Planning Motivation Control

Purpose of nuclear fuel. How does a nuclear power plant work? Types of nuclear reactors

Nuclear fuel is a material used in nuclear reactors to carry out a controlled chain reaction. It is extremely energy intensive and unsafe for humans, which imposes a number of restrictions on its use. Today we will find out what a nuclear reactor fuel is, how it is classified and produced, where it is used.

Chain reaction progress

During a nuclear chain reaction, the nucleus splits into two parts, which are called fission fragments. At the same time, several (2-3) neutrons are released, which subsequently cause the fission of the next nuclei. The process occurs when a neutron enters the nucleus of the original substance. Fission fragments have high kinetic energy. Their deceleration in matter is accompanied by the release of a huge amount of heat.

Fission fragments, together with their decay products, are called fission products. Nuclei that divide neutrons of any energy are called nuclear fuel. As a rule, they are substances with an odd number of atoms. Some nuclei are fission purely neutrons, the energy of which is above a certain threshold value... These are mainly elements with an even number of atoms. Such nuclei are called raw material, since at the moment of capture of a neutron by a threshold nucleus, fuel nuclei are formed. The combination of fuel and raw material is called nuclear fuel.

Classification

Nuclear fuel is divided into two classes:

  1. Natural uranium. It contains the fissile nuclei of uranium-235 and the raw material uranium-238, which is capable of forming plutonium-239 by capturing a neutron.
  2. Non-naturally occurring secondary fuel. This includes, among other things, plutonium-239, which is obtained from the first type of fuel, as well as uranium-233, which is formed when neutrons are captured by thorium-232 nuclei.

From point of view chemical composition, there are such types nuclear fuel:

  1. Metallic (including alloys);
  2. Oxide (for example, UO 2);
  3. Carbide (for example PuC 1-x);
  4. Mixed;
  5. Nitride.

TVEL and TVS

Fuel for nuclear reactors is used in the form of small pellets. They are placed in hermetically sealed fuel elements (fuel rods), which, in turn, are combined in several hundreds into fuel assemblies (FA). Nuclear fuel has high requirements for compatibility with fuel element cladding. It should have a sufficient melting and evaporation temperature, good thermal conductivity, and not greatly increase in volume under neutron irradiation. Also, the manufacturability of production is taken into account.

Application

Fuel comes to nuclear power plants and other nuclear installations in the form of fuel assemblies. They can be loaded into the reactor both during its operation (in place of burned-out fuel assemblies) and during a repair campaign. In the latter case, the fuel assemblies change large groups... In this case, only a third of the fuel is completely replaced. The most burned-out assemblies are unloaded from the central part of the reactor, and in their place are partially burned-out assemblies that were previously located in less active areas. Consequently, new fuel assemblies are installed in place of the latter. This simple permutation scheme is considered traditional and has a number of advantages, the main of which is to ensure uniform power release. Of course, this is a conditional diagram that only gives a general idea of ​​the process.

Excerpt

After removing the spent nuclear fuel from the reactor core, it is sent to a spent fuel pool, which is usually located nearby. The fact is that spent fuel assemblies contain a huge amount of uranium fission fragments. After unloading from the reactor, each fuel element contains about 300 thousand Curies of radioactive substances, emitting 100 kW / h of energy. Due to it, the fuel is self-heating and becomes highly radioactive.

The temperature of recently unloaded fuel can reach 300 ° C. Therefore, it is kept for 3-4 years under a layer of water, the temperature of which is maintained within the specified range. As it is stored under water, the radioactivity of the fuel and the power of its residual emissions decrease. After about three years, the self-heating of the fuel assembly reaches 50-60 ° C. Then the fuel is removed from the pools and sent for processing or disposal.

Uranium metal

Uranium metal is used as fuel for nuclear reactors relatively rare. When a substance reaches a temperature of 660 ° C, a phase transition occurs, accompanied by a change in its structure. Simply put, uranium expands, which can lead to the destruction of the fuel element. In the case of prolonged irradiation at a temperature of 200-500 ° C, the substance undergoes radiation growth. The essence of this phenomenon lies in the elongation of the irradiated uranium rod by a factor of 2-3.

The use of metallic uranium at temperatures above 500 ° C is difficult due to its swelling. After fission of the nucleus, two fragments are formed, the total volume of which exceeds the volume of that very nucleus. Some of the fission fragments are represented by gas atoms (xenon, krypton, etc.). Gas accumulates in the pores of the uranium and forms an internal pressure that increases as the temperature rises. By increasing the volume of atoms and increasing the pressure of gases, nuclear fuel begins to swell. Thus, this refers to the relative volume change associated with nuclear fission.

The swelling force depends on the fuel rod temperature and burnout. With an increase in burnup, the number of fission fragments increases, and with an increase in temperature and burnup, the internal pressure of gases. If the fuel has higher mechanical properties, then it is less prone to swelling. Metallic uranium does not belong to such materials. Therefore, its use as a fuel for nuclear reactors limits the burnup, which is one of the main characteristics of such fuel.

The mechanical properties of uranium and its radiation resistance are improved by alloying the material. This process involves adding aluminum, molybdenum and other metals to it. Due to dopants, the number of fission neutrons required per capture is reduced. Therefore, for these purposes, materials are used that weakly absorb neutrons.

Refractory compounds

Some refractory uranium compounds are considered good nuclear fuel: carbides, oxides and intermetallic compounds. The most common of these is uranium dioxide (ceramics). Its melting point is 2800 ° C, and its density is 10.2 g / cm 3.

Since this material has no phase transitions, it is less prone to swelling than uranium alloys. Thanks to this feature, the burnout temperature can be increased by several percent. At high temperatures, ceramics do not interact with niobium, zirconium, stainless steel and other materials. Its main disadvantage is its low thermal conductivity - 4.5 kJ (m * K), which limits the specific power of the reactor. In addition, hot ceramics are prone to cracking.

Plutonium

Plutonium is considered a low-melting metal. It melts at 640 ° C. Due to its poor plastic properties, it practically does not lend itself to mechanical processing. The toxicity of the substance complicates the technology for the manufacture of fuel rods. In the nuclear industry, there have been several attempts to use plutonium and its compounds, but they have not been crowned with success. It is impractical to use plutonium-containing fuel for nuclear power plants due to an approximately 2-fold reduction in the acceleration period, which is not designed for standard reactor control systems.

For the manufacture of nuclear fuel, as a rule, plutonium dioxide, alloys of plutonium with minerals, and a mixture of plutonium carbides with uranium carbides are used. Dispersion fuels possess high mechanical properties and thermal conductivity, in which particles of uranium and plutonium compounds are placed in metal matrix from molybdenum, aluminum, of stainless steel and other metals. The radiation resistance and thermal conductivity of the dispersion fuel depend on the matrix material. For example, at the first nuclear power plant, dispersion fuel consisted of uranium alloy particles with 9% molybdenum, which were filled with molybdenum.

As for thorium fuel, today it is not used due to the difficulties in the production and processing of fuel rods.

Mining

Significant volumes of uranium, the main raw material for nuclear fuel, are concentrated in several countries: Russia, USA, France, Canada and South Africa. Its deposits are usually found near gold and copper, so all of these materials are mined at the same time.

The health of people working in the development is subject to great danger. The fact is that uranium is a toxic material, and the gases released during its extraction can cause cancer. And this despite the fact that the ore contains no more than 1% of this substance.

Receiving

The production of nuclear fuel from uranium ore includes stages such as:

  1. Hydrometallurgical processing. Includes leaching, crushing and extraction or sorption recovery. The result of hydrometallurgical processing is a purified suspension of oxiuranium oxide, sodium diuranate or ammonium diuranate.
  2. Conversion of a substance from oxide to tetrafluoride or hexafluoride used to enrich uranium-235.
  3. Substance enrichment by centrifugation or gas thermal diffusion.
  4. Conversion of the enriched material into dioxide, from which fuel rod “tablets” are produced.

Regeneration

During the operation of a nuclear reactor, the fuel cannot completely burn out, therefore free isotopes are reproduced. In this regard, the spent fuel elements are subject to regeneration for the purpose of reuse.

Today this problem is solved by means of the purex process, which consists of such stages as:

  1. Cutting fuel rods into two parts and dissolving them in nitric acid;
  2. Cleaning the solution from fission products and parts of the shell;
  3. Isolation of pure compounds of uranium and plutonium.

After that, the obtained plutonium dioxide is used for the production of new cores, and uranium - for enrichment or also for the manufacture of cores. Reprocessing nuclear fuel is a complex and costly process. Its cost has a significant impact on the economic feasibility of using nuclear power plants. The same can be said about the disposal of waste nuclear fuel that is not suitable for regeneration.

Nuclear Power Plants - NPP Are thermal power plants. On the nuclear power plants the energy of controlled nuclear reactions is used as a source. The unit capacity of NPP power units reaches 1.5 GW.

Nuclear Power Plants - Nuclear Power Plants - Fuels

As a common fuel for nuclear power plants, it is used U- uranium. The fission reaction is carried out in the main block of a nuclear power plant - a nuclear reactor. In a chain reaction of fission nuclear matter a significant amount of thermal energy is released, which is used to generate electricity.

Nuclear power plants - NPP - principle of operation

Fission of uranium nuclei produces fast neutrons. The fission rate is a chain reaction, at nuclear power plants it is regulated by moderators: heavy water or graphite. Neutrons contain a lot of thermal energy. Energy enters the steam generator through the coolant. High pressure steam is directed to turbine generators. The resulting electricity goes to transformers and then to switchgear. Part of the electricity is directed to meet the own needs of a nuclear power plant (NPP). The circulation of the coolant at nuclear power plants is provided by pumps: main and condensate. Excess heat from the nuclear power plant is directed to cooling towers.

Russian nuclear power plants - nuclear power plants - types of nuclear reactors:

  • RBMK - high-power channel reactor,
  • VVER - pressurized water power reactor,
  • BN - fast neutron reactor.

Nuclear power plants - nuclear power plants - ecology

Nuclear Power Plants - Nuclear power plants do not emit flue gases into the atmosphere. There is no waste in the form of ash and slag at the NPP. Problems in nuclear power plants are excess heat and storage of radioactive waste. To protect people and the atmosphere from radioactive emissions at nuclear power plants, special measures are taken:

  • improving the reliability of NPP equipment,
  • duplication of vulnerable systems,
  • high requirements for the qualifications of personnel,
  • protection and protection from external influences.

Nuclear power plants are surrounded by a sanitary protection zone.

How nuclear fuel is produced for nuclear power plants aslan wrote in November 17th, 2015

The Novosibirsk Chemical Concentrate Plant is one of the world's leading manufacturers of nuclear fuel for nuclear power plants and research reactors in Russia and foreign countries. The only Russian manufacturer of metallic lithium and its salts. It is part of the TVEL Fuel Company of Rosatom State Corporation.

Attention, comments under the photo!

Despite the fact that in 2011 NCCP produced and sold 70% of the world consumption of lithium-7 isotope, the main activity of the plant is the production of nuclear fuel for power and research reactors.
The current photo reportage is dedicated to this species.

The roof of the building of the main production complex

Shop for the production of fuel rods and fuel assemblies for research reactors

Section for the manufacture of uranium dioxide powder by the method of high-temperature pyrohydrolysis

Loading containers with uranium hexafluoride

Operator room
From here comes the control of the uranium dioxide powder production process, from which fuel pellets are then made.

Uranium pellet manufacturing site
In the foreground are the bicones where the uranium dioxide powder is stored.
In them, the powder and plasticizer are mixed, which allows the tablet to be compressed better.

Nuclear ceramic fuel pellets
Then they are sent to the furnace for annealing.

Torch (afterburning hydrogen) on the tablet sintering furnace
The tablets are annealed in ovens at a temperature of at least 1750 degrees in a hydrogen reducing atmosphere for more than 20 hours.

Production and technical control of nuclear ceramic fuel pellets
One tablet weighing 4.5 g is equivalent in energy release to 400 kg coal, 360 cc m of gas or 350 kg of oil.

All work is carried out in the boxes with special gloves.

Unloading containers with tablets

Workshop for the production of fuel rods and fuel assemblies for nuclear power plants

Automated line for the production of fuel rods

Here the zirconium tubes are filled with uranium dioxide pellets.
As a result, finished fuel elements are obtained about 4 m in length - fuel elements.
Fuel assemblies are already being assembled from fuel elements, in other words, nuclear fuel.

Moving finished fuel rods in shipping containers
Shoe covers even on wheels.

Fuel assembly assembly area
Installation of lacquer coating on fuel rods

Fastening of fuel rods in the loading mechanism

Frame fabrication - welding of channels and spacer grids
This frame will then be fitted with 312 fuel rods.

Frame technical control

Channels and spacers

Automated stands for equipping a bundle of fuel elements

Bundle assembly

Technical control of fuel assemblies

Fuel rods with bar-code markings by which you can literally trace the entire production path of the product.

Stands for control and packaging of finished fuel assemblies

Control of finished fuel assemblies
Check that the distance between the fuel elements is the same.

Finished fuel assembly

Two-pipe containers for transportation of fuel assemblies
Fuel for nuclear power plants produced at NCCP is used at Russian nuclear power plants, and is also supplied to Ukraine, Bulgaria, China, India and Iran.

Taken from gelio in NZHK. Nuclear fuel production for nuclear power plants (2012)

If you have a production or service that you want to tell our readers about, write to me - Aslan ( [email protected] ) Lera Volkova ( [email protected] ) and Sasha Kuksa ( [email protected] ) and we will make the best report that will be seen not only by the readers of the community, but also by the site http://bigpicture.ru/ and http://ikaketosdelano.ru

Subscribe also to our groups in facebook, vkontakte,classmates and in google + plus where the most interesting from the community will be posted, plus materials that are not here and videos about how things work in our world.

Click on the icon and subscribe!

The Novosibirsk Chemical Concentrate Plant in 2011 produced and sold 70% of the world consumption of lithium-7 isotope (1300 kg), setting a new record in the history of the plant. However, the main product of NZHK production is nuclear fuel.

This phrase has an impressive and frightening effect on the consciousness of Novosibirsk people, making them imagine anything about the enterprise: from three-legged workers and a separate underground city to a radioactive wind.

So what is actually hidden behind the fences of the most mysterious plant in Novosibirsk, which produces nuclear fuel within the city?

JSC Novosibirsk Chemical Concentrates Plant is one of the world's leading manufacturers of nuclear fuel for nuclear power plants and research reactors in Russia and foreign countries. The only Russian manufacturer of metallic lithium and its salts. It is part of the TVEL Fuel Company of Rosatom State Corporation.

We came to the shop where fuel assemblies are made - fuel assemblies that are loaded into nuclear power reactors. This is nuclear fuel for nuclear power plants. To enter the production, you need to put on a robe, hat, shoe covers made of fabric, on your face - "Petal".

The workshop concentrates all work related to uranium-containing materials. This technological complex is one of the main ones for NCCP (fuel assemblies for NPPs occupy approximately 50% in the structure products sold JSC "NZHK").

The operator's room, from where the process of production of uranium dioxide powder comes from, from which fuel pellets are then made.

The workers carry out routine maintenance: at regular intervals, even the newest equipment is stopped and checked. There is always a lot of air in the workshop itself - the exhaust ventilation is constantly working.

Such bicones store uranium dioxide powder. In them, the powder and plasticizer are mixed, which allows the tablet to be compressed better.

Installation that produces the pressing of fuel pellets. As children make cakes from sand by pressing on a mold, so here too: a uranium tablet is pressed under pressure.

Molybdenum boat with tablets waiting to be sent to the furnace for annealing. Before annealing, the tablets have a greenish tint and a different size.

Contact of powder, tablets and the environment reduced to a minimum: all work is carried out in boxes. In order to correct something inside, special gloves are built into the boxes.

The torches on top are burning out hydrogen. The tablets are annealed in ovens at a temperature of at least 1750 degrees in a hydrogen reducing atmosphere for more than 20 hours.

Black cabinets are hydrogen high temperature furnaces in which the molybdenum boat goes through different temperature zones. The damper opens, and a molybdenum boat enters the furnace, from where the tongues of flame escape.

Finished tablets are sanded, since they must be of a strictly defined size. And at the exit, inspectors check each tablet so that there are no chips, no cracks, no defects.

One tablet weighing 4.5 g in terms of energy release is equivalent to 640 kg of firewood, 400 kg of coal, 360 cubic meters. m of gas, 350 kg of oil.

Uranium dioxide tablets after annealing in a hydrogen furnace.

Here, zirconium tubes are filled with uranium dioxide pellets. At the exit, we have finished fuel elements (about 4 m in length) - fuel elements. Fuel assemblies are already being assembled from fuel elements, in other words, nuclear fuel.

Such machines with soda can no longer be found on the streets of the city, perhaps, only at NZHK. Although in Soviet times they were very common.

In this machine, a glass can be washed and then filled with carbonated, still or chilled water.

According to the assessment of the Department of Natural Resources and Environmental Protection, expressed in 2010, NZHK does not have a significant impact on environmental pollution.

A pair of such thoroughbred hens permanently lives and lays eggs in a solid wooden enclosure, which is located on the territory of the workshop.

Workers weld the frame for the fuel assembly. The frames are different, depending on the modification of the fuel assembly.

The plant employs 2,277 people, the average age of the personnel is 44.3 years, 58% are men. Average wage exceeds 38,000 rubles.

Large tubes are channels for the reactor protection control system. This frame will then be fitted with 312 fuel rods.

CHP-4 is located next to the NZHK. With reference to ecologists, representatives of the plant reported that one CHP plant emits 7.5 times more radioactive substances than NZHK per year.

Fitter-assembler Viktor Pustozerov, a veteran of the plant and nuclear energy, has 2 Orders of Labor Glory

Head and shank for fuel assemblies. They are installed at the very end, when all 312 fuel rods are already in the frame.

Final control: finished fuel assemblies are checked with special probes so that the distance between the fuel elements is the same. Supervisors are most often women, this is a very painstaking job.

In such containers, fuel assemblies are sent to the consumer - 2 cassettes in each. Inside they have their own cozy felt bed.

Fuel for nuclear power plants produced by JSC NCCP is used at Russian nuclear power plants and is also supplied to Ukraine, Bulgaria, China, India and Iran. The cost of fuel assemblies is a commercial secret.

Work at NZHK is not at all more dangerous than work on any industrial enterprise... The health status of employees is constantly monitored. In recent years, not a single case of occupational diseases has been identified among workers.

Life cycle nuclear fuel based on uranium or plutonium begins at mining enterprises, chemical plants, in gas centrifuges, and does not end when the fuel assembly is unloaded from the reactor, since each fuel assembly has a long way to go through disposal and then reprocessing.

Extraction of raw materials for nuclear fuel

Uranium is the heaviest metal on earth. About 99.4% of terrestrial uranium is uranium-238, and only 0.6% is uranium-235. The Red Book of the International Atomic Energy Agency contains data on the growth of production and demand for uranium, despite the accident at the Fukushima-1 nuclear power plant, which caused many to think about the prospects for nuclear power. In the past few years alone, the explored uranium reserves have grown by 7%, which is associated with the discovery of new deposits. The largest producers remain Kazakhstan, Canada and Australia, they mine up to 63% of the world's uranium. In addition, there are metal reserves in Australia, Brazil, China, Malawi, Russia, Niger, USA, Ukraine, China and other countries. Earlier, Pronedra wrote that in 2016, 7.9 thousand tons of uranium were mined in the Russian Federation.

Today, uranium is mined in three different ways. The open method does not lose its relevance. It is used when deposits are close to the surface of the earth. At open way bulldozers create a quarry, then ore with impurities is loaded into dump trucks for transportation to processing facilities.

Often the ore body lies at great depths, in which case an underground mining method is used. A mine is dug up to a depth of two kilometers, the rock, by drilling, is mined in horizontal drifts, transported upward in freight elevators.

The mixture that is transported upstairs in this way has many constituents. The rock must be crushed, diluted with water and removed excess. Then sulfuric acid is added to the mixture to carry out the leaching process. In the course of this reaction, chemists obtain a yellow precipitate of uranium salts. Finally, uranium with impurities is purified at the refinery. Only after this is uranium nitrous oxide obtained, which is traded on the exchange.

There is a much safer, more environmentally friendly and economically viable method called downhole in-situ leaching (BLE).

With this method of field development, the territory remains safe for personnel, and the radiation background corresponds to the background in large cities. To extract uranium by leaching, 6 wells must be drilled at the corners of the hexagon. Sulfuric acid is pumped into the uranium deposits through these wells, it mixes with its salts. This solution is produced, namely pumped through the well in the center of the hexagon. To achieve the desired concentration of uranium salts, the mixture is passed several times through sorption columns.

Nuclear fuel production

The production of nuclear fuel cannot be imagined without gas centrifuges, which are used to obtain enriched uranium. After reaching the required concentration, so-called tablets are pressed from uranium dioxide. They are created using lubricants that are removed during firing in ovens. The firing temperature reaches 1000 degrees. After that, the tablets are checked for compliance with the stated requirements. The surface quality, moisture content, oxygen to uranium ratio are important.

At the same time, in another shop, tubular casings for fuel elements are being prepared. The above processes, including the subsequent dosage and packing of tablets into shell tubes, sealing, decontamination, are called fuel fabrication. In Russia, the creation of fuel assemblies (FA) is carried out by the enterprises "Machine-building plant" in the Moscow region, "Novosibirsk plant of chemical concentrates" in Novosibirsk, "Moscow plant of polymetals" and others.

Each batch of fuel assemblies is created for a specific type of reactor. European fuel assemblies are made in the form of a square, and Russian ones with a hexagonal section. Reactors of the VVER-440 and VVER-1000 types are widespread in the Russian Federation. The first fuel rods for VVER-440 began to be developed in 1963, and for VVER-1000 - since 1978. Despite the fact that new reactors with post-Fukushima safety technologies are being actively introduced in Russia, there are many old-style nuclear installations in the country and abroad, therefore, fuel assemblies for different types reactors.

For example, to provide fuel assemblies for one core of the RBMK-1000 reactor, more than 200 thousand components made of zirconium alloys are needed, as well as 14 million sintered uranium dioxide pellets. Sometimes the cost of manufacturing a fuel assembly can exceed the cost of the fuel contained in the elements, which is why it is so important to ensure high energy efficiency from each kilogram of uranium.

Costs for production processes in %

Separately, it should be said about fuel assemblies for research reactors. They are designed in such a way as to make observation and study of the neutron generation process as comfortable as possible. Such fuel elements for experiments in the fields of nuclear physics, production of isotopes, radiation medicine in Russia are produced by the Novosibirsk Plant of Chemical Concentrates. Fuel assemblies are created on the basis of seamless elements with uranium and aluminum.

The production of nuclear fuel in the Russian Federation is carried out by the TVEL Fuel Company (a division of Rosatom). The enterprise works on enrichment of raw materials, assembly of fuel elements, and also provides fuel licensing services. "Kovrovsky mechanical plant" in the Vladimir region and "Ural plant of gas centrifuges" in Sverdlovsk region create equipment for Russian fuel assemblies.

Features of transportation of fuel rods

Natural uranium is characterized by a low level of radioactivity, however, before the production of fuel assemblies, the metal undergoes an enrichment procedure. The content of uranium-235 in natural ore does not exceed 0.7%, and the radioactivity is 25 becquerels per 1 milligram of uranium.

Uranium pellets, which are placed in fuel assemblies, contain uranium with a concentration of 5% uranium-235. Finished fuel assemblies with nuclear fuel are transported in special high-strength metal containers. For transportation, rail, road, sea and even air transport are used. Two assemblies are placed in each container. The transportation of non-irradiated (fresh) fuel does not pose a radiation hazard, since the radiation does not go beyond the zirconium tubes, into which pressed uranium pellets are placed.

For a consignment of fuel, a special route is developed, the cargo is transported accompanied by the security personnel of the manufacturer or customer (more often), which is primarily due to the high cost of equipment. In the entire history of nuclear fuel production, not a single transport accident involving fuel assemblies has been recorded that would affect the radiation background of the environment or lead to casualties.

Fuel in the reactor core

A unit of nuclear fuel - TVEL - is capable of releasing a huge amount of energy over a long period of time. Neither coal nor gas can be compared with such volumes. The life cycle of fuel at any nuclear power plant begins with the unloading, removal and storage of fresh fuel in the fuel assembly warehouse. When the previous batch of fuel in the reactor burns out, the personnel completes the fuel assemblies for loading into the core (the working zone of the reactor where the decay reaction takes place). As a rule, the fuel is partially reloaded.

Fully fuel is loaded into the core only at the moment of the first launch of the reactor. This is due to the fact that the fuel elements in the reactor burn out unevenly, since the neutron flux differs in intensity in different zones of the reactor. Thanks to the metering devices, the station personnel has the ability to monitor the degree of burnup of each unit of fuel in real time and make a replacement. Sometimes, instead of loading new fuel assemblies, assemblies move among themselves. Burnout occurs most intensively in the center of the core.

Fuel assemblies after the nuclear power plant

Uranium that worked in a nuclear reactor is called irradiated or burned out. And such fuel assemblies are spent nuclear fuel. SNF is positioned separately from radioactive waste, since it has at least 2 useful components - unburnt uranium (the metal burn-up rate never reaches 100%) and transuranium radionuclides.

IN recent times physicists began to use radioactive isotopes accumulating in spent nuclear fuel in industry and medicine. After the fuel has worked out its campaign (the time spent by the assembly in the reactor core under conditions of operation at rated power), it is sent to the spent fuel pool, then to the storage directly in the reactor compartment, and then to reprocessing or disposal. The spent fuel pool is designed to remove heat and protect against ionizing radiation, since the fuel assembly remains hazardous after being removed from the reactor.

In the USA, Canada or Sweden, spent nuclear fuel is not sent for reprocessing. Other countries, including Russia, are working on a closed fuel cycle. It can significantly reduce the cost of nuclear fuel production, since part of the spent nuclear fuel is reused.

The fuel rods dissolve in the acid, after which the researchers separate the plutonium and unused uranium from the waste. It is impossible to reuse about 3% of the raw material; it is high-level waste that undergoes bituminization or vitrification procedures.

From spent nuclear fuel, 1% of plutonium can be obtained. This metal does not need to be enriched; Russia uses it in the production of innovative MOX fuel. A closed fuel cycle makes it possible to make one fuel assembly approximately 3% cheaper, but this technology requires large investments in the construction of industrial units, therefore it has not yet become widespread in the world. Nevertheless, the Rosatom fuel company does not stop researching in this direction. Pronedra recently wrote that in Russian Federation are working on fuel capable of utilizing the isotopes of americium, curium and neptunium in the reactor core, which are included in the same 3% of highly radioactive waste.

Nuclear fuel producers: rating

  1. Until recently, the French company Areva provided 31% of the world market for fuel assemblies. The company is engaged in the production of nuclear fuel and the assembly of components for nuclear power plants. In 2017, Areva underwent a qualitative renewal, new investors came to the company, and the colossal loss of 2015 was reduced by 3 times.
  2. Westinghouse - American division Japanese company Toshiba. It actively develops the market in Eastern Europe, supplies fuel assemblies to Ukrainian nuclear power plants. Together with Toshiba, it provides 26% of the global nuclear fuel production market.
  3. TVEL Fuel Company of Rosatom State Corporation (Russia) is in third place. TVEL provides 17% of the world market, has a 10-year portfolio of contracts worth $ 30 billion and supplies fuel to more than 70 reactors. TVEL develops fuel assemblies for VVER reactors, and also enters the market of Western-designed nuclear installations.
  4. Japan Nuclear Fuel Limited, according to the latest data, provides 16% of the world market, supplies fuel assemblies to most of the nuclear reactors in Japan itself.
  5. Mitsubishi Heavy Industries is a Japanese giant that produces turbines, tankers, air conditioners, and more recently nuclear fuel for Western-style reactors. Mitsubishi Heavy Industries (a division of the parent company) is engaged in the construction of nuclear reactors APWR, research activities with Areva. It was this company that was chosen by the Japanese government to develop new reactors.