How uranium is transported for a power plant. Nuclear fuel. Nuclear power plants in Russia

Japan, like the United States, stores spent fuel rods in temporary storage pools directly at nuclear power plants, where they are protected with the same degree of safety as provided for the plant.
Data provided yesterday by Tokyo Electric Power (operates the plant): in total, 11,195 fuel rod assemblies (colloquially fuel rods) were stored at Fukushima-1 . Each is over 4 meters long and contains (on average) 135 kilograms of uranium. There are also fuel rods with plutonium (MOX).

More Each of the six reactors contains an average of 500 fuel rods (from 400 to 600 in each). This is about 70 tons of uranium (or uranium oxide with plutonium). Approximately three times less (if my memory serves me correctly) than in the exploded reactor at Chernobyl. Of the 200 tons, about ten were scattered in Chernobyl. This is what allows people to be fooled. They say the scale here is not the same. Only the main problem and the uranium is not in the reactors.

In the pool above reactor No. 4 itself there were 548 fuel rods, removed only in November-December (that is, the hottest ones).

The 6,291 assemblies are located in a common cooling pool immediately outside the outer shell of reactor No. 4. 32 of the 514 fuel assemblies in the pool at reactor No. 3 contain MOX (a mixture of uranium and plutonium).
Thus on the territory of the nuclear power plant there are only 14 thousand 195 fuel rods, each containing 135 kilograms of uranium (and plutonium) in everyone. Almost in total TWO THOUSAND TONS!!! TEN TIMES MORE than in our 4th block that exploded. And these thousands of tons were located before the accident in a dozen different places - in the reactors, the pools above them and next to block No. 4.
Now let's study the pictures of block No. 4. Above - immediately after the explosion-fire. Below are photos from yesterday (March 17). As we see on the first top one, it was not the roof that was blown away, as in the explosion of accumulated hydrogen - it only sank, even retaining some integrity. But the side wall at the level of the cooling pool was completely blown away. By the way, there is a hole at the same level in block No. 2.

From left to right, blocks No. 4, 3, 2, 1.
In the diagram, the spent fuel pools are colored blue above the reactor:

Now let’s ask ourselves a simple question after viewing the already completely destroyed blocks No. 3 and No. 4 in yesterday’s photo. What caused this destruction and what happened to the 143 tons of uranium and plutonium in 1062 fuel rods stored in the pools of the destroyed power units? And where are the pools themselves, if the skeletons are visible right through?

Read more about what Japanese atomic cuisine is below. At least now I understand why the Japanese love to eat puffer fish. A little mistake - and hello, spirits of ancestors. A version of Russian roulette on a national scale.

The vast majority of fuel assemblies at problem reactors are located in cooling pools rather than in the reactors themselves.
The water in the pools either boils away or leaks out of holes, or the pools are completely destroyed, and attempts to add water fail. Although spent fuel rods generate significantly less heat than in a reactor, they still melt, emitting extremely high levels of radiation.

Very high levels of radiation above the cooling pools indicate that the water in the 13-meter-deep pools had receded so much that the fuel assemblies, more than 4 meters high, became exposed and began to melt. Spent fuel rod assemblies emit less heat than new assemblies inside the core of an operating reactor, but they generate enough heat and radioactivity that they must be covered with a 9-meter layer of circulating water to prevent excessive heating. Now calculate the volume of water to fill the pool yourself. I'm not even talking about replacing it with a cold one. A 13-meter layer of water and more than half a thousand fuel rods in each. These are not tens or hundreds - more than a thousand tons of water. What kind of fire trucks are there? What 64 tons, sprayed from a helicopter?

On Wednesday, the chairman of the US Nuclear Regulatory Commission, Gregory Jaczko, made a sensational announcement that there was virtually no water left in the cooling pool located on top of the No. 4 reactor and expressed serious concerns about the radioactivity that could be released as a result. Let me remind you that 548 assemblies of fuel rods are stored in this cooling pool, which were removed from the reactor only last year in November and December, during the preparation of the reactor for Maintenance, and may generate more heat than older assemblies in other cooling pools.

Michael Friedlander, a former senior nuclear power plant operator who worked for 13 years at three US reactors, says spent fuel pools typically have a 20mm thick stainless steel caisson supported by a reinforced concrete base. So even if the caisson is damaged, he says, “without destruction of the concrete, the water will have nowhere to go.” And we are seeing enough destruction.

On each of the opposite sides of the pool there are steel gates, more than 5 meters high, with rubber seals, used to load fresh fuel assemblies into the reactor, as well as unload and store spent assemblies. Mr. Friedlander said the gates were designed to withstand earthquakes, but the leaks could have been caused by the strength of last Friday's earthquake, which is currently estimated to have been a magnitude 9.0 earthquake. Even if water has poured out of the gate, there should still be about 3 meters of water to the top of the fuel rod assemblies.

When the water in the pool disappears, the residual heat in the uranium fuel rods from their time in the nuclear reactor continues to heat the zirconium cladding of the rods. This causes the zirconium to oxidize, rust to form, possibly even catch fire, which destroys the integrity of the rod's shell, releasing radioactive gases under pressure, such as iodine vapor, that have accumulated in the rods over the time they spent in the reactor, Mr. Albrecht said.
Each rod within the assembly contains a vertical stack of cylindrical uranium oxide granules (pellets). These granules sometimes sinter together while they are in the reactor, in which case they may continue to stand even after the shell is burned. According to Mr. Albrecht, if the granules stand upright, then even if the water and zirconium disappear, the nuclear fission reaction will not begin.

However, TEPCO said this week that there is a chance of "subcriticality" in the cooling pools - that is, the uranium in the fuel rods could become critical, in the nuclear sense, and restart the fission process that previously took place inside the reactor, spewing out radioactive byproducts.
Mr Albrecht said this was very unlikely, but could happen if stacks of pellets fell and were mixed together on the floor of the cooling pond. TEPCO in last years changed the arrangement of shelving in the pool in order to fit more assemblies into the limited space of the spent fuel pool.

If “subcriticality” has occurred, then adding pure water can actually only speed up the fission process. Especially sea, with an abundance of salts. Authorities should add water from big amount boron, because boron absorbs neutrons and breaks the nuclear chain reaction. Only for now there is no word on this.

If “subcriticality” occurs, the uranium begins to heat up. If a large number of fissions occur, which can only happen as a last resort, the uranium will melt through everything underneath it. If water is encountered along its path, a steam explosion will occur and molten uranium will scatter. This is Chernobyl.

Each assembly has either 64 large fuel rods or 81 slightly smaller fuel rods, depending on the supplier that supplies it. Typical assemblies contain a total of approximately 135 kilograms of uranium.

One big problem for Japanese officials is that the No. 3 reactor, a prime target for helicopters and water cannons on Thursday, is using new and different kinds fuel. It uses a mixture of oxides, or MOX fuel, which contains a mixture uranium and plutonium, and may release a more dangerous radioactive plume if dissipated during a fire or explosion.

Japan hopes to solve the problem of spent fuel stockpiling with a large-scale plan to reprocess the rods into fuel that would be returned to the nuclear program. But even before Friday's earthquake, the plan had been plagued by numerous setbacks.

Central to Japan's plans is a $28 billion reprocessing facility in the village of Rokkase, north of the earthquake zone, that could extract uranium and plutonium from the rods used to create MOX fuel. After countless construction delays, test runs began in 2006, and the plant's operator, Japan Nuclear Fuel, said work would begin in 2010. However, at the end of 2010, its opening was postponed for another two years. A MOX fuel production facility is also still under construction.

To complete the nuclear fuel reprocessing process, Japan also built Monju, a fast breeder reactor, which became fully operational in 1994. However, after a year, After a fire caused by a sodium leak, the plant was closed.
Despite suspicions that the operator, Japan's parastatal Atomic Energy Agency, had covered up the severity of the accident, Monju began operating at partial capacity again, reaching criticality, or a sustained nuclear chain reaction in the reactor, in May.

Another The Tokaimura nuclear reprocessing facility was closed in 1999 after an experimental fast reactor accident exposed hundreds of people nearby and killed two workers.

Materials used:
from an article by KEITH BRADSHER and HIROKO TABUCHI/ Original publication www.nytimes.com/2011/03/18/world/asia/18 spent.html
Photo:

http://forum.ixbt.com/topic.cgi?id=64:2968-12
http://nnm.ru/blogs/oldustas/opasnost_ot_basseynov_vyderzhki_pereveshivaet_ugrozu_ot_reaktorov/
and from my earlier materials.

Nuclear energy consists of large quantity enterprises for various purposes. The raw materials for this industry are mined from uranium mines. It is then delivered to fuel production plants.

The fuel is then transported to nuclear power plants, where it enters the reactor core. When nuclear fuel reaches the end of its useful life, it is subject to disposal. It is worth noting that hazardous waste appears not only after fuel reprocessing, but also at any stage - from uranium mining to work in the reactor.

Nuclear fuel

There are two types of fuel. The first is uranium mined in mines, which is of natural origin. It contains raw materials that are capable of forming plutonium. The second is fuel that is created artificially (secondary).

Nuclear fuel is also divided according to chemical composition: metal, oxide, carbide, nitride and mixed.

Uranium mining and fuel production

A large share of uranium production comes from just a few countries: Russia, France, Australia, the USA, Canada and South Africa.

Uranium is the main element for fuel in nuclear power plants. To get into the reactor, it goes through several stages of processing. Most often, uranium deposits are located next to gold and copper, so its extraction is carried out with the extraction of precious metals.

During mining, human health is at great risk because uranium is a toxic material, and the gases that appear during its mining cause various forms of cancer. Although the ore itself contains a very small amount of uranium - from 0.1 to 1 percent. The population living near uranium mines is also at great risk.

Enriched uranium is the main fuel for nuclear power plants, but after its use a huge amount of radioactive waste remains. Despite all its dangers, uranium enrichment is an integral process of creating nuclear fuel.

In its natural form, uranium practically cannot be used anywhere. In order to be used, it must be enriched. Gas centrifuges are used for enrichment.

Enriched uranium is used not only in nuclear energy, but also in weapons production.

Transportation

At any stage of the fuel cycle there is transportation. It is carried out by everyone accessible ways: by land, sea, air. This is a big risk and a big danger not only for the environment, but also for humans.

During the transportation of nuclear fuel or its elements, many accidents occur, resulting in the release of radioactive elements. This is one of the many reasons why it is considered unsafe.

Decommissioning of reactors

None of the reactors have been dismantled. Even the infamous Chernobyl The whole point is that, according to experts, the cost of dismantling is equal to, or even exceeds, the cost of building a new reactor. But no one can say exactly how much money will be needed: the cost was calculated based on the experience of dismantling small stations for research. Experts offer two options:

1. Place reactors and spent nuclear fuel in repositories.
2. Build sarcophagi over decommissioned reactors.

In the next ten years, about 350 reactors around the world will reach their end of life and must be taken out of service. But since the most suitable method in terms of safety and price has not been invented, this issue is still being resolved.

There are currently 436 reactors operating around the world. Of course, this is a big contribution to the energy system, but it is very unsafe. Research shows that in 15-20 years, nuclear power plants will be able to be replaced by stations that run on wind energy and solar panels.

Nuclear waste

A huge amount of nuclear waste is generated as a result of the activities of nuclear power plants. Reprocessing nuclear fuel also leaves behind hazardous waste. However, none of the countries found a solution to the problem.

Today, nuclear waste is kept in temporary storage facilities, in pools of water, or buried shallowly underground.

The safest method is storage in special storage facilities, but radiation leakage is also possible here, as with other methods.

In fact, nuclear waste has some value, but requires strict compliance with the rules for its storage. And this is the most pressing problem.

An important factor is the time during which the waste is hazardous. Each has its own decay period during which it is toxic.

Types of nuclear waste

During the operation of any nuclear power plant, its waste enters the environment. This is water for cooling turbines and gaseous waste.

Nuclear waste is divided into three categories:

1. Low level - clothing of nuclear power plant employees, laboratory equipment. Such waste can also come from medical institutions, scientific laboratories. They do not pose a great danger, but require compliance with safety measures.
2. Intermediate level - metal containers in which fuel is transported. Their radiation level is quite high, and those who are close to them must be protected.
3. The high level is spent nuclear fuel and its reprocessing products. The level of radioactivity is rapidly decreasing. Waste high level very little, about 3 percent, but they contain 95 percent of all radioactivity.

In 2011, the Novosibirsk Chemical Concentrates Plant produced and sold 70% of the world's consumption of the lithium-7 isotope (1300 kg), setting a new record in the history of the plant. However, the main product produced by NCCP is nuclear fuel.

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

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

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

We came to the workshop where fuel assemblies are made - fuel assemblies, which 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, a cap, fabric shoe covers, and a “Petal” on your face.

All work related to uranium-containing materials is concentrated in the workshop. This technological complex is one of the main ones for NCCP (fuel assemblies for nuclear power plants occupy approximately 50% of the structure products sold OJSC "NZHK").

The control room, from where the process of producing uranium dioxide powder is controlled, from which fuel pellets are then made.

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

Uranium dioxide powder is stored in such bicones. They mix the powder and plasticizer, which allows the tablet to be better compressed.

An installation that compresses fuel pellets. Just as children make Easter cakes out of sand by pressing on a mold, so here: a uranium tablet is pressed under pressure.

A 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 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 hydrogen. The tablets are annealed in ovens at a temperature of at least 1750 degrees in a hydrogen reducing environment 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 flames burst out.

The finished tablets are polished because they must be of a strictly defined size. And at the exit, inspectors check each tablet to ensure there are no chips, cracks, or defects.

One tablet weighing 4.5 g is equivalent in energy release 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 output we have ready-made fuel rods (about 4 m in length) - fuel elements. Fuel rods are already used to assemble fuel assemblies, in other words, nuclear fuel.

You won’t find such soda fountains on city streets anymore, perhaps only at NZHK. Although in Soviet times they were very common.

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

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

A pair of such purebred hens constantly lives and lays eggs in a high-quality 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, average age personnel - 44.3 years old, 58% are men. Average wage exceeds 38,000 rubles.

Large tubes are channels for the reactor protection control system. 312 fuel rods will then be installed into this frame.

Next to the NCCP there is CHPP-4. With reference to environmentalists, representatives of the plant reported: per year, one thermal power plant emits 7.5 times more radioactive substances than the NCCP.

Assembly mechanic Viktor Pustozerov, a veteran of the plant and nuclear power industry, 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 rods is the same. Controllers 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 trade secret.

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

Nuclear fuel

Nuclear fuel is almost ready to go.

Nuclear fuel- a substance that is used in nuclear reactors to carry out a nuclear fission chain reaction. Nuclear fuel is fundamentally different from other types of fuel used by mankind; it is extremely highly efficient, but also very dangerous for humans and can cause very serious accidents, which imposes many restrictions on its use for safety reasons. For this and many other reasons, nuclear fuel is much more difficult to use than any type of organic fuel, and requires many special technical and organizational measures when using it, as well as highly qualified personnel dealing with him.

general information

A nuclear chain reaction involves the division of a nucleus into two parts, called fission fragments, with the simultaneous release of several (2-3) neutrons, which, in turn, can cause the fission of subsequent nuclei. This fission occurs when a neutron hits the nucleus of an atom of the original substance. The fission fragments formed during nuclear fission have high kinetic energy. The inhibition of fission fragments in matter is accompanied by the release of a large amount of heat. Fission fragments are nuclei formed directly as a result of fission. Fission fragments and their radioactive decay products are usually called fission products. Nuclei fissioned by neutrons of any energy are called nuclear fuel (as a rule, these are substances with an odd atomic number). There are nuclei that are fissioned only by neutrons with energies above a certain threshold value (as a rule, these are elements with an even atomic number). Such nuclei are called raw materials, since when a neutron is captured by a threshold nucleus, nuclear fuel nuclei are formed. The combination of nuclear fuel and raw material is called nuclear fuel. Below is the distribution of the fission energy of the 235 U nucleus between the various fission products (in MeV):

Natural uranium consists of three isotopes: 238 U (99.282%), 235 U (0.712%) and 234 U (0.006%). It is not always suitable as nuclear fuel, especially if the structural materials and moderator intensively absorb neutrons. In this case, nuclear fuel is made from enriched uranium. Thermal neutron power reactors use uranium with an enrichment of less than 6%, while fast and intermediate neutron reactors use uranium enrichment exceeding 20%. Enriched uranium is produced at special enrichment plants.

Classification

Nuclear fuel is divided into two types:

• Natural uranium containing fissile nuclei 235 U, as well as raw materials 238 U, capable of forming plutonium 239 Pu upon neutron capture;
• Secondary fuels that do not occur in nature, including 239 Pu, obtained from the first type of fuel, as well as 233 U isotopes formed when neutrons are captured by 232 Th thorium nuclei.

According to the chemical composition, nuclear fuel can be:

Theoretical aspects of application

In a selected fragment of this dummy fuel assembly with fuel element sectors cut out for ease of viewing, fuel pellets are visible.

Nuclear fuel is used in nuclear reactors in the form of tablets several centimeters in size, where it is usually located in hermetically sealed fuel elements (fuel elements), which in turn, for ease of use, are combined in several hundred into fuel assemblies (FA).

Apply to nuclear fuel high requirements in terms of chemical compatibility with fuel rod claddings, it must have a sufficient melting and evaporation temperature, good thermal conductivity, a slight increase in volume during neutron irradiation, and manufacturability.

The use of uranium metal, especially at temperatures above 500 °C, is difficult due to its swelling. After nuclear fission, two fission fragments are formed, the total volume of which is greater than the volume of a uranium (plutonium) atom. Some of the fission fragment atoms are gas atoms (krypton, xenon, etc.). Gas atoms accumulate in the pores of uranium and create internal pressure, which increases with increasing temperature. Due to changes in the volume of atoms during fission and an increase in the internal pressure of gases, uranium and other nuclear fuels begin to swell. Swelling refers to the relative change in the volume of nuclear fuel associated with nuclear fission.

Swelling depends on burnout and temperature of fuel rods. The number of fission fragments increases with increasing burnup, and the internal gas pressure increases with increasing burnup and temperature. Swelling of nuclear fuel can lead to destruction of the fuel rod cladding. Nuclear fuel is less susceptible to swelling if it has high mechanical properties. Uranium metal is not one of these materials. Therefore, the use of uranium metal as nuclear fuel limits the burnup depth, which is one of the main characteristics of nuclear fuel.

Radiation resistance and mechanical properties fuels are improved by doping the uranium, a process in which small amounts of molybdenum, aluminum, and other metals are added to the uranium. Alloying additives reduce the number of fission neutrons per neutron captured by nuclear fuel. Therefore, they tend to select alloying additives for uranium from materials that weakly absorb neutrons.

Good nuclear fuels include some refractory uranium compounds: oxides, carbides and intermetallic compounds. Most wide application received ceramics - uranium dioxide UO 2. Its melting point is 2800 °C, density is 10.2 g/cm³. Uranium dioxide has no phase transitions and is less susceptible to swelling than uranium alloys. This allows you to increase burnout to several percent. Uranium dioxide does not react with zirconium, niobium, stainless steel and other materials at high temperatures. The main disadvantage of ceramics is low thermal conductivity - 4.5 kJ/(m K), which limits the specific power of the reactor in terms of melting temperature. Thus, the maximum heat flux density in VVER reactors on uranium dioxide does not exceed 1.4 10 3 kW/m², while the maximum temperature in fuel rods reaches 2200 °C. In addition, hot ceramic is very brittle and can crack.

Practical use

Receipt

Uranium fuel

Regeneration

When a nuclear reactor operates, the fuel does not burn out completely; the process of reproduction of individual isotopes (Pu) takes place. In this regard, spent fuel rods are sent for recycling to regenerate fuel and reuse it.

Currently, the most widely used process for these purposes is the Purex process, the essence of which is as follows: fuel rods are cut into pieces and dissolved in nitric acid, then the solution is purified from fission products and shell elements, and pure U and Pu compounds are isolated. Then, the resulting plutonium dioxide PuO 2 is sent for the production of new cores, and the uranium is either used for the production of cores or for enrichment with 235 U.

Reprocessing and regeneration of highly radioactive substances is a complex and expensive process. After removal from reactors, fuel rods are aged for several years (usually 3-6) in special storage facilities. Difficulties are also caused by the processing and disposal of waste that is unsuitable for regeneration. The cost of all these measures has a significant impact on economic efficiency nuclear power plants.

Notes

Literature

• Petunin V. P. Thermal power engineering of nuclear installations M.: Atomizdat, 1960.
• Levin V. E. Nuclear physics and nuclear reactors 4th ed. - M.: Atomizdat, 1979.

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