Ionizing radiation (hereinafter referred to as IR) is radiation whose interaction with matter leads to the ionization of atoms and molecules, i.e. this interaction leads to the excitation of the atom and the separation of individual electrons (negatively charged particles) from atomic shells. As a result, deprived of one or more electrons, the atom turns into a positively charged ion - primary ionization occurs. AI includes electromagnetic radiation(gamma radiation) and flows of charged and neutral particles - corpuscular radiation (alpha radiation, beta radiation, and neutron radiation).

Alpha radiation refers to corpuscular radiation. This is a stream of heavy positively charged alpha particles (nuclei of helium atoms) resulting from the decay of atoms of heavy elements such as uranium, radium and thorium. Since the particles are heavy, the range of alpha particles in a substance (that is, the path along which they produce ionization) turns out to be very short: hundredths of a millimeter in biological media, 2.5-8 cm in air. Thus, a regular sheet of paper or the outer dead layer of skin can trap these particles.

However, substances that emit alpha particles are long-lived. As a result of such substances entering the body with food, air or through wounds, they are carried throughout the body by the bloodstream, deposited in organs responsible for metabolism and protection of the body (for example, the spleen or The lymph nodes), thus causing internal irradiation of the body. The danger of such internal irradiation of the body is high, because these alpha particles create very big number ions (up to several thousand pairs of ions per 1 micron path in tissues). Ionization, in turn, determines a number of features of those chemical reactions that occur in matter, in particular in living tissue (the formation of strong oxidizing agents, free hydrogen and oxygen, etc.).

Beta radiation(beta rays, or stream of beta particles) also refers to the corpuscular type of radiation. This is a stream of electrons (β- radiation, or, most often, just β-radiation) or positrons (β+ radiation) emitted during the radioactive beta decay of the nuclei of certain atoms. Electrons or positrons are produced in the nucleus when a neutron converts to a proton or a proton to a neutron, respectively.

Electrons are much smaller than alpha particles and can penetrate 10-15 centimeters deep into a substance (body) (cf. hundredths of a millimeter for alpha particles). When passing through matter, beta radiation interacts with the electrons and nuclei of its atoms, expending its energy on this and slowing down the movement until it stops completely. Due to these properties, to protect against beta radiation, it is enough to have an organic glass screen of appropriate thickness. The use of beta radiation in medicine for superficial, interstitial and intracavitary radiation therapy is based on these same properties.

Neutron radiation- another type of corpuscular type of radiation. Neutron radiation is a flow of neutrons (elementary particles that have no electrical charge). Neutrons do not have an ionizing effect, but a very significant ionizing effect occurs due to elastic and inelastic scattering on the nuclei of matter.

Substances irradiated by neutrons can acquire radioactive properties, that is, receive so-called induced radioactivity. Neutron radiation is generated during the operation of particle accelerators, in nuclear reactors, industrial and laboratory installations, during nuclear explosions, etc. Neutron radiation has the greatest penetrating ability. The best materials for protection against neutron radiation are hydrogen-containing materials.

Gamma rays and x-rays belong to electromagnetic radiation.

The fundamental difference between these two types of radiation lies in the mechanism of their occurrence. X-ray radiation is of extranuclear origin, gamma radiation is a product of nuclear decay.

X-ray radiation was discovered in 1895 by the physicist Roentgen. This is invisible radiation capable of penetrating, although varying degrees, in all substances. It is electromagnetic radiation with a wavelength of the order of - from 10 -12 to 10 -7. The source of X-rays is an X-ray tube, some radionuclides (for example, beta emitters), accelerators and electron storage devices (synchrotron radiation).

The X-ray tube has two electrodes - the cathode and the anode (negative and positive electrodes, respectively). When the cathode is heated, electron emission occurs (the phenomenon of the emission of electrons by the surface solid or liquid). Electrons escaping from the cathode are accelerated electric field and hit the surface of the anode, where they are sharply decelerated, resulting in the generation of X-ray radiation. Like visible light, X-ray radiation causes blackening of photographic film. This is one of its properties, fundamental for medicine - that it is penetrating radiation and, accordingly, the patient can be illuminated with its help, and since tissues of different densities absorb x-rays differently - we can diagnose this on our own early stage many types of diseases of internal organs.

Gamma radiation is of intranuclear origin. It occurs during the decay of radioactive nuclei, the transition of nuclei from an excited state to the ground state, during the interaction of fast charged particles with matter, the annihilation of electron-positron pairs, etc.

The high penetrating power of gamma radiation is explained by its short wavelength. To weaken the flow of gamma radiation, substances with a significant mass number (lead, tungsten, uranium, etc.) and various compositions are used high density(various concretes with metal fillers).

Kinds ionizing radiation

Ionizing radiation (IR) - flows of elementary particles (electrons, positrons, protons, neutrons) and quanta electromagnetic energy, the passage of which through a substance leads to ionization (formation of oppositely polar ions) and excitation of its atoms and molecules. Ionization - the transformation of neutral atoms or molecules into electrically charged particles - ions. bII reach the Earth in the form of cosmic rays, arise as a result of the radioactive decay of atomic nuclei (απ β-particles, γ- and X-rays), are created artificially at accelerators of charged particles. Of practical interest are the most common types of IR - fluxes of a- and β-particles, γ-radiation, X-rays and neutron fluxes.

Alpha radiation(a) – flow of positively charged particles – helium nuclei. Currently, more than 120 artificial and natural alpha radioactive nuclei are known, which, when emitting an alpha particle, lose 2 protons and 2 neutrons. The speed of particles during decay is 20 thousand km/s. At the same time, α-particles have the smallest penetrating ability; their path length (the distance from the source to absorption) in the body is 0.05 mm, in air - 8–10 cm. They cannot even pass through a sheet of paper, but the ionization density per unit The range is very large (by 1 cm up to tens of thousands of pairs), so these particles have the greatest ionizing ability and are dangerous inside the body.

Beta radiation(β) – flow of negatively charged particles. Currently, about 900 beta radioactive isotopes are known. The mass of β-particles is several tens of thousands of times less than α-particles, but they have greater penetrating power. Their speed is 200–300 thousand km/s. The path length of the flow from the source in air is 1800 cm, in human tissue - 2.5 cm. β-particles are completely retained hard materials(3.5 mm aluminum plate, organic glass); their ionizing ability is 1000 times less than that of α particles.

Gamma radiation(γ) – electromagnetic radiation with a wavelength from 1 · 10 -7 m to 1 · 10 -14 m; emitted when fast electrons in a substance decelerate. It occurs during the decay of most radioactive substances and has great penetrating power; travels at the speed of light. In electrical and magnetic fieldsγ-rays are not deflected. This radiation has a lower ionizing ability than a- and beta-radiation, since the ionization density per unit length is very low.

X-ray radiation can be obtained in special X-ray tubes, in electron accelerators, during the deceleration of fast electrons in matter and during the transition of electrons from the outer electron shells of an atom to the inner ones, when ions are created. X-rays, like γ-radiation, have a low ionizing ability, but a large penetration depth.

Neutrons - elementary particles atomic nucleus, their mass is 4 times less than the mass of α-particles. Their life time is about 16 minutes. Neutrons have no electrical charge. The path length of slow neutrons in air is about 15 m, in biological environment– 3 cm; for fast neutrons - 120 m and 10 cm, respectively. The latter have high penetrating ability and represent the most great danger.

There are two types of ionizing radiation:

Corpuscular, consisting of particles with a rest mass different from zero (α-, β– and neutron radiation);

Electromagnetic (γ- and X-ray radiation) - with a very short wavelength.

To assess the impact of ionizing radiation on any substances and living organisms, special quantities are used - radiation doses. The main characteristic of the interaction of ionizing radiation and the environment is the ionization effect. In the initial period of development of radiation dosimetry, it was most often necessary to deal with X-ray radiation propagating in the air. Therefore, the degree of ionization of the air in X-ray tubes or devices was used as a quantitative measure of the radiation field. A quantitative measure based on the amount of ionization of dry air at normal atmospheric pressure, which is fairly easy to measure, is called the exposure dose.

Exposure dose determines the ionizing ability of x-rays and γ-rays and expresses the radiation energy converted into the kinetic energy of charged particles per unit mass atmospheric air. Exposure dose is the ratio of the total charge of all ions of the same sign in an elementary volume of air to the mass of air in this volume. The SI unit of exposure dose is the coulomb divided by kilogram (C/kg). The non-systemic unit is the roentgen (R). 1 C/kg = 3880 R. When expanding the circle known species ionizing radiation and the areas of its application, it turned out that the measure of the impact of ionizing radiation on matter cannot be easily determined due to the complexity and diversity of the processes occurring in this case. The most important of them, giving rise to physical and chemical changes in the irradiated substance and leading to a certain radiation effect, is the absorption of the energy of ionizing radiation by the substance. As a result, the concept of absorbed dose arose.

Absorbed dose shows how much radiation energy is absorbed per unit mass of any irradiated substance, and is determined by the ratio of the absorbed energy of ionizing radiation to the mass of the substance. The unit of measurement of absorbed dose in the SI system is the gray (Gy). 1 Gy is the dose at which 1 J of ionizing radiation energy is transferred to a mass of 1 kg. The extrasystemic unit of absorbed dose is the rad. 1 Gy = 100 rad. A study of individual consequences of irradiation of living tissues showed that at the same absorbed doses different kinds Radiation produces different biological effects on the body. This is due to the fact that a heavier particle (for example, a proton) produces more ions per unit path in the tissue than a lighter particle (for example, an electron). For the same absorbed dose, the higher the radiobiological destructive effect, the denser the ionization created by the radiation. To take this effect into account, the concept of equivalent dose was introduced.

Equivalent dose is calculated by multiplying the value of the absorbed dose by a special coefficient - the coefficient of relative biological effectiveness (RBE) or quality coefficient. The coefficient values ​​for various types of radiation are given in table. 7.

Table 7

Relative biological effectiveness coefficient for various types of radiation

The SI unit of dose equivalent is the sievert (Sv). The value of 1 Sv is equal to the equivalent dose of any type of radiation absorbed in 1 kg of biological tissue and creating the same biological effect as the absorbed dose of 1 Gy of photon radiation. The non-systemic unit of measurement of equivalent dose is the rem (biological equivalent of rad). 1 Sv = 100 rem. Some human organs and tissues are more sensitive to the effects of radiation than others: for example, with the same equivalent dose, cancer is more likely to occur in the lungs than in thyroid gland, and irradiation of the gonads is especially dangerous due to the risk of genetic damage. Therefore, radiation doses different organs and tissues should be taken into account with different coefficients, which is called the radiation risk coefficient. Multiplying the equivalent dose value by the corresponding radiation risk coefficient and summing over all tissues and organs, we obtain effective dose, reflecting the total effect on the body. Weighted coefficients are established empirically and calculated in such a way that their sum for the entire organism is unity. Units effective dose coincide with the units of measurement of the equivalent dose. It is also measured in sieverts or rem.

Introduction………………………………………………………………………………..3

1. Types of radiation……………………………………………………………….5

2. Radiation safety regulation…………………………………10

3. Main dose limits................................................................... ...........................13

4. Permissible and control levels of exposure……………………………18

Conclusion………………………………………………………………………………….26

List of sources used…………………………………………….28

INTRODUCTION

Among the questions of scientific interest, few attract such constant public attention and cause so much controversy as the question of the effects of radiation on humans and environment.

Unfortunately, reliable scientific information on this issue very often does not reach the population, which therefore uses all sorts of rumors. Too often, the arguments of opponents of nuclear energy are based solely on feelings and emotions, just as often the speeches of supporters of its development come down to poorly substantiated reassuring assurances.

The UN Scientific Committee on the Effects of Atomic Radiation collects and analyzes all available information about the sources of radiation and its effects on humans and the environment. He studies a wide range of natural and man-made sources of radiation, and his findings may surprise even those who closely follow public discourse on the topic.

Radiation is truly deadly. At large doses it causes severe tissue damage, and in minor cases it can cause cancer and induce genetic defects that may appear in the children and grandchildren of the person exposed to radiation, or in his more distant descendants.

But for the bulk of the population, the most dangerous sources of radiation are not the ones that are talked about the most. The highest dose a person receives from natural sources radiation. Radiation associated with the development of nuclear energy is only a small fraction of the radiation generated by human activity; We receive significantly larger doses from other forms of this activity that cause much less criticism, for example, from the use of X-rays in medicine. In addition, forms of daily activity such as burning coal and the use of air transport, especially constant exposure to well-sealed rooms, can lead to significant increases in exposure levels due to natural radiation. The greatest reserves for reducing radiation exposure of the population lie precisely in such “indisputable” forms of human activity.

This work covers various types of radiation, both from natural and man-made sources, affecting humans and the environment, provides regulatory sources of information on radiation safety, dose limits of exposure and their permissible and control levels.

TYPES OF RADIATION

Penetrating radiation poses a great danger to human health and life. In large doses it causes serious damage to body tissues, acute radiation sickness develops, in small doses it causes cancer, and provokes genetic defects. In nature, there are a number of elements whose atomic nuclei transform into the nuclei of other elements. These transformations are accompanied by radiation - radioactivity. Ionizing radiation is a stream of elementary particles and quanta of electromagnetic radiation that can cause ionization of atoms and molecules of the medium in which they propagate.

Different types of radiation are accompanied by the release of different amounts of energy and have different penetrating abilities, so they have different effects on the tissues of a living organism (Fig. 1). Alpha radiation, which is a stream of heavy particles consisting of neutrons and protons, is blocked by, for example, a sheet of paper and is practically unable to penetrate the outer layer of skin formed by dead cells. Therefore, it does not pose a danger until radioactive substances emitting α-particles enter the body through an open wound, with food or with inhaled air; then they become extremely dangerous. Beta radiation has greater penetrating power: it penetrates the body tissue to a depth of one to two centimeters. The penetrating power of gamma radiation, which travels at the speed of light, is very high: only a thick lead or concrete slab can stop it. Due to their very high penetrating power, gamma radiation poses a great danger to humans. The peculiarity of ionizing radiation is that a person will begin to feel its effects only after some time has passed.

Rice. 1. Three types of radiation and their penetrating ability

Sources of radiation can be natural, present in nature, and independent of humans.

The population of the globe receives the bulk of exposure from natural sources of radiation (Fig. 2).

Rice. 2. Average annual effective equivalent doses of radiation from natural and man-made sources of radiation (the numbers indicate the dose in millisieverts)

Most of them are such that it is absolutely impossible to avoid exposure to radiation from them. Throughout the history of the Earth different types radiation falls on the surface of the Earth from space and comes from radioactive substances located in earth's crust. A person is exposed to radiation in two ways. Radioactive substances can be outside the body and irradiate it from the outside; in this case we talk about external irradiation. Or they may end up in the air a person breathes, in food or water and enter the body. This method of irradiation is called internal.

Every inhabitant of the Earth is exposed to radiation from natural sources of radiation, but some of them receive higher doses than others. This depends, in part, on where they live. The level of radiation in some places on the globe, where particularly radioactive rocks occur, turns out to be significantly higher than average, and in other places it is correspondingly lower. The radiation dose also depends on people's lifestyle. The use of certain building materials, the use of gas for cooking, open charcoal grills, sealing of rooms and even flying in airplanes all increase exposure through natural sources of radiation.

Terrestrial sources of radiation are collectively responsible for the majority of exposure to which humans are exposed through natural radiation. On average, they provide more than 5/6 of the annual effective equivalent dose received by the population, mainly due to internal exposure. The rest is contributed by cosmic rays, mainly through external irradiation (Fig. 3).

Rice. 3. Average annual effective equivalent doses of radiation from natural radiation sources (numbers indicate dose in millisieverts)

According to some data, the average effective equivalent dose of external radiation that a person receives per year from terrestrial sources of natural radiation is approximately 350 microsieverts, i.e. slightly more than the average individual radiation dose due to background radiation created by cosmic rays at sea level.

On average, approximately 2/3 of the effective equivalent dose of radiation that a person receives from natural sources of radiation comes from radioactive substances that enter the body through food, water and air.

It has been established that of all natural sources of radiation, the greatest danger is radon, a heavy, colorless and odorless gas. It is released from the earth's crust everywhere, but its concentration in the outside air varies significantly at different points Globe. A person receives the main radiation from radon while in indoors. Radon concentrates in the air indoors only when they are sufficiently isolated from the external environment. Seeping through the foundation and floor from the soil or, less commonly, from building materials, radon accumulates indoors. The most common building materials - wood, brick and concrete - emit relatively little radon. Granite, pumice, products made from alumina raw materials, and phosphogypsum have much greater specific radioactivity.

Another source of radon entering residential premises is water and natural gas. The concentration of radon in commonly used water is extremely low, but water from deep wells or artesian wells contains very high levels of radon. However, the main danger does not come from drinking, even with high radon levels. Usually people use boiled water or in the form of hot drinks, and when boiled, radon almost completely evaporates. The greatest danger is the ingress of water vapor from high content radon into the lungs along with the inhaled air, which most often occurs in the bathroom or in the steam room. Radon enters natural gas underground. As a result of pre-processing and during the storage of gas before it reaches the consumer, most of the radon evaporates, but the concentration of radon can increase if the cookstoves are not equipped with an exhaust hood. Consequently, radon is especially dangerous for low-rise buildings with carefully sealed rooms (to retain heat) and when using alumina as an additive to building materials.

Other sources of radiation that pose a danger, unfortunately, are created by man himself. Radiation is currently widely used in various fields: medicine, industry, agriculture, chemistry, science, etc. The sources of artificial radiation are artificial radionuclides created with the help of nuclear reactors and accelerators, a beam of neutrons and charged particles. They are called man-made sources of ionizing radiation. All activities related to the production and use of artificial radiation are strictly controlled. The tests of nuclear weapons in the atmosphere, accidents at nuclear power plants and nuclear reactors and the results of their work, manifested in radioactive fallout and radioactive waste, stand out specially in terms of their impact on the human body. When radioactive fallout occurs in some areas of the Earth, radiation can enter the human body directly through agricultural products and food.

An important property of radioactivity is ionizing radiation. Researchers discovered the danger of this phenomenon for a living organism from the very beginning of the discovery of radioactivity. Thus, A. Becquerel and M. Curie-Sklodowska, who studied the properties of radioactive elements, received severe skin burns from radium radiation.

Ionizing radiation is any radiation whose interaction with a medium leads to the formation of electrical charges of different signs. The following types of ionizing radiation are distinguished: α-, β-radiation, photon and neutron radiation. Ultraviolet radiation and visible part light spectrum is not classified as ionizing radiation. The above types of radiation have different penetrating powers (Fig. 3.6), depending on the carrier and radiation energy.

Radiation energy is measured in electron volts (eV). The energy that an electron acquires when moving in an accelerating electric field with a potential difference of 1 V is taken as 1 eV. In practice, decimal multiples are more often used: kiloelectron-volt (1 keV = 103 eV) and megaelectronvolt (1 MeV = 10 eV). The relationship between the electron volt and the system unit of energy J is given by the expression: 1 eV = 1.6 10 -19 J.

Alpha radiation (α-radiation) is ionizing radiation, which is a stream of relatively heavy particles (helium nuclei consisting of two protons and two neutrons) emitted during nuclear transformations. The energy of α particles is on the order of several megaelectron volts and varies for different radionuclides. In this case, some radionuclides emit α-particles of several energies.

This type of radiation, having a short path length of particles, is characterized by weak penetrating ability, being delayed even by a piece of paper. For example, the range of alpha particles with an energy of 4 MeV in air is 2.5 cm, but in biological tissue it is only 31 microns. Radiation is practically unable to penetrate the outer layer of skin formed by dead cells. Therefore, alpha radiation is not dangerous until radioactive substances emitting alpha particles enter the body through the respiratory, digestive or open wounds and burn surfaces. The degree of danger of a radioactive substance depends on the energy of the particles it emits. Since the ionization energy of one atom is a few to tens of electron volts, each α particle is capable of ionizing up to 100,000 molecules inside the body.

Beta radiation is a stream of β-particles (electrons and positrons), which have greater penetrating power compared to α-radiation. Emitted particles have a continuous energy spectrum, distributed in energy from zero to a certain maximum value, characteristic of a given radionuclide. The maximum energy of the β spectrum of various radionuclides lies in the range from several keV to several MeV.

The range of β-particles in the air can reach several meters, and in biological tissue several centimeters. Thus, the range of electrons with an energy of 4 MeV in air is 17.8 m, and in biological tissue 2.6 cm. However, they are easily retained by a thin sheet of metal. Like α-radiation sources, β-active radionuclides are more dangerous when ingested.

Photon radiation includes x-rays and gamma radiation (γ-rays). After radioactive decay, the atomic nucleus of the final product often appears in an excited state. The transition of the nucleus from this state to a lower energy level (to the normal state) occurs with the emission of gamma quanta. Thus, γ-radiation is of intranuclear origin and is a rather hard electromagnetic radiation with a wavelength of 10 -8 –10 -11 nm.

The energy of a γ-radiation quantum E (in eV) is related to the wavelength by the relation

where λ is expressed in nanometers (1 nm = 10 -9 m).

Propagating at the speed of light, γ-rays have a high penetrating ability, much greater than α and β particles. They can only be stopped by a thick lead or concrete slab. The higher the energy of γ-radiation and, accordingly, the shorter its wavelength, the higher the penetrating ability. Typically, the energy of gamma rays lies in the range from several keV to several MeV.

Unlike γ-rays, X-rays are of atomic origin. It is formed in excited atoms during the transition of electrons from distant orbits to an orbit closer to the nucleus or occurs when charged particles in matter decelerate. Accordingly, the first has a discrete energy spectrum and is called characteristic, the second has a continuous spectrum and is called bremsstrahlung. The X-ray energy range is from hundreds of electron volts to tens of kiloelectron volts. Despite the different origins of these radiations, their nature is the same, and therefore X-ray and γ-radiation are called photon radiation.

Under the influence of photon radiation, the entire body is irradiated. It is the main damaging factor when the body is exposed to radiation from external sources.

Neutron radiation occurs during the fission of heavy nuclei and in other nuclear reactions. Sources of neutron radiation at nuclear power plants are nuclear reactors, the neutron flux density in which is 10 10 –10 14 neutrons/(cm s); isotope sources containing natural or artificial radionuclides mixed with a substance that emits neutrons under the influence of bombardment by its α -particles or γ-quanta. Such sources are used for calibration of control and measuring equipment. They produce fluxes of the order of 10 7 –10 8 neutrons/s.

Depending on the energy, neutrons are divided into the following types: slow, or thermal (with average energy ~ 0.025 eV); resonant (with energy up to 0.5 keV); intermediate (with energy from 0.5 keV to 0.5 MeV); fast (with energy from 0.5 to 20 MeV); ultrafast (with energy above 20 MeV).

When neutrons interact with matter, two types of processes are observed: neutron scattering and nuclear reactions, including forced fission of heavy nuclei. It is with the latter type of interactions that the occurrence of a chain reaction that occurs during an atomic explosion is associated (uncontrollable chain reaction) and in nuclear reactors (controlled chain reaction) and accompanied by the release of huge amounts of energy.

The penetrating power of neutron radiation is comparable to γ ​​radiation. Thermal neutrons are effectively absorbed by materials containing boron, graphite, lead, lithium, gadolinium and some other substances; Fast neutrons are effectively slowed down by paraffin, water, concrete, etc.

Basic concepts of dosimetry. Having different penetrating abilities, ionizing radiation various types have different effects on the tissues of a living organism. In this case, the more damage caused by radiation will be, the greater the energy that affects the biological object. The amount of energy transferred to the body during ionizing exposure is called the dose.

The physical basis of the dose of ionizing radiation is the transformation of radiation energy in the process of its interaction with atoms or their nuclei, electrons and molecules of the irradiated medium, as a result of which part of this energy is absorbed by the substance. Absorbed energy is the root cause of the processes leading to the observed radiation-induced effects, and therefore dosimetric quantities are related to the absorbed radiation energy.

The radiation dose can be received from any radionuclide or from a mixture of them, regardless of whether they are outside the body or inside it as a result of exposure to food, water or air. Doses are calculated differently depending on the size of the irradiated area and where it is located, whether one person or a group of people were exposed, and for how long.

The amount of energy absorbed per unit mass of the irradiated organism is called the absorbed dose and is measured in SI units in grays (Gy). The unit of gray is joule divided by kilogram of mass (J/kg). However, the absorbed dose value does not take into account the fact that, at the same absorbed dose, α-radiation and neutron radiation are much more dangerous than β-radiation or γ-radiation. Therefore, for a more accurate assessment of the degree of damage to the body, the absorbed dose must be increased by a certain coefficient, reflecting the ability of radiation of a given type to damage biological objects. This factor is called the radiation weighting factor. Its value for β and γ radiation is taken equal to 1, for α radiation – 20, for neutron radiation varies in the range of 5–20 depending on the neutron energy.

The dose recalculated in this way is called the equivalent dose, which is measured in sieverts (Sv) in the SI system. The dimension of a sievert is the same as that of a gray – J/kg. The dose received per unit time is classified in the SI system as dose rate and has the dimension Gy/s or Sv/s. In the SI system, it is permissible to use non-system units of time, such as hour, day, year, therefore, when calculating doses, such dimensions as Sv/h, Sv/day, Sv/year are used.

Until now, in geophysics, geology and partly in radioecology, a non-systemic dose unit is used - the x-ray. This value was introduced at the dawn of the atomic era (in 1928) and was used to measure the exposure dose. X-rays are equal to the dose of γ-radiation that creates in one cubic centimeter of dry air a total charge of ions equal to one unit of electric charge. When measuring the exposure dose of γ-radiation in air, the relationship between X-rays and gray is used: 1 P = 8.77 mJ/kg or 8.77 mGy. Accordingly, 1 Gy = 114 R.

In dosimetry, one more extra-systemic unit has been preserved - the rad, equal to the absorbed radiation dose, at which 1 kg of the irradiated substance absorbs energy equal to 0.01 J. Accordingly, I rad = 100 erg/g = 0.01 Gy. This unit is currently falling out of use.

When calculating doses received by the body, it should be taken into account that some parts of the body (organs, tissues) are more sensitive to radiation than others. In particular, at the same equivalent dose, lung damage is more likely than e.g. thyroid gland. Interna

The Russian Commission on Radiation Protection (ICRP) has developed conversion factors that are recommended for use when assessing the radiation dose to various human organs and biological tissues (Fig. 3.7).

After multiplying the equivalent dose value for of this body by the appropriate coefficient and summing it over all organs and tissues, an effective equivalent dose is obtained, reflecting the total effect of radiation on the body. This dose is also measured in sieverts. The described concept of dose characterizes only individually received doses.

When it is necessary to study the effects of radiation on a group of people, the concept of collective effective equivalent dose is used, which is equal to the sum of individual effective equivalent doses and is measured in man-sieverts (man-Sv).

Since many radionuclides decay very slowly and will affect the population in the distant future, many more generations of people living on the planet will receive a collective effective equivalent dose from such sources. To assess the indicated dose, the concept of the expected (total) collective effective equivalent dose has been introduced, which makes it possible to predict the damage to a group of people from the action of constant sources of radiation. For clarity, the system of concepts described above is illustrated in Fig. 3.8.

Beta, gamma.

How are they formed?

All of the above types of radiation are generated by the process of isotope decay simple substances. The atoms of all elements consist of a nucleus and electrons that revolve around it. The nucleus is one hundred thousand times smaller than the entire atom, but due to its extremely high density, its mass is almost equal to the total mass of the entire atom. The nucleus contains positively charged particles - protons and neutrons that have no electrical charge. Both of them are interconnected very tightly. The number of protons in the nucleus determines which particular atom belongs to, for example, 1 proton in the nucleus is hydrogen, 8 protons are oxygen, 92 protons are uranium. in an atom corresponds to the number of protons in its nucleus. Each electron has a negative electrical charge equal to that of a proton, which is why the atom as a whole is neutral.

Those atoms that have nuclei identical in the number of protons, but different in the number of neutrons, are variants of one chemical substance and are called its isotopes. In order to somehow distinguish them, a number is assigned to the symbol denoting an element, which is the sum of all particles located in the nucleus of this isotope. For example, the nucleus of the element uranium-238 includes 92 protons, as well as 146 neutrons, and uranium-235 also has 92 protons, but there are already 143 neutrons. Most isotopes are unstable. For example, uranium-238, the bonds between protons and neutrons in the nucleus of which are very weak and sooner or later a compact group consisting of a pair of neutrons and a pair of protons will separate from it, turning uranium-238 into another element - thorium-234, also an unstable element, the nucleus of which contains 144 neutrons and 90 protons. Its decay will continue a chain of transformations that will end with the formation of a lead atom. During each of these decays, energy is released, giving rise to various types of

To simplify the situation, we can describe the emergence of different types as follows: a nucleus emits a nucleus, which consists of a pair of neutrons and a pair of protons; beta rays come from an electron. And there are situations in which the isotope is so excited that the output of the particle does not completely stabilize it, and then it dumps excess pure energy in one portion, this process is called gamma radiation. Types of radiation such as gamma rays and similar x-rays are formed without the emission of material particles. The time it takes for half of all atoms of any particular isotope in any radioactive source to decay is called the half-life. The process of atomic transformations is continuous, and its activity is estimated by the number of decays that occur in one second and is measured in becquerels (1 atom per second).

Different types of radiation are characterized by the release of different amounts of energy, and their penetrating ability is also different, therefore they also have different effects on the tissues of living organisms.

Alpha radiation, which is a stream of heavy particles, can trap even a piece of paper; it is not able to penetrate the layer of dead epidermal cells. It is not dangerous until substances that emit alpha particles enter the body through wounds or through food and/or inhaled air. That's when they will become extremely dangerous.

Beta radiation is capable of penetrating 1-2 centimeters into the tissues of a living organism.

Gamma rays, which travel at the speed of light, are the most dangerous and can only be stopped by a thick slab of lead or concrete.

All types of radiation can cause damage to a living organism, and the greater the damage, the more energy has been transferred to the tissues.

In case of various accidents at nuclear facilities and during military operations with the use of nuclear weapons, it is important to consider the damaging factors affecting the body in a comprehensive manner. In addition to the obvious physical effects, different types of electromagnetic radiation also have a detrimental effect on humans.