Iodine 131 an Chernobyl nuclear power plant. Radioactive isotopes formed during fission (Digest). Iodine and the thyroid gland

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The consequences of the release of the radioisotope 131 I after the Chernobyl accident and a description of the biological effect of radioiodine on the human body are presented.

Biological effect of radioiodine

Iodine-131- radionuclide with a half-life of 8.04 days, beta and gamma emitter. Due to its high volatility, almost all of the iodine-131 present in the reactor (7.3 MCi) was released into the atmosphere. Its biological effect is associated with the characteristics of the functioning thyroid gland. Its hormones - thyroxine and triiodothyroyanine - contain iodine atoms. Therefore, normally the thyroid gland absorbs about 50% of the iodine entering the body. Naturally, iron does not distinguish radioactive isotopes of iodine from stable ones. The thyroid gland of children is three times more active in absorbing radioiodine that enters the body. Besides, iodine-131 easily penetrates the placenta and accumulates in the fetal gland.

The accumulation of large amounts of iodine-131 in the thyroid gland leads to radiation damage secretory epithelium and to hypothyroidism - thyroid dysfunction. The risk of malignant tissue degeneration also increases. The minimum dose at which there is a risk of developing hypothyroidism in children is 300 rads, in adults - 3400 rads. The minimum doses at which there is a risk of developing thyroid tumors are in the range of 10-100 rads. The risk is greatest at doses of 1200-1500 rads. In women, the risk of developing tumors is four times higher than in men, and in children it is three to four times higher than in adults.

The magnitude and rate of absorption, accumulation of radionuclide in organs, and rate of excretion from the body depend on age, gender, stable iodine content in the diet and other factors. In this regard, when the same amount of radioactive iodine enters the body, the absorbed doses differ significantly. Particularly large doses are formed in thyroid gland children, which is associated with the small size of the organ, and can be 2-10 times higher than the dose of radiation to the gland in adults.

Prevention of iodine-131 entry into the human body

Taking stable iodine preparations effectively prevents the entry of radioactive iodine into the thyroid gland. In this case, the gland is completely saturated with iodine and rejects radioisotopes that have entered the body. Taking stable iodine even 6 hours after a single dose of 131 I can reduce the potential dose to the thyroid gland by approximately half, but if iodine prophylaxis is delayed for a day, the effect will be small.

Admission iodine-131 into the human body can occur mainly in two ways: inhalation, i.e. through the lungs, and orally through consumed milk and leafy vegetables.

Environmental pollution 131 I after the Chernobyl accident

Intense hair loss 131 I in the city of Pripyat apparently began on the night of April 26-27. Its entry into the body of city residents occurred through inhalation, and therefore depended on the time spent in the open air and on the degree of ventilation of the premises.

The situation in villages caught in the radioactive fallout zone was much more serious. Due to the uncertainty of the radiation situation, not all rural residents received iodine prophylaxis in a timely manner. Main route of admission131 I into the body was food, with milk (up to 60% according to some data, according to other data - up to 90%). This radionuclide appeared in the milk of cows already on the second or third day after the accident. It should be noted that a cow eats feed from an area of 150 m2 every day on pasture and is an ideal concentrator of radionuclides in milk. On April 30, 1986, the USSR Ministry of Health issued recommendations on a widespread ban on the consumption of milk from cows on pastures in all areas adjacent to the accident zone. In Belarus, the cattle were still kept in stalls, but in Ukraine the cows were already grazing. This ban worked at state-owned enterprises, but in private households, prohibition measures usually work less well. It should be noted that in Ukraine at that time about 30% of milk was consumed from personal cows. In the very first days, a standard was established for the content of iodine-13I in milk, subject to which the dose to the thyroid gland should not exceed 30 rem. In the first weeks after the accident, the concentration of radioiodine in individual milk samples exceeded this standard tens and hundreds of times.

The following facts can help to imagine the scale of pollution of the natural environment with iodine-131. According to existing standards, if the density of pollution on a pasture reaches 7 Ci/km 2, the consumption of contaminated products should be eliminated or limited, and livestock should be transferred to uncontaminated pastures or feed. On the tenth day after the accident (when one half-life of iodine-131 had passed), the Kiev, Zhytomyr and Gomel regions of the Ukrainian SSR, the entire west of Belarus, the Kaliningrad region, the west of Lithuania and the north-east of Poland were subject to this standard.

If the pollution density is in the range of 0.7-7 Ci/km 2, then the decision should be made depending on the specific situation. Such pollution densities were observed throughout almost all of Right Bank Ukraine, throughout Belarus, the Baltic states, in the Bryansk and Oryol regions of the RSFSR, in the east of Romania and Poland, southeast Sweden and southwest Finland.

Emergency care for radioiodine contamination.

When working in an area contaminated with radioisotopes of iodine, for the purpose of prevention, take 0.25 g of potassium iodide daily (under medical supervision). Decontamination of the skin with soap and water, rinsing the nasopharynx and oral cavity. When radionuclides enter the body - potassium iodide 0.2 g, sodium iodide 0.2 g, sayodine 0.5 or tereostatics (potassium perchlorate 0.25 g). Emetics or gastric lavage. Expectorants with repeated administration of iodine salts and tereostatics. Drink plenty of fluids, diuretics.

Literature:

Chernobyl does not let go... (to the 50th anniversary of radioecological research in the Komi Republic). – Syktyvkar, 2009 – 120 p.

Tikhomirov F.A. Radioecology of iodine. M., 1983. 88 p.

Cardis et al., 2005. Risk of Thyroid Cancer After Exposure to 131I in Childhood -- Cardis et al. 97 (10): 724 -- JNCI Journal of the National Cancer Institute

Rating: / 29
Details Parent category: Exclusion zone Category: Radioactive contamination

The consequences of the release of the radioisotope 131 I after the Chernobyl accident and a description of the biological effect of radioiodine on the human body are presented.

Biological effect of radioiodine

Prevention of iodine-131 entry into the human body

Admission iodine-131 into the human body can occur mainly in two ways: inhalation, i.e. through the lungs, and orally through consumed milk and leafy vegetables.

Environmental pollution 131 I after the Chernobyl accident

Emergency care for radioiodine contamination.

Literature:

Chernobyl does not let go... (to the 50th anniversary of radioecological research in the Komi Republic). – Syktyvkar, 2009 – 120 p.

Tikhomirov F.A. Radioecology of iodine. M., 1983. 88 p.

Cardis et al., 2005. Risk of Thyroid Cancer After Exposure to 131I in Childhood -- Cardis et al. 97 (10): 724 -- JNCI Journal of the National Cancer Institute

During fission, various isotopes are formed, one might say, half of the periodic table. The probability of isotope formation varies. Some isotopes are formed with a higher probability, some with a much lower probability (see figure). Almost all of them are radioactive. However, most of them have very short half-lives (minutes or less) and decay quickly into stable isotopes. However, among them there are isotopes that, on the one hand, are readily formed during fission, and on the other, have half-lives of days and even years. They are the main danger to us. Activity, i.e. the number of decays per unit time and, accordingly, the number of “radioactive particles”, alpha and/or beta and/or gamma, is inversely proportional to the half-life. Thus, if there are the same number of isotopes, the activity of the isotope with a shorter half-life will be higher than that with a longer half-life. But the activity of an isotope with a shorter half-life will decay faster than with a longer one. Iodine-131 is formed during fission with approximately the same “hunting” as cesium-137. But iodine-131 has a half-life of “only” 8 days, and cesium-137 has a half-life of about 30 years. During the fission of uranium, at first the amount of its fission products, both iodine and cesium, increases, but soon equilibrium occurs for iodine – as much of it is formed, so much of it disintegrates. With cesium-137, due to its relatively long half-life, this equilibrium is far from achieved. Now, if there is a release of decay products into the external environment, at the initial moments, of these two isotopes, iodine-131 poses the greatest danger. Firstly, due to the peculiarities of its fission, a lot of it is formed (see figure), and secondly, due to its relatively short half-life, its activity is high. Over time (after 40 days), its activity will decrease by 32 times, and soon it will practically not be visible. But cesium-137 may not “shine” so much at first, but its activity will decrease much more slowly.
Below we talk about the most “popular” isotopes that pose a danger during accidents at nuclear power plants.

Radioactive iodine

Among the 20 radioisotopes of iodine formed in the fission reactions of uranium and plutonium, a special place is occupied by 131-135 I (T 1/2 = 8.04 days; 2.3 hours; 20.8 hours; 52.6 minutes; 6.61 hours), characterized by a high yield in fission reactions, high migration ability and bioavailability.

During normal operation of nuclear power plants, emissions of radionuclides, including radioisotopes of iodine, are small. In emergency conditions, as evidenced by major accidents, radioactive iodine, as a source of external and internal irradiation, was the main damaging factor in the initial period of the accident.

Simplified diagram of the breakdown of iodine-131. The decay of iodine-131 produces electrons with energies up to 606 keV and gamma rays, mainly with energies of 634 and 364 keV.

The main source of radioiodine for the population in areas of radionuclide contamination was local food products of plant and animal origin. A person can receive radioiodine through the following chains:

plants → people,
plants → animals → humans,
water → hydrobionts → humans.

Milk, fresh dairy products and leafy vegetables that are surface contaminated are usually the main source of radioiodine for the population. The absorption of the nuclide by plants from the soil, given its short lifespan, is of no practical importance.

In goats and sheep, the radioiodine content in milk is several times higher than in cows. Hundredths of incoming radioiodine accumulate in animal meat. Radioiodine accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding the content in water) of 131 I in marine fish, algae, and mollusks reach 10, 200-500, 10-70, respectively.

The isotopes 131-135 I are of practical interest. Their toxicity is low compared to other radioisotopes, especially alpha-emitting ones. Acute radiation injuries of severe, moderate and mild degrees in an adult can be expected with oral intake of 131 I in amounts of 55, 18 and 5 MBq/kg body weight. The toxicity of the radionuclide during inhalation is approximately two times higher, which is associated with a larger area of contact beta irradiation.

All organs and systems are involved in the pathological process, especially severe damage to the thyroid gland, where the highest doses are formed. Radiation doses to the thyroid gland in children due to its small mass when receiving the same amounts of radioiodine are significantly higher than in adults (the mass of the gland in children, depending on age, is 1:5-7 g, in adults – 20 g).

Radioactive iodine contains much detailed information about radioactive iodine, which, in particular, may be useful to medical professionals.

Radioactive cesium

Radioactive cesium is one of the main dose-forming radionuclides of fission products of uranium and plutonium. The nuclide is characterized by a high migration ability in the external environment, including food chains. The main source of radiocesium for humans is food of animal and plant origin. Radioactive cesium supplied to animals with contaminated feed mainly accumulates in muscle tissue (up to 80%) and in the skeleton (10%).

After the decay of radioactive isotopes of iodine, the main source of external and internal radiation is radioactive cesium.

In goats and sheep, the content of radioactive cesium in milk is several times higher than in cows. It accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding the content in water) of 137 Cs in the muscles of fish reaches 1000 or more, in mollusks - 100-700,
crustaceans – 50-1200, aquatic plants – 100-10000.

The intake of cesium to humans depends on the nature of the diet. Thus, after the Chernobyl accident in 1990, the contribution of various products to the average daily intake of radiocesium in the most contaminated areas of Belarus was as follows: milk - 19%, meat - 9%, fish - 0.5%, potatoes - 46%, vegetables - 7.5%, fruits and berries – 5%, bread and bakery products – 13%. Increased levels of radiocesium are recorded in residents who consume large quantities of “gifts of nature” (mushrooms, wild berries and especially game).

Radiocesium, entering the body, is distributed relatively evenly, which leads to almost uniform irradiation of organs and tissues. This is facilitated by the high penetrating ability of gamma rays of its daughter nuclide 137m Ba, equal to approximately 12 cm.

In the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive cesium contains much detailed information about radioactive cesium, which, in particular, may be useful to medical professionals.

Radioactive strontium

After the radioactive isotopes of iodine and cesium, the next most important element, the radioactive isotopes of which make the greatest contribution to pollution, is strontium. However, the share of strontium in irradiation is much less.

Natural strontium is a trace element and consists of a mixture of four stable isotopes 84 Sr (0.56%), 86 Sr (9.96%), 87 Sr (7.02%), 88 Sr (82.0%). According to its physicochemical properties, it is an analogue of calcium. Strontium is found in all plant and animal organisms. The adult human body contains about 0.3 g of strontium. Almost all of it is in the skeleton.

Under normal operating conditions of a nuclear power plant, radionuclide emissions are insignificant. They are mainly caused by gaseous radionuclides (radioactive noble gases, 14 C, tritium and iodine). During accidents, especially large ones, releases of radionuclides, including strontium radioisotopes, can be significant.

89 Sr is of greatest practical interest
(T 1/2 = 50.5 days) and 90 Sr
(T 1/2 = 29.1 years), characterized by high yield in fission reactions of uranium and plutonium. Both 89 Sr and 90 Sr are beta emitters. The decay of 89 Sr produces a stable isotope of ytrium (89 Y). The decay of 90 Sr produces beta-active 90 Y, which in turn decays to form a stable isotope of zirconium (90 Zr).

C diagram of the decay chain 90 Sr → 90 Y → 90 Zr. The decay of strontium-90 produces electrons with energies up to 546 keV, and the subsequent decay of ytrium-90 produces electrons with energies up to 2.28 MeV.

In the initial period, 89 Sr is one of the components of environmental pollution in areas of nearby radionuclide fallout. However, 89 Sr has a relatively short half-life and, over time, 90 Sr begins to dominate.

Animals receive radioactive strontium mainly through food and, to a lesser extent, through water (about 2%). In addition to the skeleton, the highest concentration of strontium is observed in the liver and kidneys, the minimum is in muscles and especially in fat, where the concentration is 4–6 times lower than in other soft tissues.

Radioactive strontium is classified as an osteotropic biologically hazardous radionuclide. As a pure beta emitter, it poses the main danger when it enters the body. The population mainly receives the nuclide through contaminated products. The inhalation route is less important. Radiostrontium selectively deposits in bones, especially in children, exposing the bones and the bone marrow they contain to constant radiation.

Everything is described in detail in the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive strontium.

Iodine-131 is a radioactive isotope of iodine. What does it mean? As you know, an atom consists of a nucleus of small negatively charged particles - electrons - rotating around it.

A positively charged nucleus consists of nucleons: protons (positive particles) and neutrons (neutral particles). Thanks to protons, the nucleus can attract a certain number of electrons with a certain force. Neutrons do not affect this ability of the nucleus in any way.

All atoms that contain op A limited number of protons belong to one chemical element. Iodine is a chemical element. All nuclei of iodine atoms have 53 protons. But the number of neutrons may differ. Atoms with different numbers of neutrons but the same number of protons are called isotopes.

Each atom has a mass number - the sum of the number of protons and neutrons. The most common and stable isotope of iodine has a mass number of 127 - it contains 74 neutrons and 53 protons. The isotope iodine-131 has a mass number of 131 and has four more neutrons.

Where can he be found?

Iodine-131 is called radioiodine. It is very unstable - half of its atoms disintegrate after 8 days. It is produced in nuclear reactors. During the accidents at the Chernobyl nuclear power plant and Fukushima, huge amounts of iodine were released into the atmosphere, which caused radiation sickness of the thyroid gland and thyrotoxicosis in people. However, in small quantities, iodine-131 does not cause significant harm to the body and is used in the treatment of thyroid diseases. It is also used in the diagnosis of thyroid diseases.

Iodine-131 is included in tablets for the treatment of excessive thyroid function - thyrotoxicosis.

Cha Most often they treat diseases associated with thyrotoxicosis: Graves' disease, cancer, AIT - autoimmune thyroiditis. The dose of the drug depends on the volume of the thyroid gland and the speed of its work.

Typically, a dose of 80 to 150 μC is used per gram of organ mass (microcoulombs, one millionth of a coulomb - a unit of measurement of the charge of a particle. A huge number of electrons or protons have this charge: 6 times more particles than a unit with 18 zeros!).

What is the best treatment: take iodine isotope preparations or undergo surgery?

There are few contraindications for the use of iodine isotope - pregnancy, kidney failure, disorders of the formation of leukocytes and platelets. Some researchers claim that after such treatment, patients have more cases of cardiovascular diseases than before it.

Povre germ cells are expected, and an overdose of iodine can lead to the development of myxedema - a lack of thyroid hormones, as well as vomiting, diarrhea, gastritis, damage to the skin of the neck, absence of menstruation in women and, as a result, infertility.

Anecdotal evidence suggests that patients may experience increased bulging eyes after repeated doses of iodine-131.

Other experts claim that the procedure does not harm the health of the body. The same number of patients have cancer before radioiodine therapy as after it. Treatment with isotopes does not require surgery and is much easier to tolerate by the patient.

However, surgery does not require a special diet or isolation of the patient from other people. So if severe thyroid diseases associated with thyrotoxicosis occur, the choice of treatment method remains with the patient.

Most often, young patients undergo surgery, and older people are treated with radiation, since older people tolerate surgery much more difficult, and for young people, surgical removal is better, because radiation can cause unpleasant consequences, such as mutations in germ cells. This treatment is not advisable before pregnancy.

In what cases is isotope treatment vital?

Cancer is treated this way more often than milder diseases associated with thyrotoxicosis. The tumor accumulates isotopes, they decay, destroying the tumor tissue, and the cancer disappears. This treatment of cancer is especially effective in the early stages of tumor development.

How to take medications correctly?

Sodium iodide, for example, must be administered intravenously, along with distilled water. 60% of the active substance is excreted in urine and feces, the remaining 40% is absorbed by the thyroid gland during the day.

Iodine preparations are also available in capsule form. The patient should take one tablet with one large or two small glasses of water.

What should you pay attention to: consequences and diet?

Since a few weeks before therapy the patient has to give up hormonal medications, he may experience unpleasant consequences, such as depression, memory loss, poor health, weight gain, which is not helped by exercise and diet, cessation of menstruation, low resistance to stress and to the cold. All these symptoms are a consequence of a lack of hormones, they will go away after therapy.

Before treatment you will have to follow a special diet. This diet allows any foods except those rich in iodine.

Compliance with the diet is very important: violation of the diet negatively affects the results of treatment. Also, during the diet, you should give up multivitamins containing iodine.

European media continue to discuss news about radioactive iodine, which monitoring stations in several countries began to record recently. The main question is what caused the release of this radionuclide and where the release occurred.

It is known that for the first time the excess of iodine-131 was recorded in Norway, in the second week of January. The first radionuclide to be detected was the Svanhovd research station in northern Norway.

which is located just a few hundred meters from the Russian border.

Later, the excess was caught at a station in the Finnish town of Rovaniemi. Over the next two weeks, traces of the isotope were discovered in other areas of Europe - Poland, the Czech Republic, Germany, France and Spain.

And although Norway became the first country to detect a radioactive isotope, France was the first to inform the population about it. “Initial data suggests that the first detection occurred in northern Norway in the second week of January,” the French Institute for Radiation Protection and Nuclear Safety (IRSN) said in a statement.

Norwegian authorities said they did not announce the discovery due to the low concentration of the substance. “The data in Svankhovd was very, very low. The level of contamination did not raise concerns for people and equipment, so we did not recognize this as worthy news,” said Astrid Leland, a spokeswoman for the Norwegian Radiation Monitoring Service. According to her, there is a network of 33 tracking stations in the country, and anyone can check the data themselves.

According to published According to IRSN, the iodine concentration measured in northern Norway from January 9 to 16 was 0.5 microbecquerels per cubic meter (Bq/m3).

In France, the indicators range from 01 to 0.31 Bq/m 3 . The highest rates were noted in Poland - almost 6 Bq/m 3 . The proximity of the first place where iodine was discovered to the Russian border immediately provoked emergence of rumors that the release could have been caused by secret nuclear weapons tests in the Russian Arctic, and possibly in the Novaya Zemlya area, where the USSR historically tested various weapons.

Iodine-131 is a radionuclide with a half-life of 8.04 days, also called radioiodine, a beta and gamma emitter. The biological effect is related to the functioning of the thyroid gland. Its hormones - thyroxine and triiodothyroyain - contain iodine atoms, so normally the thyroid gland absorbs about half of the iodine entering the body. The gland does not distinguish radioactive isotopes of iodine from stable ones, therefore the accumulation of large amounts of iodine-131 in the thyroid gland leads to radiation damage to the secretory epithelium and to hypothyroidism - dysfunction of the thyroid gland.

As a source at the Obninsk Institute for Environmental Monitoring Problems (IPM) told Gazeta.Ru, there are two main sources of air pollution with radioactive iodine - nuclear power plants and pharmaceutical production.

“Nuclear plants emit radioactive iodine. It is a component of a gas-aerosol release, the technological cycle of any nuclear power plant,” the expert explained, however, according to him, during the release, filtration occurs so that most short-lived isotopes have time to decay.

It is known that after the accidents at the Chernobyl station and Fukushima, emissions of radioactive iodine were recorded by specialists in different countries of the world. However, after such accidents, other radioactive isotopes, including cesium, are released into the atmosphere and, accordingly, are detected.

In Russia, monitoring of radioactive iodine content is carried out at only two points - in Kursk and Obninsk.
The emissions recorded in Europe are indeed vanishingly small concentrations given the current limits set for iodine. Thus, in Russia the maximum concentration of radioactive iodine in the atmosphere is 7.3 Bq/m 3

A million times higher than the level recorded in Poland.

“These levels are kindergarten. These are very small quantities. But if all monitoring stations during this period recorded iodine concentrations in aerosol and molecular form, there was a source somewhere, there was a release,” the expert explained.

Meanwhile, in Obninsk itself, an observation station located there monthly records the presence of iodine-131 in the atmosphere, this is due to the source located there - the Karpov Research Institute of Chemical Physics. This company produces radiopharmaceuticals based on iodine-131, which are used for the diagnosis and treatment of cancer.

A number of European experts are also inclined to believe that the source of the release of iodine-131 was pharmaceutical production. "Since only iodine-131 was detected and no other substances were detected, we believe that it comes from some kind of pharmaceutical company that produces radioactive drugs," Leland explained to Motherboard. “If it had come from the reactor, we would have detected other elements in the air,” said Didier Champion, head of one of the IRSN divisions.

Experts recall that a similar situation arose in 2011, when radioactive iodine was detected in several European countries at once. Interestingly, just last week, scientists explained the 2011 iodine release. They concluded that the leak was due to a failure of the filter system at a Budapest institute that produces isotopes for medical purposes.