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 is changed, 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 irradiation 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 exposure. Deaths are not recorded.
Radiation sickness of moderate severity occurs at a dose of 2.5 ... 4.0 Gy. Almost all irradiated people experience nausea, vomiting on the first day, 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, of interest are 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.
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 (P) - 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 over time in the event of an accidental release of a radioactive substance into the environment, to select 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 fulfillment by citizens and organizations carrying 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.
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 whole 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 closed 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.
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
Thus, 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. A water-alcohol 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 against 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 sealed premises.
51. Ionizing radiation. Types of ionizing radiation, main characteristics.
AI are divided into 2 types:
Corpuscular radiation
- 𝛼-radiation is a stream of helium nuclei emitted by a substance during radioactive decay or during nuclear reactions;
- 𝛽-radiation - a stream of electrons or positrons arising from radioactive decay;
Neutron radiation (With elastic interactions, the usual ionization of matter occurs. With inelastic interactions, secondary radiation occurs, which can consist of both charged particles and quanta).
2. Electromagnetic radiation
- 𝛾-radiation is electromagnetic (photon) radiation emitted during nuclear transformations or interaction of particles;
X-ray radiation - occurs in the environment surrounding the radiation source, in x-ray tubes.
AI characteristics: energy (MeV); speed (km/s); mileage (in air, in living tissue); ionizing capacity (pair of ions per 1 cm path in air).
The lowest ionizing ability of α-radiation.
Charged particles lead to direct, strong ionization.
Activity (A) of a radioactive substance is the number of spontaneous nuclear transformations (dN) in this substance in a short period of time (dt):
1 Bq (becquerel) is equal to one nuclear transformation per second.
52. Ionizing radiation. Doses of ionizing radiation and units of their measurement.
Ionizing radiation (IR) is radiation, the interaction of which with the medium leads to the formation of charges of opposite signs. Ionizing radiation occurs during radioactive decay, nuclear transformations, as well as during the interaction of charged particles, neutrons, photon (electromagnetic) radiation with matter.
Radiation dose is the value used to assess exposure to ionizing radiation.
Exposure dose(characterizes the radiation source by the ionization effect):
Exposure dose at the workplace when working with radioactive substances:
where A is the activity of the source [mCi], K is the gamma constant of the isotope [Rcm2/(hmCi)], t is the exposure time, r is the distance from the source to the workplace [cm].
Dose rate(irradiation intensity) - the increment of the corresponding dose under the influence of this radiation per unit. time.
Exposure dose rate [rh -1 ].
Absorbed dose shows how much AI energy is absorbed by the unit. masses of the irradiated in-va:
D absorption = D exp. K 1
where K 1 - coefficient taking into account the type of irradiated substance
Absorption dose, Gray, [J/kg]=1Gy
Dose equivalent characterized by chronic exposure to radiation of arbitrary composition
H = D Q [Sv] 1 Sv = 100 rem.
Q is a dimensionless weighting factor for a given type of radiation. For X-ray and -radiation Q=1, for alpha-, beta-particles and neutrons Q=20.
Effective equivalent dose character sensitivity decomp. organs and tissues to radiation.
Irradiation of inanimate objects - Absorb. dose
Irradiation of living objects - Equiv. dose
53. The effect of ionizing radiation(AI) on the body. External and internal exposure.
The biological effect of AI is based on the ionization of living tissue, which leads to the breaking of molecular bonds and a change in the chemical structure of various compounds, which leads to a change in the DNA of cells and their subsequent death.
Violation of the vital processes of the body is expressed in such disorders as
Inhibition of the functions of the hematopoietic organs,
Violation of normal blood clotting and increased fragility of blood vessels,
Disorder of the gastrointestinal tract,
Decreased resistance to infections
Depletion of the body.
External exposure occurs when the source of radiation is outside the human body and there are no ways for them to get inside.
Internal exposure origin when the source of AI is inside a person; while the internal Irradiation is also dangerous due to the proximity of the IR source to organs and tissues.
threshold effects (Н > 0.1 Sv/year) depend on the IR dose, occur with lifetime exposure doses
Radiation sickness is a disease that is characterized by symptoms that occur when exposed to AI, such as a decrease in hematopoietic ability, gastrointestinal upset, and a decrease in immunity.
The degree of radiation sickness depends on the radiation dose. The most severe is the 4th degree, which occurs when exposed to AI with a dose of more than 10 Gray. Chronic radiation injuries are usually caused by internal exposure.
Non-threshold (stochastic) effects appear at doses of H<0,1 Зв/год, вероятность возникновения которых не зависит от дозы излучения.
Stochastic effects include:
Somatic changes
Immune changes
genetic changes
The principle of rationing – i.e. non-exceeding of permissible limits individual. Radiation doses from all AI sources.
Justification principle – i.e. prohibition of all types of activity on the use of AI sources, in which the benefit received for a person and society does not exceed the risk of possible harm caused in addition to natural radiation. fact.
Optimization principle - maintenance at the lowest possible and achievable level, taking into account the economic. and social individual factors. exposure doses and the number of exposed persons when using an AI source.
SanPiN 2.6.1.2523-09 "Radiation safety standards".
In accordance with this document, 3 gr. persons:
gr.A - these are faces, for sure. working with man-made sources of AI
gr .B - these are persons, conditions for the work of the cat nah-Xia in the immediate. breeze from the AI source, but deyat. these persons immediately. is not connected with the source.
gr .AT is the rest of the population, incl. persons gr. A and B outside of their production activities.
The main dose limit is set. by effective dose:
For persons gr.A: 20mSv per year on Wed. for the next 5 years, but not more than 50 mSv in year.
For persons group B: 1mSv per year on Wed. for the next 5 years, but not more than 5 mSv in year.
For persons group B: should not exceed ¼ of the values for personnel group A.
In case of an emergency caused by a radiation accident, there is a so-called. peak increased exposure, cat. is allowed only in those cases when it is not possible to take measures excluding harm to the body.
The use of such doses can be justified only by saving lives and preventing accidents, additional only for men over 30 years of age with a voluntary written agreement.
AI protection m/s:
Qty protection
time protection
Distance protection
Zoning
Remote control
Shielding
For protection againstγ -radiation: metallic screens made with a large atomic weight (W, Fe), as well as from concrete, cast iron.
For protection against β-radiation: materials with a low atomic mass (aluminum, plexiglass) are used.
For protection against α-radiation: use metals containing H2 (water, paraffin, etc.)
Screen thickness К=Ро/Рdop, Ро – power. dose, measured per rad. place; Rdop - maximum allowable dose.
Zoning - division of the territory into 3 zones: 1) shelter; 2) objects and premises in which people can find; 3) zone post. stay of people.
Dosimetric control based on isp-ii trace. methods: 1. Ionization 2. Phonographic 3. Chemical 4. Calorimetric 5. Scintillation.
Basic appliances , used for dosimetric. control:
X-ray meter (for measuring powerful exp. doses)
Radiometer (to measure AI flux density)
Individual. dosimeters (for measuring exposure or absorbed dose).
The main effect of all ionizing radiation on the body is to ionize the tissues of those organs and systems that are exposed to them. The charges acquired as a result of this cause the occurrence of oxidative reactions unusual for the normal state in cells, which, in turn, cause a number of responses. Thus, in the irradiated tissues of a living organism, a series of chain reactions occur that disrupt the normal functional state of individual organs, systems, and the organism as a whole. There is an assumption that as a result of such reactions in the tissues of the body, products harmful to health are formed - toxins, which have an adverse effect.
When working with products that have ionizing radiation, the ways of exposure to the latter can be twofold: through external and internal radiation. External exposure can occur when working on accelerators, X-ray machines and other installations that emit neutrons and X-rays, as well as when working with sealed radioactive sources, that is, radioactive elements sealed in glass or other blind ampoules, if the latter remain intact. Sources of beta and gamma radiation can pose a risk of both external and internal exposure. alpha radiation practically poses a danger only with internal exposure, since due to the very low penetrating power and small range of alpha particles in the air, a slight distance from the radiation source or a small shielding eliminates the danger of external exposure.
With external irradiation with rays with a significant penetrating power, ionization occurs not only on the irradiated surface of the skin and other integuments, but also in deeper tissues, organs and systems. The period of direct external exposure to ionizing radiation - exposure - is determined by the exposure time.
Internal exposure occurs when radioactive substances enter the body, which can occur when inhaling vapors, gases and aerosols of radioactive substances, entering them into the digestive tract or entering the bloodstream (in cases of contamination of damaged skin and mucous membranes). Internal irradiation is more dangerous, because, firstly, in direct contact with tissues, even radiation of low energies and with minimal penetrating power still have an effect on these tissues; secondly, when a radioactive substance is in the body, the duration of its exposure (exposure) is not limited to the time of direct work with sources, but continues uninterrupted until its complete decay or removal from the body. In addition, when ingested, some radioactive substances, having certain toxic properties, in addition to ionization, have a local or general toxic effect (see "Harmful chemicals").
In the body, radioactive substances, like all other products, are carried by the bloodstream to all organs and systems, after which they are partially excreted from the body through the excretory systems (gastrointestinal tract, kidneys, sweat and mammary glands, etc.), and some of them are deposited in certain organs and systems, exerting a predominant, more pronounced effect on them. Some radioactive substances (for example, sodium - Na24) are distributed throughout the body relatively evenly. The predominant deposition of various substances in certain organs and systems is determined by their physicochemical properties and the functions of these organs and systems.
The complex of persistent changes in the body under the influence of ionizing radiation is called radiation sickness. Radiation sickness can develop both as a result of chronic exposure to ionizing radiation, and with short-term exposure to significant doses. It is characterized mainly by changes in the central nervous system (depression, dizziness, nausea, general weakness, etc.), blood and hematopoietic organs, blood vessels (bruising due to vascular fragility), endocrine glands.
As a result of prolonged exposure to significant doses of ionizing radiation, malignant neoplasms of various organs and tissues can develop, which: are the long-term consequences of this exposure. The latter also include a decrease in the body's resistance to various infectious and other diseases, an adverse effect on reproductive function, and others.
