Radioactive strontium-90

Sources of environmental pollution. The most significant source of contamination of the external environment with strontium-90 is nuclear weapons testing, and there is a clearly expressed locality of fallout (the density of fallout depends on the physiographic and climatic features of certain areas). This radionuclide also enters the external environment from nuclear power plants and spent nuclear fuel reprocessing plants (it is found in emissions in a readily soluble form). Under normal operating conditions of a nuclear power plant, emissions of radioactive strontium are insignificant.

Strontium radioisotopes are characterized by high yield in fission reactions of uranium and plutonium and high mobility in ecological chains of the natural environment. All this must be taken into account in the design of nuclear reactors, when determining the duration of their operation and the radioactive waste management system.

Food paths (chains). The main food chains of radioactive strontium migration are: atmosphere - plants - humans; atmosphere - soil - plants - people; atmosphere - soil - plants - animals - humans; atmosphere - bodies of water - drinking water- Human; atmosphere - bodies of water - hydrobionts - fish - humans;

wastewater - soil - plants - humans; wastewater - soil - plants - animals - humans; wastewater - hydrobionts - fish - humans.

Strontium accumulates in green plants, in particular in cereals (grains), and enters the human body through baked goods. Through hay (feed) it enters the tissues of animals (cows). Therefore, milk is the second way, after bread, for strontium to enter the human body. Finally, radioactive strontium that falls on the surface of water bodies or is washed there by surface runoff is easily absorbed by unicellular algae (phytoplankton), accumulated along the food chain by crustaceans and other small animals (zooplankton), and then by fish.

The concentration of strontium increases as you move up the food chain; in the body of some fish it can be tens of thousands of times higher than in water. Thus, fish, especially its skeleton, is another common food route for the entry of strontium into the human body. Finally, vegetables and fruits are an important source of radioactive strontium.

Strontium in its qualities, as already mentioned, is very close to calcium and circulates in the biosphere along with it. Atmospheric air is the primary reservoir from where strontium enters water bodies and land. The deposition of radionuclides from the air is determined by gravity, deposition on inert dust, which is constantly present in the atmosphere, and removal by precipitation (rain, snow). The residence time of radioactive strontium particles in the atmosphere is 30-40 days, and in the stratosphere - several years.

The soil is of particular importance as a depot of radioactive strontium (almost all of it is in mobile form). Initially, it accumulates on its surface, and then is slowly redistributed along its profile. Strontium is absorbed by the solid phase of the soil much less readily than radioactive cesium. The migration of radioactive strontium in the soil is influenced by: climatic conditions, terrain, hydrological regime, nature of vegetation, agricultural practices and type of soil. Soils, according to the degree of increase in the absorption capacity of radioactive strontium, in turn, can be arranged in the following series: chernozem - chestnut - soddy-podzolic.

Radioactive strontium can enter plants due to direct contamination of their ground part (at the time of radionuclide fallout and secondary dust formation), absorption from the soil through root system and irrigation with waters containing it. The degree of radionuclide retention on vegetation is determined by the characteristics of plants, the size of radioactive particles and meteorological conditions. Strontium-90 deposited on the surface of plants can be absorbed by it. The retention rate of radionuclides from global fallout by wild and agricultural vegetation is approximately 25%. The time for removal (by rain, wind, etc.) from herbaceous plants of 50% of retained radionuclides for temperate climate zones is 1-5 weeks. The accumulation of radioactive strontium is inversely proportional to the amount of exchangeable calcium in the soil; in addition, it depends on the type and variety of plants. Thus, most of it accumulates in legumes, while in seeds, fruits and tubers it is much less than in leaves and stems.

Radioactive strontium mainly enters the body of animals with feed. The transition of a radionuclide into products of animal origin depends on its bioavailability, species and age characteristics of animals and their physiological state. In calves, lambs, kids and piglets, the absorption of strontium is several times greater than in adult animals. The main part of radioactive strontium accumulates in bones, mainly in epiphases (joints). Thus, the greatest accumulation of strontium is possible in a growing organism, and this radionuclide, deposited in the bones, is extremely difficult to remove from the body. According to the degree of its accumulation in the skeleton of farm animals, they can be arranged in the following row: cattle - goats - sheep - pigs - chickens. The greatest accumulation of radionuclide is observed in parenchymal organs - liver, kidneys, lungs, minimal - in muscles, and especially in glanders. According to the degree of deposition of radioactive strontium in the muscles and parenchymal organs of farm animals, they can also be arranged in a row: cattle - sheep - chickens. In adult animals, strontium is soft tissues accumulates in greater quantities than in young animals, but in young animals it is excreted much faster than in adults. An increase in calcium in the animal diet accelerates the excretion of strontium-90. In lactating animals, the radionuclide is excreted in milk in significant quantities.

Up to 96% of radioactive strontium is contained in the shell of eggs, 3.5% in the yolk and 0.5% in the white.

Reservoirs pose a particular danger because radioactive strontium accumulates in them. It is absorbed by hydrobionts, in particular fish, along the food chain and directly from the water. At the same time, the content of strontium-90 in aquatic organisms depends not only on its concentration in water, but also on the degree of its mineralization: with its decrease, the accumulation of radionuclides in aquatic organisms increases.

As a result, we can conclude that the main source of radioactive strontium entering the human body is products of plant and animal origin. Soluble forms of strontium are well absorbed from the gastrointestinal tract. The radionuclide is especially dangerous for children, into whose bodies it enters with milk and accumulates in large quantities in the bones. With age, the absorption of radioactive strontium decreases. A high calcium content in the diet prevents the absorption of radioactive strontium, which is one of the most dangerous, highly toxic radionuclides. Large doses cause acute radiation sickness in humans, while prolonged exposure to small doses leads to the development of a chronic form. The latter is characterized by long-term damage to the hematopoietic system, the development of blood diseases (leukemia) and bone tumors.

Radioactive cesium-137

Among man-made radionuclides, radioactive isotopes of cesium are particularly dangerous, especially long-lived cesium-137 with a half-life of 30±0.2 years. This radionuclide is characterized by high mobility in the ecological chains of the natural environment and the ability to accumulate in its individual links.

Sources of environmental pollution. The main source of cesium-137 formation is nuclear weapons testing and enterprises nuclear power. Large quantities of radionuclide accumulate in nuclear reactors during their operation. Under normal operating conditions of a nuclear power plant, radioactive emissions are insignificant and depend on the design of the nuclear reactor, the type of purification systems for radioactive substances and air emitted from the plant, the operating time of the reactor, etc. Cesium-137 environmental pollutants can also be plants for the reprocessing of spent fuel elements. Potential sources of cesium-137 entering the natural environment are discharges of radioactive substances from nuclear power plants into open freshwater bodies and radioactive waste storage facilities. Radiation doses to the population due to emissions from nuclear fuel cycle enterprises under normal operating conditions are insignificant and below recommended standards.

A great danger of environmental contamination with radioactive cesium arises during nuclear power plant accidents, when its emissions increase significantly. In this case, radiation doses increase sharply and fluctuate depending on the scale of the accident and the effectiveness of measures to eliminate it. The intake of cesium-137 largely determines the radiation hazard over a long period of time. The level of radioactive cesium contamination of the environment also depends on the physical, geographical and climatic characteristics of the areas, the distribution of atmospheric precipitation, etc. For example, in certain areas (Ukrainian-Belarusian Polesie, subarctic regions) the levels of cesium-137 intake from products of animal and plant origin are higher than in others. In the North, this is facilitated by the growth characteristics of lichens (the main food of deer), which favor the retention of this radionuclide and its accumulation over a long time.

Food paths (chains). Like radioactive strontium, cesium-137 is characterized by high mobility in the external environment, especially in the first time after its deposition, as well as through food chains that are similar to the migration of strontium-90. Another possible food chain for the migration of radionuclides: source of contamination - medicinal plants - medicinal plant raw materials - medicinal product - humans. It should be recognized that this food chain of radionuclide migration has not yet been sufficiently studied. In this regard, the data from a study of wild medicinal plant raw materials in the southern regions of the Kaluga region, which were subject to radioactive contamination, are of interest. As a result, it turned out that the fruits of tree species in open habitats do not actually accumulate cesium-137. The lowest values ​​of soil contamination for the harvesting of medicinal plants growing on them with a safe content of cesium-137 were identified for perennial shrubs and subshrubs grown in meadows (creeping thyme) and in forests (common lingonberry, marsh wild rosemary).

Radioactive cesium deposited on the soil surface migrates in horizontal and vertical directions, and its solubility becomes important. In soil, cesium-137 easily transforms into a form that is difficult to digest, forming poorly soluble salts. Therefore, its entry into plants through the roots is difficult. Acid rain facilitates the transition of cesium-137 into a soluble form. The migration of radionuclide in the soil is significantly influenced by the terrain, hydrological regime, type of soil, nature of vegetation, agricultural activities carried out and the strength of the bond of the radionuclide with the soil. According to the degree of increase in the absorption capacity of cesium, soils can be arranged in a row: chernozems - chestnut - soddy-podzolic.

Radioactive cesium can enter plants as a result of direct contamination of leaves, stems, inflorescences and fruits, and can also be absorbed from the soil through the root system. Levels of surface contamination of plants depend on their morphological characteristics, precipitation density, and physicochemical properties of aerosols. According to the degree of concentration of cesium-137, plants can be arranged in the following row: cabbage - beets - potatoes - wheat - natural forbs. A decrease in the pollution of pasture vegetation (due to rain, wind, biomass growth) occurs over a period of approximately 14 days. More than 90% of the deposited radionuclide is removed in the first 2 months. Soluble cesium-137 is absorbed by plant roots from the soil solution and becomes firmly anchored in the soil. According to the degree of increasing transfer of cesium-137 into plants, the following series of soils can be built: soddy-podzolic soils - red soils - meadow-carbonate soils - chernozems - gray soils. A greater transition of radioactive cesium is observed in regions with peat-boggy soils (Ukrainian-Belarusian Polesie). According to the degree of accumulation of this radionuclide in tubers and grains, plants can be arranged in a row: barley - millet - wheat - buckwheat - beans - oats - chumiza - potatoes - beans. The amount of cesium-137 accumulation in plants depends on their type, soil type and the nature of agricultural practices. At the same time, the concentration of radioactive cesium in the generative and vegetative organs of plants is approximately the same.

Sources of cesium-137 for humans can be plant (bread, vegetables, fruits) and animal (meat, fish, milk, etc.) products. Since this radionuclide has some properties in common with potassium, tissues of plant and animal origin accumulate both potassium and radioactive cesium. Cesium-137 enters the animal body mainly through food, and the radionuclide is excreted mainly through the kidneys. The main amount of it accumulates in the muscles (over 80%), followed by the skeleton (about 10%). The radionuclide content in 1 kg of muscle of cows, sheep, goats, pigs and chickens is 4, 8, 20, 26 and 45% of the daily intake, respectively. Radioactive cesium is excreted in significant quantities in the milk of lactating animals. With a long-term intake of radionuclide to cows, its content in milk reaches 0.8 - 1.2% per 1 liter of daily intake, in goats - 10 - 20%, in sheep - 5 - 15%. These differences are associated with the physiological characteristics of the animals, the nature of the food and the conditions of their keeping.

Chicken eggs are also a source of cesium-37 entering the human body, and the white contains 2-3 times more radioactive cesium than the yolk, and the shell contains 1-2% of the total amount of radionuclide in the egg.

Radioactive cesium accumulates in large quantities in aquatic organisms. Fish absorb cesium-137 directly from water and mainly through food. The degree of accumulation of this radionuclide is determined by the biological and physiological characteristics of each fish species. Weak water mineralization contributes to a higher accumulation of cesium-137. Freshwater fish contain tens to hundreds of times more radioactive cesium than sea fish. At the same time, in commercial fish Atlantic Ocean- 10-30 times lower than in fish from inland seas (for example, the Caspian). Aquatic plants, depending on the accumulation of cesium-137, can be arranged in the following row: algae - plants immersed in water - coastal aquatic plants - plants floating on the surface.

Radioactive cesium has a fairly high radiotoxicity. It can enter the human body through the respiratory system, skin, wounds and burn surfaces. However, the main way is with food. Radioactive cesium, like potassium, is evenly distributed in human tissues and organs (which leads to relatively uniform irradiation), but most of it is concentrated in muscle tissue (80% and only 10% in bones). Cesium-137 is relatively easily removed from the body. It is excreted primarily in urine and partially in feces. The half-life of this radionuclide from the body is 65-100 days. The rate of its elimination from the body is determined by individual differences in metabolic rate and depends on age, gender, diet, and numerous environmental factors. It should be borne in mind that cesium-137 passes in significant quantities from the mother’s body through the placenta to the fetus (and during the feeding period, through milk to newborns).

Radionuclides are groups of atoms that have the property of radioactivity, with a certain mass number, atomic number and nuclear energy status.

Radionuclides have found wide application in all areas of technology, science and other sectors of the national economy. In medical practice, radionuclides began to be used for diagnosing diseases, sterilizing drugs, instruments and other products. A number of prognostic and therapeutic radiotherapy drugs have been developed.

The benefits and use of radionuclides in medicine are described in detail in this video:

Radionuclides are radioactive isotopes chemical elements with different mass numbers. Let’s try briefly and without delving into scientific data to understand the issue of the harm of these substances to human health.

About classifications of radionuclides

Radioactive isotopes belong to different categories according to their properties. We will touch only on the most important of them.

Radioisotopes are divided into:

• natural;
• artificial, formed as a result of nuclear reactions due to human activity.

The latter are obtained from all elements of the periodic table. Their total number reaches 2000 and continues to increase. There are much fewer natural elements, about 100.

According to the stability of nuclei, radionuclides are classified into:

• short-lived - with a half-life of less than 10 days;
• long-lived - with a long half-life.

IN last years In the national economy, radioisotopes with a complete decay period of several minutes have increasingly begun to be used, which makes them practically harmless.

Based on radiation toxicity, radionuclides are divided into 4 categories:

• A – the most highly toxic for humans. These are isotopes of heavy elements whose nuclei are subject to spontaneous decay. They have relatively long half-lives. Also, these radioactive substances tend to accumulate in various organs of the body;
• B – highly toxic radionuclides;
• B – radioisotopes of medium toxicity;
• G – radiation isotopes of low toxicity.

Radioactive reactions are divided into alpha decay– spontaneous change in the structure of the nucleus with the appearance of alpha particles and betta decay with the emission or absorption of electrons, positrons, neutrinos or antineutrinos.

We will not dwell on more detailed characteristics of the types of decay. Let's try to touch more on the properties of radioelements.

Natural radionuclides are found in rocks, soil layers, natural and artificial water reservoirs. Together with cosmic radiation they make up .

Isotopes of uranium and thorium enter the body through food intake, water, and inhaled air and serve as sources of internal radiation.

The natural background radiation is described in detail in this video:

Technogenic background radiation is formed due to radionuclides contained in building materials, during fuel combustion and emissions from power plants.

Nuclear reactors and particle accelerators provide artificial radiation background.

Note:One of the important properties of radionuclides is half life. The processes occurring in radionuclides lead to a halving of the number of nuclei, thereby reducing the radiation activity of the isotope.

Radionuclides enter tissues and organs through inhalation of air, food intake, scratches, wounds, and burns.

Where are radionuclides found in the human body?

Radioactive isotopes have their “favorite” places in the human body.

In total, 4 groups are distinguished according to this property:

1. Radionuclides evenly distributed throughout the tissues of the body - cesium 134, cesium 137 (radiocesium), sodium 24, etc.
2. Precipitated in bone tissue - strontium 89, 90, barium 140, radium 226, 224, calcium 40, yttrium.
3. Accumulating in the reticuloendothelial organs (red bone marrow, lymph nodes, liver, spleen) - cerium, promethium, americium, plutonium, lanthanum.
4. Organotropic - isotopes of iodine in the thyroid gland, iron in erythrocytes, zinc in the pancreas, molybdenum in the iris.

How are radionuclides released?

The bulk of radioactive isotopes are excreted from the body by the intestines. Soluble ones (cesium and tritium) are excreted through the urinary system. Gaseous elements are removed by the skin and respiratory system. The main part of radionuclides is eliminated within a few days after receipt. Isotopes with a large atomic mass and radioactive colloids (polonium, radium, uranium) are retained. These elements enter the liver and bile ducts.

note: the unit of measurement for the process of removing radionuclides from the body is half-life, characterized by the release of half of the radioactive substance entering the human body.

For example: the radioisotope of iodine found in the thyroid gland has a half-life of 138 days, in the kidneys - 7 days, in bone tissue - 14 days.

Radioactive elements are removed slowly from bone tissue. In soft tissues, the release process is much faster. We are talking about cesium, molybdenum, iodine, etc. But substances such as strontium, zirconium, plutonium, etc. are released much more problematically, settling in human bones for a long time.

About the harmful effects of radionuclides on humans

Radioactive isotopes in the human body have an effect that leads to the cessation of cell growth and division, damages normal biochemical cycles, causes disruption of the structural bonds of DNA, and destroys the genetic code. As a result, the cells are destroyed.

Free radicals that enter the body in large doses cause serious tissue damage. In small doses, they can disrupt the process of cell maturation and development and cause malignant neoplasms. Genetic changes can lead to serious hereditary diseases that will manifest themselves in descendants.

Let us consider the mechanism of the destructive influence of some radionuclides.

Effect of strontium-90 and cesium-137 on the human body

Strontium-90 upon contact, it accumulates in bone tissue, bone marrow, and hematopoietic organs. The damaging effect causes anemia (anemia). Its effect lasts for decades, since the half-life of the element is 29 years, and the elimination half-life is 30 years. When ingested, strontium concentrates in the blood within 15 minutes, completely settling in target organs after 5 hours. Removing this radioactive substance is a difficult task. Not yet effective methods, resist its effects.

Cesium-137– the second most common and dangerous radionuclide for humans. It tends to accumulate in plant cells and, already in food products, penetrate the human body through the stomach and intestines. Half-life 30 years. Favorite localization is muscles. It comes out very slowly.

What products contain radionuclides?

The largest amount of radionuclides is found in bakery products. They are followed by milk and dairy products, then vegetables and fruits. The least number of radioisotopes is in meat and fish, especially in seafood. That is, animal products are cleaner in terms of radiation safety than plant products.

Sea water contains less radioactive elements compared to fresh water. Artesian waters are practically free from isotopes. Other bodies of water may contain high doses, depending on their geographical location and other factors (pollution).

Acceptable standards The contents of cesium-137 and strontium-90 radionuclides are given in the table:

On the radioprotective properties of food and medicinal substances

The radio resistance of the human body is increased by polysaccharides, lipopolysaccharides from tea leaves, grapes, medical alcohol, vitamins, minerals, almost all groups of enzymes, and many hormones.

Among medicines, antibiotics, narcotic substances, and artificially produced vitamins exhibit resistance to the effects of radiation sources.

Products that have the property of removing radionuclides

Let's consider the main groups of food products that can have an anti-radiation effect and accelerate the release of isotopes from human tissues.

These products include:

• eggshell – the calcium it contains removes radioactive strontium. Use it up to 5 g per day. The shells, previously crushed to a powder state, are added to food;
• baked goods from rye flour. They contain phytin, which binds strontium, which enters the gastrointestinal tract with products;
• citrus, chokeberry, hawthorn berries, sea buckthorn, licorice. These plants and their fruits contain flavonoids, which also have the properties of removing radionuclides.

Do you want to know which products help remove radionuclides from the body? Watch the video review:

How to best process food to remove radioactivity

Regular mechanical methods food processing helps remove strontium and cesium on their surface. Simply wash them in cold water and clean from dirt.

Vegetable crops need to be cut top part the fetus, since it is in it that about 80% of toxic and radioactive substances accumulate. Cabbage should be peeled from the top leaves, and the inner “stalk” should not be used.

Heat treatment removes about half of the radionuclides contained in the product. But frying, on the contrary, delays them.

Meat and fish semi-finished products should be soaked in water with vinegar before cooking. It is recommended to drain the meat broth; toxins and radioactive isotopes accumulate in it after cooking. If you need to prepare broth, you need to pour the meat cold water, cook for 10 minutes, then drain the broth. Take fresh water and boil the meat until done. The resulting broth will contain half as many harmful radioactive substances.

The amount of radioactive elements is reduced by cutting the meat finely and soaking it in water for several hours. It should be remembered that with such processing, both beneficial features product.

Pre-soaking mushrooms removes cesium by 30%, and cooking up to 90%. Strontium is practically not removed with these types of processing.

Refined varieties are the “cleanest” from radioactivity vegetable oil, sugar and starch.

Processing milk to the state of butter almost completely deprives it of strontium, and cesium is neutralized during the processing of milk into cheese and powdered substances.

Jerusalem artichoke is a fruit that does not accumulate radioactivity.

The ear can absorb radionuclides from the bones, fins and scales of fish. For the same reason, canned foods in which the semi-finished product is processed under pressure using high temperatures can also pose a radiation hazard. This leads to softening of the inedible parts of the fish, in which radionuclides are usually concentrated.

Grain bran products also accumulate strontium radioisotopes.

What to do if affected by radionuclides

Radioactive isotopes that enter the body require acceleration of the process of their elimination. The most important factor in resistance to the harmful effects of radionuclides is the state of the immune system. The existing natural radiation background, affecting humans for thousands of years, has created natural defense mechanisms that have a radionuclide-neutralizing effect. We are talking about the removal of foreign substances by bile, intestines, kidneys, and liver.

If the process of entry into the body of a radiation group of substances is permanent, then it is necessary:

• take calcium supplements with multivitamins that help protect bone tissue;
• eat foods high in potassium - peas, beans, lentils, dried fruits. The substances contained in them contribute to the removal of cesium from the body;
• add chicken eggs and milk to your diet. The calcium they contain is capable of removing strontium;
• eat fruits and vegetables high in pectins, which bind radionuclides
• take diuretics;
• maintain an active water regime. Drink mineral water, which will help get rid of radioactive isotopes of potassium, sodium and magnesium.

Interesting facts about the consequences of radioactive contamination

Accidents at nuclear power plants, nuclear weapons testing, and experiments in nuclear laboratories leave their mark on the atmosphere, water, and soil. Scientists have found that in this way about 20 radionuclides are released into the external environment. The majority of them do not pose long-term harm, as they are inactivated within several weeks and months. First of all, we are talking about isotopes of noble gases, which form the basis of the radioactive cloud. They can cause harm to human health.

The next dangerous element was identified as the isotope iodine-131. It quickly accumulated in foods, especially milk. It should be noted that radiation safety standards in our country are much stricter than in Europe.

An element that is not as aggressive in terms of its harmful value than the above substances, but is more stable, is plutonium. It is particularly dangerous due to its ability to cause serious lung diseases.

And yet, the greater harm is caused by the cesium and strontium we have already analyzed, which remain in the body for decades.

Note: Against the backdrop of ongoing tragedies (the accident at the Chernobyl nuclear power plant, the explosion at the Fukushima-1 nuclear power plant, other man-made disasters), a whole galaxy of charlatans has appeared, intimidating people with stories that supposedly vast territories are contaminated with radioactivity and the entire population is affected. They offer 100% cleansing of radioactive substances from the body for money. Whether there is any rational grain in these statements is a topic for a separate serious discussion. In most cases, “miracle” methods are based on deception. Therefore, any person exposed to radiation contamination should seek help only from official medicine.

Lotin Alexander Vladimirovich, radiologist

Our world today is concerned about environmental pollution. And this is understandable - the composition of the air we breathe and the food we eat have long ceased to be environmentally friendly. Since the first test of nuclear weapons (1945), our planet has been contaminated with various radionuclides with anthropogenic properties. And one of them is cesium-137. Its half-life is enormous, and its effects on the human body are varied. We will talk about this and much more in this article.

One of many

Cesium in Dmitry Mendeleev's periodic table belongs to the main subgroup of the first group of the sixth period and has atomic number 55. The chemical symbol of the element is Cs (Caesium), and it received its name due to the presence in the spectrum of relative intensity electromagnetic radiation two blue lines (from the Latin word caesius, which means "sky blue").

As a simple substance, cesium is a soft, silvery-yellow metal with pronounced alkaline characteristics.

This element was discovered in 1860 by two scientists from Germany, R. Bunsen and G. Kirchhoff. They used a method of spectral analysis, and cesium was the first element to be discovered by this method.

The many faces of cesium

In nature, cesium occurs exclusively in the form of the stable isotope Cs-133. But modern physics knows 39 artificially created radionuclides (radioactive isotopes).

Recall that isotopes are varieties of an element's atom with different numbers of neutrons in their nuclei.

The longest-living isotope (up to 2.3 million years) is Cs-135, the second in half-life is cesium-137. It is the latter that is responsible for the radiation pollution of our planet. The half-life of cesium-137 in seconds is 952066726, which is 30.17 years.

This isotope is formed during the decay of nuclei in a nuclear reactor, as well as during testing of weapons with nuclear warheads.

Unstable radionuclide

As a result of the half-life of cesium-137, it undergoes beta decay and becomes unstable barium-137m and then stable barium-137. This releases gamma radiation.

It is the full half-life of cesium-137 that is 30 years, and it decays to barium-137m in 2.55 minutes. The total energy of this process is 1175.63 ± 0.17 keV.

The formulas describing the half-life of cesium-137 are complex and are part of the decay of uranium.

Physical and chemical properties

We have already written about the physical properties of the isotope and the features of its decay. In terms of chemical properties, this element is close to rubidium and potassium.

All isotopes (including cesium-137 with a half-life of 30.17 years) when introduced into a living organism by any means are perfectly absorbed.

Main supplier of biosphere radionuclide

The source of the biosphere radioactive nuclide cesium-137 with a half-life of more than 30 years is nuclear energy.

The statistics are inexorable. According to 2000 data, all nuclear power plant reactors in the world released about 22.2 × 10 19 Bq of cesium-137 into the atmosphere, the half-life of which is more than 30 years.

It's not just the atmosphere that is polluted. This radionuclide enters the ocean every year from tankers and icebreakers with nuclear installations, and from nuclear submarines. Thus, according to experts, during the operation of one submarine reactor over one year, about 24 x 10 14 Bq will enter the ocean. When the half-life of cesium-137 is taken into account, it becomes a dangerous source of very long-term environmental pollution.

The most famous emissions

Before moving on to the effects of radionuclide cesium on the human body, let us recall several major disasters accompanied by releases of this element into the biosphere.

Few people know, but in 1971, in the Ivanovo region (Galkino village), work was carried out on deep probing of the crust of our planet. These were underground nuclear explosions, after one of which a mud fountain erupted from one well. And today, at the site of these works, radiation of 3 milliroentgens per hour is recorded, and the radionuclides strontium-90 and cesium-137 are still reaching the surface of the Earth.

Everyone knows about the Chernobyl disaster in 1986. But not everyone knows that at that time about 1850 PBq of radiation elements entered the atmosphere. And 270 PBq of them are cesium-137.

In 2011, when the accident occurred at the Japanese Fukushima nuclear power plant, 15 PBq of cesium-137 with a half-life of 30 years entered the waters Pacific Ocean.

What happens next

With radioactive fallout and waste, cesium-137 enters the soil, from where it enters plants, which have an absorption coefficient of 100%. In this case, up to 60% of the nuclide accumulates in the above-ground parts of the plant organism. At the same time, in soils poor in potassium, the effect of accumulation of cesium-137 increases noticeably.

The highest accumulation rates of this nuclide are observed in freshwater algae, lichens and plant organisms of the Arctic zone. In the body of animals, this radionuclide accumulates in the muscles and liver.

Its highest concentrations were observed in reindeer and waterfowl of the Arctic coasts.

Fungi also accumulate cesium. Especially butter mushrooms, Polish mushrooms, moss mushrooms and pig mushrooms throughout their entire half-life.

Biological properties of cesium-137

Natural cesium is one of the microelements of the animal body. In our body, cesium is contained in an amount of 0.0002-0.06 microns per 1 gram of soft tissue.

Cesium radionuclide, as already mentioned, is included in the cycle of substances in the biosphere and moves freely along biological trophic chains.

Upon oral entry into the human body, 100% absorption of this nuclide occurs in the gastrointestinal tract. However, the speed of this process varies in different departments. So, an hour after entering the body, up to 7% of cesium-137 is absorbed in the human stomach, in the duodenum, jejunum and ileum - up to 77%, in the cecum - up to 13%, and in the last section of the intestine (transverse colon) - up to 40%.

The proportion of cesium-137 that enters through the respiratory tract is 25% of the amount coming from food.

Through the blood - into the muscles

After reabsorption in the intestine, cesium-137 is approximately evenly distributed in the tissues of the body.

Recent studies on pigs have shown that this nuclide reaches its highest concentrations in muscle tissue.

When studying reindeer, it was found that cesium-137 after a single injection is distributed as follows:

• Muscles - 100%.
• Kidneys - 79%.
• Heart - 67%.
• Lungs - 55%.
• Liver - 48%.

The half-life is from 5 to 14 days and occurs primarily in the urine.

What happens in the human body

The main routes of cesium entry into the body are through the digestive tract and respiratory tract. With external contact of cesium-137 on intact skin, 0.007% penetrates inside. When ingested, 80% of it accumulates in skeletal muscles.

The element is excreted through the kidneys and intestines. Within a month, up to 80% of cesium is removed. According to the International Commission on Radiological Protection, the half-life of the radionuclide is seventy days, but the rate depends on the condition of the body, age, nutrition and other factors.

Radiation injuries, similar in symptoms to radiation sickness, develop when receiving a dose of more than 2 Gy. But even with units of MBq, signs of mild radiation damage are observed in the form of diarrhea, internal bleeding, and weakness.

How to protect yourself from infection

To determine the amount of cesium-137 in the human body, beta-gamma radiometers or human radiation counters (HRUs) measure gamma radiation from the body or from secretions.

When analyzing the spectrum peaks that correspond to a given radionuclide, its activity in the body is determined.

Prevention of contamination with liquid or solid compounds of cesium-137 involves carrying out manipulations exclusively in sealed boxes. To prevent the element from getting inside, personal protective equipment is used.

It is worth remembering that the half-life of cesium-137 is 30 years. Thus, in 1987, in Brazil (the city of Goiania), a part was stolen from a radiotherapy unit. Within 2 weeks, about 250 people were infected, four of them died within a month.

Acceptable standards and emergency assistance

The acceptable intake of this element is considered to be 7.4 x 10 2 Bq per day and 13.3 x 10 4 Bq per year. The content in the air should not exceed 18 x 10 -3 Bq per 1 cubic meter, and in water - 5.5 x 10 2 Bq per liter.

If these standards are exceeded, it is necessary to take measures to accelerate the elimination of the element from the body. First of all, measures should be taken to decontaminate surfaces (face and hands) with soap and water. If the substance enters the respiratory tract, rinse the nasopharynx with saline solution.

The use of sorbents and diuretics with water loading will speed up the elimination of the element.

In severe cases, hemodialysis is performed and specific therapy is prescribed.

But there are also benefits

In chemical research, gamma flaw detection, in radiation technologies and during various radiobiological experiments, scientists have found use for this anthropogenic element with radiating properties.

Cesium-137 is used in contact and radiation therapy, in the sterilization of medical instruments and food products.

This element has found its application in the manufacture of radioisotope current sources and in level gauges of bulk solids, where it is used in opaque sealed containers.

Biological properties of cesium-137 (137 Cs) - one of the most biologically important radionuclides entering the environment after the Chernobyl accident.

Properties of radionuclide 137 Cs

Cesium-137 is a beta emitter with a half-life of 30.174 years. 137 Cs was discovered in 1860 by German scientists Kirchhoff and Bunsen. It got its name from the Latin word caesius - blue, based on the characteristic bright line in the blue region of the spectrum. Several isotopes of cesium are currently known. Greatest practical significance It has 137 Cs, one of the longest-lived fission products of uranium.

Nuclear energy is a source of income 137 Cs into the environment. According to published data, in 2000, about 22.2 x 10 19 Bq were released into the atmosphere by nuclear power plant reactors in all countries of the world. 137 Cs. Blowout 137 Cs carried out not only into the atmosphere, but also into the oceans from nuclear submarines, tankers, icebreakers equipped with nuclear power plants. The total activity of fission products formed in the nuclear reactor of a 60 MW nuclear submarine during its continuous operation for one year reaches more than 3.7 x 10 17 VK, including 137 Cs- approximately 24 x 10 14 Bq. Naturally, during major accidents that occurred with two US nuclear submarines (Treter in 1963 and Scorpion in 1967), most of the radioactive substances, including 137 Cs, could enter the water and become a source of long-term pollution.

According to its chemical properties cesium close to rubidium and potassium - elements of group 1. Radioisotopes of cesium are used in chemical research, gamma flaw detection, radiation technology, and radiobiological experiments. 137 Cs used as a source of radiation for contact and external beam radiation therapy, as well as for radiation sterilization. Cesium isotopes are well absorbed by any route of entry into the body.

After the Chernobyl accident 1.0 MCi of cesium-137 was released into the external environment. Currently, it is the main dose-forming radionuclide in the areas affected by the accident. Chernobyl nuclear power plant. The suitability of contaminated areas for a full life depends on its content and behavior in the external environment.

The soils of Ukrainian-Belarusian Polesie have specific feature- cesium-137 is poorly fixed by them and, as a result, it easily enters plants through the root system. Therefore, even in pre-accident times, the content of this radionuclide in products grown here was 35-40 times higher than in the central regions of the country. After the Chernobyl accident, people had to be resettled from the most affected areas, not at all because of the dangerously high background radiation - farming there became impossible.

There are places in Ukraine where it is impossible to obtain pure products even with a cesium-137 contamination level of 1 Ci/km 2 .

Biological effect of 137 Cs

Cesium isotopes, being fission products of uranium, are included in the biological cycle and freely migrate through various biological chains. Currently 137 Cs found in the body of various animals and humans. It should be noted that stable cesium is included in the human and animal body in quantities from 0.002 to 0.6 μg per 1 g of soft tissue.

Suction 137 Cs in the gastrointestinal tract of animals and humans is 100%. IN separate areas Gastrointestinal tract absorption 137 Cs happens at different speeds. According to scientists, an hour after administration, it is absorbed in relation to the administered dose: 7% is absorbed in the stomach 137 Cs, in the duodenum - 77%, in the jejunum - 76%, in the ileum - 78%, in the cecum - 13%, in the transverse colon - 39%.

Through the respiratory tract into the human body 137 Cs is 0.25% of the value coming from the diet. After oral intake of cesium, significant amounts of absorbed radionuclide are secreted into the intestine and then reabsorbed in the descending intestine. The extent of cesium reabsorption may vary significantly between different types animals. Having entered the blood, it is distributed relatively evenly throughout the organs and tissues. The route of entry and the type of animal do not affect the distribution of the isotope.

L.A. Buldakov, G.K. Korolev believe that cesium isotopes accumulate most in the muscles. According to Yu. I. Moskalev after intravenous administration 137 Cs quickly leaves the bloodstream. In the first 10 - 30 minutes, its maximum concentration is recorded in the kidneys (7-10% in 1 gram of tissue). Then it is redistributed, and the main amounts - up to 52.2% - are retained in muscle tissue.

Conducted studies on the distribution 137 Cs in the body of pigs. The pigs were fed 137 Cs with food once or repeatedly for 7 days in total doses of 2.9 or 1.6 kBq. At 1, 7, 14, 28 and 60 days after the administration of the isotope, animals were killed and their content was examined. 137 Cs in muscle tissue. The content of activity in the muscle tissue of animals treated 137 Cs at a dose of 2.967 kBq, was almost 2 times higher than in animals receiving 137 Cs at a dose of 1.609 kBq. The decrease in radioactivity in muscle tissue was most pronounced in the first 14 days at both doses of the radionuclide. Removal 137 Cs from the body of pigs was carried out mainly through urine. Elimination rates 137 Cs with single and repeated administrations differed significantly. The half-life of the isotope with a single injection was 5 days, and with repeated administration it was 14 days.

In the body of reindeer, after a single injection, 137 Cs will be distributed in this way. 100% accumulates in the muscles, 79% in the kidneys, 60% in the heart, 60% in the spleen, 55% in the lungs, and 48% in the liver.

In experiments on dogs conducted in 1968, it was found that with a single intravenous administration 137 Cs in an amount of 3.5 – 14 x 10 7 Bq/kg studied the distribution among organs. It has been shown that the largest quantities 137 Cs after 19-81 days they are contained in skeletal muscles, liver, and kidneys. It is important to note that the administered dose 137 Cs and the sex of animals do not affect the distribution of the nuclide among organs and tissues.

Definition 137 Cs in the human body is carried out by measuring gamma radiation from the body and beta, gamma radiation from secretions (urine, feces). For this purpose, beta-gamma radiometers and a human radiation counter (HRU) are used. Based on individual peaks in the spectrum corresponding to different gamma emitters, their activity in the body can be determined. To prevent radiation injuries 137 Cs All work with liquid and solid compounds is recommended to be carried out in sealed boxes. To prevent the entry of cesium and its compounds into the body, it is necessary to use personal protective equipment and observe personal hygiene rules.

Opened cesium preparations with an activity of 0.37-3.7 mBq (10-100 µCi) may be present in the workplace without permission from the sanitary and epidemiological service.

Emergency care for acute injury from cesium isotopes

Emergency care for isotope damage 137 Cs consists of decontaminating hands and face with soap and water, “Era” and “Astra” washing powders. It is necessary to rinse the nasopharynx and oral cavity water or saline solution.

To accelerate the elimination of cesium from the body, it is recommended to use the following sorbents: ferrocin, 1.0: 100 ml of water, or bentonite, 20.0: 200 ml of water, followed by inducing vomiting (1% apomorphine - 0.5 ml under the skin ), or copious gastric lavage with water. After cleansing the stomach, re-prescribe a course of treatment with ferrocin (1.0 g 2-3 times a day for 15-20 days). In severe cases, hemodialysis (use of the artificial kidney apparatus). All-round increase in water-salt metabolism. Prescription of potassium acetate, 30.0: :200.0, 1 tablespoon 5 times a day. Potassium diet (raisins, dried apricots) Intravenous administration of sodium citrate 10% - 2 - 3 ml. Diuretics with water loading. Diphenhydramine 0.05 g orally, antibiotics.

Acceptable intake 137 Cs into the human body should not exceed 7.4 x 10 2 Bq/day. Allowable annual intake 137 Cs into the body of personnel through the respiratory system is 13.3 x 10 4 Bq/year. Permissible concentration 137 Cs in the air of working premises 5.18 x 10 -1 Bq/l, in water - 5.5 x 10 2 Bq/l, in atmospheric air 18 x 10 -3 Bq/l.

Migration of 137 Сs in soils

Fallen on the ground after the Chernobyl accident 137 Cs firmly retained in the upper humus layer. Over time, its physical and chemical transformations occur, migration along the soil profile, and accumulation by vegetation occur. Cesium is typically absorbed by the mineral part of soils. The element is embedded in the crystal lattices of clay minerals, firmly bound there by the very finely dispersed part of the soil. Cesium is absorbed most intensively by vermiculite, phlogopite, hydrophlogopite, ascanite, and gumbrin. The sorption of cesium by the soil absorption complex after its precipitation into the soil is carried out initially by coarse particles, then shifting towards absorption by the fine fraction. Over seven years, the proportion of cesium fixed by the mineral part of the soil increased 2.5 times in gray forest soils, 4.5 times in soddy-podzolic soils, and 7 times in chernozem soils and can reach 80-95% of the total content of the element in the soil. Cesium is firmly bound by soil organic matter, forming, in particular, humates and fulvates. The latter are characterized by significantly greater mobility. Water-soluble materials increase metal mobility organic matter, formed during the decomposition of vegetation. When cesium migrates deep into the soil horizon, two types of mass transfer are distinguished: fast (due to the movement of the metal along with fine particles) and slow (due to the movement of water-soluble forms). In loamy varieties of soddy-podzolic soils, only slow transfer is observed, in sandy loam and sandy soils - both slow and fast with a predominance of the latter. On average, the share of rapid transfer is 15% of all migrating forms of cesium.

N.V. Timofeev-Resovsky and co-authors 137 Cs allocated to a separate group of isotopes based on the nature of their behavior in the soil-solution system - into a group with signs of exchangeable and non-exchangeable behavior. Most important factor The migration of cesium in the soil-solution system is a change in its own concentration (it migrates differently in soils depending on the quantity in them: the behavior of cesium in the system is non-exchangeable at microconcentrations and exchangeable in the area of ​​macroconcentrations).

Due to insignificant hydrolysis, sorption 137 Cs weakly depends on the pH of the soil solution.

Accumulation noted 137 Cs in floodplain soils, due to additional introduction with mechanical suspensions during floods. In floodplain soils 137 Cs, as a rule, lingers in the upper 5-centimeter layer. However, in cases where the surface horizons of floodplain soils are represented by layers of light mechanical composition with a low humus content, 137 Cs is leached from these horizons and retained in the underlying ones. Migration ability 137 Cs is also increased in some peat soils, where it is vigorously supplied to plants. Japanese researchers note evidence of penetration 137 Cs into rocks (unweathered basalts) to a depth of 3-5 cm.

Accumulation of radionuclide 137 Cs by plants

Cesium is well absorbed by vegetation, the accumulation rate of the element in agricultural crops can reach 100%; accumulation occurs mainly in above-ground phytomass (up to 60% of the absorbed element). On sandy loam soils 137 Cs 7 times more accessible to plants than 137 Cs. The intense involvement of the element in the biological cycle is due to the acidity of Polesie landscapes, which favors the physiological accumulation of metal by organisms, the mobility of the metal, as well as its analogy with potassium - a biochemically active element, the deficiency of which is pronounced in Polesie landscapes, but which is vital for plants.

Literature:

• Budarnikov V.A., Kirshin V.A., Antonenko A.E. Radiobiological reference book. – Mn.: Urazhay, 1992. – 336 p.
• Chernobyl does not let go... (to the 50th anniversary of radioecological research in the Komi Republic). – Syktyvkar, 2009 – 120 p.
• Zhuravlev V.F. Toxicology of radioactive substances. – 2nd, ed., revised. and additional – M.: Energoatomizdat, 1990. – 336 p.

It was not possible to detect any isotopes other than stable 133 Cs in natural cesium. There are 33 known radioactive isotopes of cesium with mass numbers from 114 to 148. In most cases, they are short-lived: half-lives are measured in seconds and minutes, less often - several hours or days. However, three of them do not decay so quickly - these are 134 Cs, 137 Cs and 135 Cs with half-lives of 2 years, 30 years and 3·10 6 years. All three isotopes are formed during the decay of uranium, thorium and plutonium in nuclear reactors or during nuclear weapons testing.

Oxidation state +1.

In 1846, cesium silicate - pollucite - was discovered in the pegmatites of Elba Island in the Tyrrhenian Sea. When studying this mineral, cesium, unknown at that time, was mistaken for potassium. The potassium content was calculated from the mass of the platinum compound, with the help of which the element was transferred to an insoluble state. Since potassium is lighter than cesium, the calculation of the results chemical analysis showed a shortage of about 7%. This mystery was only solved by the discovery of spectral analysis by German scientists Robert Bunsen and Gustav Kirchhoff in 1859. Bunsen and Kirchhoff discovered cesium in 1861. It was originally found in mineral waters healing springs of the Black Forest. Cesium was the first element discovered by spectroscopy. Its name reflects the color of the brightest lines in the spectrum (from the Latin caesius - sky blue).

The discoverers of cesium were unable to isolate this element in the free state. Metallic cesium was first obtained only 20 years later, in 1882, by the Swedish chemist K. Setterberg C. by electrolysis of a molten mixture of cesium and barium cyanides, taken in a ratio of 4:1. Barium cyanide was added to lower the melting point, but it was difficult to work with cyanides due to their high toxicity, and barium contaminated the final product, and the yield of cesium was very small. A more rational method was found in 1890 by the famous Russian chemist N.N. Beketov, who proposed reducing cesium hydroxide with magnesium metal in a hydrogen flow at elevated temperature. Hydrogen filled the device and prevented the oxidation of cesium, which was distilled into a special receiver, however, even in this case, the cesium yield did not exceed 50% of the theoretical one.

Cesium in nature and its industrial extraction.

Cesium is a rare element. It is found in a dispersed state (on the order of thousandths of a percent) in many rocks; Minor amounts of this metal were also found in sea ​​water. It is found in higher concentrations (up to several tenths of a percent) in some potassium and lithium minerals, mainly in lepidolite. Unlike rubidium and most other rare elements, cesium forms its own minerals - pollucite, avogadrite and rodicite.

Rodicite is extremely rare. It is often classified as a lithium mineral, since its composition (M 2 O 2Al 2 O 3 3B 2 O 3, where M 2 O is the sum of alkali metal oxides) usually contains more lithium than cesium. Avogadritus (K,Cs) is also rare. Most cesium is contained in pollucite (Cs,Na) n H 2 O (Cs 2 O content is 29.8–36.7% by weight).

Data on global cesium resources are very limited. Their estimates are based on pollucite, mined as a by-product along with other pegmatite minerals.

Canada is the leader in pollucite production. The Bernick Lake deposit (southeastern Manitoba) contains 70% of the world's cesium reserves (about 73 thousand tons). Pollucite is also mined in Namibia and Zimbabwe, whose resources are estimated at 9 thousand tons and 23 thousand tons of cesium, respectively. In Russia, pollucite deposits are located on the Kola Peninsula, in the Eastern Sayan Mountains and Transbaikalia. They are also found in Kazakhstan, Mongolia and Italy (Elba Island).

To open this mineral and convert valuable components into a soluble form, it is treated by heating with concentrated mineral acids. If pollucite is decomposed with hydrochloric acid, then Cs 3 is precipitated from the resulting solution by the action of SbCl 3, which is then treated hot water or ammonia solution. When pollucite is decomposed with sulfuric acid, cesium alum CsAl(SO 4) 2 12H 2 O is obtained.

Another method is also used: pollucite is sintered with a mixture of oxide and calcium chloride, the cake is leached in an autoclave with hot water, the solution is evaporated to dryness with sulfuric acid, and the residue is treated with hot water. After separating the calcium sulfate from the solution, cesium compounds are isolated.

Modern methods for extracting cesium from pollucite are based on preliminary fusion of concentrates with excess lime and a small amount of fluorspar. If the process is carried out at 1200° C, then almost all of the cesium is sublimated in the form of Cs 2 O oxide. This sublimation is contaminated with admixtures of other alkali metals, but it is soluble in mineral acids, which simplifies further operations. Metallic cesium is extracted by heating a mixture (1:3) of crushed pollucite with calcium or aluminum to 900°C.

But, mainly, cesium is obtained as a plug product in the production of lithium from lepidolite. Lepidolite is pre-fused (or sintered) at a temperature of about 1000 ° C with gypsum or potassium sulfate and barium carbonate. Under these conditions, all alkali metals are converted into easily soluble compounds - they can be leached with hot water. After separating the lithium, it remains to process the resulting filtrates, and here the most difficult operation is the separation of cesium from rubidium and a huge excess of potassium.

To separate cesium, rubidium and potassium and obtain pure cesium compounds, methods of repeated crystallization of alum and nitrates, precipitation and recrystallization of Cs 3 or Cs 2 are used. Chromatography and extraction are also used. To obtain high-purity cesium compounds, polyhalides are used.

Most of the cesium produced comes from lithium production, so when lithium began to be used in fusion devices and was widely used in automobile lubricants in the 1950s, lithium mining, as well as cesium, increased and cesium compounds became more available than before.

Data on global production and consumption of cesium and its compounds have not been published since the late 1980s. The market for cesium is small, with annual consumption estimated at only a few thousand kilograms. As a result, there is no trade and no official market prices.

Characteristics of a simple substance, industrial production and use of metallic cesium.

Cesium is a golden-yellow metal, one of the three intensely colored metals (along with copper and gold). After mercury, it is the most fusible metal. Cesium melts at 28.44° C, boils at 669.2° C. Its vapors are colored greenish-blue.

The fusibility of cesium is combined with great lightness. Despite the rather large atomic mass of the element, its density at 20° C is only 1.904 g/cm 3 . Cesium is much lighter than its neighbors on the Periodic Table. Lanthanum, for example, having almost the same atomic mass, is more than three times more dense than cesium. Cesium is only twice as heavy as sodium, while their atomic masses are in a ratio of 6:1. Apparently, the reason for this lies in the electronic structure of cesium atoms (one electron on the last s-sublevel), leading to the fact that the metallic radius of cesium is very large (0.266 nm).

Cesium has another very important property related to its electronic structure - it loses its only valence electron more easily than any other metal; this requires very little energy - only 3.89 eV, therefore, for example, producing plasma from cesium requires much less energy than using any other chemical element.

Cesium is superior to all other metals in sensitivity to light. The cesium cathode emits a stream of electrons even when exposed to infrared rays with a wavelength of 0.80 microns. The maximum electron emission occurs for cesium when illuminated with green light, while for other photosensitive metals this maximum appears only when exposed to violet or ultraviolet rays.

Chemically, cesium is very active. In air, it instantly oxidizes with inflammation, forming superoxide CsO 2 with an admixture of peroxide Cs 2 O 2. Cesium is capable of absorbing the slightest traces of oxygen in deep vacuum conditions. It reacts explosively with water to form the hydroxide CsOH and release hydrogen. Cesium reacts even with ice at –116° C. Its storage requires great care.

Cesium also interacts with carbon. Only the most advanced modification of carbon - diamond - is able to withstand cesium. Liquid molten cesium and its vapor loosen soot, charcoal and even graphite, inserting itself between carbon atoms and producing fairly strong compounds of a golden yellow color. At 200–500° C, a compound of composition C 8 Cs 5 is formed, and at higher temperatures – C 24 Cs, C 36 Cs. They ignite in air, displace hydrogen from water, and when heated strongly, they decompose and release all the absorbed cesium.

Even at ordinary temperatures, reactions of cesium with fluorine, chlorine and other halogens are accompanied by ignition, and with sulfur and phosphorus - by explosion. When heated, cesium combines with hydrogen. Cesium does not react with nitrogen under normal conditions. Cs 3 N nitride is formed in a reaction with liquid nitrogen during an electrical discharge between electrodes made of cesium.

Cesium dissolves in liquid ammonia, alkylamines and polyethers, forming blue solutions that are electronically conductive. In an ammonia solution, cesium slowly reacts with ammonia to release hydrogen and form the amide CsNH 2.

Alloys and intermetallic compounds of cesium are relatively low-melting. Cesium auride CsAu, in which a partially ionic bond is realized between gold and cesium atoms, is a semiconductor n-type.

The best solution to the problem of obtaining metallic cesium was found in 1911 by the French chemist A. Axpil. According to his method, which still remains the most common, cesium chloride is reduced with calcium metal in a vacuum:

2CsCl + Ca → CaCl 2 + 2Cs

in this case the reaction proceeds almost to completion. The process is carried out at a pressure of 0.1–10 Pa and a temperature of 700–800° C. The released cesium evaporates and is distilled off, and the calcium chloride remains completely in the reactor, since under these conditions the volatility of the salt is negligible (the melting point of CaCl 2 is 773° C) . As a result of repeated distillation in a vacuum, absolutely pure cesium metal is obtained.

Many other methods for producing cesium metal from its compounds have been described. Calcium metal can be replaced with carbide, but the reaction temperature must be increased to 800 ° C, so the final product is contaminated with additional impurities. Electrolysis of the cesium halide melt is also carried out using a liquid lead cathode. The result is an alloy of cesium and lead, from which metallic cesium is isolated by distillation in a vacuum.

It is possible to decompose cesium azide or reduce its dichromate with zirconium, but these reactions are sometimes accompanied by an explosion. When replacing cesium dichromate with chromate, the reduction process proceeds smoothly, and although the yield does not exceed 50%, very pure metallic cesium is distilled off. This method is applicable for obtaining small amounts of metal in a special vacuum device.

World production of cesium is relatively small.

Metallic cesium is a component of cathode material for photocells, photomultiplier tubes, and television transmitting cathode ray tubes. Photocells with a complex silver-cesium photocathode are especially valuable for radar: they are sensitive not only to visible light, but also to invisible infrared rays and, unlike, for example, selenium, they operate inertia-free. Antimony-cesium solar cells are widely used in television and cinema; their sensitivity, even after 250 hours of operation, drops by only 5–6%; they operate reliably in the temperature range from –30° C to +90° C. They make up the so-called multi-stage photocells; in this case, under the influence of electrons caused by light rays in one of the cathodes, secondary emission occurs - electrons are emitted by additional photocathodes of the device. As a result, the total electric current arising in the photocell is multiplied. Increased current and increased sensitivity are also achieved by filling cesium photocells with an inert gas (argon or neon).

Cesium metal is used to make special rectifiers that are superior to mercury rectifiers in many respects. It is used as a coolant in nuclear reactors, a component of lubricants for space technology, and a getter in vacuum electronic devices. Cesium metal also exhibits catalytic activity in reactions of organic compounds.

Cesium is used in atomic time standards. Cesium clocks are incredibly accurate. Their action is based on transitions between two states of the cesium atom with parallel and antiparallel orientation of the intrinsic magnetic moments of the atomic nucleus and valence electron. This transition is accompanied by oscillations with strictly constant characteristics (wavelength 3.26 cm). In 1967, the International General Conference on Weights and Measures established: “A second is a time equal to 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.”

Recently, much attention has been paid to cesium plasma, a comprehensive study of its properties and conditions of formation; perhaps it will be used in plasma engines of the future. In addition, work on the study of cesium plasma is closely related to the problem of controlled thermonuclear fusion. Many believe that it is advisable to create cesium plasma using the thermal energy of nuclear reactors.

Cesium is stored in glass ampoules in an argon atmosphere or sealed steel vessels under a layer of dehydrated petroleum jelly. Dispose of metal residues by treating with pentanol.

Cesium compounds.

Cesium forms binary compounds with most non-metals. Cesium hydrides and deuterides are highly flammable in air, as well as in fluorine and chlorine atmospheres. Cesium compounds with nitrogen, boron, silicon and germanium are unstable and sometimes flammable and explosive. The halides and salts of most acids are more stable.

Oxygen compounds. Cesium forms nine compounds with oxygen, ranging in composition from Cs 7 O to CsO 3 .

Cesium oxide Cs 2 O forms brown-red crystals that diffuse in air. It is obtained by slow oxidation with an insufficient (2/3 of the stoichiometric) amount of oxygen. The remainder of unreacted cesium is distilled off in a vacuum at 180–200° C. Cesium oxide sublimes in a vacuum at 350–450° C, and decomposes at 500° C:

2Cs 2 O = Cs 2 O 2 + 2Cs

Reacts vigorously with water to produce cesium hydroxide.

Cesium oxide is a component of complex photocathodes, special glasses and catalysts. It has been established that when producing synthol (synthetic oil) from water gas and styrene from ethylbenzene, as well as in some other syntheses, adding a small amount of cesium oxide (instead of potassium oxide) to the catalyst increases the yield of the final product and improves the process conditions.

Hygroscopic pale yellow crystals of cesium peroxide Cs 2 O 2 can be obtained by oxidizing cesium (or its solution in liquid ammonia) with a dosed amount of oxygen. Above 650°C, cesium peroxide decomposes with the release of atomic oxygen and vigorously oxidizes nickel, silver, platinum and gold. Cesium peroxide dissolves in ice water without decomposition, and above 25° C it reacts with it:

2Cs2O2 + 2H2O = 4CsOH + O2

It dissolves in acids to form hydrogen peroxide.

When cesium is burned in air or oxygen, golden-brown cesium superoxide CsO 2 is formed. Above 350°C it dissociates with the release of oxygen. Cesium superoxide is a very strong oxidizing agent.

Cesium peroxide and superoxide serve as sources of oxygen and are used for its regeneration in spacecraft and underwater vehicles.

Sesquioxide "Cs 2 O 3" is formed in the form of a dark paramagnetic powder during the careful thermal decomposition of cesium superoxide. It can also be produced by oxidation of a metal dissolved in liquid ammonia or by controlled oxidation of peroxide. It is assumed to be a dinad peroxide-peroxide [(Cs +)4(O 2 2–)(O 2 –) 2 ].

Orange-red ozonide CsO 3 can be obtained by the action of ozone on anhydrous powder of cesium hydroxide or peroxide at low temperature. When standing, ozonide slowly decomposes into oxygen and superoxide, and upon hydrolysis it immediately turns into hydroxide.

Cesium also forms suboxides, in which the formal oxidation state of the element is significantly lower than +1. The oxide of composition Cs 7 O has a bronze color, its melting point is 4.3 ° C, and actively reacts with oxygen and water. In the latter case, cesium hydroxide is formed. When heated slowly, Cs 7 O decomposes into Cs 3 O and cesium. Violet crystals of Cs 11 O 3 melt with decomposition at 52.5 ° C. Red-violet Cs 4 O decomposes above 10.5 ° C. Non-stoichiometric phase Cs 2+ x O changes composition up to Cs 3 O, which decomposes at 166° C.

Cesium hydroxide CsOH forms colorless crystals that melt at ° C. The melting temperatures of hydrates are even lower, for example, CsOH H 2 O monohydrate melts with decomposition at 2.5 ° C, and CsOH 3H 2 O trihydrate even -5.5 ° C.

Cesium hydroxide serves as a catalyst for the synthesis of formic acid. With this catalyst, the reaction occurs at 300°C without high pressure. The yield of the final product is very high - 91.5%.

Cesium halides CsF, CsCl, CsBr, CsI (colorless crystals) melt without decomposition; above the melting point they are volatile. Thermal stability decreases when moving from fluoride to iodide; bromide and iodide in vapor partially decompose into simple substances. Cesium halides are highly soluble in water. In 100 g of water at 25 ° C, 530 g of cesium fluoride, 191.8 g of cesium chloride, 123.5 g of cesium bromide, 85.6 g of cesium iodide are dissolved. From aqueous solutions Anhydrous chloride, bromide and iodide crystallize. Cesium fluoride is released in the form of crystalline hydrates of the composition CsF· n H 2 O, where n = 1, 1,5, 3.

When interacting with halides of many elements, cesium halides easily form complex compounds. Some of them, for example Cs 3, are used for the isolation and analytical determination of cesium.

Cesium fluoride is used to produce organofluorine compounds, piezoelectric ceramics, and special glasses. Cesium chloride is an electrolyte in fuel cells, a flux for welding molybdenum.

Cesium bromide and iodide are widely used in optics and electrical engineering. The crystals of these compounds are transparent to infrared rays with wavelengths from 15 to 30 μm (CsBr) and from 24 to 54 μm (CsI). Conventional prisms made of sodium chloride transmit rays with a wavelength of 14 microns, and those of potassium chloride - 25 microns, so the use of cesium bromide and iodide instead of sodium and potassium chlorides made it possible to record the spectra of complex molecules in the far infrared region.

If, when making fluorescent screens for televisions and scientific equipment, approximately 20% cesium iodide is introduced between zinc sulfide crystals, the screens will absorb X-rays better and glow brighter when irradiated with an electron beam.

Scintillation instruments for detecting heavy charged particles containing single crystals of cesium iodide activated by thallium have the highest sensitivity of all instruments of this type.

Cesium-137.

The 137 Cs isotope is formed in all nuclear reactors (on average 6 137 Cs nuclei out of 100 uranium nuclei).

Under normal operating conditions of nuclear power plants, emissions of radionuclides, including radioactive cesium, are insignificant. The vast majority of fission products remain in the fuel. According to dosimetric monitoring data, the concentration of cesium in the areas where nuclear power plants are located almost does not exceed the concentration of this nuclide in control areas.

Difficult situations arise after accidents, when a huge amount of radionuclides enter the external environment and large areas are contaminated. The release of cesium-137 into the atmosphere was noted during an accident in the Southern Urals in 1957, where there was a thermal explosion of a radioactive waste storage facility, during a fire at a radiochemical plant in Windenale in the UK in 1957, during wind removal of radionuclides from the floodplain of Lake. Karachay in the Southern Urals in 1967. The accident at Chernobyl became a disaster nuclear power plant in 1986, cesium-137 accounted for about 15% of total radiation contamination. The main source of radioactive cesium entering the human body is food products of animal origin contaminated with the nuclide.

The radionuclide 137 Cs can also be used for human benefit. It is used in flaw detection, as well as in medicine for diagnosis and treatment. Specialists in the field of X-ray therapy became interested in cesium-137. This isotope decomposes relatively slowly, losing only 2.4% of its original activity per year. It has proven useful for the treatment of malignant tumors. Cesium-137 has certain advantages over radioactive cobalt-60: a longer half-life and less hard g-radiation. In this regard, devices based on 137 Cs are more durable, and radiation protection is less cumbersome. However, these advantages become real only in the absence of 134 Cs impurity with a shorter half-life and harder g-radiation.

From solutions obtained during the processing of radioactive waste nuclear reactors, 137 Cs is extracted by coprecipitation methods with iron, nickel, zinc hexacyanoferrates or ammonium fluorotungstate. Ion exchange and extraction are also used.

Elena Savinkina