Strontium 90 Sr is a silvery calcium-like metal coated with an oxide shell and reacts poorly, being included in the metabolism of the ecosystem as complex Ca - Fe - Al - Sr - complexes are formed. The natural content of the stable isotope in soil, bone tissue, and environment reaches 3.7 x 10 -2%, in sea water, muscle tissue 7.6 x 10 -4%. Biological functions have not been identified; non-toxic, can replace calcium. There is no radioactive isotope in the natural environment.
Strontium is an element of the main subgroup of the second group, the fifth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 38. It is designated by the symbol Sr (lat. Strontium). The simple substance strontium (CAS number: 7440-24-6) is a soft, malleable and ductile alkaline earth metal of silver-white color. It has high chemical activity; in air it quickly reacts with moisture and oxygen, becoming covered with a yellow oxide film.
The new element was discovered in the mineral strontianite, found in 1764 in a lead mine near the Scottish village of Stronshian, which later gave its name to the new element. The presence of a new metal oxide in this mineral was discovered almost 30 years later by William Cruickshank and Ader Crawford. Isolated in its pure form by Sir Humphry Davy in 1808.
Strontium is found in sea water (0.1 mg/l), in soils (0.035 wt%).
In nature, strontium occurs as a mixture of 4 stable isotopes 84 Sr (0.56%), 86 Sr (9.86%), 87 Sr (7.02%), 88 Sr (82.56%).
There are 3 ways to obtain strontium metal:
Thermal decomposition of some compounds
Electrolysis
Reduction of oxide or chloride
The main industrial method for producing strontium metal is the thermal reduction of its oxide with aluminum. Next, the resulting strontium is purified by sublimation.
The electrolytic production of strontium by electrolysis of a melted mixture of SrCl 2 and NaCl is not widespread due to the low current efficiency and contamination of strontium with impurities.
The thermal decomposition of strontium hydride or nitride produces finely dispersed strontium, which is prone to easy ignition.
Strontium is a soft, silvery-white metal that is malleable and ductile and can be easily cut with a knife.
Polymorphic - three of its modifications are known. Up to 215 o C, the cubic face-centered modification (b-Sr) is stable, between 215 and 605 o C - hexagonal (b-Sr), above 605 o C - cubic body-centered modification (g-Sr).
Melting point - 768 o C, Boiling point - 1390 o C.
Strontium in its compounds always exhibits a valence of +2. The properties of strontium are close to calcium and barium, occupying an intermediate position between them.
In the electrochemical series of voltages, strontium is among the most active metals (its normal electrode potential is equal to? 2.89 V. It reacts vigorously with water, forming hydroxide: Sr + 2H 2 O = Sr(OH) 2 + H 2 ^.
Interacts with acids, displaces heavy metals from their salts. It reacts weakly with concentrated acids (H 2 SO 4, HNO 3).
Strontium metal quickly oxidizes in air, forming a yellowish film, in which, in addition to SrO oxide, SrO 2 peroxide and Sr 3 N 2 nitride are always present. When heated in air, it ignites; powdered strontium in air is prone to self-ignition.
Reacts vigorously with non-metals - sulfur, phosphorus, halogens. Interacts with hydrogen (above 200 o C), nitrogen (above 400 o C). Practically does not react with alkalis.
At high temperatures reacts with CO 2 to form carbide:
5Sr + 2CO 2 = SrC 2 + 4SrO (1)
Easily soluble strontium salts with the anions Cl - , I - , NO 3 - . Salts with anions F -, SO 4 2-, CO 3 2-, PO 4 3- are slightly soluble.
The main areas of application of strontium and its chemical compounds are radio electronics industry, pyrotechnics, metallurgy, food industry.
Strontium is used for alloying copper and some of its alloys, for introduction into battery lead alloys, for desulfurization of cast iron, copper and steels.
Strontium with a purity of 99.99-99.999% is used for the reduction of uranium.
Hard magnetic strontium ferrites are widely used as materials for the production of permanent magnets.
In pyrotechnics, strontium carbonate, nitrate, and perchlorate are used to color the flame carmine red. The magnesium-strontium alloy has strong pyrophoric properties and is used in pyrotechnics for incendiary and signal compositions.
Radioactive 90 Sr (half-life 28.9 years) is used in the production of radioisotope current sources in the form of strontium titanite (density 4.8 g/cm³, and energy release about 0.54 W/cm³).
Strontium uranate plays an important role in the production of hydrogen (strontium-uranate cycle, Los Alamos, USA) by thermochemical method (atomic-hydrogen energy), and in particular, methods are being developed for the direct fission of uranium nuclei in the composition of strontium uranate to produce heat from the decomposition of water into hydrogen and oxygen.
Strontium oxide is used as a component of superconducting ceramics.
Strontium fluoride is used as a component of solid-state fluorine batteries with enormous energy capacity and energy density.
Strontium alloys with tin and lead are used for casting battery current leads. Strontium-cadmium alloys for galvanic cell anodes.
Radiation characteristics are given in Table 1.
Table 1 - Radiation characteristics of strontium 90
In cases where an isotope enters environment the intake of strontium into the body depends on the degree and nature of the inclusion of the metabolite in soil organic structures, food and ranges from 5 to 30%, with greater penetration into the child’s body. Regardless of the route of entry, the emitter accumulates in the skeleton (soft tissues contain no more than 1%). It is excreted from the body extremely poorly, which leads to constant accumulation of the dose due to chronic intake of strontium into the body. Unlike natural β-active analogues (uranium, thorium, etc.), strontium is an effective β-emitter, which changes the spectrum of radiation exposure, including on the gonads, endocrine glands, red bone marrow and brain. Accumulated doses (background) fluctuate within the range (up to 0.2 x 10 -6 µCi/g in bones at doses of the order of 4.5 x 10 -2 mSv/year).
The effect on the human body of natural (non-radioactive, low-toxic and, moreover, widely used for the treatment of osteoporosis) and radioactive isotopes of strontium should not be confused. The strontium isotope 90 Sr is radioactive with a half-life of 28.9 years. 90 Sr undergoes decay, turning into radioactive 90 Y (half-life 64 hours). Complete decay of strontium-90 released into the environment will occur only after several hundred years. 90 Sr is formed during nuclear explosions and emissions from nuclear power plants.
By chemical reactions Radioactive and non-radioactive isotopes of strontium are practically the same. Natural strontium -- component microorganisms, plants and animals. Regardless of the route and rhythm of entry into the body, soluble strontium compounds accumulate in the skeleton. Less than 1% is retained in soft tissues. The route of entry influences the amount of strontium deposition in the skeleton.
The behavior of strontium in the body is influenced by species, gender, age, as well as pregnancy and other factors. For example, males have higher levels of deposits in their skeletons than females. Strontium is an analogue of calcium. Strontium accumulates at a high rate in the body of children up to the age of four, when bone tissue is actively being formed. Strontium metabolism changes in certain diseases of the digestive system and cardiovascular system. Routes of entry:
Water (the maximum permissible concentration of strontium in water in the Russian Federation is 8 mg/l, and in the USA - 4 mg/l)
Food (tomatoes, beets, dill, parsley, radishes, radishes, onions, cabbage, barley, rye, wheat)
Intratracheal delivery
Through the skin (cutaneous)
Inhalation (through air)
From plants or through animals, strontium-90 can directly pass into the human body.
People whose work involves strontium (in medicine, radioactive strontium is used as applicators in the treatment of skin and eye diseases. The main areas of application of natural strontium are the radio-electronic industry, pyrotechnics, metallurgy, metallothermy, food industry, production of magnetic materials, radioactive - production of atomic electric batteries, atomic-hydrogen energy, radioisotope thermoelectric generators, etc.).
The influence of non-radioactive strontium appears extremely rarely and only under the influence of other factors (calcium and vitamin D deficiency, malnutrition, imbalances in the ratio of microelements such as barium, molybdenum, selenium, etc.). Then it can cause “strontium rickets” and “urological disease” in children - damage and deformation of joints, growth retardation and other disorders. On the contrary, radioactive strontium almost always has a negative effect on the human body:
Deposited in the skeleton (bones), affects bone tissue and bone marrow, which leads to the development radiation sickness, tumors of hematopoietic tissue and bones.
Causes leukemia and malignant tumors (cancer) of bones, as well as liver and brain damage
The strontium isotope 90 Sr is radioactive with a half-life of 28.79 years. 90 Sr undergoes β-decay, turning into radioactive yttrium 90 Y (half-life 64 hours). 90 Sr is formed during nuclear explosions and emissions from nuclear power plants.
Strontium is an analogue of calcium and is able to be firmly deposited in bones. Long-term radiation exposure to 90 Sr and 90 Y affects bone tissue and bone marrow, which leads to the development of radiation sickness, tumors of hematopoietic tissue and bones.
Once in the soil, strontium-90, together with soluble calcium compounds, enters plants, from which it can enter the human body directly or through animals. This creates a chain of transmission of radioactive strontium: soil - plants - animals - humans. Penetrating into the human body, strontium accumulates mainly in the bones and thus exposes the body to long-term internal radioactive effects. The result of this exposure, as shown by research conducted by scientists in experiments on animals (dogs, rats, etc.), is a serious illness of the body. Damage to the hematopoietic organs and the development of tumors in the bones come to the fore. Under normal conditions, the “supplier” of radioactive strontium is experimental explosions of nuclear and thermal nuclear weapons. Research by American scientists has established that even a small amount of radiation exposure is certainly harmful to a healthy person. If we take into account that even with extremely small doses of this effect, sharp changes occur in those cells of the body on which the reproduction of offspring depends, then it is quite clear that nuclear explosions carry mortal danger not yet... born! Strontium received its name from the mineral strontianite (carbon dioxide salt of strontium), found in 1787 in Scotland near the village of Strontian. The English researcher A. Crawford, studying strontianite, suggested the presence of a new, as yet unknown “earth” in it. The individual peculiarity of strontianite was also established by Klaproth. The English chemist T. Hope in 1792 proved the presence of a new metal in strontianite, isolated in free form in 1808 by G. Davy.
However, regardless of Western scientists, Russian chemist T.E. Lovitz in 1792, examining the mineral barite, came to the conclusion that, in addition to barium oxide, it also contained “strontian earth” as an impurity. Extremely cautious in his conclusions, Lovitz did not dare to publish them until the completion of the secondary verification of the experiments, which required the accumulation of a large amount of “strontian earth”. Therefore, Lovitz’s research “On strontian earth in heavy spar,” although published after Klaproth’s research, was actually carried out before him. They indicate the discovery of strontium in a new mineral - strontium sulfate, now called celestine. From this mineral, the simplest marine organisms - radiolarians, acantharia - build the spines of their skeleton. From the needles of dying invertebrates, clusters of celestine itself were formed
90 Sr-β emitter with a half-life of 28.6 years. As a result of the decay of 90 Sr, 90 Y is formed, also a β-emitter with a half-life of 64.2 hours.
Strontium isotopes falling onto the Earth's surface migrate along biological chains and, ultimately, can enter the human body.
The degree and rate of absorption of strontium from gastrointestinal tract depends on what chemical compound it is part of, on the age of the person and the functional state of the body, on the composition of the diet. Thus, in young people, strontium is absorbed faster and more completely. Increasing the content of calcium salts in the diet reduces the absorption of strontium compounds. When milk is consumed, the absorption of strontium increases. IN different conditions the absorption of strontium from the gastrointestinal tract ranges from 11 to 99%.
Absorbed strontium is actively included in mineral metabolism. Being an analogue of calcium, radioactive strontium is deposited mainly in the bones and bone marrow (critical organs).
Strontium is excreted in feces and urine. The effective half-life is 17.5 years.
IN early dates after the intake of 90 Sr in large quantities, changes are observed in the organs through which it enters or is excreted: the mucous membranes of the mouth, upper respiratory tract, and intestines. Later, liver functions are impaired. When poorly soluble strontium compounds are inhaled, the strontium isotope can be quite firmly fixed in the lungs, which in these cases, together with the respiratory tract, are critical organs. However, in the long term and after inhalation, bones and bone marrow become critical organs, in which up to 90% of all activity is deposited.
During the reaction of hematopoietic tissue to strontium over a long period of time, the morphological composition of the blood changes little. Only when large quantities are ingested does cytopenia develop and progress. No severe cases of damage with acute or subacute course were observed in humans.
With prolonged intake of strontium and subacute radiation sickness, anemia gradually develops, suppression of spermato- and oogenesis, impaired immunity, liver and kidney function, and neuroendocrine system are observed, and life expectancy is reduced.
In the long term, hyper- or hypoplastic processes in the bone marrow, leukemia, and bone sarcomas develop. Less commonly, neoplasms are observed in the pituitary gland and other endocrine organs, in the ovaries, and mammary gland.
The long half-life of 90 Sr determines the long-term persistence of high levels of contamination of territories and environmental objects after contamination with this radionuclide.
Among the nuclear fission products there is also 89 Sr, which is also a β-emitter. However, the half-life of 89 Sr is shorter - 53 days, so the degree of radioactive contamination of objects in this case decreases much faster.
Belarus still lives with the echo of Chernobyl. As a result of the Chernobyl accident, 23 main radionuclides fell in precipitation on the territory of the Republic of Belarus, but most of them decayed within a few months.
Of the long-lived nuclides, the most significant are:
Cesium-137(b- and g- radiation). Half-life 30 years. Accumulates in muscle tissue. It contaminates 23% of the territory of Belarus.
Strontium-90(b- radiation). Half-life 29 years. Accumulates in bones and vessel walls. Pollutes 10% of the territory of Belarus.
Plutonium-239(a- and g-radiation). Half-life is 24065 years. Accumulates in bones, liver, lungs. This radionuclide contaminates 2% of the territory of the Republic of Belarus (Braginsky, Rogachevsky, Svetlogorsk districts).
Americium-241(a-,g - radiation). Plutonium decay product. Half-life 432 years. The accumulation is similar to plutonium-239, but with more severe consequences. Contaminates less than 1% of the territory of Belarus.
The territory of Belarus will become absolutely safe for living and use after approximately 10 half-lives of all major radionuclides.
However, how does radiation harm our body? Briefly, the destructive effects of radiation are explained as follows:
Of course, now Belarusians are not at risk of radiation sickness, since we receive radiation in small doses. Our cells do not die, but they are damaged and mutated, and this, according to experts, leads to the following consequences:
1. Increase in the number of cancer diseases:
- the national average is 7 times (breast, skin, lung, stomach cancer);
- the incidence of thyroid cancer in the Gomel region has increased 130 times;
- V Lately the number of tumors of the bladder, kidneys, liver, rectum, and bone tissue is growing;
- increase in blood diseases - 7 times more children with anemia in the Mogilev region.
2. Increase in the number of genetic consequences:
- the frequency of detection of congenital malformations in children in the Republic of Belarus increased by an average of 40%, in contaminated areas - by 5 times (malformations of the cardiovascular and skeletal systems predominate);
- increase in the number of stillbirths.
4. Premature aging of the body and shortening of life.
Immediately after the accident, the most dangerous thing was external irradiation - through the air, with radioactive dust. The main threat of radiation exposure to the population of Belarus today is internal radiation. This is the production of radionuclides from food (about 90%), from water (4-6%) and from air (2-5%).
Therefore, the most important thing now is to limit the intake of radionuclides into the body through food. Svetlana Alshevskaya, Candidate of Medical Sciences, Associate Professor of the Department of Human Ecology, Faculty of Humanities, BSU, told the portal how to do this.
Choose the right one
Vegetables. Vegetable crops according to their ability to accumulate cesium-137 are distributed as follows in descending order: Bell pepper, cabbage, potatoes, beets, sorrel, lettuce, radishes, onions, garlic, carrots, cucumbers, tomatoes (the former accumulate 10-15 times more than the latter). Potatoes, tomatoes, cabbage, horseradish, and radishes weakly accumulate strontium-90.
Fruits. Fruits do not contain significant amounts of radionuclides. However, their surface contamination with soil is possible.
Berries. Blueberries, lingonberries, black and red currants, cranberries accumulate radionuclides more intensively, while strawberries, gooseberries, white currants, raspberries and rowan berries accumulate radionuclides less intensively.
Mushrooms. More cesium accumulates in the mushroom cap than in the stem. The least radioactive nuclides are accumulated by champignon, winter honey fungus, common milkweed, chanterelles, and russula.
Meat. More cesium is found in the meat of old animals, strontium is found in the bones of young animals. The highest concentration of radionuclides is determined in the lungs, kidneys, and liver, the lowest - in lard and fat. The content of radioactive substances is relatively less in pork than in beef, lamb and poultry. The meat of wild animals contains much more radionuclides than the meat of domestic animals.
Fish. It is recommended to catch fish only in rivers and flowing bodies of water. The most polluted are predatory and bottom fish (pike, perch, carp, crucian carp, catfish, tench). The least polluted are the inhabitants of the upper layers of water (roach, pike perch, bream, rudd).
Process thoroughly
It is necessary to thoroughly wash vegetables and fruits, remove the peels, and also soak the vegetables in water for several hours.
You need to remove the top 2-3 leaves from cabbage heads.
The meat also needs to be soaked for 2-4 hours in salted water.
Washing and peeling can remove more than 50% of the radioactive substances found in products. Thus, in potatoes and beets, when peeling them, the content of strontium-90 is reduced by 30-40%.
The entrails, tendons and heads of fish and poultry should be removed before cooking, since they contain the greatest accumulation of radionuclides.
It is necessary to exclude meat and bone broths from the diet, especially with acidic foods, since strontium mainly passes into the broth in an acidic environment. You should limit your consumption of stewed and fried foods. When cooking products, the amount of radionuclides that pass into water decreases.
The only exception is boiling eggs, since the strontium accumulated there is transferred from the shell to the protein. Therefore, it is better to fry eggs.
It is known that 80% of the radionuclides that a cow eats along with feed go into milk. When milk is processed into cream, cheese, and butter, the cesium content decreases by 10-90%; melted butter does not contain radionuclides.
When cooking potatoes, beets, mushrooms, bring the water to a boil, drain it and replace it with fresh water. This way we remove 50-80% of cesium-137.
The same should be done when preparing meat and fish dishes. This way we will remove up to 50% of radioactive cesium.
When salting and pickling vegetables and mushrooms, the content of radionuclides in them can be reduced by 1.5-2 times.
Mushrooms are washed several times first running water(the washed away water is collected separately), then they are soaked for 2-3 hours before cooking. Soaking, for example, dry porcini mushrooms for 2 hours reduces the radionuclide content by 98%. The mushrooms also need to be boiled twice (10 minutes each), draining the broth each time.
Replace radionuclides with useful microelements
Radionuclides are similar in their chemical properties to some stable elements:
cesium-137 – with potassium and rubidium;
strontium-90 – with calcium;
plutonium-239 – with ferric iron.
At the same time, the human body, when there is a deficiency of potassium, calcium, rubidium and iron in food products, absorbs their radioactive competitors.
Source of potassium (daily requirement– 3 g) are dried apricots, raisins, prunes, tea, nuts, lemon, beans, potatoes, wheat, rye, oat groats, apples, persimmons, cherries, tomatoes, cabbage, garlic, currants, beets, apricots. Pork, caviar, and butter contain potassium.
Source of rubidium are red grapes and good red wine.
Source of calcium(daily requirement - 1 g) are: cottage cheese, cheese, meat, fish, eggs, cabbage, green onions, beans, dill, turnips, parsley, horseradish, spinach, green peas, apples, cucumbers, carrots, oatmeal, wheat, oranges, lemons, potatoes, seeds.
Source of iron(daily requirement – 15-30 mg) are: meat, fish, apples, raisins, salad, chokeberry, green onions, egg yolk. Iron of animal origin is better absorbed.
In addition to food, medications are also used to saturate the body with calcium, potassium and iron.
Remove radionuclides from the body
This can be achieved by regularly consuming a large number of liquids - juices, fruit drinks, compotes. You should drink infusions of herbs that have a weak diuretic effect (chamomile, rose hips, mint, immortelle, St. John's wort, green tea).
There are products containing pectins, which “bind” radionuclides and then remove them from the body. Such products include juices with pulp, cranberries, plums, black currants, apples, cherries, strawberries, as well as marmalade, jams and marshmallows.
It is necessary to saturate the body with antioxidants that can inhibit or eliminate free radical oxidation of organic substances. Vitamins A, C, E have antioxidant properties; microelements selenium, zinc, copper, cobalt.
Remove radioactive dust
To do this, it is necessary to regularly carry out wet cleaning of the premises, more often clean carpets and furniture, and other objects that absorb dust. IN summer time ventilate the premises at least 5 hours a day, but only at low wind speeds, close the vents and windows when strong wind. It’s a good idea to have dust nets on windows and vents.
Before eating you need to gargle, wash your hands with soap; take a shower more often (in the summer - 2 times a day), use a bathhouse with a steam room, wash more often, dry clean and change outerwear.
You should not drink water from unfamiliar sources or swim in them. It is necessary to limit the time spent in the forest; it is especially not recommended to lie on the ground, light fires in the forest and breathe smoke from them.
Work clothes and shoes in rural areas must be cleaned after returning from the street and left outside living quarters.
After burning stoves and fireplaces with wood, you need to “bury” the ash; in rural areas, stove chimneys should be cleaned more often.
Strontium-90 (radiostrontium) is a radioactive strontium nuclide formed in nuclear reactors or during nuclear weapons testing. The half-life of strontium-90 is close to 28.79 years. After decay, another is formed radioactive isotope– yttrium-90. Its half-life is 64 hours.
Place of accumulation of strontium 90 in the body and harm to humans and animals
If cesium-137 replaces potassium and is deposited mainly in the muscles, then strontium-90 acts as an analogue of calcium and remains in the bones of the skeleton and teeth. Bone tissue and bone marrow are also affected. Severe damage leads to the development of radiation sickness, bone tumors, and anemia. The half-life of strontium-90 from the body is about 15 years, which creates a constant source of disease in humans. Just imagine if all the calcium in your bones was replaced with strontium-90, how fragile they would become - only permanent fractures would become a common problem. But at the same time, the issue of constant radioactive radiation on neighboring cells will not be resolved.
At the same time, strontium itself (not the radioactive isotope strontium-90) is very useful for the body, playing a significant role in metabolism. The benefits of ginger have long been proven, especially for older people, who, using it in their diet, increased the strontium content in the body, thereby promoting better absorption of calcium and, as a result, strengthening the condition of their bones and teeth.
Applications of radioactive strontium
Radiostrontium is used in dosimetric instruments for civil and military purposes. It is also used in medicine for radiation therapy of eye tumors or skin lesions. Since strontium-90 radiation is weakly penetrating and is used mainly on superficial foci of diseases.
The sources are sealed with glue. They consist of a substrate coated with a preparation containing strontium-90+yttrium-90 radionuclides, placed between the body and the source lid.
Application area:
Radioisotope instruments
Note:
The strength classes of the sources correspond to C 34444 according to GOST 25926 (ISO 2919). Designated service life is 3.5 years from the date of issue. Tightness control is carried out in accordance with GOST R 51919-2002 (ISO 9978:1992(E)) using the immersion method, the passing limit is 200 Bq (~5 nCi). The sources are supplied in sets consisting of one BIS-R source and one BIS-K source or nine BIS-6A sources and one BIS-F source. Upon request, it is possible to supply individual sources included in the kit.
Main technical characteristics:
They are a substrate with a thickness of 1.1 max mm, on the working surface of which (the recess) a layer of a radioactive drug is applied, protected by a film of metal oxide. Designated service life is 10 years from the date of issue.
Application area:
For verification and calibration of radiometric equipment as measures of radionuclide activity.
Note:
The strength classes of the sources correspond to C 24324 according to GOST 25926 (ISO 2919). Tightness control is carried out in accordance with GOST R 51919-2002 (ISO 9978:1992(E)) using the dry swab method from a non-working surface, the passing limit is 2 Bq (~0.05 nCi). Sources are supplied individually, in sets and in kits.
* The measured values of radionuclide activity do not differ from the nominal values by more than 30%.
