Ionizing (radioactive) radiation includes X-ray and γ-radiation, which are electromagnetic oscillations with a very short wavelength, as well as α- and β-radiation, positron and neutron radiation, which are a stream of particles with or without a charge. X-ray and γ-radiation are collectively referred to as photon radiation.

The main property of radioactive radiation is its ionizing effect. When they pass through the tissues, neutral atoms or molecules acquire a positive or negative charge and turn into ions. Alpha radiation, which is a positively charged helium nucleus, has a high ionizing ability (up to several tens of thousands of pairs of ions per 0.01 m of its path), but a small range: in air 0.02 ... 0.11 m, in biological tissues (2..,6)10-6 m. Beta-radiation and positron radiation are, respectively, flows of electrons and positrons with a much lower ionizing ability, which, at the same energy, is 1000 times less than that of β-particles. Neutron radiation has a very large penetrating power. Passing through tissues, neutrons - particles that do not have a charge, cause the formation of radioactive substances in them (induced activity). X-rays arising from β-radiation or in X-ray tubes, electron accelerators, etc., as well as γ-radiation emitted by radionuclides - the nuclei of radioactive elements, have the lowest ability to ionize the medium, but the highest penetrating ability. Their range in air is several hundred meters, and in materials used for protection against ionizing radiation (lead, concrete), tens of centimeters.

Exposure can be external, when the source of radiation is outside the body, and internal, arising from the ingestion of radioactive substances through the respiratory tract, gastrointestinal tract, or absorption through damaged skin. Entering the lungs or digestive tract, radioactive substances are distributed throughout the body with the bloodstream. At the same time, some substances are distributed evenly in the body, while others accumulate only in certain (critical) organs and tissues: radioactive iodine - in the thyroid gland, radioactive radium and strontium - in the bones, etc. Internal exposure can occur when eating food crop and livestock production obtained from contaminated agricultural land.

The duration of the presence of radioactive substances in the body depends on the rate of release and the half-life - the time during which the radioactivity is halved. The removal of such substances from the body occurs mainly through the gastrointestinal tract, kidneys and lungs, partly through the skin, oral mucosa, with sweat and milk.

Ionizing radiation can cause local and general damage. Local skin lesions are in the form of burns, dermatitis and other forms. Sometimes there are benign neoplasms, it is also possible the development of skin cancer. Prolonged exposure to radiation on the lens causes cataracts.

General lesions occur in the form of acute and chronic radiation sickness. Acute forms are characterized by specific lesions of the hematopoietic organs, the gastrointestinal tract and the nervous system against the background of general toxic symptoms (weakness, nausea, memory loss, etc.). In the early stage of the chronic form, increasing physical and neuropsychic weakness, a reduced level of red blood cells in the blood, and increased bleeding are observed. Inhalation of radioactive dust causes pneumosclerosis, sometimes cancer of the bronchi and lungs. Ionizing radiation inhibits the reproductive function of the body, affecting the health of future generations.

Works with sealed sources of radiation and open radioactive substances can be performed at the production site.

Sealed sources are sealed; most often these are steel ampoules containing a radioactive substance. As a rule, they use γ- and less often β-emitters. Sealed sources also include X-ray machines and accelerators. Installations with such sources are used to control the quality of welds, determine the wear of parts, decontaminate skin and wool, treat seeds to kill insect pests, and in medicine and veterinary medicine. Working at these installations is fraught with danger only from external radiation.

Works with radioactive substances in the open form are encountered in the diagnosis and treatment in medicine and veterinary medicine, when radioactive substances are applied as part of luminous paints on dials, in factory laboratories, etc. For work in this category, both external and internal exposure are dangerous, since radioactive substances can enter the air of the working area in the form of vapors, gases and aerosols.

To take into account the unequal danger of different types of ionizing radiation, the concept of equivalent dose has been introduced. It is measured in sieverts and is determined by the formula

where k is the quality factor that takes into account the biological efficiency of various types of radiation compared to X-rays: k = 20 for α-radiation, k- 10 for the proton and neutron flux; k- 1 for photon and β-radiation; D is the absorbed dose characterizing the absorption of the energy of any ionizing radiation by a unit mass of a substance, Sv.

The effective dose makes it possible to assess the consequences of irradiation of individual organs and tissues of a person, taking into account their radiosensitivity.

The radiation safety standards NRB-96, approved by Decree No. 7 of the State Committee for Sanitary and Epidemiological Surveillance of the Russian Federation on April 19, 1996, established the following categories of exposed persons:

personnel - people working with man-made radiation sources (group A) or who, due to working conditions, are in the area of ​​their influence (group B);

the entire population, including personnel, outside the scope and conditions of their production activities (Table 21.2).

21.2. Basic exposure dose limits, mSv

Normalized value	Service staff (Group A)	Population
Effective dose	20 per year on average for any 5 years, but not more than 50 per 1 year	1 per year on average for any 5 years, but not more than 5 per 1 year
Equivalent dose per year:
in the lens
on the skin
on hands and feet

The annual dose of exposure of the population from natural background radiation averages (0.1 ... 0.12) 10-2 Sv, with fluorography 0.37 * 10-2 Sv, with radiography of teeth 3 o 10-2 Sv.

The main dose limits for exposed people do not include doses from natural and medical sources of ionizing radiation and the dose received as a result of radiation accidents. There are special restrictions on these types of exposure.

Protection from external radiation is carried out in three directions: 1) by shielding the source; 2) increasing the distance from him to the workers; 3) reduction of the time spent by people in the irradiation zone. As screens, materials that absorb ionizing radiation well, such as lead, concrete, are used. The thickness of the protective layer is calculated depending on the type and power of radiation. It should be taken into account that the radiation power decreases in proportion to the square of the distance from the source. This dependency is used when implementing remote process control. The time spent by workers in the zone of exposure to radiation is limited from the condition of compliance with the maximum radiation doses indicated in Table 21.2.

When working with open sources of radiation, the room where radioactive substances are located is isolated as much as possible. The walls must be of sufficient thickness. The surfaces of enclosing structures and equipment are covered with materials that are easy to clean (plastic, oil paint, etc.). Work with radioactive substances polluting the air of the working area is carried out only in closed fume hoods (boxes) with filtration of the exhaust air. At the same time, sufficient attention should be paid to the efficiency of general and local ventilation, as well as the use of personal protective equipment (respirators, insulating pneumosuits with clean air supplied to them, goggles, overalls, aprons, rubber gloves and shoes), which are selected depending on the properties of the used radioactive substances, their activity and type of work. Important preventive measures include dosimetric control and medical examination of workers. For individual dosimetric control devices IFKU-1, TLD, KID-6 and others are used; - and neutron radiation is measured with RUP-1, UIM2-1eM devices, and the volumetric activity of radioactive gases and aerosols in the air - with RV-4, RGB-3-01 devices.

Radiation in the 20th century represents a growing threat to all mankind. Radioactive substances processed into nuclear energy, getting into building materials and finally used for military purposes, have a harmful effect on human health. Therefore, protection from ionizing radiation ( radiation safety) is becoming one of the most important tasks for ensuring the safety of human life.

radioactive substances(or radionuclides) are substances capable of emitting ionizing radiation. The reason for it is the instability of the atomic nucleus, as a result of which it undergoes spontaneous decay. Such a process of spontaneous transformations of the nuclei of atoms of unstable elements is called radioactive decay, or radioactivity.

Ionizing radiation - radiation that is created during radioactive decay and forms ions of various signs when interacting with the environment.

The act of decay is accompanied by the emission of radiation in the form of gamma rays, alpha, beta particles and neutrons.

Radioactive radiation is characterized by different penetrating and ionizing (damaging) ability. Alpha particles have such a low penetrating power that they are retained by a sheet of plain paper. Their range in the air is 2-9 cm, in the tissues of a living organism - fractions of a millimeter. In other words, these particles, when externally exposed to a living organism, are unable to penetrate the skin layer. At the same time, the ionizing ability of such particles is extremely high, and the danger of their impact increases when they enter the body with water, food, inhaled air or through an open wound, since they can damage those organs and tissues into which they have penetrated.

Beta particles are more penetrating than alpha particles, but less ionizing; their range in the air reaches 15 m, and in the tissues of the body - 1-2 cm.

Gamma radiation travels at the speed of light, has the greatest penetration depth, and can only be weakened by a thick lead or concrete wall. Passing through matter, radioactive radiation reacts with it, losing its energy. Moreover, the higher the energy of radioactive radiation, the greater its damaging ability.

The amount of radiation energy absorbed by a body or substance is called absorbed dose. As a unit of measurement of the absorbed radiation dose in the SI system, Gray (Gr). In practice, an off-system unit is used - glad(1 rad = 0.01 Gy). However, with an equal absorbed dose, alpha particles have a much greater damaging effect than gamma radiation. Therefore, to assess the damaging effect of various types of ionizing radiation on biological objects, a special unit of measurement is used - rem(biological equivalent of X-ray). The SI unit for this equivalent dose is sievert(1 Sv = 100 rem).

To assess the radiation situation on the ground, in a working or residential area, due to exposure to X-ray or gamma radiation, use exposure dose. The unit of exposure dose in the SI system is a coulomb per kilogram (C/kg). In practice, it is most often measured in roentgens (R). The exposure dose in roentgens quite accurately characterizes the potential hazard of exposure to ionizing radiation with a general and uniform exposure of the human body. An exposure dose of 1 R corresponds to an absorbed dose approximately equal to 0.95 rad.

Under other identical conditions, the dose of ionizing radiation is the greater, the longer the exposure, i.e. dose accumulates over time. The dose related to the unit of time is called the dose rate, or radiation level. So, if the level of radiation in the area is 1 R / h, this means that for 1 hour of being in this area a person will receive a dose of 1 R.

The roentgen is a very large unit of measurement, and radiation levels are usually expressed in fractions of an roentgen - thousandths (milliroentgen per hour - mR / h) and millionths (micro roentgen per hour - microR / h).

Dosimetric instruments are used to detect ionizing radiation, measure their energy and other properties: radiometers and dosimeters.

Radiometer is a device designed to determine the amount of radioactive substances (radionuclides) or radiation flux.

Dosimeter- a device for measuring the exposure or absorbed dose rate.

A person is exposed to ionizing radiation throughout his life. This is first of all natural radiation background Earths of cosmic and terrestrial origin. On average, the exposure dose from all natural sources of ionizing radiation is about 200 mR per year, although this value in different regions of the Earth can vary between 50-1000 mR / year and more.

Natural radiation background– radiation generated by cosmic radiation, natural radionuclides naturally distributed in the earth, water, air, and other elements of the biosphere (for example, food products).

In addition, a person encounters artificial sources of radiation. (technogenic radiation background). It includes, for example, ionizing radiation used for medical purposes. A certain contribution to the technogenic background is made by enterprises of the nuclear fuel cycle and coal-fired thermal power plants, aircraft flights at high altitudes, watching TV programs, using clocks with luminous dials, etc. In general, the technogenic background ranges from 150 to 200 mrem.

Technogenic radiation background - natural radiation background, modified as a result of human activity.

Thus, each inhabitant of the Earth annually on average receives radiation dose of 250-400 mrem. This is the normal state of the human environment. The adverse effect of this level of radiation on human health has not been established.

A completely different situation arises during nuclear explosions and accidents at nuclear reactors, when vast zones of radioactive contamination (contamination) with a high level of radiation are formed.

Any organism (plant, animal or person) does not live in isolation, but in one way or another is connected with all animate and inanimate nature. In this chain, the path of radioactive substances is approximately as follows: plants assimilate them with leaves directly from the atmosphere, roots from the soil (soil water), i.e. accumulate, and therefore the concentration of RS in plants is higher than in the environment. All farm animals receive RS from food, water, and from the atmosphere. Radioactive substances, entering the human body with food, water, air, are included in the molecules of bone tissue and muscles and, remaining in them, continue to irradiate the body from the inside. Therefore, human safety in conditions of radioactive contamination (contamination) of the environment is achieved by protection from external radiation, contamination by radioactive fallout, as well as protection of the respiratory and gastrointestinal tract from the ingress of radioactive substances into the body with food, water and air. In general, the actions of the population in the area of ​​infection are mainly reduced to the observance of the relevant rules of conduct and the implementation of sanitary and hygienic measures. When reporting a radiation hazard, it is recommended that the following be carried out immediately:

1. Take shelter in residential buildings or office space. It is important to know that the walls of a wooden house attenuate ionizing radiation by 2 times, and a brick house by 10 times. Deep shelters (basements) weaken the radiation dose even more: with a wooden coating - by 7 times, with brick or concrete - by 40-100 times.

2. Take measures to protect against penetration into the apartment (house) of radioactive substances with air: close the windows, ventilation hatches, vents, seal the frames and doorways.

3. Create a supply of drinking water: collect water in closed containers, prepare the simplest sanitary products (for example, soap solutions for hand treatment), turn off the taps.

4. Carry out emergency iodine prophylaxis (as soon as possible, but after a special notification!). Iodine prophylaxis consists in taking stable iodine preparations: potassium iodide tablets or a water-alcohol solution of iodine. Potassium iodide should be taken after meals with tea or water once a day for 7 days, one tablet (0.125 g) at a time. A water-alcohol solution of iodine should be taken after meals 3 times a day for 7 days, 3-5 drops per glass of water.

You should know that an overdose of iodine is fraught with a number of side effects, such as an allergic condition and inflammatory changes in the nasopharynx.

5. Start preparing for a possible evacuation. Prepare documents and money, essentials, pack medicines that you often turn to, a minimum of linen and clothes (1-2 shifts). Gather a supply of canned food you have for 2-3 days. All this should be packed in plastic bags and bags. Turn on the radio to listen to the information messages of the Commission for Emergency Situations.

6. Try to follow the rules of radiation safety and personal hygiene, namely:

Eat only canned milk and food products that have been stored indoors and have not been exposed to radioactive contamination. Do not drink milk from cows that continue to graze in contaminated fields: radioactive substances have already begun to circulate through the so-called biological chains;

Do not eat vegetables that grew in the open field and are plucked after the release of radioactive substances into the environment;

Eat only in enclosed spaces, wash hands thoroughly with soap before eating, and rinse your mouth with a 0.5% solution of baking soda;

Do not drink water from open sources and running water after the official announcement of the radiation hazard; cover the wells with foil or covers;

Avoid long-term movement on the contaminated area, especially on a dusty road or grass, do not go to the forest, refrain from swimming in the nearest body of water;

Change shoes when entering the premises from the street (“dirty” shoes should be left on the landing or on the porch);

7. In the case of movement in open areas, it is necessary to use improvised means of protection:

Respiratory organs - cover your mouth and nose with a gauze bandage moistened with water, a handkerchief, a towel or any part of clothing;

Skin and hairline - cover yourself with any items of clothing - hats, scarves, capes, gloves. If you absolutely must go outside, we recommend that you wear rubber boots.

The following are precautions in conditions of increased radiation, recommended by the famous American doctor Gale - a specialist in radiation safety.

NECESSARY:

1. Good nutrition.

2. Daily stool.

3. Decoctions of flax seeds, prunes, nettles, laxative herbs.

4. Drink plenty of water, sweat more often.

5. Juices with coloring pigments (grape, tomato).

6. Chokeberry, pomegranates, raisins.

7. Vitamins P, C, B, beet juice, carrots, red wine (3 tablespoons daily).

8. Grated radish (grate in the morning, eat in the evening and vice versa).

9. 4-5 walnuts daily.

10. Horseradish, garlic.

11. Buckwheat, oatmeal.

12. Bread kvass.

13. Ascorbic acid with glucose (3 times a day).

14. Activated charcoal (1-2 pieces before meals).

15. Vitamin A (no more than two weeks).

16. Quademite (3 times a day).

Of dairy products, it is best to eat cottage cheese, cream, sour cream, butter. Peel vegetables and fruits up to 0.5 cm, remove at least three leaves from cabbage heads. Onions and garlic have an increased ability to absorb radioactive elements. From meat products, there are mainly pork and poultry. Avoid meat broths. Cook the meat in this way: drain the first broth, refill it with water and cook until tender.

PRODUCTS WITH ANTI-RADIOACTIVE ACTION:

1. Carrot.

2. Vegetable oil.

3. Curd.

4. Calcium tablets.

DO NOT EAT:

2. Aspic, bones, bone fat.

3. Cherries, apricots, plums.

4. Beef: This is the most likely to be contaminated.

1. Department of BJD

1. Test

discipline: Life safety

on the topic: Ionizing radiation

1. Perm, 2004

Introduction

Ionizing radiation is called radiation, the interaction of which with the environment leads to the formation of electric charges of various signs.

Ionizing radiation is the radiation that radioactive substances possess.

Under the influence of ionizing radiation, a person develops radiation sickness.

The main goal of radiation safety is to protect the health of the population, including personnel, from the harmful effects of ionizing radiation by observing the basic principles and norms of radiation safety without unreasonable restrictions on useful activities when using radiation in various areas of the economy, in science and medicine.

Radiation safety standards (NRB-2000) are used to ensure human safety under the influence of ionizing radiation of artificial or natural origin.

Main characteristics of ionizing radiation

Ionizing radiation is called radiation, the interaction of which with the environment leads to the formation of electric charges of various signs. The sources of these radiations are widely used in engineering, chemistry, medicine, agriculture and other areas, for example, in measuring soil density, detecting leaks in gas pipelines, measuring the thickness of sheets, pipes and rods, antistatic treatment of fabrics, polymerization of plastics, radiation therapy of malignant tumors, etc. However, it should be remembered that sources of ionizing radiation pose a significant threat to the health and life of people using them.

There are 2 types of ionizing radiation:

corpuscular, consisting of particles with a rest mass other than zero (alpha and beta radiation and neutron radiation);

electromagnetic (gamma radiation and x-rays) with a very short wavelength.

alpha radiation is a stream of helium nuclei with high speed. These nuclei have a mass of 4 and a charge of +2. They are formed during the radioactive decay of nuclei or during nuclear reactions. Currently, more than 120 artificial and natural alpha-radioactive nuclei are known, which, emitting an alpha particle, lose 2 protons and 2 neurons.

The energy of alpha particles does not exceed a few MeV (mega-electron-volt). The emitted alpha particles move almost in a straight line at a speed of about 20,000 km/s.

Under the path length of a particle in air or other media, it is customary to call the greatest distance from the radiation source at which it is still possible to detect a particle before it is absorbed by a substance. The path length of a particle depends on the charge, mass, initial energy, and the medium in which the motion occurs. With an increase in the initial energy of the particle and a decrease in the density of the medium, the path length increases. If the initial energy of the emitted particles is the same, then heavy particles have lower velocities than light ones. If the particles move slowly, then their interaction with the atoms of the substance of the medium is more efficient and the particles quickly waste their energy reserve.

The path length of alpha particles in air is usually less than 10 cm. Due to their large mass, alpha particles quickly lose their energy when interacting with matter. This explains their low penetrating power and high specific ionization: when moving in air, an alpha particle forms several tens of thousands of pairs of charged particles - ions per 1 cm of its path.

beta radiation is a stream of electrons or positrons resulting from radioactive decay. About 900 beta radioactive isotopes are currently known.

The mass of beta particles is several tens of thousands of times less than the mass of alpha particles. Depending on the nature of the source of beta radiation, the speed of these particles can lie within 0.3 - 0.99 of the speed of light. The energy of beta particles does not exceed several MeV, the path length in air is approximately 1800 cm, and in the soft tissues of the human body ~ 2.5 cm. The penetrating power of beta particles is higher than that of alpha particles (due to their smaller mass and charge).

neutron radiation is a stream of nuclear particles that do not have an electric charge. The mass of a neutron is approximately 4 times less than the mass of alpha particles. Depending on the energy, slow neutrons are distinguished (with an energy of less than 1 KeV (kilo-electron-Volt) \u003d 10 3 eV), neutrons of intermediate energies (from 1 to 500 KeV) and fast neutrons (from 500 KeV to 20 MeV). During the inelastic interaction of neutrons with the nuclei of atoms of the medium, secondary radiation arises, consisting of charged particles and gamma quanta (gamma radiation). During elastic interactions of neutrons with nuclei, the usual ionization of matter can be observed. The penetrating power of neutrons depends on their energy, but it is much higher than that of alpha or beta particles. Neutron radiation has a high penetrating power and represents the greatest danger to humans of all types of corpuscular radiation. The neutron flux power is measured by the neutron flux density.

Gamma radiation It is electromagnetic radiation with high energy and short wavelength. It is emitted during nuclear transformations or the interaction of particles. High energy (0.01 - 3 MeV) and short wavelength determines the high penetrating power of gamma radiation. Gamma rays are not deflected in electric and magnetic fields. This radiation has a lower ionizing power than alpha and beta radiation.

x-ray radiation can be obtained in special X-ray tubes, in electron accelerators, in the environment surrounding the source of beta radiation, etc. X-ray radiation is one of the types of electromagnetic radiation. Its energy usually does not exceed 1 MeV. X-ray radiation, like gamma radiation, has a low ionizing ability and a large penetration depth.

To characterize the effect of ionizing radiation on a substance, the concept of radiation dose has been introduced. The dose of radiation is the part of the energy transferred by radiation to the substance and absorbed by it. The quantitative characteristic of the interaction of ionizing radiation and matter is absorbed radiation dose(E), equal to the ratio of the average energy dE transferred by ionizing radiation to a substance in an elementary volume, to the mass of the irradiated substance in this volume dm:

Until recently, only X-ray and gamma radiation, based on their ionizing effect, was taken as a quantitative characteristic. exposure dose X is the ratio of the total electric charge dQ of ions of the same sign, arising in a small volume of dry air, to the mass of air dm in this volume, i.e.

To assess the possible damage to health during chronic exposure to ionizing radiation of arbitrary composition, the concept equivalent dose(H). This value is defined as the product of the absorbed dose D and the average radiation quality factor Q (dimensionless) at a given point in the tissue of the human body, i.e.:

There is another characteristic of ionizing radiation - dose rate X (respectively absorbed, exposure or equivalent) representing the dose increment over a small period of time dx divided by this period dt. Thus, the exposure dose rate (x or w, C / kg s) will be:

X \u003d W \u003d dx / dt

The biological effect of the considered radiations on the human body is different.

Alpha particles, passing through matter and colliding with atoms, ionize (charge) them, knocking out electrons. In rare cases, these particles are absorbed by the nuclei of atoms, transferring them to a state of higher energy. This excess energy contributes to the flow of various chemical reactions that do not proceed without irradiation or proceed very slowly. Alpha radiation has a strong effect on the organic substances that make up the human body (fats, proteins and carbohydrates). On the mucous membranes, this radiation causes burns and other inflammatory processes.

Under the action of beta radiation, radiolysis (decomposition) of water contained in biological tissues occurs, with the formation of hydrogen, oxygen, hydrogen peroxide H 2 O 2, charged particles (ions) OH - and HO - 2. The decomposition products of water have oxidizing properties and cause the destruction of many organic substances that make up the tissues of the human body.

The action of gamma and X-ray radiation on biological tissues is mainly due to the free electrons formed. Neutrons passing through matter produce the strongest changes in it in comparison with other ionizing radiations.

Thus, the biological effect of ionizing radiation is reduced to a change in the structure or destruction of various organic substances (molecules) that make up the human body. This leads to a violation of the biochemical processes occurring in the cells, or even to their death, resulting in damage to the body as a whole.

Distinguish between external and internal irradiation of the body. External exposure is understood as the effect on the body of ionizing radiation from sources external to it. Internal exposure is carried out by radioactive substances that have entered the body through the respiratory organs, the gastrointestinal tract or through the skin. Sources of external radiation - cosmic rays, natural radioactive sources in the atmosphere, water, soil, food, etc., sources of alpha, beta, gamma, X-ray and neutron radiation used in engineering and medicine, charged particle accelerators, nuclear reactors (including accidents at nuclear reactors) and a number of others.

Radioactive substances that cause internal irradiation of the body enter it when eating, smoking, drinking contaminated water. The entry of radioactive substances into the human body through the skin occurs in rare cases (if the skin has damage or open wounds). Internal irradiation of the body lasts until the radioactive substance decays or is removed from the body as a result of physiological metabolic processes. Internal exposure is dangerous because it causes long-term non-healing ulcers of various organs and malignant tumors.

When working with radioactive substances, the hands of operators are exposed to significant radiation. Under the influence of ionizing radiation, a chronic or acute (radiation burn) damage to the skin of the hands develops. Chronic lesion is characterized by dry skin, cracking, ulceration and other symptoms. In acute lesions of the hands, edema, tissue necrosis, ulcers occur, at the site of formation of which the development of malignant tumors is possible.

Under the influence of ionizing radiation, a person develops radiation sickness. There are three degrees of it: the first (light), second and third (severe).

Symptoms of radiation sickness of the first degree are weakness, headaches, sleep disturbance and appetite, which increase in the second stage of the disease, but they are additionally accompanied by disturbances in the activity of the cardiovascular system, metabolism and blood composition change, and digestive organs are upset. At the third stage of the disease, hemorrhages are observed, hair loss, the activity of the central nervous system and sex glands is disrupted. In people who have undergone radiation sickness, the likelihood of developing malignant tumors and diseases of the hematopoietic organs increases. Radiation sickness in an acute (severe) form develops as a result of irradiation of the body with large doses of ionizing radiation in a short period of time. The impact on the human body and small doses of radiation is dangerous, since in this case a violation of the hereditary information of the human body can occur, mutations occur.

A low level of development of a mild form of radiation sickness occurs at an equivalent radiation dose of approximately 1 Sv, a severe form of radiation sickness, in which half of all exposed people die, occurs at an equivalent radiation dose of 4.5 Sv. A 100% lethal outcome from radiation sickness corresponds to an equivalent radiation dose of 5.5–7.0 Sv.

Currently, a number of chemical preparations (protectors) have been developed that significantly reduce the negative effect of ionizing radiation on the human body.

In Russia, the maximum permissible levels of ionizing radiation and the principles of radiation safety are regulated by the "Radiation Safety Standards" NRB-76, "Basic Sanitary Rules for Working with Radioactive Substances and Other Sources of Ionizing Radiation" OSP72-80. In accordance with these regulatory documents, exposure standards are established for the following three categories of persons:

For category A persons, the main dose limit is the individual equivalent dose of external and internal radiation per year (Sv / year) depending on the radiosensitivity of organs (critical organs). This is the maximum allowable dose (MAD) - the highest value of the individual equivalent dose per year, which, with uniform exposure for 50 years, will not cause adverse changes in the health of personnel detected by modern methods.

For category A personnel, the individual equivalent dose ( H, Sv) accumulated in the critical organ over time T(years) from the beginning of professional work, should not exceed the value determined by the formula:

H = SDA ∙ T. In addition, the dose accumulated by the age of 30 should not exceed 12 SDA.

For category B, a dose limit per year (PD, Sv/year) is set, which is understood as the highest average value of the individual equivalent dose per calendar year for a critical group of people, at which uniform exposure for 70 years cannot cause adverse changes in the state of health, detected by modern methods. Table 1 shows the main dose limits of external and internal exposures depending on the radiosensitivity of organs.

Table 1 - Basic values ​​of dose limits for external and internal exposure

ionizing radiation causes a chain of reversible and irreversible changes in the body. The triggering mechanism of influence is the processes of ionization and excitation of atoms and molecules in tissues. The dissociation of complex molecules as a result of breaking chemical bonds is a direct effect of radiation. An important role in the formation of biological effects is played by radiation-chemical changes caused by the products of water radiolysis. Free radicals of hydrogen and hydroxyl group, having high activity, enter into chemical reactions with protein molecules, enzymes and other elements of biological tissue, which leads to disruption of biochemical processes in the body. As a result, metabolic processes are disturbed, tissue growth slows down and stops, new chemical compounds appear that are not characteristic of the body. This leads to disruption of the activity of individual functions and systems of the body.

Chemical reactions induced by free radicals develop with a high yield, involving hundreds and thousands of molecules that are not involved in radiation. This is the specificity of the action of ionizing radiation on biological objects. Effects develop over different periods of time: from a few seconds to many hours, days, years.

Ionizing radiation, when exposed to the human body, can cause two types of effects that clinical medicine refers to diseases: deterministic threshold effects (radiation sickness, radiation burn, radiation cataract, radiation infertility, anomalies in the development of the fetus, etc.) and stochastic (probabilistic) non-threshold effects (malignant tumors, leukemia, hereditary diseases).

Acute lesions develop with a single uniform gamma irradiation of the whole body and an absorbed dose above 0.5 Gy. At a dose of 0.25-0.5 Gy, temporary changes in the blood can be observed, which quickly normalize. In the dose range of 0.5-1.5 Gy, a feeling of fatigue occurs, less than 10% of those exposed may experience vomiting, moderate changes in the blood. At a dose of 1.5-2.0 Gy, a mild form of acute radiation sickness is observed, which is manifested by prolonged lymphopenia, in 30-50% of cases - vomiting on the first day after irradiation. Deaths are not recorded.

Radiation sickness of moderate severity occurs at a dose of 2.5-4.0 Gy. Almost all irradiated people experience nausea, vomiting on the first day, the content of leukocytes in the blood decreases sharply, subcutaneous hemorrhages appear, in 20% of cases death is possible, death occurs 2-6 weeks after irradiation. At a dose of 4.0-6.0 Gy, a severe form of radiation sickness develops, leading to death in 50% of cases during the first month. At doses exceeding 6.0 Gy, an extremely severe form of radiation sickness develops, which in almost 100% of cases ends in death due to hemorrhage or infectious diseases. The given data refer to cases where there is no treatment. Currently, there are a number of anti-radiation agents, which, with complex treatment, make it possible to exclude a lethal outcome at doses of about 10 Gy.

Chronic radiation sickness can develop with continuous or repeated exposure to doses significantly lower than those that cause an acute form. The most characteristic signs of chronic radiation sickness are changes in the blood, a number of symptoms from the nervous system, local skin lesions, lesions of the lens, pneumosclerosis (with plutonium-239 inhalation), and a decrease in the body's immunoreactivity.

The degree of exposure to radiation depends on whether the exposure is external (when a radioactive isotope enters the body) or internal. Internal exposure is possible through inhalation, ingestion of radioisotopes and their penetration into the body through the skin.

Some radioactive substances are absorbed and accumulated in specific organs, resulting in high local doses of radiation. Calcium, radium, strontium, etc. accumulate in the bones, iodine isotopes cause damage to the thyroid gland, rare earth elements cause predominantly liver tumors. Isotopes of cesium and rubidium are evenly distributed, causing oppression of hematopoiesis, testicular atrophy, and soft tissue tumors. With internal irradiation, the most dangerous alpha-emitting isotopes of polonium and plutonium.

The ability to cause long-term consequences: leukemia, malignant neoplasms, early aging is one of the insidious properties of ionizing radiation.

Hygienic regulation of ionizing radiation is carried out by the Radiation Safety Standards NRB-99 (Sanitary Rules SP 2.6.1.758-99). The main dose exposure limits and permissible levels are established for the following categories of exposed persons:

• - personnel - persons working with technogenic sources (group A) or who, due to the working conditions, are in the sphere of their influence (group B);
• - the entire population, including persons from the staff, outside the scope and conditions of their production activities.

For categories of exposed persons, three classes of standards are established: the main dose limits - PD (Table 3.13), permissible levels corresponding to the main dose limits, and control levels.

Table 3.13. Basic dose limits (extracted from NRB-99)

* For group B individuals, all dose limits should not exceed 0.25 of the group A dose limits.

Dose equivalent to NT n - absorbed dose in an organ or tissue From n, multiplied by the appropriate weighting factor for that radiation UYA:

The equivalent dose unit is J o kg-1, which has a special name - sievert (Sv).

The value of Ng for photons, electrons and muons of any energy is 1, for a-particles, fission fragments, heavy nuclei - 20.

Dose effective - a value used as a measure of the risk of long-term consequences of irradiation of the entire human body and its individual organs, taking into account their radiosensitivity. It is the sum of the products of the equivalent dose in the organ NxT to the appropriate weighting factor for a given organ or tissue ]¥t:

where NxT- equivalent dose in tissue G over time t.

The unit of measurement of the effective dose is the same as the equivalent dose, - J o kg "(sievert).

The Y/y values ​​for individual types of tissue and organs are given below.

Type of tissue, organ: ¥t

gonads .................................................. .............................................0.2

Bone marrow................................................ ...............................0.12

liver, mammary gland, thyroid gland...................0.05

leather................................................. ...............................................0.01

The main exposure dose limits do not include doses from natural and medical exposure, as well as doses resulting from radiation accidents. These types of exposure are subject to special restrictions.

The effective dose for personnel should not exceed 1000 mSv for the period of labor activity (50 years), and 7 mSv for the population for the period of life (70 years).

In table. 3.14 shows the values ​​of permissible radioactive contamination of work surfaces, leather, overalls, footwear, personal protective equipment for personnel.

Table 3.14. Permissible levels of radioactive contamination of work surfaces, leather, overalls, special footwear and personal protective equipment, part / (cm-1 - min) (extracted from NRB-99)

Object of pollution	a-active nuclides		(i-active nuclides
	separate	others
Intact skin, towels, special underwear, the inner surface of the front parts of personal protective equipment
Basic overalls, inner surface of additional personal protective equipment, outer surface of special footwear
The outer surface of additional personal protective equipment, removed in the sanitary locks
Surfaces of premises for periodic stay of personnel and equipment located in them