AT everyday life human ionizing radiation is constantly encountered. We do not feel them, but we cannot deny their impact on living and inanimate nature. Not so long ago, people learned to use them both for the good and as a weapon of mass destruction. When used correctly, these radiation can change the life of mankind for the better.
Types of ionizing radiation
To understand the peculiarities of the influence on living and inanimate organisms, you need to find out what they are. It is also important to know their nature.
Ionizing radiation is a special wave that is able to penetrate through substances and tissues, causing the ionization of atoms. There are several types of it: alpha radiation, beta radiation, gamma radiation. They all have a different charge and ability to act on living organisms.
Alpha radiation is the most charged of all. It possesses enormous energy, capable of causing radiation sickness even in small doses. But with direct irradiation, it penetrates only the upper layers of human skin. Even a thin sheet of paper is protected from alpha rays. At the same time, entering the body with food or inhalation, the sources of this radiation quickly become the cause of death.
Beta rays are slightly less charged. They are able to penetrate deeply into the body. With prolonged exposure, they cause death of a person. Smaller doses cause changes in cellular structure. A thin sheet of aluminum can serve as protection. Radiation from within the body is also fatal.
The most dangerous is gamma radiation. It penetrates the body. In large doses, it causes radiation burns, radiation sickness, and death. Only lead and a thick layer of concrete can protect against it.
A special type of gamma radiation is considered to be X-rays, which are generated in an X-ray tube.
Research history
The world first 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 on, 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 radiation.
The Curies 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, this is radiation from the sun's rays and space. Most of it is absorbed by the ozone ball, which is located 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 were created by man for a variety of research and production. In this case, the strength of the radiation can be many times higher than the natural indicators.
Even in conditions of protection and compliance with safety measures, people receive doses of radiation hazardous to health.
Units and Doses
It is customary to correlate ionizing radiation with its interaction with the human body. Therefore, all units of measurement in one way or another are related to a person's ability to absorb and accumulate ionization energy.
In the SI system, doses of ionizing radiation are measured in a unit called the gray (Gy). It shows the amount of energy per unit of the irradiated substance. One Gy is equal to one J / kg. But for convenience, the off-system unit is often used, glad. It is equal to 100 Gy.
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 X-ray (P). To obtain an absorbed dose of 1 rad, one must succumb to irradiation with an exposure dose of about 1 R.
Since different types of ionizing radiation have different energy charges, it is customary to compare its measurement with biological influence. In the SI system, the unit of such an equivalent is the sievert (Sv). Its non-systemic analogue is rem.
The stronger and longer the radiation, the more energy is absorbed by the body, the more dangerous its influence. To find out the permissible time of a person's stay in radiation contamination, special devices are used - dosimeters that measure ionizing radiation. These can be both individual devices 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 the pigment melanin, which gives a beautiful tan. But prolonged exposure to radiation causes severe burns and can lead to skin cancer.
AT last years the effect of ionizing radiation on the human body and its practical application are being actively studied.
In small doses, radiation does not cause any harm to the body. Up to 200 mR X-rays can reduce the number of white blood cells. Symptoms of such radiation are nausea and dizziness. About 10% of people die after receiving this dose.
Large doses cause digestive upset, hair loss, skin burns, changes in the body's cellular structure, the development of cancer cells and death.
Radiation sickness
Long-term action of ionizing radiation on the body and receiving a large dose of radiation can cause radiation sickness. More than half of the cases of this disease are fatal. The rest are the cause of a number of genetic and somatic diseases.
On genetic level mutations occur in the germ cells. Their changes become evident in the next generations.
Somatic diseases are expressed by carcinogenesis, irreversible changes in various organs. The treatment for these diseases is long and difficult.
Treatment of radiation injuries
As a result of the pathogenic effect of radiation on the body, various damage to human organs occurs. Different methods of therapy are carried out depending on the radiation dose.
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 to facilitate the rapid elimination of radionuclides from the body.
If the lesion is severe, a bone marrow transplant may be needed. From radiation, it loses its ability to reproduce red blood cells.
But in most cases, the treatment of minor lesions is reduced to anesthetizing the affected areas, stimulating cell regeneration. Much attention is paid to rehabilitation.
Effects of ionizing radiation on aging and cancer
In connection with the influence of ionizing rays on the human body, scientists have carried out various experiments proving the dependence of aging and carcinogenesis on the radiation dose.
Groups of cell cultures were irradiated under laboratory conditions. As a result, it was possible to prove that even a slight irradiation contributes to the acceleration of cell aging. Moreover, the older the culture, the more it is subject to this process.
Long-term 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 stopping the processes of their division. This discovery helped develop a method for the treatment of human cancers.
Practical application of radiation
For the first time, radiation began to be used in medical practice. With the help of X-rays, doctors were able to look inside the human body. At the same time, practically no harm was done to him.
Further, with the help of radiation, they began to treat cancer. In most cases, this method has a positive effect, despite the fact that the entire body is exposed to strong radiation, which entails a number of symptoms of radiation sickness.
Apart from medicine, ionizing rays are used in other industries. Geodesists using radiation can study the structural features of the earth's crust in its individual areas.
Mankind has learned to use the ability of some fossils to release large amounts of energy for their own purposes.
Nuclear power
The future of the entire population of the Earth belongs to atomic energy. 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 pollution of the environment with both excess heat and production waste.
At the same time, scientists have developed weapons of mass destruction on the basis of atomic energy. At the moment on the planet atomic bombs so much that the launch of an insignificant number of them can cause a nuclear winter, as a result of which almost all living organisms inhabiting it will die.
Means and methods of protection
The daily use of radiation 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 their 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, you should avoid close contact with places where there is ionizing radiation. This is guaranteed to save you from unwanted consequences.
If it is possible to use sources with minimal radiation, they are primarily preferred. This is protection by quantity.
Shielding means creating barriers through which harmful rays do not penetrate. Lead screens in X-ray rooms are an example of this.
Household protection
In the event that a radiation catastrophe is declared, all windows and doors should be closed immediately, and you should try to stock up on water from sealed sources. Food should only be canned. When moving in open areas, cover the body with clothing as much as possible, and cover the face with a respirator or damp 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 clothing, water and food for 2-3 days.
Ionizing radiation as an environmental factor
There are quite a few 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 their own health. At the same time, it is not always possible to find out in advance about radiation pollution. Sometimes even an uncritical radiation background can cause a disaster.
The reason for this is the ability of living organisms to absorb and accumulate radiation. In doing so, they themselves turn into sources of ionizing radiation. The well-known "black" jokes about the Chernobyl mushrooms are based on this very property.
In such cases, protection from ionizing radiation comes down to the fact that all consumer products are amenable to careful radiological examination. At the same time, there is always a chance to buy the famous "Chernobyl mushrooms" at the spontaneous markets. Therefore, it is worth refraining from buying from unverified sellers.
The human body tends to accumulate hazardous substances, as a result of which a gradual poisoning occurs from the inside. It is not known when exactly the effects of the influence of these poisons will make themselves felt: in a day, a year, or in a generation.
Ionizing radiation - the type of radiation that everyone associates exclusively with the explosions of atomic bombs and accidents at nuclear power plants.
However, in fact, ionizing radiation surrounds a person and represents a natural background radiation: it is formed in household appliances, on electric towers, etc. When exposed to sources, a person is exposed to this radiation.
Should you be afraid of serious consequences - radiation sickness or organ damage?
The strength of the radiation effect depends on the duration of contact with the source and its radioactivity. Household appliances that create a slight "noise" are not dangerous to humans.
But some types of sources can cause serious harm to the body. To prevent negative impact, you need to know basic information: what is ionizing radiation and where it comes from, as well as how it affects a person.
Ionizing radiation occurs when radioactive isotopes decay.
There are many such isotopes, they are used in electronics, nuclear industry, energy production:
- uranium-238;
- thorium-234;
- uranium-235, etc.
Isotopes of a radioactive nature naturally decay over time. The decay rate depends on the type of isotope and is calculated in the half-life.
After a certain period of time (some elements may have several seconds, others - hundreds of years), the number of radioactive atoms is reduced by exactly half.
The energy that is released during the decay and destruction of nuclei is released in the form of ionizing radiation. It penetrates into various structures, knocking out ions from them.
Ionizing waves are based on gamma rays and are measured in gamma quanta. During the transfer of energy, no particles are released: atoms, molecules, neutrons, protons, electrons or nuclei. The effect of ionizing radiation is purely wave.
Radiation Penetration
All species differ in penetrating ability, that is, the ability to quickly overcome distances and pass through various physical obstacles.
Alpha radiation is the smallest, and gamma rays are the basis of ionizing radiation - the most penetrating of the three types of waves. In this case, alpha radiation has the most negative effect.
What is the difference between gamma radiation?
It is dangerous due to the following characteristics:
- spreads at the speed of light;
- passes through soft fabrics, wood, paper, drywall;
- stops only with a thick layer of concrete and a metal sheet.
To delay the waves that propagate this radiation, special boxes are installed at NPPs. Thanks to them, radiation cannot ionize living organisms, that is, disrupt the molecular structure of people.
Outside, the boxes are made of thick concrete, interior upholstered with a sheet of pure lead. Lead and concrete reflect or trap rays in their structure, preventing them from spreading and harming the living environment.
Types of radiation sources
The opinion that radiation occurs only as a result of human activity is erroneous. Almost all living objects and the planet itself have a weak background radiation, respectively. Therefore, it is very difficult to avoid ionizing radiation.
Based on the nature of occurrence, all sources are divided into natural and anthropogenic. The most dangerous are anthropogenic ones, such as the release of waste into the atmosphere and water bodies, an emergency or the operation of an electrical appliance.
The danger of the latter source is debatable: it is believed that small emitting devices do not pose a serious threat to humans.
The action is individual: someone may feel a deterioration in well-being against the background of weak radiation, while the other individual will be completely unaffected by the natural background.
Natural sources of radiation
The main danger to humans is represented by mineral rocks. Their cavities accumulate the greatest amount of radioactive gas, which is invisible to human receptors, - radon.
It naturally stands out from the earth's crust and is poorly recorded by testing instruments. When supplying building materials, contact with radioactive rocks is possible, and as a result - the process of ionization of the body.
You should be afraid:
- granite;
- pumice;
- marble;
- phosphogypsum;
- alumina.
These are the most porous materials and are the best at trapping radon. This gas is released from building materials or soil.
It is lighter than air, therefore it rises to a great height. If, instead of an open sky above the ground, an obstacle (canopy, roof of a room) is detected, gas will accumulate.
The high saturation of the air with its elements leads to irradiation of people, which can only be compensated for by removing radon from residential areas.
To get rid of radon, you need to start simple ventilation. You should try not to inhale the air in the room where the infection occurred.
Registration of the occurrence of accumulated radon is carried out only with the help of specialized symptoms. Without them, it is possible to draw a conclusion about the accumulation of radon only on the basis of non-specific reactions of the human body ( headache, nausea, vomiting, dizziness, darkening of the eyes, weakness and burning).
When radon is detected, an Emergency Situations Ministry team is called, which eliminates the radiation and checks the effectiveness of the procedures performed.
Sources of anthropogenic origin
Another name for man-made sources is technogenic. The main focus of radiation is nuclear power plants located around the world. Being in station zones without protective clothing entails the onset of serious illness and death.
At a distance of several kilometers from the nuclear power plant, the risk is reduced to zero. With proper isolation, all ionizing radiation remains inside the station, and you can be in the immediate vicinity of the working area, while not receiving any radiation dose.
In all spheres of life, one can encounter a radiation source, even without living in a city near a nuclear power plant.
Artificial ionizing radiation is widely used in various industries:
- medicine;
- industry;
- agriculture;
- knowledge-intensive industries.
However, it is impossible to receive radiation from devices that are manufactured for these industries.
The only thing that is permissible is the minimum penetration of ion waves, which is not harmful for a short duration of exposure.
Fallout
A serious problem of our time associated with the recent tragedies at nuclear power plants is the spread of radioactive rains. Emissions of radiation into the atmosphere end in the accumulation of isotopes in the atmospheric liquid - clouds. With an excess of liquid, precipitation begins, which pose a serious threat to crops and humans.
The liquid is absorbed into agricultural lands where rice, tea, corn, and reeds grow. These cultures are typical for the eastern part of the planet, where the problem of radioactive rains is most urgent.
Ionic radiation has less impact on other parts of the world because precipitation does not reach Europe and the island states in the UK area. However, in the USA and Australia, rains sometimes exhibit radiation properties, so you need to be careful when buying vegetables and fruits from there.
Radioactive fallout can fall over water bodies, and then liquid through water treatment canals and water supply systems can get into residential buildings. Treatment facilities do not have equipment sufficient to reduce radiation. There is always a risk that the water you receive is ionic.
How to protect yourself from radiation
A device that measures whether there is ion radiation in the background of the product is freely available. It can be purchased for little money and used to check purchases. The name of the verification device is dosimeter.
It is unlikely that a housewife will check purchases right in the store. Shyness in front of strangers usually interferes. But at least at home, those products that came from areas prone to radioactive rain need to be checked. It is enough to bring the counter to the object, and it will show the level of emission of dangerous waves.
The effect of ionizing radiation on the human body
It has been scientifically proven that radiation has a negative effect on a person. This was also found out on real experience: unfortunately, the accidents at the Chernobyl nuclear power plant, in Hiroshima, etc. proven biological and radiation.
The effect of radiation is based on the "dose" received - the amount of energy transferred. A radionuclide (emitting elements in waves) can have an effect both from the inside and outside of the body.
The received dose is measured in conventional units - Gray. It should be borne in mind that the dose may be equal, but the effect of radiation is different. This is due to the fact that different radiations cause reactions of different strengths (the most pronounced for alpha particles).
The strength of the impact is also influenced by which part of the body the waves hit. The genitals and lungs are the most susceptible to structural changes, the thyroid gland is less susceptible.
The result of biochemical exposure
Radiation affects the structure of cells in the body, causing biochemical changes: disturbances in the circulation of chemicals and in body functions. The influence of the waves appears gradually, and not immediately after irradiation.
If a person falls under the permissible dose (150 rem), then the negative effects will not be expressed. At higher irradiation, the ionization effect increases.
Natural radiation is equal to about 44 rem per year, the maximum is 175. The maximum number is only slightly outside the normal range and does not cause negative changes in the body, except for headaches or mild nausea in hypersensitive people.
Natural radiation is formed on the basis of the background radiation of the Earth, the use of contaminated products, the use of technology.
If the proportion is exceeded, the following diseases develop:
- genetic changes in the body;
- sexual dysfunction;
- brain cancers;
- dysfunction of the thyroid gland;
- lung and respiratory system cancer;
- radiation sickness.
Radiation sickness is an extreme stage of all diseases associated with radionuclides and manifests itself only in those who are in the accident zone.
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, the content
reap the same number of positively charged protons and different co-
number of particles without charge - neutrons.
2. The positive charge of the nucleus, due to the number of protons, is
is suspended by a negative charge of electrons. Therefore the atom is electrically
neutral.
3. Atoms of the same element with the same charge, but different
the 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) by their stability are divided into stable and
decaying, i.e. radioactive.
6. Radioactivity - spontaneous transformation of the nuclei of atoms of some
cops to others, accompanied by the emission of ionizing radiation
7. Radioactive isotopes decay at a certain rate, measuring
my half-life, that is, the time when the original number
nuclei is halved. From here, radioactive isotopes are classified into
short-lived (half-life is calculated from fractions of a second to non-
how many days) and long-lived (with a half-life of several months
up to billions of years).
8. Radioactive decay cannot be stopped, accelerated or slowed down by
in any way.
9. The rate of nuclear transformations is characterized by activity; number
decays per unit time. The unit of activity is the becquerel
(Bq) - one transformation per second. Non-systemic unit of activity -
curie (Ki), 3.7 x 1010 times larger than the becquerel.
There are the following types of radioactive transformations: corpus-
polar and wave.
Corpuscular ones include:
1. Alpha decay. It is characteristic of natural radioactive elements with
large serial numbers and represents a flux 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
energy levels. In this case, excited nuclei arise, which
which, passing into the ground state, emit gamma quanta. When interconnecting
the interaction of alpha particles with matter, their energy is spent on excitation
formation and ionization of atoms of the medium.
Alpha particles have the greatest degree of ionization -
60,000 ion pairs on a path in 1 cm of air. Particle trajectory first
gii, collision with nuclei), which increases the ionization density at the end
particle paths.
With a relatively large mass and charge, alpha particles
have a low penetrating power. So, for an alpha particle
with an energy of 4 MeV, the path length in air is 2.5 cm, and biological
fabric 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. It is characteristic for both natural and
artificial radioactive elements. The nucleus emits an electron and
in this case, the nucleus of the new element disappears with a constant mass number and
large serial number.
Example: ----- + ē
When the nucleus emits an electron, it is accompanied by a neutrino emission.
(1/2000 electron rest mass).
When beta particles are emitted, the nuclei of atoms can be in an excited
condition. Their transition to an unexcited state is accompanied by an emission
kaniya gamma quanta. The mean free path of a beta particle in air at 4 MeV 17
cm, while 60 pairs of ions are formed.
3. Positron beta decay. It is observed in some artificial
dioactive isotopes. The mass of the nucleus practically does not change, and the order
the first number is decremented by one.
4. K-capture of an orbital electron by a nucleus. The nucleus captures an electron from K-
shell, while a neutron is emitted from the nucleus and a characteristic
x-ray radiation.
5. Neutron radiation is also referred to as corpuscular radiation. Neutrons are not
having charge elementary particles with a mass equal to 1. Depending
from their energy are distinguished slow (cold, thermal and epithermal)
resonant, intermediate, fast, very fast and super fast
neutrons. Neutron radiation is the shortest: after 30-40 seconds
kund neutron decays into an electron and a proton. Penetrating ability
the neutron flux is comparable to that for gamma radiation. With penetrating
the appearance of neutron radiation in tissue to a depth of 4-6 cm, a
given radioactivity: stable elements become radioactive.
6. Spontaneous fission of nuclei. This process is observed in radioactive
elements with a large atomic number when captured by nuclei of slow
electrons. The same nuclei form different pairs of fragments with
the daily amount of neutrons. When nuclei fission, energy is released.
If neutrons are used again for the subsequent fission of other nuclei,
the reaction will be chain.
In radiation therapy of tumors, pi-mesons are used - elementary parts
particles with a negative charge and a mass 300 times the mass of the electric
throne. Pi-mesons interact with atomic nuclei only at the end of their range, 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 speed of propagation is close to the speed of light. Penetrating
ability is high: 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 quantum is almost
10,000 times the energy of a quantum of visible light.
2. X-rays. Electromagnetic radiation, artificially
read in x-ray tubes. When high voltage is applied to
cathode, electrons fly out of it, which move at high speed
push to the anti-cathode and hit its surface made of gravity
yellow metal. Bremsstrahlung X-ray radiation appears,
high penetrating power.
Features of radiation radiation
1. No source radiation not defined by any
ganom 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
contamination of the territory of one country is affected by radiation and others.
4. Under the action of radioactive radiation in the body, specific
chemical reactions.
Qualities inherent in radioactive elements
and ionizing radiation
1. Change in physical properties.
2. Ability to ionize the environment.
3. Penetrating power.
4. Half-life.
5. The half-life.
6. The presence of a critical body, i.e. tissue, organ or body part, radiation
which can cause the greatest damage to human health or
offspring.
3. Stages of the action of ionizing radiation on the human body.
The effect of ionizing radiation on the body
Immediate direct violations in cells and tissues occurring
following radiation, are negligible. So, for example, under the action of radiation, you
the death of the experimental animal, the temperature in its body increased
rises by only one hundredth of a degree. However, under the action of
dioactive radiation in the body, there are very serious various
violations that should be addressed in stages.
1. Physicochemical stage
The phenomena that occur at this stage are called primary or
launchers. It is they who determine the entire further course of the development of ray
defeats.
First, ionizing radiation interacts with water, knocking out
its molecules are electrons. Molecular ions are formed that carry positive
ny and negative charges. The so-called radiolysis of water is in progress.
Н2О - ē → Н2О +
H2O + ē → H2O-
The H2O molecule can be destroyed: H and OH
Hydroxyls can recombine: OH
OH hydrogen peroxide H2O2 is formed
During the interaction of H2O2 and OH, HO2 (hydroperoxide) and H2O are formed
Ionized and excited atoms and molecules within 10 seconds
they interact with each other and with various molecular systems,
giving rise to chemically active centers (free radicals, ions, ion-
radicals, etc.). In the same period, bond breaks in molecules are possible as in
due to direct interaction with the ionizing agent, and
account of intra- and intermolecular transfer of excitation energy.
2. Biochemical stage
The permeability of the membranes increases, through them diffuse
put 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
comes down to changes in proteins, lipids, carbohydrates and enzymes.
In proteins occur:
Configuration changes in protein structure.
Aggregation of molecules due to the formation of disulfide bonds
Breaking peptide or carbon bonds leading to the destruction of proteins
A decrease in the level of methionine, a donor of sulfhydryl groups, trypto-
fun, which leads to a sharp slowdown in protein synthesis
Decrease in 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 fer-
cops for their destruction (the effect of peroxidase is insignificant)
Antioxidants are suppressed
In carbohydrates:
Polysaccharides break down to simple sugars
Irradiation of simple sugars leads to their oxidation and decay 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 disrupted
The content of glycogen in muscles and liver decreases.
In the enzyme system, oxidative phosphorylation is disturbed and
the activity of a number of enzymes changes, reactions develop chemically active
substances with various biological structures, in which
both destruction and the formation of new ones that are not characteristic of irradiation
the organism, compounds.
The subsequent stages of 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 radiation is associated with changes taking place,
both in cellular organelles, and in the relationship between them.
Organelles of the body cells most sensitive to radiation
mammals are the nucleus and mitochondria. Damage to these structures
occur at low doses and at the earliest possible date. In the nuclei of radiosensitivity
body cells, energy processes are inhibited, the function
membranes. Proteins are formed that have lost their normal biological
tivity. More pronounced radiosensitivity than nuclei, they have
tochondria. These changes are manifested in the form of swelling of mitochondria,
damage to their membranes, a sharp suppression of oxidative phosphorylation.
Cell radiosensitivity is highly dependent on speed
metabolic processes occurring in them. Cells that are characterized by
intensive biosynthetic processes, high level oxidized
phosphorylation and a significant growth rate, have a higher
with a higher radiosensitivity than cells in the stationary phase.
The most biologically significant in an irradiated cell are
dNA changes: DNA strand breaks, chemical modification of purine and
pyrimidine bases, their detachment from the DNA chain, destruction of phosphoether
bonds in the macromolecule, damage to the DNA-membrane complex, destruction
dNA-protein bonds and many other disorders.
In all dividing cells, immediately after irradiation, it temporarily stops
xia mitotic activity ("radiation block of mitosis"). Violation of meta-
bolic processes in the cell leads to an increase in the severity of molecular
lesions in the cell. This phenomenon is called biological
increase in primary radiation damage. However, along with
by this, reparation 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, sex glands, less sensitive
nominative: connective, muscle, cartilaginous, bone and nervous tissue.
Cell death can occur both in the reproductive phase, directly
related to the process of division, as well as in any phase of the cell cycle.
Newborns are more sensitive to ionizing radiation (due to
high mitotic activity of cells), old people (the ability to
cells to regenerate) and pregnant women. Sensitivity to
ionizing radiation and with the introduction of certain chemical compounds
(the so-called radiosensitization).
The biological effect depends on:
From the type of radiation
From the absorbed dose
From dose distribution over time
From the specifics of the irradiated organ
The most dangerous is irradiation of crypts of the small intestine, testes, bone
forebrain of flat bones, abdominal area and radiation of the whole organism.
Single-celled organisms are about 200 times less sensitive to
to radiation than multicellular organisms.
4. Natural and man-made sources of ionizing radiation.
Sources of ionizing radiation are natural and artificial
of natural origin.
Natural radiation is caused by:
1. Cosmic radiation (protons, alpha particles, lithium nuclei, beryllium,
carbon, oxygen, nitrogen constitute the primary cosmic radiation.
The atmosphere of the earth absorbs the primary cosmic radiation, then the form
secondary radiation, represented by protons, neutrons,
electrons, mesons and photons).
2. Radiation of radioactive elements of the earth (uranium, thorium, actinium, ra-
diy, radon, thoron), water, air, building materials of residential buildings,
radon and radioactive carbon (C-14) present in the inhaled
3. Radiation of radioactive elements contained in the animal kingdom
and the human body (K-40, uranium-238, thorium-232 and radium -228 and 226).
Note: starting from polonium (no. 84), all elements are radioactive
spontaneous and capable of spontaneous nuclear fission upon capture of their nucleus
mi of slow neutrons (natural radioactivity). However, the natural
radioactivity is also found in some light elements (isotopes
rubidium, samarium, lanthanum, rhenium).
5. Deterministic and stochastic clinical effects arising in humans when exposed to ionizing radiation.
The most important biological reactions of the human body to action
ionizing radiation is divided into two types of biological effects
1. Deterministic (causal) biological effects
you for whom there is a threshold dose of action. Below the threshold is disease
does not appear, but when a certain threshold is reached, diseases
nor, directly proportional to the dose: radiation burns, radiation
dermatitis, radiation cataract, radiation fever, radiation infertility, ano-
malias of fetal development, acute and chronic radiation sickness.
2. Stochastic (probabilistic) biological effects have no porosity
ha of action. May occur at any dose. They are characterized by the 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 subdivided into:
1. direct - can occur during the week, month. It is 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 chromosome number, chromosomal mutation or chromosomal
aberrations - structural and numerical changes in chromosomes, point (gene-
ny) mutations: changes in the molecular structure of genes.
Corpuscular radiation - fast neutrons and alpha particles, causing
chromosomal rearrangements occur more often than electromagnetic radiation .__
6. Radiotoxicity and radiogenetics.
Radiotoxicity
As a result of radiation disorders of metabolic processes in the body
accumulate radiotoxins - this chemical compoundswho play
a certain role in the pathogenesis of radiation injuries.
Radiotoxicity depends on a number of factors:
1. Kind of radioactive transformations: alpha radiation is 20 times more toxic than
ta-radiation.
2. The average energy of the decay act: the energy of P-32 is greater than C-14.
3. Schemes of radioactive decay: an isotope is more toxic if it gives rise to
new radioactive substance.
4. Routes of admission: entry through the gastrointestinal tract in 300
times more toxic than intact skin.
5. Time spent in the body: more toxicity with significant
half-life and low half-life.
6. Distribution of organs and tissues and specificity of the irradiated organ:
osteotropic, hepatotropic and evenly distributed isotopes.
7. Duration of intake of isotopes in the body: accidental ingestion-
the ingestion of a radioactive substance can end safely, if
the accumulation of a dangerous amount of radiation is possible
body.
7. Acute radiation sickness. Prevention.
Melnichenko - p. 172
8. Chronic radiation sickness. Prevention.
Melnichenko p. 173
9. Using sources of ionizing radiation in medicine (the concept of closed and open sources of radiation).
Sources of ionizing radiation are divided into sealed and isolated
covered. Depending on this classification, they are interpreted differently and
methods of protection against these emissions.
Closed sources
Their device excludes the ingress of radioactive substances into the environment
environment under conditions of use and wear. It can be needles sealed
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 when working with sealed sources
1. Protection by quantity (reduction of the dose rate at the workplace - than
the lower the dose, the lower the radiation exposure. However, the manipulation technology is not
always allows you to reduce the dose rate to a minimum).
2. Time protection (reducing the time of contact with ionizing radiation
can be achieved by training without an emitter).
3. Distance (remote control).
4. Screens (screens-containers for storage and transportation of radioac-
drugs in an idle position, for equipment, mobile
nye - screens in X-ray rooms, parts of building structures
to protect territories - walls, doors, personal protective equipment -
plexiglass shields, leaded gloves).
Alpha and beta radiation is delayed by hydrogen-containing substances
materials (plastic) and aluminum, gamma radiation is attenuated by materials
with high density - lead, steel, cast iron.
To absorb neutrons, the shield must have three layers:
1.layer - to slow down neutrons - materials with a large amount of atoms
mov of hydrogen - water, paraffin, plastic and concrete
2.layer - for absorption of slow and thermal neutrons - boron, cadmium
3. layer - for absorbing gamma radiation - lead.
To assess the protective properties of a material, its ability
trap ionizing radiation use the layer index half
th weakening, denoting the thickness of the layer of this material, after passing
whose intensity of gamma radiation is halved.
Open sources of radioactive radiation
An open source is a source of radiation that, when used,
ingress of radioactive substances into the environment is possible. When
this does not exclude not only external, but also internal exposure of personnel
(gases, aerosols, solid and liquid radioactive substances, radioactive
isotopes).
All work with open isotopes is divided into three classes. Class ra-
the bot is installed depending on the radioactive toxicity group
th isotope (A, B, C, D) and its actual amount (activity) at the working
location.
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
from danger.
2. Planning activities. For the first class of hazard - specially
insulated enclosures where unauthorized people are not allowed. For the second
only a floor or part of a building is allocated to the first class. Works of the third class
can be carried out in a conventional laboratory with a fume hood.
3. Equipment sealing.
4. The use of non-absorbent materials for covering tables and walls,
rational ventilation device.
5. Personal protective equipment: clothing, shoes, isolation 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
its ionizing radiation of artificial or natural origin
radiation safety standards are applied.
The norms establish the following categories of exposed persons:
Personnel (group A - persons who constantly work with sources of ion-
radiation and group B - a limited part of the population, which is
where may be exposed to ionizing radiation - cleaning women,
locksmiths, etc.)
The entire population, including personnel, outside the scope and conditions of their production
management activities.
The main dose limits for group B personnel are ¼ values \u200b\u200bfor
personnel of group A. The effective dose for personnel should not exceed
the period of employment (50 years) 1000 mSv, and for the population for the period
life (70 years) - 70 mSv.
Planned exposure of personnel of group A above the established pre-
business in 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 possible radiation doses and risks 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 normal operation of the ROO are subdivided into design and beyond design basis.
Design basis accident is an accident for which initiating events and final states are defined by the project, in connection with which safety systems are provided.
Beyond design basis accident is caused by initiating events not considered for design basis accidents and leads to severe consequences. In this case, the release of radioactive products may occur in quantities leading to radioactive contamination of the adjacent territory, possible exposure of the population above the established standards. In severe cases, thermal and nuclear explosions can occur.
Potential accidents at NPPs 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, and transboundary.
If, in a regional accident, the number of people who have received a dose of radiation above the levels established for normal operation may exceed 500 people, or the number of people whose living conditions may be violated exceeds 1,000 people, or material damage exceeds 5 million minimum wages labor, then such an accident will be federal.
In transboundary accidents, the radiation consequences of the accident go beyond the territory Russian Federationor given accident occurred abroad and affects the territory of the Russian Federation.
12. Sanitary and hygienic measures in emergency situations at radiation-hazardous facilities.
Measures, methods and means to ensure the protection of the population from radiation exposure in a radiation accident include:
detection of the fact of a radiation accident and notification of it;
identification of the radiation situation in the accident area;
organization of radiation monitoring;
establishment and maintenance of the radiation safety regime;
conducting, 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 means;
sheltering the population in shelters and anti-radiation shelters;
sanitization;
decontamination of the emergency facility, other facilities, technical equipment, etc.
evacuation or resettlement of the population from areas in which the level of contamination or radiation doses exceed the permissible for the population.
The identification of the radiation situation is carried out to determine the scale of the accident, to establish the size of the zones of radioactive contamination, the dose rate and the level of radioactive contamination in the zones of optimal routes for the movement of people, transport, as well as to determine possible routes for the evacuation of the population and farm animals.
Radiation monitoring under conditions of a radiation accident is carried out in order to comply with the permissible time spent by people in the accident zone, to 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 (protective kits), as well as respiratory and vision protection (cotton-gauze dressings, various types of respirators, filtering and insulating 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 at an early stage of the accident, iodine prophylaxis is carried out. 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 at 0.125 g, up to two years at 0.04 g, taken orally after meals with jelly, tea, water once a day for 7 days. A solution of iodine water-alcohol (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 old are given 1-2 drops per 100 ml of milk or nutritional formula for 7 days.
The maximum protective effect (reduction of the radiation dose by about 100 times) is achieved with the preliminary and simultaneous intake of radioactive iodine with 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, even in this case, effective protection against radiation occurs in the event of repeated inflows of radioactive iodine.
Protection from external exposure can only be provided by protective structures, which must be equipped with filters that absorb iodine radionuclides. Temporary shelters for the population prior to evacuation can be provided by almost any pressurized room.
"The attitude of people to a particular danger is determined by how well they are familiar with it."
This material is a generalized answer to numerous questions arising from users of devices for detecting and measuring radiation in a domestic environment.
The minimal use of the specific terminology of nuclear physics when presenting the material will help you to freely navigate this environmental problem, without succumbing to radiophobia, but also without undue complacency.
The danger of RADIATION, real and perceived
"One of the first discovered natural radioactive elements was named" radium "
- translated from Latin - emitting rays, radiating. "
Of every person in environment lie in wait various phenomenainfluencing him. These include heat, cold, magnetic and normal storms, torrential rains, heavy snowfalls, strong winds, sounds, explosions, etc.
Thanks to the presence of the senses allotted to him by nature, he can quickly respond to these phenomena with the help of, for example, a canopy from the sun, clothes, housing, medicines, screens, shelters, etc.
However, in nature there is a phenomenon to which a person, due to the lack of the necessary sense organs, cannot instantly respond - this is radioactivity. Radioactivity is not a new phenomenon; radioactivity and accompanying radiation (so-called ionizing) have always existed in the Universe. Radioactive materials are part of the Earth and even a person is slightly radioactive, because any living tissue contains trace amounts of radioactive substances.
The most unpleasant property of radioactive (ionizing) radiation is its effect on the tissues of a living organism, therefore, appropriate measuring instruments are needed that would provide operational information for making useful decisions before a long time passes and undesirable or even disastrous consequences appear. will begin to feel not immediately, but only after some time. Therefore, information on the presence of radiation and its power must be obtained as early as possible.
Enough riddles, however. Let's talk about what radiation and ionizing (i.e. radioactive) radiation are.
Ionizing radiation
Any medium consists of the smallest neutral particles atoms, which are made up of positively charged nuclei and surrounding negatively charged electrons. Every atom is like solar system in miniature: "planets" move around a tiny nucleus in orbits - electrons.
Atom nucleus consists of several elementary particles, protons and neutrons, confined by nuclear forces.
Protons particles with a positive charge equal in absolute value to the charge of electrons.
Neutrons neutral, non-charged particles. The number of electrons in an atom is exactly equal to the number of protons in the nucleus, so each atom is generally neutral. The mass of a proton is almost 2000 times the mass of an electron.
The number of neutral particles (neutrons) present in the nucleus can be different for the same number of protons. Such atoms, having nuclei with the same number of protons, but differing in the number of neutrons, belong to varieties of the same chemical element, called "isotopes" of this element. To distinguish them from each other, a number is assigned to the symbol of the element, equal to the sum of all particles in the nucleus of a given isotope. So uranium-238 contains 92 protons and 146 neutrons; uranium 235 also has 92 protons, but 143 neutrons. All isotopes of a chemical element form a group of "nuclides". Some nuclides are stable, i.e. do not undergo any transformations, while others emitting particles are unstable and turn into other nuclides. As an example, let's take an atom of uranium - 238. From time to time, a compact group of four particles escapes from it: two protons and two neutrons - an "alpha particle (alpha)". Uranium-238 is thus converted into an element with 90 protons and 144 neutrons in its nucleus - thorium-234. But thorium-234 is also unstable: one of its neutrons turns into a proton, and thorium-234 turns into an element with 91 protons and 143 neutrons in its nucleus. This transformation also affects the electrons (beta) moving in their orbits: one of them becomes, as it were, superfluous, without a pair (proton), so it leaves the atom. A chain of numerous transformations, accompanied by alpha or beta radiation, ends with a stable lead nuclide. Of course, there are many similar chains of spontaneous transformations (decays) of different nuclides. The half-life is a period of time during which the initial number of radioactive nuclei, on average, is halved.
With each act of decay, energy is released, which is transmitted in the form of radiation. Often an unstable nuclide turns out to be in an excited state and the emission of a particle does not lead to a complete removal of the excitation; then it emits a portion of energy in the form of gamma radiation (gamma quantum). As in the case of X-rays (which differ from gamma rays only in frequency), there is no emission of any particles. The whole process of spontaneous decay of an unstable nuclide is called radioactive decay, and the nuclide itself is called a radionuclide.
Different types of radiation are accompanied by the release of different amounts of energy and have different penetrating power; therefore, they have a different effect on the tissues of a living organism. Alpha radiation is trapped, for example, by a sheet of paper and practically unable to penetrate the outer layer of the skin. Therefore, it is not dangerous as long as the radioactive substances emitting alpha particles do not enter the body through an open wound, with food, water or inhaled air or steam, for example, in a bath; then they become extremely dangerous. Beta - a particle has a greater penetrating ability: it penetrates into the tissues of the body to a depth of one to two centimeters or more, depending on the amount of energy. The penetrating power of gamma rays, which travels at the speed of light, is very high: only a thick lead or concrete slab can stop it. Ionizing radiation is characterized by a number of measurable physical quantities... These include energy quantities. At first glance, it may seem that there are enough of them to register and assess the impact of ionizing radiation on living organisms and humans. However, these energetic values \u200b\u200bdo not reflect the physiological effects of ionizing radiation on the human body and other living tissues, they are subjective, and for different people are different. Therefore, averaged values \u200b\u200bare used.
Sources of radiation are natural, present in nature, and not dependent on humans.
It has been established that of all natural sources of radiation, the greatest danger is represented by radon, a heavy gas without taste, smell and at the same time invisible; with their daughter products.
Radon is released from the earth's crust everywhere, but its concentration in the outside air differs significantly at different points in the world. Paradoxical as it may seem at first glance, a person receives the main radiation from radon while being in a closed, unventilated room. Radon concentrates in indoor air only when they are sufficiently isolated from the external environment. Escaping through the foundation and the floor from the ground or, less often, being released from building materials, radon accumulates in the room. Sealing the premises for the purpose of insulation only aggravates the matter, since it makes it even more difficult for the radioactive gas to leave the room. The radon problem is especially important for low-rise buildings with careful sealing of the premises (in order to preserve heat) and the use of alumina as an additive to building materials (the so-called "Swedish problem"). The most common building materials - wood, brick and concrete - emit relatively little radon. Granite, pumice, alumina products, and phosphogypsum have a much higher specific radioactivity.
Another, usually less important, source of radon entering the premises is water and natural gas used for cooking and heating homes.
The concentration of radon in commonly used water is extremely low, but water from deep wells or artesian wells contains a lot of radon. However, the main danger does not come from drinking water, even with a high content of radon in it. Usually, people consume most of the water in food and in the form of hot drinks, and when boiling water or preparing hot dishes, radon almost completely evaporates. A much greater danger is the ingress of water vapor with a high content of radon into the lungs along with the inhaled air, which most often occurs in a bathroom or steam room (steam room).
Radon penetrates into natural gas underground. As a result of preliminary processing and during the storage of gas before it enters the consumer, most of the radon evaporates, but the concentration of radon in the room can increase noticeably if stoves and other heating gas appliances are not equipped with an exhaust hood. In the presence of supply and exhaust ventilation, which communicates with the outside air, the concentration of radon in these cases does not occur. This also applies to the house as a whole - focusing on the readings of radon detectors, you can set the ventilation mode of the premises, which completely eliminates the threat to health. However, given that the release of radon from the soil is seasonal, it is necessary to control the ventilation efficiency three to four times a year, preventing the excess of radon concentration standards.
Other sources of radiation, unfortunately potentially dangerous, were created by man himself. Sources of artificial radiation are artificial radionuclides, beams of neutrons and charged particles created using nuclear reactors and accelerators. They are called technogenic sources of ionizing radiation. It turned out that along with a dangerous character for humans, radiation can be put at the service of humans. Here is a far from complete list of fields of application of radiation: medicine, industry, agriculture, chemistry, science, etc. A calming factor is the controlled nature of all activities related to the production and use of artificial radiation.
Tests stand apart in terms of their effect on humans. nuclear weapons in the atmosphere, accidents at nuclear power plants and nuclear reactors and the results of their work, manifested in radioactive fallout and radioactive waste. However, only emergency situations, such as the Chernobyl accident, can have an uncontrolled impact on humans.
The rest of the work is easily supervised at a professional level.
When radioactive fallout occurs in some areas of the Earth, radiation can enter the human body directly through agricultural products and food. It is very simple to protect yourself and your loved ones from this danger. When buying milk, vegetables, fruits, herbs, and any other products, it will not be superfluous to turn on the dosimeter and bring it to the purchased product. No radiation is visible - but the device will instantly detect the presence of radioactive contamination. This is our life in the third millennium - the dosimeter is becoming an attribute of everyday life, like a handkerchief, a toothbrush, or soap.
EFFECT OF IONIZING RADIATION ON BODY TISSUE
The damage caused in a living organism by ionizing radiation will be the greater, the more energy it transfers to the tissues; the amount of this energy is called a dose, by analogy with any substance entering the body and fully assimilated by it. The body can receive a dose of radiation regardless of whether the radionuclide is outside the body or inside it.
The amount of radiation energy absorbed by the irradiated tissues of the body, per unit mass, is called the absorbed dose and is measured in Grays. But this value does not take into account the fact that with the same absorbed dose, alpha radiation is much more dangerous (twenty times) than beta or gamma radiation. The dose recalculated in this way is called the equivalent dose; it is measured in units called Sieverts.
It should also be borne in mind that some parts of the body are more sensitive than others: for example, with the same equivalent dose of radiation, the occurrence of cancer in the lungs is more likely than in the thyroid gland, and irradiation of the gonads is especially dangerous because of the risk of genetic damage. Therefore, human doses should be taken into account with different coefficients. Multiplying the equivalent doses by the appropriate coefficients and summing up over all organs and tissues, we obtain the effective equivalent dose, reflecting the total effect of radiation on the body; it is also measured in Sievert.
Charged particles.
Alpha and beta particles penetrating into the tissues of the body lose energy due to electrical interactions with the electrons of those atoms near which they pass. (Gamma rays and X-rays transfer their energy to matter in several ways, which ultimately also lead to electrical interactions.)
Electrical interactions.
In a time of the order of ten trillionth of a second after the penetrating radiation reaches the corresponding atom in the tissue of the body, an electron is detached from this atom. The latter is negatively charged, so the rest of the initially neutral atom becomes positively charged. This process is called ionization. The detached electron can further ionize other atoms.
Physicochemical changes.
Both a free electron and an ionized atom usually cannot stay in this state for a long time, and for the next ten billionths of a second they participate in a complex chain of reactions, as a result of which new molecules are formed, including such extremely reactive ones as "free radicals".
Chemical changes.
Over the next millionths of a second, the formed free radicals react both with each other and with other molecules, and through a chain of reactions not yet fully understood, they can cause chemical modification of biologically important molecules necessary for the normal functioning of the cell.
Biological effects.
Biochemical changes can occur both in a few seconds and in decades after irradiation and cause immediate cell death or changes in them.
UNITS OF MEASUREMENT OF RADIOACTIVITY |
||
|
Becquerel (Bq, Bq); |
1 Bq \u003d 1 decay per second. |
Radionuclide activity units. They represent the number of decays per unit time. |
|
Gray (Gr, Gy); |
1 Gy \u003d 1 J / kg |
Absorbed dose units. They represent the amount of energy of ionizing radiation absorbed by a unit of mass of a physical body, for example, body tissues. |
|
Sievert (Sv, Sv) |
1 Sv \u003d 1 Gy \u003d 1 J / kg (for beta and gamma) 1 μSv \u003d 1/1000000 Sv 1 ber \u003d 0.01 Sv \u003d 10 mSv Units of equivalent dose. |
Equivalent dose units. They are a unit of absorbed dose, multiplied by a factor that takes into account the unequal hazard of different types of ionizing radiation. |
|
Gray per hour (Gy / h); Sievert per hour (Sv / h); X-rays per hour (R / h) |
1 Gy / h \u003d 1 Sv / h \u003d 100 R / h (for beta and gamma) 1 μ Sv / h \u003d 1 μGy / h \u003d 100 μR / h 1 μR / h \u003d 1/1000000 R / h |
Dose rate units. They represent the dose received by the body per unit of time. |
For information, and not for intimidation, especially people who have decided to devote themselves to working with ionizing radiation, you should know the maximum permissible doses. Units of measurement of radioactivity are given in Table 1. According to the conclusion of the International Commission on Radiation Protection for 1990, harmful effects can occur at equivalent doses of at least 1.5 Sv (150 rem) received during the year, and in cases of short-term exposure at doses higher 0.5 Sv (50 rem). When radiation exposure exceeds a certain threshold, radiation sickness occurs. Distinguish between chronic and acute (with a single massive exposure) forms of this disease. In terms of severity, acute radiation sickness is divided into four degrees, ranging from a dose of 1-2 Sv (100-200 rem, 1st degree) to a dose of more than 6 Sv (600 rem, 4th degree). The fourth degree can be fatal.
Doses received under normal conditions are negligible compared to those indicated. The equivalent dose rate generated by natural radiation ranges from 0.05 to 0.2 μSv / h, i.e. from 0.44 to 1.75 mSv / year (44-175 mrem / year).
For medical diagnostic procedures - X-rays, etc. - a person receives approximately 1.4 mSv / year.
Since there are small doses of radioactive elements in brick and concrete, the dose increases by another 1.5 mSv / year. Finally, due to emissions from modern coal-fired thermal power plants and when flying by plane, a person receives up to 4 mSv / year. In total, the existing background can reach 10 mSv / year, but on average does not exceed 5 mSv / year (0.5 rem / year).
Such doses are completely harmless to humans. The dose limit, in addition to the existing background for a limited part of the population in areas of high radiation, is 5 mSv / year (0.5 rem / year), i.e. with a 300-fold margin. For personnel working with sources of ionizing radiation, the maximum permissible dose is 50 mSv / year (5 rem / year), i.e. 28 μSv / h at a 36-hour work week.
According to the hygienic standards NRB-96 (1996), the permissible dose rate levels for external irradiation of the whole body from man-made sources for the premises of permanent residence of personnel are 10 μGy / h, for residential premises and territories where people from the population are constantly located - 0 , 1 μGy / h (0.1 μSv / h, 10 μR / h).
HOW TO MEASURE RADIATION
A few words about registration and dosimetry of ionizing radiation. There are various methods of registration and dosimetry: ionization (associated with the passage of ionizing radiation in gases), semiconductor (in which the gas is replaced solid body), scintillation, luminescent, photographic. These methods are the basis of work dosimeters radiation. Among the gas-filled sensors of ionizing radiation, one can note ionization chambers, fission chambers, proportional counters and geiger-Muller counters ... The latter are relatively simple, the cheapest, not critical to the working conditions, which led to their widespread use in professional dosimetry equipment designed to detect and evaluate beta and gamma radiation. When a Geiger-Müller counter is used as a sensor, any ionizing particle entering the sensitive volume of the counter causes a self-discharge. Precisely falling into the sensitive volume! Therefore, alpha particles are not registered, because they cannot get there. Even when registering beta particles, it is necessary to bring the detector closer to the object to make sure that there is no radiation, because in the air, the energy of these particles can be weakened, they may not pass through the device housing, they will not enter the sensitive element and will not be detected.
Doctor of Physical and Mathematical Sciences, Professor MEPhI N.M. Gavrilov
the article was written for the company "Kvarta-Rad"
Ionizing radiation (IR) - flows of elementary particles (electrons, positrons, protons, neutrons) and quanta of electromagnetic energy, the passage of which through a substance leads to ionization (the formation of ions of different polarity) and the excitation of its atoms and molecules. Ionization - the transformation of neutral atoms or molecules into electrically charged particles - ions. and the IR fall on the Earth in the form cosmic rays, arise as a result of the radioactive decay of atomic nuclei (απ β-particles, γ– and X-rays), are created artificially on charged particle accelerators. Of practical interest are the most common types of IR — fluxes of a- and β-particles, γ-radiation, X-rays and neutron fluxes.
Alpha radiation (a) - flux of positively charged particles - helium nuclei. Currently, more than 120 artificial and natural alpha-radioactive nuclei are known, which, emitting an alpha-particle, lose 2 protons and 2 neutrons. The particle velocity during decay is 20 thousand km / s. At the same time, α-particles have the least penetrating ability, their path length (distance from the source to absorption) in the body is 0.05 mm, in air - 8-10 cm. They cannot pass even through a sheet of paper, but the ionization density per unit the range is very large (by 1 cm to tens of thousands of pairs), therefore these particles have the greatest ionizing ability and are dangerous inside the body.
Beta radiation (β) is the flow of negatively charged particles. Currently, about 900 beta radioactive isotopes are known. The mass of β-particles is several tens of thousands of times less than α-particles, but they have a greater penetrating power. Their speed is 200-300 thousand km / s. The length of the flow from the source in air is 1800 cm, in human tissues - 2.5 cm. Β-particles are completely retained by solid materials (3.5 mm aluminum plate, organic glass); their ionizing capacity is 1000 times less than that of α-particles.
Gamma radiation (γ) - electromagnetic radiation with a wavelength from 1 · 10 -7 m to 1 · 10 -14 m; is emitted during deceleration of fast electrons in matter. It arises from the decay of most radioactive substances and has a high penetrating power; propagates at the speed of light. In electrical and magnetic fields Gamma rays are not deflected. This radiation is less ionizing than a- and β-radiation, since the ionization density per unit length is very low.
X-ray radiation can be obtained in special X-ray tubes, in electron accelerators, during deceleration of fast electrons in matter and during the transition of electrons from the outer electron shells of the atom to the inner one, when ions are created. X-rays, like gamma-rays, have a low ionizing ability, but a large penetration depth.
Neutrons - elementary particles of the atomic nucleus, their mass is 4 times less than the mass of α-particles. Their lifetime is about 16 minutes. Neutrons have no electrical charge. The path length of slow neutrons in air is about 15 m, in a biological environment - 3 cm; for fast neutrons - respectively 120 m and 10 cm. The latter have a high penetrating power and pose the greatest danger.
There are two types of ionizing radiation:
Corpuscular, consisting of particles with a rest mass different from zero (α-, β- and neutron radiation);
Electromagnetic (γ– and X-ray radiation) - with a very short wavelength.
To assess the impact of ionizing radiation on any substances and living organisms, special values \u200b\u200bare used - radiation dose. The main characteristic of the interaction of ionizing radiation and the environment is the ionization effect. In the initial period of the development of radiation dosimetry, it was most often necessary to deal with X-rays propagating in the air. Therefore, the degree of air ionization of X-ray tubes or apparatus was used as a quantitative measure of the radiation field. A quantitative measure based on the amount of ionization of dry air at normal atmospheric pressure, which is quite easy to measure, is called the exposure dose.
Exposure dose determines the ionizing capacity of X-rays and γ-rays and expresses the radiation energy converted into kinetic energy of charged particles per unit mass of atmospheric air. The exposure dose is the ratio of the total charge of all ions of the same sign in an elementary volume of air to the mass of air in this volume. In the SI system, the unit for measuring the exposure dose is the pendant divided by the kilogram (C / kg). Non-systemic unit - X-ray (R). 1 C / kg \u003d 3880 R. With the expansion of the range of known types of ionizing radiation and the spheres of its application, it turned out that the measure of the effect of ionizing radiation on a substance does not lend itself to simple determination due to the complexity and diversity of the processes taking place. The most important of them, giving rise to physicochemical changes in the irradiated substance and leading to a certain radiation effect, is the absorption of the energy of ionizing radiation by the substance. As a result, the concept of absorbed dose arose.
Absorbed dose shows the amount of radiation energy absorbed per unit mass of any irradiated substance, and is determined by the ratio of the absorbed energy of ionizing radiation to the mass of the substance. Gray (Gy) is taken as the unit of measurement of the absorbed dose in the SI system. 1 Gy is a dose at which 1 J of ionizing radiation energy is transferred to a mass of 1 kg. The non-systemic unit of the absorbed dose is rad. 1 Gr \u003d 100 glad. The study of individual consequences of irradiation of living tissues showed that at the same absorbed doses, different types of radiation produce unequal biological impact on the body. This is due to the fact that a heavier particle (for example, a proton) produces more ions per unit path in the tissue than a light one (for example, an electron). At the same absorbed dose, the more dense the ionization created by radiation, the higher the radiobiological destructive effect. To take this effect into account, the concept of an equivalent dose was introduced.
Equivalent dose is calculated by multiplying the value of the absorbed dose by a special coefficient - the coefficient of relative biological effectiveness (RBE) or quality coefficient. The values \u200b\u200bof the coefficient for various types of radiation are given in table. 7.
Table 7
The coefficient of relative biological effectiveness for various types of radiation
The SI unit of equivalent dose is the sievert (Sv). The value of 1 Sv is equal to the equivalent dose of any kind of radiation absorbed in 1 kg of biological tissue and creating the same biological effect as the absorbed dose of 1 Gy of photon radiation. The non-systemic unit of measurement of the equivalent dose is rem (biological equivalent of rad). 1 Sv \u003d 100 rem. Some human organs and tissues are more sensitive to the effects of radiation than others: for example, at the same equivalent dose, the occurrence of cancer in the lungs is more likely than in the thyroid gland, and irradiation of the gonads is especially dangerous because of the risk of genetic damage. Therefore, the radiation doses to different organs and tissues should be taken into account with a different coefficient, which is called the radiation risk coefficient. Multiplying the value of the equivalent dose by the corresponding radiation risk factor and summing over all tissues and organs, we obtain effective dose, reflecting the total effect on the body. Weighted coefficients are established empirically and calculated in such a way that their sum for the whole organism is one. The effective dose units are the same as the equivalent dose units. It is also measured in sievert or rem.