ionizing called radiation, which, passing through the medium, causes ionization or excitation of the molecules of the medium. Ionizing radiation, like electromagnetic radiation, is not perceived by the human senses. Therefore, it is especially dangerous, since a person does not know that he is exposed to it. Ionizing radiation is otherwise called radiation.
Radiation is a stream of particles (alpha particles, beta particles, neutrons) or electromagnetic energy of very high frequencies (gamma or x-rays).
Pollution of the production environment with substances that are sources of ionizing radiation is called radioactive contamination.
Nuclear pollution is a form of physical (energy) pollution associated with the excess of the natural level of radioactive substances in the environment as a result of human activities.
Substances are made up of tiny particles of chemical elements - atoms. The atom is divisible and has a complex structure. At the center of an atom of a chemical element is a material particle called the atomic nucleus, around which electrons revolve. Most of the atoms of chemical elements have great stability, i.e., stability. However, in a number of elements known in nature, the nuclei spontaneously decay. Such elements are called radionuclides. The same element can have several radionuclides. In this case they are called radioisotopes chemical element. Spontaneous decay of radionuclides is accompanied by radioactive radiation.
Spontaneous decay of the nuclei of certain chemical elements (radionuclides) is called radioactivity.
Radioactive radiation can be of various types: streams of particles with high energy, an electromagnetic wave with a frequency of more than 1.5.10 17 Hz.
The emitted particles come in many forms, but the most commonly emitted are alpha particles (α-radiation) and beta particles (β-radiation). The alpha particle is heavy and has high energy; it is the nucleus of the helium atom. A beta particle is about 7336 times lighter than an alpha particle, but can also have high energy. Beta radiation is a stream of electrons or positrons.
Radioactive electromagnetic radiation (it is also called photon radiation), depending on the frequency of the wave, is X-ray (1.5.10 17 ... 5.10 19 Hz) and gamma radiation (more than 5.10 19 Hz). Natural radiation is only gamma radiation. X-ray radiation is artificial and occurs in cathode ray tubes at voltages of tens and hundreds of thousands of volts.
Radionuclides, emitting particles, turn into other radionuclides and chemical elements. Radionuclides decay at different rates. The decay rate of radionuclides is called activity. The unit of measure of activity is the number of decays per unit of time. One disintegration per second is called a becquerel (Bq). Often another unit is used to measure activity - curie (Ku), 1 Ku = 37.10 9 Bq. One of the first radionuclides studied in detail was radium-226. It was studied for the first time by the Curies, after whom the unit of measure of activity is named. The number of decays per second occurring in 1 g of radium-226 (activity) is 1 Ku.
The time it takes for half of a radionuclide to decay is called half-life(T 1/2). Each radionuclide has its own half-life. The range of T 1/2 for various radionuclides is very wide. It changes from seconds to billions of years. For example, the best known natural radionuclide, uranium-238, has a half-life of about 4.5 billion years.
During decay, the amount of the radionuclide decreases and its activity decreases. The pattern by which activity decreases obeys the law of radioactive decay:
where BUT 0 - initial activity, BUT- activity over a period of time t.
Types of ionizing radiation
Ionizing radiation occurs during the operation of devices based on radioactive isotopes, during the operation of vacuum devices, displays, etc.
Ionizing radiations are corpuscular(alpha, beta, neutron) and electromagnetic(gamma, x-ray) radiation, capable of creating charged atoms and ion molecules when interacting with matter.
alpha radiation is a stream of helium nuclei emitted by matter during radioactive decay of nuclei or during nuclear reactions.
The greater the energy of the particles, the greater the total ionization caused by it in the substance. The range of alpha particles emitted by a radioactive substance reaches 8-9 cm in air, and in living tissue - several tens of microns. Having a relatively large mass, alpha particles quickly lose their energy when interacting with matter, which determines their low penetrating ability and high specific ionization, amounting to several tens of thousands of pairs of ions per 1 cm of the path in air.
Beta radiation - the flow of electrons or positrons resulting from radioactive decay.
The maximum range in the air of beta particles is 1800 cm, and in living tissues - 2.5 cm. The ionizing ability of beta particles is lower (several tens of pairs per 1 cm of run), and the penetrating power is higher than that of alpha particles.
Neutrons, the flux of which forms neutron radiation, transform their energy in elastic and inelastic interactions with atomic nuclei.
With inelastic interactions, secondary radiation arises, which can consist of both charged particles and gamma quanta (gamma radiation): with elastic interactions, ordinary ionization of a substance is possible.
The penetrating power of neutrons largely depends on their energy and the composition of the matter of the atoms with which they interact.
Gamma radiation - electromagnetic (photon) radiation emitted during nuclear transformations or particle interactions.
Gamma radiation has a high penetrating power and a low ionizing effect.
x-ray radiation arises in the environment surrounding the source of beta radiation (in X-ray tubes, electron accelerators) and is a combination of bremsstrahlung and characteristic radiation. Bremsstrahlung is photon radiation with a continuous spectrum emitted when the kinetic energy of charged particles changes; characteristic radiation is photon radiation with a discrete spectrum, emitted when the energy state of atoms changes.
Like gamma radiation, X-rays have a low ionizing power and a large penetration depth.
Sources of ionizing radiation
The type of radiation damage to a person depends on the nature of the sources of ionizing radiation.
The natural radiation background consists of cosmic radiation and radiation of naturally distributed radioactive substances.
In addition to natural exposure, a person is exposed to exposure from other sources, for example: in the production of x-rays of the skull - 0.8-6 R; spine - 1.6-14.7 R; lungs (fluorography) - 0.2-0.5 R; chest with fluoroscopy - 4.7-19.5 R; gastrointestinal tract with fluoroscopy - 12-82 R: teeth - 3-5 R.
A single irradiation of 25-50 rem leads to minor short-lived changes in the blood; at doses of 80-120 rem, signs of radiation sickness appear, but without a lethal outcome. Acute radiation sickness develops with a single irradiation of 200-300 rem, while a lethal outcome is possible in 50% of cases. Lethal outcome in 100% of cases occurs at doses of 550-700 rem. Currently, there are a number of anti-radiation drugs. weakening the effect of radiation.
Chronic radiation sickness can develop with continuous or repeated exposure to doses significantly lower than those that cause an acute form. The most characteristic signs of the chronic form of radiation sickness are changes in the blood, disorders of the nervous system, local skin lesions, damage to the lens of the eye, and a decrease in immunity.
The degree depends on whether the exposure is external or internal. Internal exposure is possible by inhalation, ingestion of radioisotopes and their penetration into the human body through the skin. Some substances are absorbed and accumulated in specific organs, resulting in high local doses of radiation. For example, iodine isotopes accumulating in the body can cause damage to the thyroid gland, rare earth elements can cause liver tumors, cesium and rubidium isotopes can cause soft tissue tumors.
Artificial sources of radiation
In addition to exposure from natural sources of radiation, which were and are always and everywhere, in the 20th century, additional sources of radiation associated with human activity appeared.
First of all, this is the use of X-rays and gamma radiation in medicine in the diagnosis and treatment of patients. , obtained with appropriate procedures, can be very large, especially in the treatment of malignant tumors with radiation therapy, when directly in the tumor zone they can reach 1000 rem or more. During x-ray examinations, the dose depends on the time of the examination and the organ that is being diagnosed, and can vary widely - from a few rem when taking a picture of a tooth to tens of rem when examining the gastrointestinal tract and lungs. Fluorographic images give the minimum dose, and preventive annual fluorographic examinations should by no means be abandoned. The average dose people receive from medical research is 0.15 rem per year.
In the second half of the 20th century, people began to actively use radiation for peaceful purposes. Various radioisotopes are used in scientific research, in the diagnostics of technical objects, in instrumentation, etc. And finally, nuclear power. Nuclear power plants are used at nuclear power plants (NPPs), icebreakers, ships, and submarines. Currently, more than 400 nuclear reactors with a total electrical capacity of over 300 million kW are operating at nuclear power plants alone. For the production and processing of nuclear fuel, a whole complex of enterprises united in nuclear fuel cycle(NFC).
The nuclear fuel cycle includes enterprises for the extraction of uranium (uranium mines), its enrichment (enrichment plants), the manufacture of fuel elements, nuclear power plants themselves, enterprises for the secondary processing of spent nuclear fuel (radiochemical plants), for the temporary storage and processing of nuclear fuel waste generated, and, finally, permanent disposal of radioactive waste (burial grounds). At all stages of the NFC, radioactive substances affect the operating personnel to a greater or lesser extent, at all stages, releases (normal or accidental) of radionuclides into the environment can occur and create an additional dose for the population, especially those living in the area of the NFC enterprises.
Where do radionuclides come from during normal operation of nuclear power plants? The radiation inside a nuclear reactor is enormous. Fuel fission fragments, various elementary particles can penetrate protective shells, microcracks and enter the coolant and air. A number of technological operations in the production of electrical energy at nuclear power plants can lead to water and air pollution. Therefore, nuclear power plants are equipped with a water and gas cleaning system. Emissions to the atmosphere are carried out through a tall chimney.
During normal operation of nuclear power plants, emissions to the environment are small and have little impact on the population living in the vicinity.
The greatest danger from the point of view of radiation safety is posed by plants for the processing of spent nuclear fuel, which has a very high activity. These enterprises generate a large amount of liquid waste with high radioactivity, there is a danger of developing a spontaneous chain reaction (nuclear hazard).
The problem of dealing with radioactive waste, which is a very significant source of radioactive contamination of the biosphere, is very difficult.
However, complex and costly from radiation at NFC enterprises make it possible to ensure the protection of humans and the environment to very small values, significantly less than the existing technogenic background. Another situation occurs when there is a deviation from the normal mode of operation, and especially during accidents. Thus, the accident that occurred in 1986 (which can be attributed to global catastrophes - the largest accident at the nuclear fuel cycle enterprises in the entire history of the development of nuclear power) at the Chernobyl nuclear power plant led to the release of only 5% of all fuel into the environment. As a result, radionuclides with a total activity of 50 million Ci were released into the environment. This release led to the exposure of a large number of people, a large number of deaths, the contamination of very large areas, the need for mass relocation of people.
The accident at the Chernobyl nuclear power plant clearly showed that the nuclear method of generating energy is possible only if large-scale accidents at nuclear fuel cycle enterprises are ruled out in principle.
- 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 useful applications, including 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 per second. The half-life is the time required for the activity of a radionuclide to decay to half of 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 intentional 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.
Ionizing radiation is called radiation, the interaction of which with a substance leads to the formation of ions of different signs in this substance. Ionizing radiation consists of charged and uncharged particles, which also include photons. The energy of particles of ionizing radiation is measured in off-system units - electron volts, eV. 1 eV = 1.6 10 -19 J.
There are corpuscular and photon ionizing radiation.
Corpuscular ionizing radiation- a stream of elementary particles with a rest mass different from zero, formed during radioactive decay, nuclear transformations, or generated at accelerators. It includes: α- and β-particles, neutrons (n), protons (p), etc.
α-radiation is a stream of particles that are the nuclei of the helium atom and have two units of charge. The energy of α-particles emitted by various radionuclides lies in the range of 2-8 MeV. In this case, all the nuclei of a given radionuclide emit α-particles with the same energy.
β-radiation is a stream of electrons or positrons. During the decay of the nuclei of a β-active radionuclide, in contrast to α-decay, various nuclei of a given radionuclide emit β-particles of different energies, so the energy spectrum of β-particles is continuous. The average energy of the β spectrum is approximately 0.3 E tah. The maximum energy of β-particles in currently known radionuclides can reach 3.0-3.5 MeV.
Neutrons (neutron radiation) are neutral elementary particles. Since neutrons do not have an electric charge, when passing through matter, they interact only with the nuclei of atoms. As a result of these processes, either charged particles (recoil nuclei, protons, neutrons) or g-radiation are formed, causing ionization. According to the nature of interaction with the medium, which depends on the level of neutron energy, they are conditionally divided into 4 groups:
1) thermal neutrons 0.0-0.5 keV;
2) intermediate neutrons 0.5-200 keV;
3) fast neutrons 200 KeV - 20 MeV;
4) relativistic neutrons over 20 MeV.
Photon radiation- a stream of electromagnetic oscillations that propagate in vacuum at a constant speed of 300,000 km/s. It includes g-radiation, characteristic, bremsstrahlung and X-ray
radiation.
Possessing the same nature, these types of electromagnetic radiation differ in the conditions of formation, as well as in properties: wavelength and energy.
Thus, g-radiation is emitted during nuclear transformations or during the annihilation of particles.
Characteristic radiation - photon radiation with a discrete spectrum, emitted when the energy state of the atom changes, due to the rearrangement of the internal electron shells.
Bremsstrahlung - associated with a change in the kinetic energy of charged particles, has a continuous spectrum and occurs in the environment surrounding the source of β-radiation, in X-ray tubes, in electron accelerators, etc.
X-ray radiation is a combination of bremsstrahlung and characteristic radiation, the photon energy range of which is 1 keV - 1 MeV.
Radiations are characterized by their ionizing and penetrating power.
Ionizing ability radiation is determined by specific ionization, i.e., the number of pairs of ions created by a particle per unit volume of the mass of the medium or per unit path length. Different types of radiation have different ionizing abilities.
penetrating power radiation is determined by the range. A run is the path traveled by a particle in a substance until it stops completely, due to one or another type of interaction.
α-particles have the highest ionizing power and the lowest penetrating power. Their specific ionization varies from 25 to 60 thousand pairs of ions per 1 cm path in air. The path length of these particles in air is several centimeters, and in soft biological tissue - several tens of microns.
β-radiation has a significantly lower ionizing power and greater penetrating power. The average value of specific ionization in air is about 100 pairs of ions per 1 cm of path, and the maximum range reaches several meters at high energies.
Photon radiations have the lowest ionizing power and the highest penetrating power. In all processes of interaction of electromagnetic radiation with the medium, part of the energy is converted into the kinetic energy of secondary electrons, which, passing through the substance, produce ionization. The passage of photon radiation through matter cannot be characterized at all by the concept of range. The weakening of the flow of electromagnetic radiation in a substance obeys an exponential law and is characterized by the attenuation coefficient p, which depends on the energy of the radiation and the properties of the substance. But whatever the thickness of the substance layer, one cannot completely absorb the photon radiation flux, but one can only weaken its intensity by any number of times.
This is the essential difference between the nature of the attenuation of photon radiation and the attenuation of charged particles, for which there is a minimum thickness of the layer of the absorbing substance (path), where the charged particle flux is completely absorbed.
Biological effect of ionizing radiation. Under the influence of ionizing radiation on the human body, complex physical and biological processes can occur in the tissues. As a result of ionization of living tissue, molecular bonds are broken and the chemical structure of various compounds changes, which in turn leads to cell death.
An even more significant role in the formation of biological consequences is played by the products of water radiolysis, which makes up 60-70% of the mass of biological tissue. Under the action of ionizing radiation on water, free radicals H· and OH· are formed, and in the presence of oxygen also a free radical of hydroperoxide (HO· 2) and hydrogen peroxide (H 2 O 2), which are strong oxidizing agents. Radiolysis products enter into chemical reactions with tissue molecules, forming compounds that are not characteristic of a healthy organism. This leads to a violation of individual functions or systems, as well as the vital activity of the organism as a whole.
The intensity of chemical reactions induced by free radicals increases, and many hundreds and thousands of molecules not affected by radiation are involved in them. This is the specificity of the action of ionizing radiation on biological objects, that is, the effect produced by radiation is due not so much to the amount of absorbed energy in the irradiated object, but to the form in which this energy is transmitted. No other type of energy (thermal, electrical, etc.), absorbed by a biological object in the same amount, leads to such changes as ionizing radiation does.
Ionizing radiation, when exposed to the human body, can cause two types of effects that clinical medicine refers to diseases: deterministic threshold effects (radiation sickness, radiation burn, radiation cataract, radiation infertility, anomalies in the development of the fetus, etc.) and stochastic (probabilistic) non-threshold effects (malignant tumors, leukemia, hereditary diseases).
Violations of biological processes can be either reversible, when the normal functioning of the cells of the irradiated tissue is completely restored, or irreversible, leading to damage to individual organs or the whole organism and the occurrence radiation sickness.
There are two forms of radiation sickness - acute and chronic.
acute form occurs as a result of exposure to high doses in a short period of time. At doses of the order of thousands of rads, damage to the body can be instantaneous ("death under the beam"). Acute radiation sickness can also occur when large amounts of radionuclides enter the body.
Acute lesions develop with a single uniform gamma irradiation of the whole body and an absorbed dose above 0.5 Gy. At a dose of 0.25 ... 0.5 Gy, temporary changes in the blood can be observed, which quickly normalize. In the dose range of 0.5...1.5 Gy, a feeling of fatigue occurs, less than 10% of those exposed may experience vomiting, moderate changes in the blood. At a dose of 1.5 ... 2.0 Gy, a mild form of acute radiation sickness is observed, which is manifested by prolonged lymphopenia (a decrease in the number of lymphocytes - immunocompetent cells), in 30 ... 50% of cases - vomiting on the first day after irradiation. Deaths are not recorded.
Radiation sickness of moderate severity occurs at a dose of 2.5 ... 4.0 Gy. Almost all irradiated patients experience nausea, vomiting on the first day, a sharp decrease in the content of leukocytes in the blood, subcutaneous hemorrhages appear, in 20% of cases a fatal outcome is possible, death occurs 2–6 weeks after irradiation. At a dose of 4.0...6.0 Gy, a severe form of radiation sickness develops, leading to death in 50% of cases within the first month. At doses exceeding 6.0 Gy, an extremely severe form of radiation sickness develops, which in almost 100% of cases ends in death due to hemorrhage or infectious diseases. The given data refer to cases where there is no treatment. Currently, there are a number of anti-radiation agents, which, with complex treatment, make it possible to exclude a lethal outcome at doses of about 10 Gy.
Chronic radiation sickness can develop with continuous or repeated exposure to doses significantly lower than those that cause an acute form. The most characteristic signs of chronic radiation sickness are changes in the blood, a number of symptoms from the nervous system, local skin lesions, lesions of the lens, pneumosclerosis (with plutonium-239 inhalation), and a decrease in the body's immunoreactivity.
The degree of exposure to radiation depends on whether the exposure is external or internal (when a radioactive isotope enters the body). Internal exposure is possible through inhalation, ingestion of radioisotopes and their penetration into the body through the skin. Some substances are absorbed and accumulated in specific organs, resulting in high local doses of radiation. Calcium, radium, strontium and others accumulate in the bones, iodine isotopes cause damage to the thyroid gland, rare earth elements - mainly liver tumors. Isotopes of cesium and rubidium are evenly distributed, causing oppression of hematopoiesis, testicular atrophy, and soft tissue tumors. With internal irradiation, the most dangerous alpha-emitting isotopes of polonium and plutonium.
The ability to cause long-term consequences - leukemia, malignant neoplasms, early aging - is one of the insidious properties of ionizing radiation.
To address the issues of radiation safety, first of all, the effects observed at "low doses" - on the order of several centisieverts per hour and below, which actually occur in the practical use of atomic energy, are of interest.
It is very important here that, according to modern concepts, the output of adverse effects in the range of "low doses" encountered under normal conditions does not depend much on the dose rate. This means that the effect is determined primarily by the total accumulated dose, regardless of whether it was received in 1 day, 1 second, or 50 years. Thus, when assessing the effects of chronic exposure, one should keep in mind that these effects accumulate in the body over a long period of time.
Dosimetric quantities and units of their measurement. The action of ionizing radiation on a substance is manifested in the ionization and excitation of the atoms and molecules that make up the substance. The quantitative measure of this effect is the absorbed dose. D p is the average energy transferred by radiation to a unit mass of matter. The unit of absorbed dose is gray (Gy). 1 Gy = 1 J/kg. In practice, an off-system unit is also used - 1 rad \u003d 100 erg / g \u003d 1 10 -2 J / kg \u003d 0.01 Gy.
The absorbed radiation dose depends on the properties of the radiation and the absorbing medium.
For charged particles (α, β, protons) of low energies, fast neutrons and some other radiations, when the main processes of their interaction with matter are direct ionization and excitation, the absorbed dose serves as an unambiguous characteristic of ionizing radiation in terms of its effect on the medium. This is due to the fact that between the parameters characterizing these types of radiation (flux, flux density, etc.) and the parameter characterizing the ionization ability of radiation in the medium - the absorbed dose, it is possible to establish adequate direct relationships.
For X-ray and g-radiation, such dependences are not observed, since these types of radiation are indirectly ionizing. Consequently, the absorbed dose cannot serve as a characteristic of these radiations in terms of their effect on the environment.
Until recently, the so-called exposure dose has been used as a characteristic of X-ray and g-radiation by the ionization effect. The exposure dose expresses the photon radiation energy converted into the kinetic energy of secondary electrons producing ionization per unit mass of atmospheric air.
A pendant per kilogram (C/kg) is taken as a unit of exposure dose of X-ray and g-radiation. This is such a dose of X-ray or g-radiation, when exposed to 1 kg of dry atmospheric air, under normal conditions, ions are formed that carry 1 C of electricity of each sign.
In practice, the off-system unit of exposure dose, the roentgen, is still widely used. 1 roentgen (R) - exposure dose of x-ray and g-radiation, at which ions are formed in 0.001293 g (1 cm 3 of air under normal conditions) that carry a charge of one electrostatic unit of the amount of electricity of each sign or 1 P \u003d 2.58 10 -4 C/kg. With an exposure dose of 1 R, 2.08 x 10 9 pairs of ions will be formed in 0.001293 g of atmospheric air.
Studies of the biological effects caused by various ionizing radiations have shown that tissue damage is associated not only with the amount of absorbed energy, but also with its spatial distribution, characterized by the linear ionization density. The higher the linear ionization density, or, in other words, the linear energy transfer of particles in the medium per unit path length (LET), the greater the degree of biological damage. To take this effect into account, the concept of equivalent dose has been introduced.
Dose equivalent H T , R - absorbed dose in an organ or tissue D T , R , multiplied by the appropriate weighting factor for that radiation W R:
H t , r=W R D T , R
The unit of equivalent dose is J kg -1, which has the special name sievert (Sv).
Values W R for photons, electrons and muons of any energy is 1, for α-particles, fission fragments, heavy nuclei - 20. Weighting coefficients for individual types of radiation when calculating the equivalent dose:
Photons of any energy…………………………………………………….1
Electrons and muons (less than 10 keV)……………………………………….1
Neutrons with energy less than 10 keV……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
from 10 keV to 100 keV ……....………………………………………………10
from 100 keV to 2 MeV………………………………………………………..20
from 2 MeV to 20 MeV………………………………………………………..10
over 20 MeV……………………………………………………………………5
Protons other than recoil protons
energy more than 2 MeV………………………………….………………5
The alpha particles
fission fragments, heavy nuclei………………………………………….20
Dose effective- the value used as a measure of the risk of long-term consequences of irradiation of the entire human body and its individual organs, taking into account their radiosensitivity. It represents the sum of products of the equivalent dose in the organ N τT to the appropriate weighting factor for that organ or tissue WT:
where H τT - tissue equivalent dose T during τ .
The unit of measure for effective dose is J × kg -1, called the sievert (Sv).
Values W T for certain types of tissue and organs are given below:
Type of tissue, organ W 1
Gonads ................................................. ................................................. .............0.2
Bone marrow, (red), lungs, stomach………………………………0.12
Liver, breast, thyroid. …………………………...0.05
Skin………………………………………………………………………………0.01
Absorbed, exposure and equivalent doses per unit time are called the corresponding dose rates.
Spontaneous (spontaneous) decay of radioactive nuclei follows the law:
N = N0 exp(-λt),
where N0- the number of nuclei in a given volume of matter at time t = 0; N- the number of cores in the same volume by the time t ; λ is the decay constant.
The constant λ has the meaning of the probability of nuclear decay in 1 s; it is equal to the fraction of nuclei decaying in 1 s. The decay constant does not depend on the total number of nuclei and has a well-defined value for each radioactive nuclide.
The above equation shows that over time, the number of nuclei of a radioactive substance decreases exponentially.
Due to the fact that the half-life of a significant number of radioactive isotopes is measured in hours and days (the so-called short-lived isotopes), it must be known to assess the radiation hazard in time in the event of an accidental release of a radioactive substance into the environment, to choose a decontamination method, and also during processing radioactive waste and their subsequent disposal.
The described types of doses refer to an individual person, that is, they are individual.
By summing up the individual effective equivalent doses received by a group of people, we arrive at the collective effective equivalent dose, which is measured in man-sieverts (man-Sv).
One more definition needs to be introduced.
Many radionuclides decay very slowly and will remain in the distant future.
The collective effective equivalent dose that generations of people will receive from any radioactive source over the entire time of its existence is called expected (total) collective effective equivalent dose.
The activity of the drug it is a measure of the amount of radioactive material.
Activity is determined by the number of decaying atoms per unit time, that is, the rate of decay of the nuclei of the radionuclide.
The unit of activity is one nuclear transformation per second. In the SI system of units, it is called becquerel (Bq).
Curie (Ci) is taken as an off-system unit of activity - the activity of such a number of a radionuclide in which 3.7 × 10 10 decay acts per second occur. In practice, Ki derivatives are widely used: millicurie - 1 mCi = 1 × 10 -3 Ci; microcurie - 1 μCi = 1 × 10 -6 Ci.
Measurement of ionizing radiation. It must be remembered that there are no universal methods and devices applicable to all conditions. Each method and device has its own area of application. Failure to take these notes into account can lead to gross errors.
In radiation safety, radiometers, dosimeters and spectrometers are used.
radiometers- these are devices designed to determine the amount of radioactive substances (radionuclides) or radiation flux. For example, gas-discharge counters (Geiger-Muller).
Dosimeters- these are devices for measuring the exposure or absorbed dose rate.
Spectrometers serve to register and analyze the energy spectrum and identify emitting radionuclides on this basis.
Rationing. Radiation safety issues are regulated by the Federal Law “On radiation safety of the population”, radiation safety standards (NRB-99) and other rules and regulations. The law "On radiation safety of the population" states: "Radiation safety of the population is the state of protection of the present and future generations of people from the harmful effects of ionizing radiation on their health" (Article 1).
“Citizens of the Russian Federation, foreign citizens and stateless persons residing on the territory of the Russian Federation have the right to radiation safety. This right is ensured through the implementation of a set of measures to prevent the radiation impact on the human body of ionizing radiation above the established norms, rules and regulations, the implementation by citizens and organizations that carry out activities using sources of ionizing radiation, the requirements for ensuring radiation safety” (Article 22).
Hygienic regulation of ionizing radiation is carried out by the Radiation Safety Standards NRB-99 (Sanitary Rules SP 2.6.1.758-99). The main dose exposure limits and permissible levels are established for the following categories
exposed persons:
Personnel - persons working with technogenic sources (group A) or who, due to 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.
1. Ionizing radiation, their types, nature and basic properties.
2. Ionizing radiation, their features, basic qualities, units of measurement. (2 in 1)
For a better perception of the subsequent material, it is necessary to
thread some concepts.
1. The nuclei of all atoms of one element have the same charge, that is, they contain
harvest the same number of positively charged protons and different co-
number of particles without a charge - neutrons.
2. The positive charge of the nucleus, due to the number of protons, equalizes
weighed by the negative charge of the electrons. Therefore, the atom is electrically
neutral.
3. Atoms of the same element with the same charge, but different
number of neutrons are called isotopes.
4. Isotopes of the same element have the same chemical, but different
personal physical properties.
5. Isotopes (or nuclides) according to their stability are divided into stable and
decaying, i.e. radioactive.
6. Radioactivity - spontaneous transformation of the nuclei of atoms of one element
cops to others, accompanied by the emission of ionizing radiation
7. Radioactive isotopes decay at a certain rate, measured
my half-life, that is, the time when the original number
nuclei are halved. From here, radioactive isotopes are divided into
short-lived (half-life is calculated from fractions of a second to not-
how many days) and long-lived (with a half-life of several
weeks to billions of years).
8. Radioactive decay cannot be stopped, accelerated or slowed down by any
in some way.
9. The rate of nuclear transformations is characterized by activity, i.e. number
decays per unit time. The unit of activity is the becquerel.
(Bq) - one transformation per second. Off-system unit of activity -
curie (Ci), 3.7 x 1010 times greater than becquerel.
There are the following types of radioactive transformations:
polar and wave.
Corpuscular include:
1. Alpha decay. Characteristic of natural radioactive elements with
large serial numbers and is a stream of helium nuclei,
carrying a double positive charge. The emission of alpha particles is different
energy by nuclei of the same type occurs in the presence of different
ny energy levels. In this case, excited nuclei arise, which
which, passing into the ground state, emit gamma quanta. When mutual
interaction of alpha particles with matter, their energy is spent on excitation
ionization and ionization of the atoms of the medium.
Alpha particles have the highest degree of ionization - they form
60,000 pairs of ions on the way to 1 cm of air. First the particle trajectory
gie, collision with nuclei), which increases the ionization density at the end
particle path.
With relatively large mass and charge, alpha particles
have little penetrating power. So, for an alpha particle
with an energy of 4 MeV, the path length in air is 2.5 cm, and the biological
cloth 0.03mm. Alpha decay leads to a decrease in the ordinal
a measure of a substance by two units and a mass number by four units.
Example: ----- +
Alpha particles are considered as internal feeds. Per-
shield: tissue paper, clothing, aluminum foil.
2. Electronic beta decay. characteristic of both natural and
artificial radioactive elements. The nucleus emits an electron and
at the same time, the nucleus of the new element vanishes at a constant mass number and with
big serial number.
Example: ----- + ē
When the nucleus emits an electron, it is accompanied by the release of a neutrino.
(1/2000 electron rest mass).
When emitting beta particles, the nuclei of atoms can be in an excited state.
condition. Their transition to an unexcited state is accompanied by
by gamma rays. The path length of a beta particle in air at 4 MeV 17
cm, with the formation of 60 pairs of ions.
3. Positron beta decay. Observed in some artificial plants
diactive isotopes. The mass of the nucleus practically does not change, and the order
the number is reduced by one.
4. K-capture of an orbital electron by a nucleus. The nucleus captures an electron with K-
shell, while a neutron flies out of the nucleus and a characteristic
x-ray radiation.
5. Corpuscular radiation also includes neutron radiation. Neutrons-not
having a charge elementary particles with a mass equal to 1. Depending on
from their energy, slow (cold, thermal and suprathermal)
resonant, intermediate, fast, very fast and extra fast
neutrons. Neutron radiation is the shortest-lived: after 30-40 seconds
kund neutron decays into an electron and a proton. penetrating power
the neutron flux is comparable to that for gamma radiation. When penetrating
introduction of neutron radiation into the tissue to a depth of 4-6 cm, a
Immediate radioactivity: stable elements become radioactive.
6. Spontaneous nuclear fission. This process is observed in radioactive
elements with a large atomic number when captured by their nuclei of slow
ny electrons. The same nuclei form different pairs of fragments with
excess number of neutrons. Nuclear fission releases energy.
If neutrons are reused for the subsequent fission of other nuclei,
the reaction will be chain.
In radiation therapy of tumors, pi-mesons are used - elementary particles
particles with a negative charge and a mass 300 times the mass of an electric
throne. Pi-mesons interact with atomic nuclei only at the end of the path, where
they destroy the nuclei of the irradiated tissue.
Wave types of transformations.
1. Gamma rays. This is a stream of electromagnetic waves with a length of 0.1 to 0.001
nm. Their propagation speed is close to the speed of light. Penetrating
high ability: they can penetrate not only through the human body
ka, but also through denser media. In the air, the range of gamma-
rays reaches several hundred meters. The energy of a gamma ray is almost
10,000 times higher than the energy of visible light quantum.
2. X-rays. Electromagnetic radiation, artificially semi-
found in x-ray tubes. When high voltage is applied to
cathode, electrons fly out of it, which move at high speed
cling to the anticathode and hit its surface, made of heavy
yellow metal. There is bremsstrahlung X-rays, possessing
with high penetrating power.
Features of radiation
1. Not a single source of radioactive radiation is determined by any ordinance
genome of feelings.
2. Radioactive radiation is a universal factor for various sciences.
3. Radioactive radiation is a global factor. In the case of a nuclear
pollution of the territory of one country, the effect of radiation is received by others.
4. Under the action of radioactive radiation in the body, specific
cal reactions.
Qualities inherent in radioactive elements
and ionizing radiation
1. Change in physical properties.
2. The ability to ionize the environment.
3. Penetration.
4. Half-life.
5. Half-life.
6. The presence of a critical organ, i.e. tissue, organ or part of the body, irradiation
which can cause the greatest harm to human health or
offspring.
3. Stages of action of ionizing radiation on the human body.
The effect of ionizing radiation on the body
Immediate direct disturbances in cells and tissues occurring
following the radiation, are negligible. So, for example, under the action of radiation, you
causing the death of an experimental animal, the temperature in his body
rises by only one hundredth of a degree. However, under the action of
dioactive radiation in the body there are very serious
nye violations, which should be considered in stages.
1. Physical and chemical stage
The phenomena that occur at this stage are called primary or
launchers. It is they who determine the entire further course of development of radiation
defeats.
First, ionizing radiation interacts with water, knocking out
its molecules are electrons. Molecular ions are formed that carry positive
nye and negative charges. There is a so-called radiolysis of water.
H2O - ē → H2O+
H2O + ē → H2O-
The H2O molecule can be destroyed: H and OH
Hydroxyls can recombine: OH
OH forms hydrogen peroxide H2O2
The interaction of H2O2 and OH produces HO2 (hydroperoxide) and H2O
Ionized and excited atoms and molecules for 10 seconds
waters interact with each other and with different molecular systems,
giving rise to chemically active centers (free radicals, ions, ion-
radicals, etc.). During the same period, ruptures of bonds in molecules are possible as
due to direct interaction with an ionizing agent, and due to
account of intra- and intermolecular transfer of excitation energy.
2. Biochemical stage
The permeability of membranes increases, diffusion begins through them.
rove electrolytes, water, enzymes into organelles.
Radicals resulting from the interaction of radiation with water
interact with dissolved molecules of various compounds, giving
the beginning of secondary radical products.
Further development of radiation damage to molecular structures
reduced to changes in proteins, lipids, carbohydrates and enzymes.
What happens in proteins:
Configuration changes in the protein structure.
Aggregation of molecules due to the formation of disulfide bonds
Breakage of peptide or carbon bonds leading to protein degradation
Decrease in the level of methionine, a donator of sulfhydryl groups, trypto-
Fana, which leads to a sharp slowdown in protein synthesis
Reducing the content of sulfhydryl groups due to their inactivation
Damage to the nucleic acid synthesis system
In lipids:
Fatty acid peroxides are formed that do not have specific enzymes.
cops to destroy them (the effect of peroxidase is negligible)
Antioxidants are inhibited
In carbohydrates:
Polysaccharides are broken down into simple sugars
Irradiation of simple sugars leads to their oxidation and decomposition to organic
nic acids and formaldehyde
Heparin loses its anticoagulant properties
Hyaluronic acid loses its ability to bind to protein
Decreased glycogen levels
The processes of anaerobic glycolysis are disturbed
Decreased glycogen content in muscles and liver.
In the enzyme system, oxidative phosphorylation is disrupted and
the activity of a number of enzymes changes, chemically active reactions develop
substances with different biological structures, in which
both destruction and the formation of new ones that are not characteristic of irradiation occur.
of a given organism, compounds.
The subsequent stages in the development of radiation injury are associated with a violation
metabolism in biological systems with changes in the corresponding
4. Biological stage or fate of the irradiated cell
So, the effect of the action of radiation is associated with the changes that occur,
both in cellular organelles and in the relationships between them.
The most sensitive to radiation organelles of body cells
mammals are the nucleus and mitochondria. Damage to these structures
occur at low doses and at the earliest possible time. In the nuclei of radiosensing
body cells, energy processes are inhibited, the function of
membranes. Proteins are formed that have lost their normal biological
activity. More pronounced radiosensitivity than the nuclei have mi-
tochondria. These changes are manifested in the form of swelling of the mitochondria,
damage to their membranes, a sharp inhibition of oxidative phosphorylation.
The radiosensitivity of cells largely depends on the speed
their metabolic processes. Cells that are characterized by in-
intensive biosynthetic processes, a high level of oxidized
positive phosphorylation and a significant growth rate, have more
higher radiosensitivity than cells in the stationary phase.
The most biologically significant changes in an irradiated cell are
DNA changes: DNA chain breaks, chemical modification of purine and
pyrimidine bases, their separation from the DNA chain, the destruction of phosphoester
bonds in the macromolecule, damage to the DNA-membrane complex, destroying
DNA-protein bonding and many other disorders.
In all dividing cells, immediately after irradiation, it temporarily stops
mitotic activity (“radiation block of mitoses”). Violation of the meta-
bolic processes in the cell leads to an increase in the severity of molecular
lar damage in the cell. This phenomenon is called biological
th amplification of the primary radiation damage. However, along with
this, repair processes develop in the cell, as a result of which
is a complete or partial restoration of structures and functions.
The most sensitive to ionizing radiation are:
lymphatic tissue, bone marrow of flat bones, gonads, less sensitive
positive: connective, muscle, cartilage, bone and nervous tissues.
Cell death can occur both in the reproductive phase, directly
directly associated with the process of division, and in any phase of the cell cycle.
Newborns are more sensitive to ionizing radiation (due to
due to high mitotic activity of cells), old people (the way
ability of cells to recover) and pregnant women. Increased sensitivity to
ionizing radiation and with the introduction of certain chemical compounds
(so-called radiosensitization).
The biological effect depends on:
From the type of irradiation
From the absorbed dose
From dose distribution over time
From the specifics of the irradiated organ
The most dangerous irradiation of the crypts of the small intestine, testes, bones
of the brain of flat bones, the abdominal region and irradiation of the whole organism.
Single-celled organisms are about 200 times less sensitive to
exposure to radiation than multicellular organisms.
4. Natural and man-made sources of ionizing radiation.
Sources of ionizing radiation are natural and artificial
natural origin.
Natural radiation is due to:
1. Cosmic radiation (protons, alpha particles, nuclei of lithium, beryllium,
carbon, oxygen, nitrogen make up the primary cosmic radiation.
The earth's atmosphere absorbs primary cosmic radiation, then forms
secondary radiation, represented by protons, neutrons,
electrons, mesons and photons).
2. Radiation of radioactive elements of the earth (uranium, thorium, actinium, radioactive
diy, radon, thoron), water, air, building materials of residential buildings,
radon and radioactive carbon (C-14) present in inhaled
3. Radiation of radioactive elements contained in the animal world
and the human body (K-40, uranium -238, thorium -232 and radium -228 and 226).
Note: starting with polonium (No. 84), all elements are radioactive
active and capable of spontaneous fission of nuclei during the capture of their nuclei -
mi slow neutrons (natural radioactivity). However, natural
radioactivity is also found in some light elements (isotopes
rubidium, samarium, lanthanum, rhenium).
5. Deterministic and stochastic clinical effects that occur in humans when exposed to ionizing radiation.
The most important biological reactions of the human body to the action
ionizing radiation is divided into two types of biological effects
1. Deterministic (causal) biological effects
you for which there is a threshold dose of action. Below the disease threshold
does not manifest itself, but when a certain threshold is reached, diseases occur
nor directly proportional to the dose: radiation burns, radiation
dermatitis, radiation cataract, radiation fever, radiation infertility, ano-
Malia of fetal development, acute and chronic radiation sickness.
2. Stochastic (probabilistic) biological effects are not
ha action. May occur at any dose. They have an effect
small doses and even one cell (a cell becomes cancerous if it is irradiated
occurs in mitosis): leukemia, oncological diseases, hereditary diseases.
By the time of occurrence, all effects are divided into:
1. immediate - may occur within a week, a month. It's spicy
and chronic radiation sickness, skin burns, radiation cataracts...
2. distant - arising during the life of an individual: oncological
diseases, leukemia.
3. arising after an indefinite time: genetic consequences - due to
changes in hereditary structures: genomic mutations - multiple changes
haploid number of chromosomes, chromosomal mutations, or chromosomal
aberrations - structural and numerical changes in chromosomes, point (gene-
nye) mutations: changes in the molecular structure of genes.
Corpuscular radiation - fast neutrons and alpha particles, causing
cause chromosomal rearrangements more often than electromagnetic radiation.__
6. Radiotoxicity and radiogenetics.
Radiotoxicity
As a result of radiation disturbances of metabolic processes in the body
radiotoxins accumulate - these are chemical compounds that play
a certain role in the pathogenesis of radiation injuries.
Radiotoxicity depends on a number of factors:
1. Type of radioactive transformations: alpha radiation is 20 times more toxic than be-
ta radiation.
2. The average energy of the decay act: the energy of P-32 is greater than C-14.
3. Radioactive decay schemes: an isotope is more toxic if it gives rise to
new radioactive material.
4. Routes of entry: entry through the gastrointestinal tract in 300
times more toxic than through intact skin.
5. Time of residence in the body: more toxicity with significant
half-life and low half-life.
6. Distribution by organs and tissues and the specifics of the irradiated organ:
osteotropic, hepatotropic and evenly distributed isotopes.
7. Duration of receipt of isotopes in the body: accidental ingestion -
The use of a radioactive substance can end safely, with chronic
nic intake, accumulation of a dangerous amount of radiation is possible
body.
7. Acute radiation sickness. Prevention.
Melnichenko - page 172
8. Chronic radiation sickness. Prevention.
Melnichenko page 173
9. The use of sources of ionizing radiation in medicine (the concept of closed and open sources of radiation).
Sources of ionizing radiation are divided into closed and
covered. Depending on this classification, they are interpreted differently and
ways to protect against these radiations.
closed sources
Their device excludes the ingress of radioactive substances into the environment.
environment under application and wear conditions. It could be needles soldered
in steel containers, tele-gamma-irradiation units, ampoules, beads,
sources of continuous radiation and generating radiation periodically.
Radiation from sealed sources is only external.
Protection Principles for Working with Sealed Sources
1. Protection by quantity (reducing the dose rate at the workplace - than
The lower the dose, the lower the exposure. However, manipulation technology
always allows you to reduce the dose rate to a minimum value).
2. Time protection (reducing the time of contact with ionizing radiation
can be achieved by exercising without a transmitter).
3. Distance (remote control).
4. Screens (screens-containers for storage and transportation of radioactive
drugs in a non-working position, for equipment, mobile
nye - screens in x-ray rooms, parts of building structures
for the protection of territories - walls, doors, personal protective equipment -
plexiglass shields, lead-coated gloves).
Alpha and beta radiation is delayed by hydrogen-containing substances
materials (plastic) and aluminium, gamma radiation is attenuated by materials
with high density - lead, steel, cast iron.
To absorb neutrons, the screen must have three layers:
1st layer - to slow down neutrons - materials with a large number of atoms
mov hydrogen - water, paraffin, plastic and concrete
2. layer - for the absorption of slow and thermal neutrons - boron, cadmium
3. layer - to absorb gamma radiation - lead.
To assess the protective properties of a particular material, its ability
to delay ionizing radiation use a half-layer index
attenuation, indicating the thickness of the layer of this material, after passing
during which the intensity of gamma radiation is halved.
Open sources of radioactive radiation
An open source is a source of radiation, when using which
It is also possible for radioactive substances to enter the environment. At
this does not exclude not only external, but also internal exposure of personnel
(gases, aerosols, solid and liquid radioactive substances, radioactive
isotopes).
All works with open isotopes are divided into three classes. Ra-class
the bot is installed depending on the radiotoxicity group of radioactive
th isotope (A, B, C, D) and its actual amount (activity) on the working
place.
10. Ways to protect a person from ionizing radiation. Radiation safety of the population of the Russian Federation. Radiation safety standards (NRB-2009).
Methods of protection against open sources of ionizing radiation
1. Organizational measures: the allocation of three classes of work depending on
get out of danger.
2. Planning activities. For the first class of danger - specially
isolated buildings where unauthorized people are not allowed. For the second
th class, only a floor or part of a building is allocated. Third grade work
can be carried out in a conventional laboratory with a fume hood.
3. Sealing equipment.
4. The use of non-absorbent materials for table and wall coverings,
rational ventilation device.
5. Personal protective equipment: clothes, shoes, insulating suits,
respiratory protection.
6. Compliance with radiation asepsis: gowns, gloves, personal hygiene.
7. Radiation and medical control.
To ensure human safety in all conditions of exposure to
ionizing radiation of artificial or natural origin
radiation safety standards apply.
The following categories of exposed persons are established in the norms:
Personnel (group A - persons constantly working with sources of ion-
radiation and group B - a limited part of the population, which is otherwise
where it can be exposed to ionizing radiation - cleaners,
locksmiths, etc.)
The entire population, including persons from the staff, outside the scope and conditions of their production
water activity.
The main dose limits for group B personnel are ¼ of the values for
group A personnel. The effective dose for personnel should not exceed
period of labor activity (50 years) 1000 mSv, and for the population for the period
life (70 years) - 70 mSv.
The planned exposure of group A personnel is higher than the established pre-
cases in the liquidation or prevention of an accident can be resolved
only if it is necessary to save people or prevent their exposure
cheniya. Allowed for men over 30 years old with their voluntary written
consent, informing about the possible doses of radiation and the risk to health
ditch. In emergency situations, exposure should not exceed 50 mSv.__
11. Possible causes of emergencies at radiation hazardous facilities.
Classification of radiation accidents
Accidents associated with disruption of the normal operation of the ROO are divided into design and beyond design.
Design basis accident is an accident for which the initial events and final states are determined by the design, in connection with which safety systems are provided.
A beyond design basis accident is caused by initiating events that are not taken into account for design basis accidents and leads to severe consequences. In this case, radioactive products may be released in quantities that lead to radioactive contamination of the adjacent territory, and possible exposure of the population above the established norms. In severe cases, thermal and nuclear explosions can occur.
Potential accidents at nuclear power plants are divided into six types depending on the boundaries of the zones of distribution of radioactive substances and radiation consequences: local, local, territorial, regional, federal, transboundary.
If during a regional accident the number of people who received radiation doses above the levels established for normal operation may exceed 500 people, or the number of people whose living conditions may be impaired exceeds 1,000 people, or material damage exceeds 5 million minimum wages labor, then such an accident will be federal.
In case of transboundary accidents, the radiation consequences of the accident go beyond the territory of the Russian Federation, or this accident occurred abroad and affects the territory of the Russian Federation.
12. Sanitary and hygienic measures in emergency situations at radiation hazardous facilities.
The measures, methods and means that ensure the protection of the population from radiation exposure during a radiation accident include:
detection of the fact of a radiation accident and notification of it;
identification of the radiation situation in the area of the accident;
organization of radiation monitoring;
establishment and maintenance of the radiation safety regime;
carrying out, if necessary, at an early stage of the accident, iodine prophylaxis of the population, personnel of the emergency facility and participants in the liquidation of the consequences of the accident;
providing the population, personnel, participants in the liquidation of the consequences of the accident with the necessary personal protective equipment and the use of these funds;
shelter of the population in shelters and anti-radiation shelters;
sanitization;
decontamination of the emergency facility, other facilities, technical means, etc.;
evacuation or resettlement of the population from areas in which the level of contamination or radiation doses exceed the allowable for the population.
Identification of the radiation situation is carried out to determine the scale of the accident, to determine the size of the zones of radioactive contamination, the dose rate and the level of radioactive contamination in the areas of optimal routes for the movement of people, vehicles, as well as to determine possible evacuation routes for the population and farm animals.
Radiation control in the conditions of a radiation accident is carried out in order to comply with the permissible time for people to stay in the accident zone, control radiation doses and levels of radioactive contamination.
The radiation safety regime is ensured by the establishment of a special procedure for access to the accident zone, zoning of the accident area; carrying out emergency rescue operations, carrying out radiation monitoring in the zones and at the exit to the “clean” zone, etc.
The use of personal protective equipment consists in the use of insulating skin protection equipment (protective kits), as well as respiratory and eye protection equipment (cotton-gauze bandages, various types of respirators, filtering and isolating gas masks, goggles, etc.). They protect a person mainly from internal radiation.
To protect the thyroid gland of adults and children from exposure to radioactive isotopes of iodine, iodine prophylaxis is carried out at an early stage of the accident. It consists in taking stable iodine, mainly potassium iodide, which is taken in tablets in the following doses: for children from two years of age and older, as well as for adults, 0.125 g, up to two years, 0.04 g, ingestion after meals, along with jelly, tea, water 1 time per day for 7 days. An aqueous-alcoholic iodine solution (5% tincture of iodine) is indicated for children from two years of age and older, as well as for adults, 3-5 drops per glass of milk or water for 7 days. Children under two years of age are given 1-2 drops per 100 ml of milk or formula for 7 days.
The maximum protective effect (reducing the radiation dose by about 100 times) is achieved with the preliminary and simultaneous intake of radioactive iodine by taking its stable analogue. The protective effect of the drug is significantly reduced when it is taken more than two hours after the start of exposure. However, in this case, there is an effective protection against exposure to repeated intakes of radioactive iodine.
Protection from external radiation can only be provided by protective structures, which must be equipped with filters-absorbers of iodine radionuclides. Temporary shelters of the population before the evacuation can provide almost any pressurized premises.
Radioactive radiation (or ionizing) is the energy that is released by atoms in the form of particles or waves of an electromagnetic nature. Man is exposed to such influence both through natural and anthropogenic sources.
The useful properties of radiation have made it possible to successfully use it in industry, medicine, scientific experiments and research, agriculture and other fields. However, with the spread of the use of this phenomenon, a threat to human health has arisen. A small dose of radiation exposure can increase the risk of acquiring serious diseases.
The difference between radiation and radioactivity
Radiation, in a broad sense, means radiation, that is, the propagation of energy in the form of waves or particles. Radioactive radiation is divided into three types:
- alpha radiation - a stream of helium-4 nuclei;
- beta radiation - the flow of electrons;
- gamma radiation is a stream of high-energy photons.
The characterization of radioactive emissions is based on their energy, transmission properties and the type of emitted particles.
Alpha radiation, which is a stream of positively charged corpuscles, can be blocked by air or clothing. This species practically does not penetrate the skin, but when it enters the body, for example, through cuts, it is very dangerous and has a detrimental effect on internal organs.
Beta radiation has more energy - electrons move at high speed, and their size is small. Therefore, this type of radiation penetrates through thin clothing and skin deep into tissues. Shielding of beta radiation can be done with an aluminum sheet of a few millimeters or a thick wooden board.
Gamma radiation is a high-energy radiation of an electromagnetic nature, which has a strong penetrating power. To protect against it, you need to use a thick layer of concrete or a plate made of heavy metals such as platinum and lead.
The phenomenon of radioactivity was discovered in 1896. The discovery was made by the French physicist Becquerel. Radioactivity - the ability of objects, compounds, elements to emit ionizing study, that is, radiation. The reason for the phenomenon is the instability of the atomic nucleus, which releases energy during decay. There are three types of radioactivity:
- natural - characteristic of heavy elements, the serial number of which is greater than 82;
- artificial - initiated specifically with the help of nuclear reactions;
- induced - characteristic of objects that themselves become a source of radiation if they are strongly irradiated.
Elements that are radioactive are called radionuclides. Each of them is characterized by:
- half-life;
- the type of radiation emitted;
- radiation energy;
- and other properties.
Sources of radiation
The human body is regularly exposed to radioactive radiation. Approximately 80% of the amount received annually comes from cosmic rays. Air, water and soil contain 60 radioactive elements that are sources of natural radiation. The main natural source of radiation is the inert gas radon released from the ground and rocks. Radionuclides also enter the human body with food. Some of the ionizing radiation to which people are exposed comes from anthropogenic sources, ranging from nuclear power generators and nuclear reactors to radiation used for medical treatment and diagnostics. To date, common artificial sources of radiation are:
- medical equipment (the main anthropogenic source of radiation);
- radiochemical industry (mining, enrichment of nuclear fuel, processing of nuclear waste and their recovery);
- radionuclides used in agriculture, light industry;
- accidents at radiochemical plants, nuclear explosions, radiation releases
- Construction Materials.
Radiation exposure according to the method of penetration into the body is divided into two types: internal and external. The latter is typical for radionuclides dispersed in the air (aerosol, dust). They get on the skin or clothes. In this case, the sources of radiation can be removed by washing them away. External irradiation causes burns of the mucous membranes and skin. In the internal type, the radionuclide enters the bloodstream, for example by injection into a vein or through wounds, and is removed by excretion or therapy. Such radiation provokes malignant tumors.
The radioactive background significantly depends on the geographical location - in some regions, the radiation level can exceed the average by hundreds of times.
Effect of radiation on human health
Radioactive radiation due to the ionizing effect leads to the formation of free radicals in the human body - chemically active aggressive molecules that cause cell damage and death.
Cells of the gastrointestinal tract, reproductive and hematopoietic systems are especially sensitive to them. Radioactive exposure disrupts their work and causes nausea, vomiting, stool disorders, and fever. By acting on the tissues of the eye, it can lead to radiation cataracts. The consequences of ionizing radiation also include such damage as vascular sclerosis, impaired immunity, and a violation of the genetic apparatus.
The system of transmission of hereditary data has a fine organization. Free radicals and their derivatives can disrupt the structure of DNA - the carrier of genetic information. This leads to mutations that affect the health of future generations.
The nature of the impact of radioactive radiation on the body is determined by a number of factors:
- type of radiation;
- radiation intensity;
- individual characteristics of the organism.
The results of radiation exposure may not appear immediately. Sometimes its effects become noticeable after a considerable period of time. At the same time, a large single dose of radiation is more dangerous than long-term exposure to small doses.
The absorbed amount of radiation is characterized by a value called Sievert (Sv).
- The normal radiation background does not exceed 0.2 mSv/h, which corresponds to 20 microroentgens per hour. When X-raying a tooth, a person receives 0.1 mSv.
- The lethal single dose is 6-7 Sv.
Application of ionizing radiation
Radioactive radiation is widely used in technology, medicine, science, military and nuclear industry and other areas of human activity. The phenomenon underlies such devices as smoke detectors, power generators, icing alarms, air ionizers.
In medicine, radioactive radiation is used in radiation therapy to treat cancer. Ionizing radiation allowed the creation of radiopharmaceuticals. They are used for diagnostic tests. On the basis of ionizing radiation, instruments for the analysis of the composition of compounds and sterilization are arranged.
The discovery of radioactive radiation was, without exaggeration, revolutionary - the use of this phenomenon brought humanity to a new level of development. However, it has also become a threat to the environment and human health. In this regard, maintaining radiation safety is an important task of our time.
