Impact on the body of ionizing radiation. Consequences of exposure to ionizing radiation on the human body during external and internal exposure, surface contamination with radioactive substances

Ionizing radiation is a type of energy released by atoms in the form of electromagnetic waves or particles.
People are exposed to natural sources of ionizing radiation such as soil, water, plants, and man-made sources such as X-rays and medical devices.
Ionizing radiation has numerous beneficial uses, including in medicine, industry, agriculture, and scientific research.
As the use of ionizing radiation increases, so does the potential for health hazards if it is used or restricted inappropriately.
Acute health effects such as skin burn or acute radiation syndrome can occur when the radiation dose exceeds certain levels.
Low doses of ionizing radiation may increase the risk of longer term effects such as cancer.

What is ionizing radiation?

Ionizing radiation is a form of energy released by atoms in the form of electromagnetic waves (gamma or x-rays) or particles (neutrons, beta or alpha). The spontaneous decay of atoms is called radioactivity, and the excess energy that results from this is a form of ionizing radiation. Unstable elements formed during decay and emitting ionizing radiation are called radionuclides.

All radionuclides are uniquely identified by the type of radiation they emit, the energy of the radiation, and their half-life.

Activity, used as a measure of the amount of radionuclide present, is expressed in units called becquerels (Bq): one becquerel is one decay event per second. The half-life is the time required for the activity of a radionuclide to decay to half its original value. The half-life of a radioactive element is the time it takes for half of its atoms to decay. It can range from fractions of a second to millions of years (for example, the half-life of iodine-131 is 8 days, and the half-life of carbon-14 is 5730 years).

Radiation sources

People are exposed to natural and artificial radiation every day. Natural radiation comes from numerous sources, including over 60 naturally occurring radioactive substances in soil, water and air. Radon, a naturally occurring gas, is formed from rocks and soil and is the main source of natural radiation. Every day people inhale and absorb radionuclides from air, food and water.

Humans are also exposed to natural radiation from cosmic rays, especially at high altitudes. On average, 80% of the annual dose that a person receives from background radiation is from naturally occurring terrestrial and space sources of radiation. The levels of such radiation vary in different rheographic zones, and in some areas the level can be 200 times higher than the global average.

Humans are also exposed to radiation from man-made sources, from nuclear power generation to the medical use of radiation diagnosis or treatment. Today, the most common artificial sources of ionizing radiation are medical devices, such as x-ray machines, and other medical devices.

Exposure to ionizing radiation

Exposure to radiation can be internal or external and can occur in a variety of ways.

Internal impact Ionizing radiation occurs when radionuclides are inhaled, ingested, or otherwise enter the circulation (eg, by injection, injury). Internal exposure stops when the radionuclide is excreted from the body, either spontaneously (with feces) or as a result of treatment.

External radioactive contamination can occur when radioactive material in the air (dust, liquid, aerosols) is deposited on the skin or clothing. Such radioactive material can often be removed from the body by simple washing.

Exposure to ionizing radiation may also occur as a result of external radiation from a suitable external source (eg, such as exposure to radiation emitted by medical x-ray equipment). External exposure stops when the radiation source is closed, or when a person goes outside the radiation field.

Exposure to ionizing radiation can be classified into three types of exposure.

The first case is planned exposure, which is due to the deliberate use and operation of radiation sources for specific purposes, for example, in the case of medical use of radiation for the diagnosis or treatment of patients, or use of radiation in industry or for scientific research purposes.

The second case is existing sources of exposure, where radiation exposure already exists and for which appropriate control measures need to be taken, such as exposure to radon in homes or workplaces, or exposure to natural background radiation in environmental conditions.

The last case is exposure to emergencies caused by unexpected events requiring prompt action, such as nuclear incidents or malicious acts.

Health effects of ionizing radiation

Radiation damage to tissues and/or organs depends on the received radiation dose or absorbed dose, which is expressed in grays (Gy). The effective dose is used to measure ionizing radiation in terms of its potential to cause harm. Sievert (Sv) is a unit of effective dose, which takes into account the type of radiation and the sensitivity of tissues and organs.

Sievert (Sv) is a unit of weighted dose of radiation, also called effective dose. It makes it possible to measure ionizing radiation in terms of the potential for harm. Sv takes into account the type of radiation and the sensitivity of organs and tissues.
Sv is a very large unit, so it is more practical to use smaller units such as millisievert (mSv) or microsievert (µSv). One mSv contains 1000 µSv, and 1000 mSv equals 1 Sv. In addition to the amount of radiation (dose), it is often useful to show the release rate of that dose, such as µSv/hour or mSv/year.

Above certain thresholds, exposure may impair tissue and/or organ function and may cause acute reactions such as reddening of the skin, hair loss, radiation burns, or acute radiation syndrome. These reactions are stronger at higher doses and higher dose rates. For example, the threshold dose for acute radiation syndrome is approximately 1 Sv (1000 mSv).

If the dose is low and/or a long period of time is applied (low dose rate), the resulting risk is significantly reduced, since in this case the likelihood of repair of damaged tissues increases. However, there is a risk of long-term consequences, such as cancer that may take years or even decades to appear. Effects of this type do not always appear, but their probability is proportional to the radiation dose. This risk is higher in the case of children and adolescents, as they are much more sensitive to the effects of radiation than adults.

Epidemiological studies in exposed populations, such as atomic bomb survivors or radiotherapy patients, have shown a significant increase in the likelihood of cancer at doses above 100 mSv. In some cases, more recent epidemiological studies in humans exposed as children for medical purposes (Childhood CT) suggest that the likelihood of cancer may be increased even at lower doses (in the range of 50-100 mSv) .

Prenatal exposure to ionizing radiation can cause fetal brain damage at high doses in excess of 100 mSv between 8 and 15 weeks of gestation and 200 mSv between 16 and 25 weeks of gestation. Human studies have shown that there is no radiation-related risk to fetal brain development before 8 weeks or after 25 weeks of gestation. Epidemiological studies suggest that the risk of developing fetal cancer after exposure to radiation is similar to the risk after exposure to radiation in early childhood.

WHO activities

WHO has developed a radiation program to protect patients, workers and the public from the health hazards of radiation in planned, existing and emergency exposures. This program, which focuses on public health aspects, covers activities related to exposure risk assessment, management and communication.

Under its core function of “norm-setting, enforcement and monitoring”, WHO is collaborating with 7 other international organizations to revise and update international standards for basic radiation safety (BRS). WHO adopted new international PRSs in 2012 and is currently working to support the implementation of PRSs in its Member States.

In everyday life, ionizing radiation is constantly encountered. We do not feel them, but we cannot deny their impact on animate and inanimate nature. Not so long ago, people learned to use them both for good and as weapons of mass destruction. With proper use, these radiations can change the life of mankind for the better.

Types of ionizing radiation

To understand the peculiarities of the influence on living and non-living organisms, you need to find out what they are. It is also important to know their nature.

Ionizing radiation is a special wave that can penetrate through substances and tissues, causing ionization of atoms. There are several types of it: alpha radiation, beta radiation, gamma radiation. All of them have a different charge and ability to act on living organisms.

Alpha radiation is the most charged of all types. It has tremendous energy, capable of causing radiation sickness even in small doses. But with direct irradiation, it penetrates only into the upper layers of human skin. Even a thin sheet of paper protects against alpha rays. At the same time, getting into the body with food or with inhalation, the sources of this radiation quickly become the cause of death.

Beta rays carry a slightly lower charge. They are able to penetrate deep into the body. With prolonged exposure, they cause death of a person. Smaller doses cause a change in the cellular structure. A thin sheet of aluminum can serve as protection. Radiation from within the body is also deadly.

The most dangerous is considered to be gamma radiation. It penetrates through the body. In large doses, it causes radiation burns, radiation sickness, and death. The only protection against it can be lead and a thick layer of concrete.

X-rays are considered to be a special kind of gamma radiation, which are generated in an X-ray tube.

Research History

For the first time, the world learned about ionizing radiation on December 28, 1895. It was on this day that Wilhelm K. Roentgen announced that he had discovered a special kind of rays that could pass through various materials and the human body. From that moment, many doctors and scientists began to actively work with this phenomenon.

For a long time, no one knew about its effect on the human body. Therefore, in history there are many cases of death from excessive exposure.

The Curies have studied in detail the sources and properties that ionizing radiation has. This made it possible to use it with maximum benefit, avoiding negative consequences.

Natural and artificial sources of radiation

Nature has created a variety of sources of ionizing radiation. First of all, it is the radiation of sunlight and space. Most of it is absorbed by the ozone layer, which is high above our planet. But some of them reach the surface of the Earth.

On the Earth itself, or rather in its depths, there are some substances that produce radiation. Among them are isotopes of uranium, strontium, radon, cesium and others.

Artificial sources of ionizing radiation are created by man for a variety of research and production. At the same time, the strength of radiation can be many times higher than natural indicators.

Even in conditions of protection and compliance with safety measures, people receive doses of radiation that are hazardous to health.

Units of measurement and doses

Ionizing radiation is usually correlated with its interaction with the human body. Therefore, all units of measurement are somehow related to the ability of a person to absorb and accumulate ionization energy.

In the SI system, doses of ionizing radiation are measured in units called grays (Gy). It shows the amount of energy per unit of irradiated substance. One Gy equals one J/kg. But for convenience, the off-system unit rad is more often used. It is equal to 100 Gr.

The radiation background on the ground is measured by exposure doses. One dose is equal to C/kg. This unit is used in the SI system. The off-system unit corresponding to it is called the roentgen (R). To obtain an absorbed dose of 1 rad, one must succumb to an exposure dose of about 1 R.

Since different types of ionizing radiation have a different charge of energy, its measurement is usually compared with biological influence. In the SI system, the unit of such an equivalent is the sievert (Sv). Its off-system counterpart is rem.

The stronger and longer the radiation, the more energy absorbed by the body, the more dangerous its influence. To find out the permissible time for a person to stay in radiation pollution, special devices are used - dosimeters that measure ionizing radiation. These are both devices for individual use, and large industrial installations.

Effect on the body

Contrary to popular belief, any ionizing radiation is not always dangerous and deadly. This can be seen in the example of ultraviolet rays. In small doses, they stimulate the generation of vitamin D in the human body, cell regeneration and an increase in melanin pigment, which gives a beautiful tan. But prolonged exposure causes severe burns and can cause skin cancer.

In recent years, the effect of ionizing radiation on the human body and its practical application has been actively studied.

In small doses, radiation does not cause any harm to the body. Up to 200 milliroentgens can reduce the number of white blood cells. The symptoms of such exposure will be nausea and dizziness. About 10% of people die after receiving such a dose.

Large doses cause digestive upset, hair loss, skin burns, changes in the cellular structure of the body, the development of cancer cells and death.

Radiation sickness

Prolonged action of ionizing radiation on the body and its receipt of a large dose of radiation can cause radiation sickness. More than half of the cases of this disease are fatal. The rest become the cause of a number of genetic and somatic diseases.

At the genetic level, mutations occur in germ cells. Their changes become evident in the next generations.

Somatic diseases are expressed by carcinogenesis, irreversible changes in various organs. Treatment of these diseases is long and rather difficult.

Treatment of radiation injuries

As a result of the pathogenic effects of radiation on the body, various lesions of human organs occur. Depending on the dose of radiation, different methods of therapy are carried out.

First of all, the patient is placed in a sterile ward to avoid the possibility of infection of open affected skin areas. Further, special procedures are carried out that contribute to the rapid removal of radionuclides from the body.

For severe lesions, a bone marrow transplant may be needed. From radiation, it loses the ability to reproduce red blood cells.

But in most cases, the treatment of mild lesions comes down to anesthesia of the affected areas, stimulating cell regeneration. Much attention is paid to rehabilitation.

Impact of ionizing radiation on aging and cancer

In connection with the influence of ionizing rays on the human body, scientists conducted various experiments proving the dependence of the processes of aging and carcinogenesis on the dose of radiation.

Groups of cell cultures were irradiated under laboratory conditions. As a result, it was possible to prove that even slight irradiation contributes to the acceleration of cell aging. Moreover, the older the culture, the more it is subject to this process.

Prolonged irradiation leads to cell death or abnormal and rapid division and growth. This fact indicates that ionizing radiation has a carcinogenic effect on the human body.

At the same time, the impact of waves on the affected cancer cells led to their complete death or to a stop in their division processes. This discovery helped develop a technique for treating human cancers.

Practical applications of radiation

For the first time, radiation began to be used in medical practice. With the help of X-rays, doctors managed to look inside the human body. At the same time, almost no harm was done to him.

Further, with the help of radiation, they began to treat cancer. In most cases, this method has a positive effect, despite the fact that the entire body is exposed to a strong effect of radiation, which entails a number of symptoms of radiation sickness.

In addition to medicine, ionizing rays are used in other industries. Surveyors using radiation can study the structural features of the earth's crust in its individual sections.

The ability of some fossils to release a large amount of energy, humanity has learned to use for its own purposes.

Nuclear power

Nuclear energy is the future of the entire population of the Earth. Nuclear power plants are sources of relatively inexpensive electricity. Provided that they are properly operated, such power plants are much safer than thermal power plants and hydroelectric power plants. From nuclear power plants, there is much less environmental pollution, both with excess heat and production waste.

At the same time, on the basis of atomic energy, scientists developed weapons of mass destruction. At the moment, there are so many atomic bombs on the planet that the launch of a small number of them can cause a nuclear winter, as a result of which almost all living organisms that inhabit it will die.

Means and methods of protection

The use of radiation in everyday life requires serious precautions. Protection against ionizing radiation is divided into four types: time, distance, number and shielding of sources.

Even in an environment with a strong radiation background, a person can stay for some time without harm to his health. It is this moment that determines the protection of time.

The greater the distance to the radiation source, the lower the dose of absorbed energy. Therefore, close contact with places where there is ionizing radiation should be avoided. This is guaranteed to protect against unwanted consequences.

If it is possible to use sources with minimal radiation, they are given preference in the first place. This is protection by quantity.

Shielding, on the other hand, means creating barriers through which harmful rays do not penetrate. An example of this is the lead screens in x-ray rooms.

household protection

In the event of a radiation disaster being declared, all windows and doors should be immediately closed, and try to stock up on water from sealed sources. Food should only be canned. When moving in an open area, cover the body as much as possible with clothing, and the face with a respirator or wet gauze. Try not to bring outerwear and shoes into the house.

It is also necessary to prepare for a possible evacuation: collect documents, a supply of clothes, water and food for 2-3 days.

Ionizing radiation as an environmental factor

There are quite a lot of areas contaminated with radiation on planet Earth. The reason for this is both natural processes and man-made disasters. The most famous of them are the Chernobyl accident and the atomic bombs over the cities of Hiroshima and Nagasaki.

In such places, a person cannot be without harm to his own health. At the same time, it is not always possible to find out in advance about radiation pollution. Sometimes even a non-critical radiation background can cause a disaster.

The reason for this is the ability of living organisms to absorb and accumulate radiation. At the same time, they themselves turn into sources of ionizing radiation. The well-known "black" jokes about Chernobyl mushrooms are based precisely on this property.

In such cases, protection against ionizing radiation is reduced to the fact that all consumer products are subject to careful radiological examination. At the same time, there is always a chance to buy the famous "Chernobyl mushrooms" in spontaneous markets. Therefore, you should refrain from buying from unverified sellers.

The human body tends to accumulate dangerous substances, resulting in a gradual poisoning from the inside. It is not known when exactly the effects of these poisons will make themselves felt: in a day, a year or a generation.

Ionizing radiation is electromagnetic radiation that is created during radioactive decay, nuclear transformations, deceleration of charged particles in matter and forms ions of various signs when interacting with the environment.

Interaction with matter of charged particles, gamma rays and x-rays. Corpuscular particles of nuclear origin (-parts, particles, neutrons, protons, etc.), as well as photon radiation (-quanta and X-ray and bremsstrahlung) have significant kinetic energy. Interacting with matter, they lose this energy mainly as a result of elastic interactions with atomic nuclei or electrons (as happens during the interaction of billiard balls), giving them all or part of their energy to excite atoms (i.e. transfer of an electron from a closer to orbit more distant from the nucleus), as well as the ionization of atoms or molecules of the medium (i.e., the separation of one or more electrons from atoms)

Elastic interaction is characteristic of neutral particles (trons) and photons that have no charge. In this case, the neutron, interacting with atoms, can, in accordance with the laws of classical mechanics, transfer part of the energy proportional to the masses of the colliding particles. If it is a heavy atom, then only part of the energy is transferred. If it is a hydrogen atom equal to the mass of a neutron, then all the energy is transferred. In this case, the neutron is slowed down to thermal energies of the order of fractions of an electric volt and then enters into nuclear reactions. Hitting an atom, a neutron can transfer to it such an amount of energy that is enough for the nucleus to “jump out” of the electron shell. In this case, a charged particle is formed, which has a significant speed, which is capable of ionizing the medium.

Similarly, the interaction with matter and photon. It is not capable of ionizing the medium on its own, but knocks out electrons from the atom, which produce the ionization of the medium. Neutrons and photon radiation are indirectly ionizing radiation.

Charged particles (- and -particles), protons and others are able to ionize the medium due to interaction with the electric field of the atom and the electric field of the nucleus. In this case, the charged particles slow down and deviate from the direction of their movement, while emitting bremsstrahlung, one of the varieties of photon radiation.

Charged particles can, due to inelastic interactions, transfer to the atoms of the medium an amount of energy that is insufficient for ionization. In this case, atoms in an excited state are formed, which transfer this energy to other atoms, either emit quanta of characteristic radiation, or, colliding with other excited atoms, can obtain energy sufficient to ionize the atoms.

As a rule, when radiation interacts with substances, all three types of consequences of this interaction occur: elastic collision, excitation, and ionization. On the example of the interaction of electrons with matter in Table. 3.15 shows the relative share and energy lost by them for various interaction processes.

Table 3.15

Relative share of energy lost by electrons as a result of various interaction processes, %

Energy, eV	Elastic interaction	Atom excitation	Ionization

The ionization process is the most important effect on which almost all methods of dosimetry of nuclear radiation are built, especially indirectly ionizing radiation.

In the process of ionization, two charged particles are formed: a positive ion (or an atom that has lost an electron from its outer shell) and a free electron. With each act of interaction, one or more electrons can be torn off.

The true work of ionization of an atom is 10 ... 17 eV, i.e. how much energy is required to detach an electron from an atom. It has been experimentally established that the energy transferred to the formation of one pair of ions in air is, on average, 35 eV for -particles and 34 eV for electrons, and for the substance of a biological tissue, approximately 33 eV. The difference is defined as follows. The average energy spent on the formation of one pair of ions is determined experimentally as the ratio of the energy of the primary particle to the average number of pairs of ions formed by one particle along its entire path. Since charged particles spend their energy on the processes of excitation and ionization, the experimental value of the ionization energy includes all types of energy losses related to the formation of one pair of ions. Table 1 provides experimental confirmation of the above. 3.14.

doses of radiation. When ionizing radiation passes through a substance, it is affected only by that part of the radiation energy that is transferred to the substance, absorbed by it. The portion of energy transferred by radiation to a substance is called a dose.

A quantitative characteristic of the interaction of ionizing radiation with a substance is the absorbed dose. Absorbed dose D (J / kg) is the ratio of the average energy of He transferred by ionizing radiation to a substance in an elementary volume, to a unit mass dm of a substance in this volume

In the SI system, the unit of absorbed dose is gray (Gy), named after the English physicist and radiobiologist L. Gray. 1 Gy corresponds to the absorption of an average of 1 J of ionizing radiation energy in a mass of matter equal to 1 kg. 1 Gy \u003d 1 Jkg -1.

Dose equivalent H is the absorbed dose in an organ or tissue multiplied by the appropriate weighting factor for that radiation, W R

where D T,R is the average absorbed dose in the organ or tissue T, W R is the weighting factor for radiation R. If the radiation field consists of several radiations with different values of W R , the equivalent dose is determined as:

The unit of equivalent dose is Jkg. -1, which has a special name sievert (Sv).

Effective dose E is a value used as a measure of the occurrence of long-term effects of irradiation of the entire human body and its individual organs, taking into account their radiosensitivity. It represents the sum of the products of the equivalent dose in an organ and the corresponding coefficient for a given organ or tissue:

where is the equivalent dose to tissue T over time, and W T is the weighting factor for tissue T. The unit of effective dose is Jkg -1 , which has a special name - sievert (Sv).

Dose effective collective S - the value that determines the total effect of radiation on a group of people, is defined as:

where is the average effective dose of the i-th subgroup of a group of people, is the number of people in the subgroup.

The unit of effective collective dose is man-sievert (man-Sv).

The mechanism of the biological action of ionizing radiation. The biological effect of radiation on a living organism begins at the cellular level. A living organism is made up of cells. An animal cell consists of a cell membrane surrounding a gelatinous mass - the cytoplasm, which contains a denser nucleus. The cytoplasm consists of organic compounds of a protein nature, forming a spatial lattice, the cells of which are filled with water, salts dissolved in it, and relatively small molecules of lipids - substances similar in properties to fats. The nucleus is considered the most sensitive vital part of the cell, and its main structural elements are chromosomes. At the heart of the structure of chromosomes is a molecule of dioxyribonucleic acid (DNA), which contains the hereditary information of the organism. Separate sections of DNA responsible for the formation of a certain elementary trait are called genes or "bricks of heredity." Genes are located on chromosomes in a strictly defined order, and each organism corresponds to a certain set of chromosomes in each cell. In humans, each cell contains 23 pairs of chromosomes. During cell division (mitosis), chromosomes are duplicated and arranged in a certain order in daughter cells.

Ionizing radiation causes breakage of chromosomes (chromosomal aberrations), after which the broken ends are joined into new combinations. This leads to a change in the gene apparatus and the formation of daughter cells that are not the same as the original ones. If persistent chromosomal aberrations occur in germ cells, then this leads to mutations, i.e. the appearance of offspring with other traits in irradiated individuals. Mutations are useful if they lead to an increase in the vitality of the organism, and harmful if they manifest themselves in the form of various congenital malformations. Practice shows that under the action of ionizing radiation, the probability of occurrence of beneficial mutations is small.

However, in any cell, continuously operating processes for repairing chemical damage in DNA molecules have been found. It also turned out that DNA is sufficiently resistant to breakage caused by radiation. It is necessary to make seven destructions of the DNA structure so that it can no longer be restored, i.e. only in this case does the mutation occur. With a smaller number of breaks, DNA is restored in its original form. This indicates the high strength of genes in relation to external influences, including ionizing radiation.

The destruction of molecules vital for the body is possible not only with their direct destruction by ionizing radiation (target theory), but also with indirect action, when the molecule itself does not directly absorb radiation energy, but receives it from another molecule (solvent), which initially absorbed this energy . In this case, the radiation effect is due to the secondary effect of the solvent radiolysis (decomposition) products on DNA molecules. This mechanism is explained by the theory of radicals. Repeated direct hits of ionizing particles in the DNA molecule, especially in its sensitive areas - genes, can cause its decay. However, the probability of such hits is less than hits on water molecules, which serve as the main solvent in the cell. Therefore, the radiolysis of water, i.e. decay under the action of radiation into hydrogen (H and hydroxyl (OH) radicals, followed by the formation of molecular hydrogen and hydrogen peroxide, is of paramount importance in radiobiological processes. The presence of oxygen in the system enhances these processes. Based on the theory of radicals, ions play the main role in the development of biological changes and radicals, which are formed in water along the trajectory of ionizing particles.

The high ability of radicals to enter into chemical reactions determines the processes of their interaction with biologically important molecules located in their immediate vicinity. In such reactions, the structures of biological substances are destroyed, and this, in turn, leads to changes in biological processes, including the processes of formation of new cells.

Consequences of human exposure to ionizing radiation. When a mutation occurs in a cell, then it spreads to all cells of the new organism, formed by division. In addition to genetic effects that can affect subsequent generations (congenital deformities), there are also so-called somatic (bodily) effects that are dangerous not only for the given organism itself (somatic mutation), but also for its offspring. Somatic mutation extends only to a certain circle of cells formed by ordinary division from the primary cell that has undergone a mutation.

Somatic damage to the body by ionizing radiation is the result of exposure to radiation on a large complex - groups of cells that form certain tissues or organs. Radiation slows down or even completely stops the process of cell division, in which their life is actually manifested, and sufficiently strong radiation eventually kills cells. The destructive effect of radiation is especially noticeable in young tissues. This circumstance is used, in particular, to protect the body from malignant (for example, cancerous tumors) neoplasms, which are destroyed under the influence of ionizing radiation much faster than benign cells. Somatic effects include local damage to the skin (radiation burn), eye cataract (clouding of the lens), damage to the genital organs (short-term or permanent sterilization), etc.

Unlike somatic effects, genetic effects of radiation are difficult to detect, since they act on a small number of cells and have a long latent period, measured in tens of years after exposure. Such a danger exists even with very weak radiation, which, although it does not destroy cells, can cause chromosome mutations and change hereditary properties. Most of these mutations appear only when the embryo receives chromosomes damaged in the same way from both parents. The results of mutations, including mortality from hereditary effects - the so-called genetic death, were observed long before people began to build nuclear reactors and use nuclear weapons. Mutations can be caused by cosmic rays, as well as by the natural radiation background of the Earth, which, according to experts, accounts for 1% of human mutations.

It has been established that there is no minimum level of radiation below which mutation does not occur. The total number of mutations caused by ionizing radiation is proportional to the population size and the average radiation dose. The manifestation of genetic effects depends little on the dose rate, but is determined by the total accumulated dose, regardless of whether it was received in 1 day or 50 years. It is believed that genetic effects do not have a dose threshold. Genetic effects are determined only by the effective collective dose of man-sievert (man-Sv), and the detection of an effect in an individual individual is practically unpredictable.

Unlike genetic effects, which are caused by low doses of radiation, somatic effects always begin at a certain threshold dose: at lower doses, damage to the body does not occur. Another difference between somatic and genetic damage is that the body is able to overcome the effects of exposure over time, while cellular damage is irreversible.

The values of some doses and effects of exposure to radiation on the body are given in Table. 3.16.

Table 3.16

Radiative forcing and associated biological effects

Impact
	Dose rate or duration	Irradiation	Biological effect
	In a week		Virtually absent
	Daily (for several years)		Leukemia
	at a time		Chromosomal abnormalities in tumor cells (culture of corresponding tissues)
	In a week		Virtually absent
	Accumulation of small doses		Doubling mutagenic effects in one generation
	at a time
			SD 50 for people
			Hair loss (reversible)
	0.1-0.5 Sv/day		Can be treated in hospital
	3 Sv/day or accumulation of low doses		radiation cataract
			The occurrence of cancer of highly radiosensitive organs
			The occurrence of cancer of moderately radiosensitive organs
			Dose limit for nerve tissue
			Dose limit for the gastrointestinal tract

Note. O - total body exposure; L - local irradiation; SD 50 is the dose leading to 50% mortality among exposed individuals.

Regulation of exposure to ionizing radiation. The main legal regulations in the field of radiation safety include the Radiation Safety Standards (NRB-99). The document belongs to the category of sanitary rules (SP 2.6.1.758-99), approved by the State Sanitary Doctor of the Russian Federation on July 2, 1999.

Radiation safety standards include terms and definitions that must be used in solving problems of radiation safety. They also establish three classes of guidelines: basic dose limits; allowable levels that are derived from dose limits; annual intake limits, volume allowable average annual intakes, specific activities, allowable levels of contamination of working surfaces, etc.; control levels.

Rationing of ionizing radiation is determined by the nature of the impact of ionizing radiation on the human body. At the same time, two types of effects related to diseases in medical practice are distinguished: deterministic threshold effects (radiation sickness, radiation burn, radiation cataract, fetal developmental anomalies, etc.) and stochastic (probabilistic) non-threshold effects (malignant tumors, leukemia, hereditary diseases) .

Ensuring radiation safety is determined by the following basic principles:

1. The principle of rationing is not to exceed the permissible limits of individual exposure doses of citizens from all sources of ionizing radiation.
2. The principle of justification is the prohibition of all types of activities involving the use of sources of ionizing radiation, in which the benefit received for a person and society does not exceed the risk of possible harm caused by exposure additional to the natural radiation background.
3. The principle of optimization is to maintain at the lowest possible and achievable level, taking into account economic and social factors, individual exposure doses and the number of exposed persons when using any source of ionizing radiation.

For the purpose of socio-economic assessment of the impact of ionizing radiation on people in order to calculate the probabilities of losses and justify the costs of radiation protection, when implementing the NRB-99 optimization principle, it is introduced that exposure to a collective effective dose of 1 man-Sv leads to the loss of 1 man-year of life population.

NRB -- 99 introduce the concepts of individual and collective risk, and also determine the value of the maximum value of the level of neglected risk of exposure to radiation. According to these norms, the individual and collective lifetime risk of occurrence of stochastic (probabilistic) effects is determined accordingly

where r, R -- individual and collective lifetime risk, respectively; E - individual effective dose; -- probability for the i-th individual to receive an annual effective dose from E to E + dE; r E is the coefficient of lifelong risk of reducing the duration of a full life period by an average of 15 years, one stochastic effect (from fatal cancer, serious hereditary effects and non-fatal cancer, reduced in terms of harm to consequences from fatal cancer), equal to

for industrial exposure:

1/person-Sv at mSv/year

for public exposure:

1/person-Sv at mSv/year;

1/person-Sv at mSv/year

For the purposes of radiation safety during irradiation during the year, the individual risk of a reduction in the duration of a full-fledged life as a result of the occurrence of severe consequences from deterministic effects is conservatively taken equal to:

where is the probability for the i-th individual to be irradiated with a dose greater than D when handling the source during the year; D is the threshold dose for a deterministic effect.

Potential exposure of a group of N individuals is justified if

where is the average reduction in the duration of a full life period as a result of the occurrence of stochastic effects, equal to 15 years; -- the average reduction in the duration of a full-fledged life as a result of the occurrence of severe consequences from deterministic effects, equal to 45 years; -- the monetary equivalent of the loss of 1 man-year of the life of the population; V-- income from production; P -- the cost of the main production, except for damage from protection; Y -- defense damage.

NRB-99 emphasize that risk reduction to the lowest possible level (optimization) should be carried out taking into account two circumstances:

- the risk limit regulates potential exposure from all possible sources. Therefore, for each source, the risk boundary is set during optimization;
- when reducing the risk of potential exposure, there is a minimum level of risk below which the risk is considered negligible and further risk reduction is inappropriate.

The individual risk limit for technogenic exposure of personnel is taken as 1.010 -3 for 1 year, and for the population 5.010 -5 for 1 year.

The level of negligible risk separates the area of risk optimization and the area of unconditionally acceptable risk and is 10 -6 for 1 year.

NRB-99 introduce the following categories of exposed persons:

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

Table 3.17

Basic dose limits

Notes. * Exposure doses, like all other permissible derivative levels for group B personnel, should not exceed 1/4 of the values for group A personnel.

** Refers to the average value in a 5 mg/cm2 layer under a 5 mg/cm2 cover layer. On the palms, the thickness of the cover layer is 40 mg/cm 2 .

The main dose limits for exposed personnel and the public do not include doses from natural, medical sources of ionizing radiation and the dose due to radiation accidents. These types of exposure are subject to special restrictions.

NRB-99 stipulate that with simultaneous exposure to sources of external and internal exposure, the condition must be met that the ratio of the external exposure dose to the dose limit and the ratio of annual nuclide intakes to their limits in total do not exceed 1.

For female personnel under the age of 45, the equivalent dose in the skin on the surface of the lower abdomen should not exceed 1 mSv per month, and the intake of radionuclides into the body should not exceed 1/20 of the annual intake limit for personnel per year. At the same time, the equivalent dose of irradiation of the fetus for 2 months of an undiagnosed pregnancy does not exceed 1 mSv.

When determining the pregnancy of women from the staff, employers must transfer them to other work that is not related to radiation.

For students under the age of 21 who are exposed to sources of ionizing radiation, the annual accumulated doses should not exceed the values established for members of the public.

When conducting preventive medical X-ray scientific studies of practically healthy individuals, the annual effective dose of radiation should not exceed 1 mSv.

NRB-99 also establishes requirements for limiting public exposure in a radiation accident.

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Introduction

Natural ionizing radiation is present everywhere. It comes from space in the form of cosmic rays. It is in the air in the form of radiation of radioactive radon and its secondary particles. Radioactive isotopes of natural origin penetrate with food and water into all living organisms and remain in them. Ionizing radiation cannot be avoided. The natural radioactive background has always existed on Earth, and life originated in the field of its radiation, and then - much, much later - man appeared. This natural (natural) radiation accompanies us throughout our lives.

The physical phenomenon of radioactivity was discovered in 1896, and today it is widely used in many fields. Despite radiophobia, nuclear power plants play an important role in the energy sector in many countries. X-rays are used in medicine to diagnose internal injuries and diseases. A number of radioactive substances are used in the form of labeled atoms to study the functioning of internal organs and study metabolic processes. Radiation therapy uses gamma radiation and other types of ionizing radiation to treat cancer. Radioactive substances are widely used in various control devices, and ionizing radiation (primarily X-ray) is used for the purposes of industrial flaw detection. Exit signs on buildings and planes, thanks to the content of radioactive tritium, glow in the dark in the event of a sudden power outage. Many fire alarms in homes and public buildings contain radioactive americium.

Radioactive radiation of different types with different energy spectrum are characterized by different penetrating and ionizing ability. These properties determine the nature of their impact on the living matter of biological objects.

It is believed that some of the hereditary changes and mutations in animals and plants are associated with background radiation.

In the event of a nuclear explosion, a nuclear lesion center occurs on the ground - a territory where the factors of mass destruction of people are light radiation, penetrating radiation and radioactive contamination of the area.

As a result of the damaging effect of light radiation, massive burns and eye damage can occur. Various kinds of shelters are suitable for protection, and in open areas - special clothing and goggles.

Penetrating radiation is gamma rays and a stream of neutrons emanating from the zone of a nuclear explosion. They can spread over thousands of meters, penetrate various media, causing ionization of atoms and molecules. Penetrating into the tissues of the body, gamma rays and neutrons disrupt the biological processes and functions of organs and tissues, resulting in the development of radiation sickness. Radioactive contamination of the area is created due to the adsorption of radioactive atoms by soil particles (the so-called radioactive cloud, which moves in the direction of air movement). The main danger for people in contaminated areas is external beta-gamma radiation and the ingress of nuclear explosion products into the body and onto the skin.

Nuclear explosions, releases of radionuclides by nuclear power plants and the widespread use of ionizing radiation sources in various industries, agriculture, medicine and scientific research have led to a global increase in the exposure of the Earth's population. Anthropogenic sources of external and internal exposure were added to natural exposure.

During nuclear explosions, fission radionuclides, induced activity and the undivided part of the charge (uranium, plutonium) enter the environment. Induced activity occurs when neutrons are captured by the nuclei of atoms of elements located in the structure of the product, air, soil and water. According to the nature of the radiation, all radionuclides of fission and induced activity are classified as - or, - emitters.

Fallouts are divided into local and global (tropospheric and stratospheric). Local fallout, which may include over 50% of the radioactive material generated from ground explosions, is large aerosol particles that fall out at a distance of about 100 km from the explosion site. Global fallout is due to fine aerosol particles.

Radionuclides deposited on the earth's surface become a source of long-term exposure.

The impact of radioactive fallout on humans includes external -, - exposure due to radionuclides present in the surface air and deposited on the surface of the earth, contact exposure as a result of contamination of skin and clothing, and internal exposure from radionuclides that enter the body with inhaled air and contaminated food and water. The critical radionuclide in the initial period is radioactive iodine, and subsequently 137Cs and 90Sr.

1. History of the discovery of radioactive radiation

Radioactivity was discovered in 1896 by the French physicist A. Becquerel. He was engaged in the study of the connection between luminescence and the recently discovered x-rays.

Becquerel came up with the idea: is not any luminescence accompanied by x-rays? To test his guess, he took several compounds, including one of the uranium salts, which phosphorescent yellow-green light. After illuminating it with sunlight, he wrapped the salt in black paper and placed it in a dark closet on a photographic plate, also wrapped in black paper. Some time later, having shown the plate, Becquerel really saw the image of a piece of salt. But luminescent radiation could not pass through the black paper, and only X-rays could illuminate the plate under these conditions. Becquerel repeated the experiment several times with equal success. At the end of February 1896, at a meeting of the French Academy of Sciences, he made a report on the X-ray emission of phosphorescent substances.

After some time, a plate was accidentally developed in Becquerel's laboratory, on which lay uranium salt, not irradiated by sunlight. She, of course, did not phosphoresce, but the imprint on the plate turned out. Then Becquerel began to test various compounds and minerals of uranium (including those that do not show phosphorescence), as well as metallic uranium. The plate was constantly lit up. By placing a metal cross between the salt and the plate, Becquerel obtained the weak contours of the cross on the plate. Then it became clear that new rays were discovered that pass through opaque objects, but are not X-rays.

Becquerel established that the intensity of radiation is determined only by the amount of uranium in the preparation and does not depend at all on what compounds it is included in. Thus, this property was inherent not in compounds, but in the chemical element - uranium.

Becquerel shares his discovery with the scientists with whom he collaborated. In 1898, Marie Curie and Pierre Curie discovered the radioactivity of thorium, and later they discovered the radioactive elements polonium and radium.

They found that all uranium compounds and, to the greatest extent, uranium itself have the property of natural radioactivity. Becquerel returned to the luminophores that interested him. True, he made another major discovery related to radioactivity. Once, for a public lecture, Becquerel needed a radioactive substance, he took it from the Curies and put the test tube in his vest pocket. After giving a lecture, he returned the radioactive preparation to the owners, and the next day he found redness of the skin in the form of a test tube on the body under the vest pocket. Becquerel told Pierre Curie about this, and he set up an experiment: for ten hours he wore a test tube with radium tied to his forearm. A few days later he also developed redness, which then turned into a severe ulcer, from which he suffered for two months. Thus, the biological effect of radioactivity was discovered for the first time.

But even after that, the Curies courageously did their job. Suffice it to say that Marie Curie died of radiation sickness (nevertheless, she lived to be 66 years old).

In 1955 Marie Curie's notebooks were examined. They still radiate, thanks to the radioactive contamination introduced when they were filled. On one of the sheets, a radioactive fingerprint of Pierre Curie was preserved.

The concept of radioactivity and types of radiation.

Radioactivity - the ability of some atomic nuclei to spontaneously (spontaneously) transform into other nuclei with the emission of various types of radioactive radiation and elementary particles. Radioactivity is divided into natural (observed in unstable isotopes that exist in nature) and artificial (observed in isotopes obtained through nuclear reactions).

Radioactive radiation is divided into three types:

Radiation - is deflected by electric and magnetic fields, has a high ionizing ability and low penetrating power; is a stream of helium nuclei; the charge of the -particle is +2e, and the mass coincides with the mass of the nucleus of the helium isotope 42He.

Radiation - deflected by electric and magnetic fields; its ionizing power is much less (by about two orders of magnitude), and its penetrating power is much greater than that of -particles; is a stream of fast electrons.

Radiation - is not deflected by electric and magnetic fields, has a relatively weak ionizing ability and a very high penetrating power; is short-wave electromagnetic radiation with an extremely short wavelength< 10-10 м и вследствие этого - ярко выраженными корпускулярными свойствами, то есть является поток частиц - -квантов (фотонов).

The half-life T1 / 2 is the time during which the initial number of radioactive nuclei is on average halved.

Alpha radiation is a stream of positively charged particles formed by 2 protons and 2 neutrons. The particle is identical to the nucleus of the helium-4 atom (4He2+). It is formed during the alpha decay of nuclei. For the first time, alpha radiation was discovered by E. Rutherford. Studying radioactive elements, in particular, studying such radioactive elements as uranium, radium and actinium, E. Rutherford came to the conclusion that all radioactive elements emit alpha and beta rays. And, more importantly, the radioactivity of any radioactive element decreases after a certain specific period of time. The source of alpha radiation is radioactive elements. Unlike other types of ionizing radiation, alpha radiation is the most harmless. It is dangerous only when such a substance enters the body (inhalation, eating, drinking, rubbing, etc.), since the range of an alpha particle, for example, with an energy of 5 MeV, in air is 3.7 cm, and in biological tissue 0, 05 mm. The alpha radiation of a radionuclide that has entered the body causes truly nightmarish destruction, tk. the quality factor of alpha radiation with energy less than 10 MeV is 20mm. and energy losses occur in a very thin layer of biological tissue. It practically burns him. When alpha particles are absorbed by living organisms, mutagenic (factors that cause mutation), carcinogenic (substances or a physical agent (radiation) that can cause the development of malignant neoplasms) and other negative effects can occur. Penetrating ability A. - and. small because held back by a piece of paper.

Beta particle (beta particle), a charged particle emitted as a result of beta decay. The stream of beta particles is called beta rays or beta radiation.

Negatively charged beta particles are electrons (in--), positively charged are positrons (in +).

The energies of beta particles are distributed continuously from zero to some maximum energy, depending on the decaying isotope; this maximum energy ranges from 2.5 keV (for rhenium-187) to tens of MeV (for short-lived nuclei far from the beta stability line).

Beta rays under the action of electric and magnetic fields deviate from a rectilinear direction. The speed of particles in beta rays is close to the speed of light. Beta rays are able to ionize gases, cause chemical reactions, luminescence, act on photographic plates.

Significant doses of external beta radiation can cause radiation burns to the skin and lead to radiation sickness. Even more dangerous is internal exposure from beta-active radionuclides that have entered the body. Beta radiation has a significantly lower penetrating power than gamma radiation (however, an order of magnitude greater than alpha radiation). A layer of any substance with a surface density of the order of 1 g/cm2.

For example, a few millimeters of aluminum or a few meters of air almost completely absorb beta particles with an energy of about 1 MeV.

Gamma radiation is a type of electromagnetic radiation with an extremely short wavelength --< 5Ч10-3 нм и вследствие этого ярко выраженными корпускулярными и слабо выраженными волновыми свойствами. Гамма-квантами являются фотоны высокой энергии. Обычно считается, что энергии квантов гамма-излучения превышают 105 эВ, хотя резкая граница между гамма- и рентгеновским излучением не определена. На шкале электромагнитных волн гамма-излучение граничит с рентгеновским излучением, занимая диапазон более высоких частот и энергий. В области 1-100 кэВ гамма-излучение и рентгеновское излучение различаются только по источнику: если квант излучается в ядерном переходе, то его принято относить к гамма-излучению, если при взаимодействиях электронов или при переходах в атомной электронной оболочке -- то к рентгеновскому излучению. Очевидно, физически кванты электромагнитного излучения с одинаковой энергией не отличаются, поэтому такое разделение условно.

Gamma radiation is emitted during transitions between excited states of atomic nuclei (the energies of such gamma rays range from ~1 keV to tens of MeV). During nuclear reactions (for example, during the annihilation of an electron and a positron, the decay of a neutral pion, etc.), as well as during the deflection of energetic charged particles in magnetic and electric fields.

Gamma rays, unlike b-rays and b-rays, are not deflected by electric and magnetic fields and are characterized by greater penetrating power at equal energies and other conditions being equal. Gamma rays cause the ionization of the atoms of matter. The main processes that occur during the passage of gamma radiation through matter:

Photoelectric effect (gamma quantum is absorbed by the electron of the atomic shell, transferring all the energy to it and ionizing the atom).

Compton scattering (gamma-quantum is scattered by an electron, transferring to it part of its energy).

The birth of electron-positron pairs (in the field of the nucleus, a gamma quantum with an energy of at least 2mec2=1.022 MeV turns into an electron and a positron).

Photonuclear processes (at energies above several tens of MeV, a gamma quantum is able to knock out nucleons from the nucleus).

Gamma rays, like any other photons, can be polarized.

Irradiation with gamma rays, depending on the dose and duration, can cause chronic and acute radiation sickness. Stochastic effects of radiation include various types of cancer. At the same time, gamma radiation inhibits the growth of cancerous and other rapidly dividing cells. Gamma radiation is a mutagenic and teratogenic factor.

A layer of matter can serve as protection against gamma radiation. The effectiveness of protection (that is, the probability of absorption of a gamma-quantum when passing through it) increases with an increase in the thickness of the layer, the density of the substance and the content of heavy nuclei (lead, tungsten, depleted uranium, etc.) in it.

The unit for measuring radioactivity is the becquerel (Bq, Bq). One becquerel is equal to one disintegration per second. The content of activity in a substance is often estimated per unit weight of the substance (Bq/kg) or its volume (Bq/l, Bq/m3). An off-system unit is often used - the curie (Ci, Ci). One curie corresponds to the number of disintegrations per second in 1 gram of radium. 1 Ki \u003d 3.7.1010 Bq.

The ratios between units of measurement are shown in the table below.

The well-known non-systemic unit roentgen (P, R) is used to determine the exposure dose. One X-ray corresponds to the dose of X-ray or gamma radiation, at which 2.109 pairs of ions are formed in 1 cm3 of air. 1 Р = 2, 58.10-4 C/kg.

To evaluate the effect of radiation on a substance, the absorbed dose is measured, which is defined as the absorbed energy per unit mass. The unit of absorbed dose is called the rad. One rad is equal to 100 erg/g. In the SI system, another unit is used - gray (Gy, Gy). 1 Gy \u003d 100 rad \u003d 1 J / kg.

The biological effect of different types of radiation is not the same. This is due to differences in their penetrating ability and the nature of energy transfer to organs and tissues of a living organism. Therefore, to assess the biological consequences, the biological equivalent of an x-ray, rem, is used. The dose in rems is equivalent to the dose in rads multiplied by the radiation quality factor. For x-rays, beta and gamma rays, the quality factor is considered to be equal to one, that is, rem corresponds to a rad. For alpha particles, the quality factor is 20 (meaning that alpha particles cause 20 times more damage to living tissue than the same absorbed dose of beta or gamma rays). For neutrons, the coefficient ranges from 5 to 20, depending on the energy. In the SI system for equivalent dose, a special unit called sievert (Sv, Sv) was introduced. 1 Sv = 100 rem. The equivalent dose in Sieverts corresponds to the absorbed dose in Gy multiplied by the quality factor.

2. The impact of radiation on the human body

There are two types of effect of exposure to ionizing radiation on the body: somatic and genetic. With a somatic effect, the consequences are manifested directly in the irradiated person, with a genetic effect, in his offspring. Somatic effects may be early or delayed. Early ones occur in the period from several minutes to 30-60 days after irradiation. These include redness and peeling of the skin, clouding of the lens of the eye, damage to the hematopoietic system, radiation sickness, death. Long-term somatic effects appear several months or years after irradiation in the form of persistent skin changes, malignant neoplasms, decreased immunity, and reduced life expectancy.

When studying the effect of radiation on the body, the following features were revealed:

ü High efficiency of absorbed energy, even small amounts of it can cause profound biological changes in the body.

b The presence of a latent (incubation) period for the manifestation of the action of ionizing radiation.

b Effects from low doses may be cumulative or cumulative.

b Genetic effect - effect on offspring.

Various organs of a living organism have their own sensitivity to radiation.

Not every organism (human) as a whole reacts equally to radiation.

Irradiation depends on the frequency of exposure. With the same dose of radiation, the harmful effects will be the less, the more fractionally it is received in time.

Ionizing radiation can affect the body with both external (especially X-ray and gamma radiation) and internal (especially alpha particles) radiation. Internal exposure occurs when sources of ionizing radiation enter the body through the lungs, skin and digestive organs. Internal irradiation is more dangerous than external, since sources of ionizing radiation that have got inside expose unprotected internal organs to continuous irradiation.

Under the action of ionizing radiation, water, which is an integral part of the human body, is split and ions with different charges are formed. The resulting free radicals and oxidizing agents interact with the molecules of the organic matter of the tissue, oxidizing and destroying it. Metabolism is disturbed. There are changes in the composition of the blood - the level of erythrocytes, leukocytes, platelets and neutrophils decreases. Damage to the hematopoietic organs destroys the human immune system and leads to infectious complications.

Local lesions are characterized by radiation burns of the skin and mucous membranes. With severe burns, edema, blisters are formed, tissue death (necrosis) is possible.

Lethally absorbed and maximum allowable doses of radiation.

Lethal absorbed doses for individual parts of the body are as follows:

b head - 20 Gy;

b lower abdomen - 50 Gy;

b chest -100 Gy;

e limbs - 200 Gr.

When exposed to doses 100-1000 times the lethal dose, a person can die during exposure ("death under the beam").

Depending on the type of ionizing radiation, there may be different protection measures: reducing the exposure time, increasing the distance to sources of ionizing radiation, fencing sources of ionizing radiation, sealing sources of ionizing radiation, equipment and arrangement of protective equipment, organization of dosimetric control, hygiene and sanitation measures.

A - personnel, i.e. persons permanently or temporarily working with sources of ionizing radiation;

B - a limited part of the population, i.e. persons who are not directly involved in work with sources of ionizing radiation, but due to the conditions of residence or placement of workplaces, may be exposed to ionizing radiation;

B is the entire population.

The maximum allowable dose is 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 status of personnel detected by modern methods.

Tab. 2. Maximum allowable radiation doses

Natural sources give a total annual dose of approximately 200 mrem (space - up to 30 mrem, soil - up to 38 mrem, radioactive elements in human tissues - up to 37 mrem, radon gas - up to 80 mrem and other sources).

Artificial sources add an annual equivalent dose of approximately 150-200 mrem (medical devices and research - 100-150 mrem, TV viewing - 1-3 mrem, coal-fired thermal power plant - up to 6 mrem, consequences of nuclear weapons tests - up to 3 mrem and others sources).

The World Health Organization (WHO) defines the maximum allowable (safe) equivalent radiation dose for a planetary inhabitant as 35 rem, subject to its uniform accumulation over 70 years of life.

Tab. 3. Biological disorders in a single (up to 4 days) irradiation of the entire human body

Radiation dose, (Gy)	The degree of radiation sickness	The beginning of the manifestation of the primary reaction	The nature of the primary reaction	Consequences of irradiation
Up to 0.250 - 1.0	There are no visible violations. There may be changes in the blood. Changes in the blood, impaired ability to work
		After 2-3 hours	Mild nausea with vomiting. Passes on the day of irradiation	Typically 100% recovery even with no treatment

3. Protection against ionizing radiation

Anti-radiation protection of the population includes: notification of radiation danger, the use of collective and individual protective equipment, compliance with the behavior of the population in a territory contaminated with radioactive substances. Protection of food and water from radioactive contamination, use of medical personal protective equipment, determination of levels of contamination of the territory, dosimetric monitoring of public exposure and examination of contamination of food and water with radioactive substances.

According to the Civil Defense warning signals "Radiation Hazard", the population should take refuge in protective structures. As is known, they significantly (several times) weaken the effect of penetrating radiation.

Due to the danger of getting radiation damage, it is impossible to start providing first aid to the population in the presence of high levels of radiation in the area. Under these conditions, it is of great importance to provide self- and mutual assistance to the affected population, strict observance of the rules of conduct in the contaminated territory.

On the territory contaminated with radioactive substances, you can not eat, drink water from contaminated water sources, lie down on the ground. The procedure for cooking and feeding the population is determined by the Civil Defense authorities, taking into account the levels of radioactive contamination of the area.

Gas masks and respirators (for miners) can be used to protect against air contaminated with radioactive particles. There are also general protection methods such as:

l increasing the distance between the operator and the source;

ь reduction of the duration of work in the radiation field;

l shielding of the radiation source;

l remote control;

l use of manipulators and robots;

l full automation of the technological process;

ь use of personal protective equipment and warning with a radiation hazard sign;

ü constant monitoring of the level of radiation and radiation doses to personnel.

The personal protective equipment includes an anti-radiation suit with the inclusion of lead. The best absorber of gamma rays is lead. Slow neutrons are well absorbed by boron and cadmium. Fast neutrons are pre-moderated with graphite.

The Scandinavian company Handy-fashions.com is developing protection against mobile phone radiation, for example, it introduced a vest, cap and scarf designed to protect against the harmful study of mobile phones. For their production, a special anti-radiation fabric is used. Only the pocket on the vest is made of ordinary fabric for stable signal reception. The cost of a complete protective kit is from $300.

Protection against internal exposure consists in eliminating direct contact of workers with radioactive particles and preventing them from entering the air of the working area.

It is necessary to be guided by radiation safety standards, which list the categories of exposed persons, dose limits and protection measures, and sanitary rules that regulate the location of premises and installations, the place of work, the procedure for obtaining, recording and storing radiation sources, requirements for ventilation, dust and gas cleaning, and neutralization radioactive waste, etc.

Also, to protect the premises with personnel, the Penza State Academy of Architecture and Civil Engineering is developing to create a "high-density mastic for protection against radiation." The composition of the mastics includes: binder - resorcinol-formaldehyde resin FR-12, hardener - paraformaldehyde and filler - high-density material.

Protection against alpha, beta, gamma rays.

The basic principles of radiation safety are not to exceed the established basic dose limit, to exclude any unreasonable exposure and to reduce the radiation dose to the lowest possible level. In order to implement these principles in practice, radiation doses received by personnel when working with sources of ionizing radiation are necessarily controlled, work is carried out in specially equipped rooms, protection is used by distance and time, and various means of collective and individual protection are used.

To determine the individual exposure doses of personnel, it is necessary to systematically conduct radiation (dosimetric) monitoring, the volume of which depends on the nature of work with radioactive substances. Each operator who has contact with sources of ionizing radiation is given an individual dosimeter1 to control the received dose of gamma radiation. In rooms where work with radioactive substances is carried out, it is necessary to provide general control over the intensity of various types of radiation. These rooms must be isolated from other rooms, equipped with a supply and exhaust ventilation system with an air exchange rate of at least five. The painting of the walls, ceiling and doors in these rooms, as well as the arrangement of the floor, are carried out in such a way as to exclude the accumulation of radioactive dust and avoid the absorption of radioactive aerosols. Vapors and liquids with finishing materials (painting walls, doors and, in some cases, ceilings should be done with oil paints, floors are covered with materials that do not absorb liquids - linoleum, PVC plastic compound, etc.). All building structures in rooms where work with radioactive substances is carried out should not have cracks and discontinuities; the corners are rounded to prevent the accumulation of radioactive dust in them and to facilitate cleaning. At least once a month, a general cleaning of the premises is carried out with the obligatory washing of walls, windows, doors, furniture and equipment with hot soapy water. The current wet cleaning of the premises is carried out daily.

To reduce the exposure of personnel, all work with these sources is carried out using long grips or holders. Time protection consists in the fact that work with radioactive sources is carried out for such a period of time that the radiation dose received by the personnel does not exceed the maximum permissible level.

Collective means of protection against ionizing radiation are regulated by GOST 12.4.120-83 “Means of collective protection against ionizing radiation. General requirements". In accordance with this regulatory document, the main means of protection are stationary and mobile protective screens, containers for transporting and storing sources of ionizing radiation, as well as for collecting and transporting radioactive waste, protective safes and boxes, etc.

Stationary and mobile protective screens are designed to reduce the level of radiation in the workplace to an acceptable level. If work with sources of ionizing radiation is carried out in a special room - a working chamber, then its walls, floor and ceiling, made of protective materials, serve as screens. Such screens are called stationary. For the device of mobile screens, various shields are used that absorb or attenuate radiation.

Screens are made from various materials. Their thickness depends on the type of ionizing radiation, the properties of the protective material and the required radiation attenuation factor k. The value of k shows how many times it is necessary to reduce the energy indicators of radiation (exposure dose rate, absorbed dose, particle flux density, etc.) in order to obtain acceptable values of the listed characteristics. For example, for the case of absorbed dose, k is expressed as follows:

where D is the absorbed dose rate; D0 - acceptable level of absorbed dose.

For the construction of stationary means of protecting walls, ceilings, ceilings, etc. brick, concrete, barite concrete and barite plaster are used (they include barium sulfate - BaSO4). These materials reliably protect personnel from exposure to gamma and X-rays.

Various materials are used to create mobile screens. Protection against alpha radiation is achieved by using screens of ordinary or organic glass with a thickness of several millimeters. Sufficient protection against this type of radiation is a layer of air a few centimeters. To protect against beta radiation, screens are made of aluminum or plastic (organic glass). Lead, steel, tungsten alloys effectively protect against gamma and X-ray radiation. Viewing systems are made of special transparent materials, such as lead glass. Materials containing hydrogen (water, paraffin), as well as beryllium, graphite, boron compounds, etc. protect from neutron radiation. Concrete can also be used for neutron shielding.

Protective safes are used to store sources of gamma radiation. They are made from lead and steel.

Protective glove boxes are used to work with radioactive substances with alpha and beta activity.

Protective containers and collectors for radioactive waste are made of the same materials as screens - organic glass, steel, lead, etc.

When working with sources of ionizing radiation, the hazardous area must be limited by warning labels.

A hazardous area is a space in which a worker can be exposed to hazardous and (or) harmful production factors (in this case, ionizing radiation).

The principle of operation of devices designed to monitor personnel exposed to ionizing radiation is based on various effects arising from the interaction of these radiations with a substance. The main methods for detecting and measuring radioactivity are gas ionization, scintillation and photochemical methods. The most commonly used ionization method is based on measuring the degree of ionization of the medium through which the radiation has passed.

Scintillation methods for detecting radiation are based on the ability of some materials, by absorbing the energy of ionizing radiation, to convert it into light radiation. An example of such a material is zinc sulfide (ZnS). The scintillation counter is a photoelectron tube with a window coated with zinc sulfide. When radiation enters this tube, a weak flash of light occurs, which leads to the appearance of electric current pulses in the photoelectron tube. These impulses are amplified and counted.

There are other methods for determining ionizing radiation, for example, calorimetric methods, which are based on measuring the amount of heat released during the interaction of radiation with an absorbing substance.

Dosimetric control devices are divided into two groups: dosimeters used for quantitative measurement of dose rate, and radiometers or radiation indicators used for the rapid detection of radioactive contamination.

From domestic devices, for example, dosimeters of the DRGZ-04 and DKS-04 brands are used. The first is used to measure gamma and X-ray radiation in the energy range of 0.03-3.0 MeV. The instrument scale is graduated in microroentgen/second (μR/s). The second device is used to measure gamma and beta radiation in the energy range of 0.5-3.0 MeV, as well as neutron radiation (hard and thermal neutrons). The scale of the device is graduated in milliroentgens per hour (mR/h). The industry also produces household dosimeters intended for the population, for example, the household dosimeter "Master-1" (designed to measure the dose of gamma radiation), the household dosimeter-radiometer ANRI-01 ("Pine").

nuclear radiation lethal ionizing

Conclusion

So, from the above, we can conclude the following:

ionizing radiation- in the most general sense - various types of microparticles and physical fields capable of ionizing matter. The most significant types of ionizing radiation are: short-wave electromagnetic radiation (X-ray and gamma radiation), charged particle fluxes: beta particles (electrons and positrons), alpha particles (nuclei of the helium-4 atom), protons, other ions, muons, etc. . as well as neutrons. In nature, ionizing radiation is usually generated as a result of spontaneous radioactive decay of radionuclides, nuclear reactions (fusion and induced fission of nuclei, capture of protons, neutrons, alpha particles, etc.), as well as the acceleration of charged particles in space (the nature of such acceleration of cosmic particles up to the end is not clear).

Artificial sources of ionizing radiation are artificial radionuclides (generate alpha, beta and gamma radiation), nuclear reactors (generate mainly neutron and gamma radiation), radionuclide neutron sources, elementary particle accelerators (generate fluxes of charged particles, as well as bremsstrahlung photon radiation), x-ray machines (generate bremsstrahlung x-rays). Irradiation is very dangerous for the human body, the degree of danger depends on the dose (in my abstract I gave the maximum allowable norms) and the type of radiation - the safest is alpha radiation, and the more dangerous is gamma.

Ensuring radiation safety requires a complex of diverse protective measures, depending on the specific conditions of work with sources of ionizing radiation, as well as on the type of source.

Time protection is based on reducing the time of work with the source, which makes it possible to reduce personnel exposure doses. This principle is especially often used in the direct work of personnel with low radioactivity.

Distance protection is a fairly simple and reliable way of protection. This is due to the ability of radiation to lose its energy in interactions with matter: the greater the distance from the source, the more processes of interaction of radiation with atoms and molecules, which ultimately leads to a decrease in the radiation dose of personnel.

Shielding is the most effective way to protect against radiation. Depending on the type of ionizing radiation, various materials are used for the manufacture of screens, and their thickness is determined by power and radiation.

Literature

1. “Harmful chemicals. radioactive substances. Directory." Under total ed. L.A. Ilyina, V.A. Filov. Leningrad, "Chemistry". 1990.

2. Fundamentals of protection of the population and territories in emergency situations. Ed. acad. V.V. Tarasov. Moscow University Press. 1998.

3. Life safety / Ed. S.V. Belova.- 3rd ed., revised.- M .: Higher. school, 2001. - 485s.

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§ 2. The influence of ionizing radiation on the human body

As a result of the impact of ionizing radiation on the human body, complex physical, chemical and biochemical processes can occur in the tissues. Ionizing radiation causes the ionization of atoms and molecules of a substance, as a result of which the molecules and cells of the tissue are destroyed.

It is known that 2/3 of the total composition of human tissue is water and carbon. Under the influence of radiation, water is split into hydrogen H and the hydroxyl group OH, which, either directly or through a chain of secondary transformations, form products with high chemical activity: hydrated oxide HO 2 and hydrogen peroxide H 2 O 2. These compounds interact with the molecules of the organic matter of the tissue, oxidizing and destroying it.

As a result of exposure to ionizing radiation, the normal course of biochemical processes and metabolism in the body are disrupted. Depending on the magnitude of the absorbed dose of radiation and on the individual characteristics of the organism, the changes caused may be reversible or irreversible. At small doses, the affected tissue restores its functional activity. Large doses with prolonged exposure can cause irreversible damage to individual organs or the entire body (radiation sickness).

Any type of ionizing radiation causes biological changes in the body both during external exposure, when the radiation source is outside the body, and during internal exposure, when radioactive substances enter the body, for example, by inhalation - by inhalation or by ingestion with food or water.

The biological effect of ionizing radiation depends on the dose and time of exposure to radiation, on the type of radiation, the size of the irradiated surface and the individual characteristics of the organism.

With a single irradiation of the entire human body, the following biological disorders are possible depending on the radiation dose:

0—25 rad 1 there are no visible violations;

25-50 rad. . . possible changes in the blood;

50-100 rad. . . changes in the blood, the normal state of working capacity is disturbed;

100-200 rad. . . violation of the normal state, loss of ability to work is possible;

200-400 rad. . . loss of ability to work, death is possible;

400-500 rad. . . deaths account for 50% of the total number of victims

600 rad and more fatal in almost all cases of exposure.

When exposed to doses 100-1000 times the lethal dose, a person can die during exposure.

The degree of damage to the body depends on the size of the irradiated surface. With a decrease in the irradiated surface, the risk of injury also decreases. An important factor in the impact of ionizing radiation on the body is the exposure time. The more fractional the radiation in time, the less its damaging effect.

The individual characteristics of the human body are manifested only at low doses of radiation. The younger the person, the higher their sensitivity to radiation. An adult person aged 25 years and older is most resistant to radiation.

The degree of danger of damage also depends on the rate of excretion of the radioactive substance from the body. Substances that rapidly circulate in the body (water, sodium, chlorine) and substances that are not absorbed by the body, and also do not form compounds that make up tissues (argon, xenon, krypton, etc.) do not stay for a long time. Some radioactive substances are almost not excreted from the body and accumulate in it.

At the same time, some of them (niobium, ruthenium, etc.) are evenly distributed in the body, others are concentrated in certain organs (lanthanum, actinium, thorium - in the liver, strontium, uranium, radium - in bone tissue), leading to their rapid damage. .

When evaluating the effect of radioactive substances, one should also take into account their half-life and the type of radiation. Substances with a short half-life quickly lose activity, α-emitters, being almost harmless to internal organs during external irradiation, getting inside, have a strong biological effect due to the high ionization density they create; α- and β-emitters, having very short ranges of emitted particles, in the process of decay irradiate only that organ where isotopes accumulate predominantly.

1 Rad is a unit of absorbed radiation dose. The absorbed dose of radiation is understood as the energy of ionizing radiation absorbed per unit mass of the irradiated substance.

Portal for the student. Self-training

Impact on the body of ionizing radiation. Consequences of exposure to ionizing radiation on the human body during external and internal exposure, surface contamination with radioactive substances

What is ionizing radiation?

Radiation sources

Exposure to ionizing radiation

Health effects of ionizing radiation

WHO activities

Types of ionizing radiation

Research History

Natural and artificial sources of radiation

Units of measurement and doses

Effect on the body

Radiation sickness

Treatment of radiation injuries

Impact of ionizing radiation on aging and cancer

Practical applications of radiation

Nuclear power

Means and methods of protection

household protection

Ionizing radiation as an environmental factor

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§ 2. The influence of ionizing radiation on the human body

Portal for the student. Self-training

What is ionizing radiation?

Radiation sources

Exposure to ionizing radiation

Health effects of ionizing radiation

WHO activities

Types of ionizing radiation

Research History

Natural and artificial sources of radiation

Units of measurement and doses

Effect on the body

Radiation sickness

Treatment of radiation injuries

Impact of ionizing radiation on aging and cancer

Practical applications of radiation

Nuclear power

Means and methods of protection

household protection

Ionizing radiation as an environmental factor

Send your good work in the knowledge base is simple. Use the form below

Similar Documents

§ 2. The influence of ionizing radiation on the human body

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