occasionally, reluctantly, from time to time it takes in one neutron, turning into plutonium-239. Some of this new plutonium immediately “burns up,” while some simply does not have time to do this before the end of the fuel session. That, in fact, is the whole secret.

The numbers are arbitrary, taken out of thin air, just for clarity. The initial composition of MOX fuel is 100 kilograms of plutonium oxide and 900 kilograms of uranium-238. While the plutonium was “burning”, 300 kilos of uranium-238 turned into additional plutonium, of which 150 kilos immediately “burned”, and 150 kilos did not have time. They pulled out the fuel assembly and “shaken out” the plutonium from it, but it turned out to be 50 kilos more than it was originally. Well, or the same thing, but with wood: you threw 2 logs into the firebox, your stove heated all night, and in the morning you pulled out... three logs. From 900 kg of useless uranium-238, which does not participate in the chain reaction, when used as part of MOX fuel, we obtained 150 kilograms of fuel, which immediately “burned out” for our benefit, and 150 kilograms were left for further use. And there is 300 kilos less of this waste, useless uranium-238, which is also not bad.

The actual ratios of depleted uranium-238 and plutonium in MOX fuel are, of course, different, since with 7% plutonium in MOX fuel the mixture behaves almost the same as conventional uranium fuel with about 5% enrichment in uranium-235. But the figures we came up with show the main principle of MOX fuel - useless uranium-238 is converted into nuclear fuel, its huge reserves become an energy resource. According to rough estimates, if we assume that on Earth we stop using hydrocarbon fuels to produce electricity and switch only to the use of uranium-238, it will last us for 2,500 - 3,000 years. Quite a decent amount of time to master the technology of controlled thermonuclear fusion.

MOX fuel allows us to simultaneously solve another problem - to reduce the reserves of spent fuel accumulated in all member countries of the “nuclear club”, and to reduce the amount of radioactive waste accumulated in spent fuel. It's not a matter of some wonderful properties MOX fuel, everything is more prosaic. If the spent nuclear fuel is not used and we try to send it to eternal geological burial, then all the high-level waste that it contains will have to be sent to burial along with it. But the use of technologies for reprocessing spent nuclear fuel in order to extract plutonium from it willy-nilly forces us to reduce the volume of this radioactive waste. In the struggle for the use of plutonium, we are simply forced to destroy radioactive waste, but at the same time the process of such destruction becomes much less expensive - after all, plutonium is used.

MOX fuel is an expensive pleasure that needs to be made cheap

At the same time, the production of MOX fuel in Russia began quite recently, even with the newest, most technologically advanced fast neutron reactor - BN-800, the transition to 100% use of MOX fuel is happening online, and is also not yet completed. It is quite natural that currently the production of MOX fuel is more expensive than the production of traditional uranium fuel. Reducing the cost of production, as in any other industry, is possible, first of all, through mass, “conveyor” production.

Consequently, in order for closing the nuclear fuel cycle to be feasible from an economic point of view, Russia needs a larger number of fast neutron reactors; this should become a strategic line for the development of nuclear energy. More reactors– good and different!

At the same time, it is necessary not to lose sight of the second possibility of using MOX fuel - as fuel for VVER reactors. Fast neutron reactors create such an additional amount of plutonium that they themselves cannot really use - they simply don’t need so much, there is enough plutonium for VVER reactors. We have already written above that MOX fuel, in which 93% depleted uranium-238 accounts for 7% plutonium, behaves almost the same as conventional uranium fuel. But the use of MOX fuel in thermal reactors leads to a decrease in the efficiency of the neutron absorbers used in VVERs. The reason for this is that boron-10 absorbs fast neutrons much worse - these are its physical features, which we cannot influence in any way. The same problem arises with emergency boron rods, the purpose of which is to instantly stop the chain reaction in case of emergency situations.

A reasonable solution is to reduce the amount of MOX fuel in VVER to 30-50%, which is already being implemented in some light water reactors in France, Japan and other countries. But even in this case, it may be necessary to modernize the boron system and carry out all the necessary safety justifications, cooperation with the IAEA supervisory authorities to obtain licenses for the use of MOX fuel in thermal reactors. Or, in short, the number of boron rods will have to be increased, both those that are intended for control and those that are “stored” in case of emergency. But only the development of these technologies will make it possible to move on to mass production of this type of fuel and to reduce the cost of its production. At the same time, this will make it possible to more actively solve the problem of reducing the amount of spent nuclear fuel and more actively use depleted uranium reserves.

The prospects are close, but the road is not easy

The development of this technology in combination with the construction of breeder reactors for energetic plutonium - fast neutron reactors - will allow Russia not only to close the nuclear fuel cycle, but also to make it economically attractive. There are also great prospects for the use of SNUP fuel (mixed nitride uranium-plutonium fuel). Experimental fuel assemblies, irradiated at the BN-600 reactor in 2016, have already proven their effectiveness both during reactor tests and based on the results of post-reactor studies. The results obtained provide for the continuation of work to justify the use of SNUP fuel in the creation of the BREST-300 reactor plant and on-site modules for the production of SNUP fuel at the experimental demonstration complex being built in Seversk. BREST-300 will allow us to continue developing the technologies necessary to completely close the nuclear fuel cycle, provide a more complete solution to the problems of spent nuclear fuel and radioactive waste, and implement the ideology of “returning to nature as much radioactivity as was extracted.” The BREST-300 reactor, like the BN reactors, is a fast neutron reactor, which only emphasizes the correctness of the strategic direction of nuclear energy development - a combination of pressurized water reactors and fast neutron reactors.

Mastering the technology of 100% use of MOX fuel on BN-800 also provides the opportunity to create BN-1200 reactors - not only more powerful, but also more economically profitable. The decision to create the BN-1200 reactor in Russia has been made, which means that the pace of research work by nuclear specialists will only have to increase, and the creation of the MBIR, scheduled for 2020, can significantly help in solving all problems, in mastering the technology of complete fuel closure nuclear cycle. Russia was and remains the only country that has created fast neutron power reactors, ensuring our world leadership in this most important area of ​​nuclear energy.

Of course, everything that has been said is just a first acquaintance with the features of fast neutron reactors, but we will try to continue, since this topic is important and, as it seems to us, quite interesting.

Neutrons?

Neutrons are particles that are part of most atomic nuclei, along with protons. During the nuclear fission reaction, the uranium nucleus splits into two parts and in addition emits several neutrons. They can get into other atoms and trigger one or more fission reactions. If each neutron released during the decay of uranium nuclei hits neighboring atoms, an avalanche-like chain of reactions will begin with the release of more and more energy. In the absence of restraining factors, it will happen nuclear explosion.

But in a nuclear reactor, some of the neutrons either come out or are absorbed by special absorbers. Therefore, the number of fission reactions remains the same all the time, exactly what is necessary to obtain energy. The energy from the radioactive decay reaction produces heat, which is then used to generate steam to drive a power plant's turbine.

The neutrons that keep the nuclear reaction constant can have different energies. Depending on the energy, they are called either thermal or fast (there are also cold ones, but those are not suitable for nuclear power plants). Most reactors in the world are based on the use of thermal neutrons, but the Beloyarsk NPP has a fast reactor. Why?

What are the advantages?

In a fast neutron reactor, part of the neutron energy goes, as in conventional reactors, to maintain the fission reaction of the main component of nuclear fuel, uranium-235. And part of the energy is absorbed by a shell made of uranium-238 or thorium-232. These elements are useless for conventional reactors. When neutrons hit their nuclei, they turn into isotopes suitable for use in nuclear power as fuel: plutonium-239 or uranium-233.

Enriched uranium. Unlike spent nuclear fuel, uranium is not nearly so radioactive that it needs to be handled only by robots. You can even hold it briefly with your hands wearing thick gloves. Photo: US Department of Energy


Thus, fast neutron reactors can be used not only to supply energy to cities and factories, but also to produce new nuclear fuel from relatively inexpensive raw materials. The following facts speak in favor of economic benefits: a kilogram of uranium smelted from ore costs about fifty dollars, contains only two grams of uranium-235, and the rest is uranium-238.

However, fast neutron reactors are practically not used in the world. BN-600 can be considered unique. Neither the Japanese Monju, nor the French Phoenix, nor a number of experimental reactors in the USA and Great Britain are currently operating: thermal neutron reactors turned out to be easier to construct and operate. There are a number of obstacles on the way to reactors that can combine energy production with nuclear fuel production. And the designers of the BN-600, judging by its successful operation for 35 years, were able to bypass at least some of the obstacles.

What's the problem?

In sodium. Any nuclear reactor must have several components and elements: fuel assemblies with nuclear fuel, elements for controlling the nuclear reaction, and a coolant that takes away the heat generated in the device. The design of these components, the composition of the fuel and coolant may differ, but without them the reactor is impossible by definition.

In a fast neutron reactor, it is necessary to use a material as a coolant that does not retain neutrons, otherwise they will turn from fast to slow, thermal ones. At the dawn of nuclear power, designers tried using mercury, but it dissolved the pipes inside the reactor and began to leak outside. The heated toxic metal, which also became radioactive under the influence of radiation, caused so much trouble that the mercury reactor project was quickly abandoned.

Pieces of sodium are usually stored under a layer of kerosene. Although this liquid is flammable, it does not react with sodium and does not release water vapor from the air to it. Photo: Superplus / Wikipedia


BN-600 uses liquid sodium. At first glance, sodium is little better than mercury: it is extremely chemically active, reacts violently with water (in other words, it explodes if thrown into water) and reacts even with substances contained in concrete. However, it does not interfere with neutrons, and with the proper level of construction work and subsequent maintenance, the risk of leakage is not that great. In addition, sodium, unlike water vapor, can be pumped at normal pressure. A jet of steam from a ruptured steam line under pressure of hundreds of atmospheres cuts metal, so in this sense sodium is safer. As for chemical activity, it can also be used for good. In the event of an accident, sodium reacts not only with concrete, but also with radioactive iodine. Sodium iodide no longer leaves the nuclear power plant building, while gaseous iodine accounted for almost half of the emissions during the accident at the nuclear power plant in Fukushima.

Soviet engineers who developed fast neutron reactors first built the experimental BR-2 (the same unsuccessful one, mercury), and then the experimental BR-5 and BOR-60 with sodium instead of mercury. The data obtained from them made it possible to design the first industrial “fast” reactor BN-350, which was used at a unique nuclear chemical and energy plant - a nuclear power plant combined with a seawater desalination plant. At the Beloyarsk NPP, the second reactor of the BN type - “fast, sodium” - was built.

Despite the experience accumulated by the time the BN-600 was launched, the first years were marred by a series of liquid sodium leaks. None of these incidents posed a radiation threat to the population or led to serious exposure of plant personnel, and since the early 1990s, sodium leaks have stopped altogether. To put this into global context, Japan's Monju suffered a serious leak of liquid sodium in 1995, which led to a fire and shutdown of the plant for 15 years. Only Soviet designers succeeded in translating the idea of ​​a fast neutron reactor into an industrial rather than experimental device, whose experience allowed Russian nuclear scientists to develop and build the next generation reactor - BN-800.

BN-800 has already been built. On June 27, 2014, the reactor started operating at minimum power, and a power start-up is expected in 2015. Since launching a nuclear reactor is a very complex process, experts separate the physical start-up (the beginning of a self-sustaining chain reaction) and the energy start-up, during which the power unit begins to supply the first megawatts of electricity to the network.

Beloyarsk NPP, control panel. Photo from the official website: http://www.belnpp.rosenergoatom.ru


In the BN-800, the designers implemented a number of important improvements, including, for example, an emergency air cooling system for the reactor. Developers say its advantage is independence from energy sources. If, as in Fukushima, electricity disappears at a nuclear power plant, then the flow of the cooling reactor will still not disappear - circulation will be maintained naturally, due to convection, rising heated air. And if the core melts suddenly, the radioactive melt will not go outside, but into a special trap. Finally, protection against overheating is a large supply of sodium, which in the event of an accident can absorb the heat generated even at complete refusal all cooling systems.

Following the BN-800, it is planned to build a BN-1200 reactor with even greater power. The developers expect that their brainchild will become a serial reactor and will be used not only at the Beloyarsk NPP, but also at other stations. However, these are just plans for now; for a large-scale transition to fast neutron reactors, a number of problems still need to be solved.

Beloyarsk NPP, construction site of a new power unit. Photo from the official website: http://www.belnpp.rosenergoatom.ru


What's the problem?

In economics and ecology of fuel. Fast neutron reactors operate on a mixture of enriched uranium oxide and plutonium oxide - this is the so-called mox fuel. Theoretically, it can be cheaper than conventional fuel due to the fact that it uses plutonium or uranium-233 from inexpensive uranium-238 or thorium irradiated in other reactors, but so far mox fuel is inferior in price to conventional fuel. It turns out to be a kind of vicious circle that is not so easy to break: it is necessary to fine-tune the technology for constructing reactors, the extraction of plutonium and uranium from the material irradiated in the reactor, and ensure control over the non-proliferation of high-level materials. Some ecologists, for example representatives of the non-profit center Bellona, ​​point to the large volume of waste generated during the processing of irradiated material, because along with valuable isotopes, a significant amount of radionuclides are formed in a fast neutron reactor, which need to be buried somewhere.

In other words, even the successful operation of a fast neutron reactor in itself does not guarantee a revolution in technology. nuclear energy. It is a necessary, but not sufficient condition for moving from limited reserves of uranium-235 to much more accessible uranium-238 and thorium-232. Whether the technologists involved in the processes of nuclear fuel reprocessing and nuclear waste disposal will be able to cope with their tasks is a topic for a separate story.

Many experts today believe that fast neutron reactors are the future of nuclear energy. One of the pioneers in the development of this technology is Russia, where the BN-600 fast neutron reactor at the Beloyarsk NPP has been operating for 30 years without serious incidents, the BN-800 reactor is being built there, and the creation of a commercial BN-1200 reactor is planned. France and Japan have experience in operating fast neutron nuclear power plants, and plans to build fast neutron nuclear power plants in India and China are being considered. The question arises: why are there no practical programs for the development of fast neutron energy in a country with a very highly developed nuclear energy industry - the USA?

In fact, there was such a project in the USA. It's about about the Clinch River Breeder Reactor project (in English - The Clinch River Breeder Reactor, abbreviated as CRBRP). The goal of this project was to design and build a sodium fast reactor, which was to be a demonstration prototype for the next class of similar American reactors called LMFBRs (short for Liquid Metal Fast Breeder Reactors). At the same time, the Clinch River reactor was conceived as a significant step towards the development of liquid metal fast reactor technology with the aim of commercial use in the electric power industry. The location of the Clinch River reactor was to be an area of ​​6 km 2, administratively part of the city of Oak Ridge in Tennessee.

The reactor was supposed to have a thermal power of 1000 MW and an electrical power in the range of 350-380 MW. The fuel for it was to be 198 hexagonal assemblies assembled in the shape of a cylinder with two fuel enrichment zones. The interior of the reactor was to consist of 108 assemblies containing plutonium enriched to 18%. They were to be surrounded by an outer zone consisting of 90 assemblies with plutonium enriched to 24%. This configuration was supposed to provide the best conditions for heat release.

The project was first presented in 1970. In 1971, US President Richard Nixon established this technology as one of the nation's top research and development priorities.

What prevented its implementation?

One of the reasons for this decision was the ongoing escalation of project costs. In 1971, the Commission on atomic energy The United States has determined that the cost of the project will be about $400 million. The private sector has pledged to finance most of the project, committing $257 million. In subsequent years, however, the cost of the project jumped to 700 million. As of 1981, a billion dollars of budget funds had already been spent, despite the fact that the cost of the project was estimated at that time at 3 - 3.2 billion dollars, not counting another billion , which was necessary for the construction of a plant for the production of generated fuel. In 1981, a congressional committee uncovered cases of various abuses, which further increased the cost of the project.

Before the decision to close, the cost of the project was already estimated at $8 billion.

Another reason was the high cost of building and operating the breeder reactor itself to produce electricity. In 1981, it was estimated that the cost of building a fast reactor would be twice that of a standard light water reactor of the same power. It was also estimated that for the breeder to be economically competitive with conventional light water reactors, the price of uranium would have to be $165 per pound, when in reality the price was then $25 per pound. Private generating companies did not want to invest in such a risky technology.

Another serious reason for curtailing the breeder program was the threat possible violation non-proliferation regime, since this technology produces plutonium, which can also be used for the production of nuclear weapons. Due to international concerns about nuclear proliferation issues, in April 1977, US President Jimmy Carter called for an indefinite delay in the construction of commercial fast reactors.

President Carter was generally a consistent opponent of the Clinch River project. In November 1977, after vetoing a bill to continue funding, Carter said it would be "prohibitively expensive" and "become technically obsolete and economically unfeasible once completed." In addition, he stated that fast reactor technology in general is futile. Instead of investing resources in a fast neutron demonstration project, Carter proposed instead "spending money on improving the safety of existing nuclear technologies."

The Clinch River Project was resumed after Ronald Reagan took office in 1981. Despite growing opposition from Congress, he overturned his predecessor's ban and construction resumed. However, on October 26, 1983, despite the successful progress of construction work, the US Senate by a majority (56 to 40) called for no further funding for construction and the site was abandoned.

Once again, it was remembered quite recently, when the project of a low-power mPower reactor began to be developed in the USA. The site of the planned construction of the Clinch River Nuclear Power Plant is being considered as the site for its construction.