IONIZING RADIATIONS, THEIR NATURE AND IMPACT ON THE HUMAN BODY
Radiation and its varieties
ionizing radiation
Sources of radiation hazard
The device of ionizing radiation sources
Ways of penetration of radiation into the human body
Measures of ionizing influence
The mechanism of action of ionizing radiation
Consequences of irradiation
Radiation sickness
Ensuring safety when working with ionizing radiation
Radiation and its varieties
Radiation is all types of electromagnetic radiation: light, radio waves, solar energy and many other radiations around us.
The sources of penetrating radiation that create the natural background of exposure are galactic and solar radiation, the presence of radioactive elements in soil, air and materials used in economic activities, as well as isotopes, mainly potassium, in the tissues of a living organism. One of the most significant natural sources of radiation is radon, a gas that has no taste or smell.
Of interest is not any radiation, but ionizing, which, passing through the tissues and cells of living organisms, is able to transfer its energy to them, breaking chemical bonds within molecules and causing serious changes in their structure. Ionizing radiation occurs during radioactive decay, nuclear transformations, deceleration of charged particles in matter and forms ions of different signs when interacting with the medium.
ionizing radiation
All ionizing radiations are divided into photon and corpuscular.
Photon-ionizing radiation includes:
a) Y-radiation emitted during the decay of radioactive isotopes or particle annihilation. Gamma radiation is, by its nature, short-wavelength electromagnetic radiation, i.e. a stream of high-energy quanta of electromagnetic energy, the wavelength of which is much less than the interatomic distances, i.e. y< 10 см. Не имея массы, Y-кванты двигаются со скоростью света, не теряя её в окружающей среде. Они могут лишь поглощаться ею или отклоняться в сторону, порождая пары ионов: частица- античастица, причём последнее наиболее значительно при поглощении Y- квантов в среде. Таким образом, Y- кванты при прохождении через вещество передают энергию электронам и, следовательно, вызывают ионизацию среды. Благодаря отсутствию массы, Y- кванты обладают большой проникающей способностью (до 4- 5 км в воздушной среде);
b) X-ray radiation that occurs when the kinetic energy of charged particles decreases and / or when the energy state of the electrons of the atom changes.
Corpuscular ionizing radiation consists of a stream of charged particles (alpha, beta particles, protons, electrons), the kinetic energy of which is sufficient to ionize atoms in a collision. Neutrons and other elementary particles do not directly produce ionization, but in the process of interaction with the medium they release charged particles (electrons, protons) that can ionize the atoms and molecules of the medium through which they pass:
a) neutrons are the only uncharged particles formed in some reactions of nuclear fission of uranium or plutonium atoms. Since these particles are electrically neutral, they penetrate deeply into any substance, including living tissues. A distinctive feature of neutron radiation is its ability to convert atoms of stable elements into their radioactive isotopes, i.e. create induced radiation, which dramatically increases the danger of neutron radiation. The penetrating power of neutrons is comparable to Y-radiation. Depending on the level of carried energy, fast neutrons (with energies from 0.2 to 20 MeV) and thermal neutrons (from 0.25 to 0.5 MeV) are conditionally distinguished. This difference is taken into account when carrying out protective measures. Fast neutrons are slowed down, losing ionization energy, by substances with a low atomic weight (the so-called hydrogen-containing ones: paraffin, water, plastics, etc.). Thermal neutrons are absorbed by materials containing boron and cadmium (boron steel, boral, boron graphite, cadmium-lead alloy).
Alpha -, beta particles and gamma - quanta have an energy of only a few megaelectronvolts, and cannot create induced radiation;
b) beta particles - electrons emitted during the radioactive decay of nuclear elements with an intermediate ionizing and penetrating power (run in air up to 10-20 m).
c) alpha particles - positively charged nuclei of helium atoms, and in outer space and atoms of other elements, emitted during the radioactive decay of isotopes of heavy elements - uranium or radium. They have a low penetrating ability (run in the air - no more than 10 cm), even human skin is an insurmountable obstacle for them. They are dangerous only when they enter the body, as they are able to knock out electrons from the shell of a neutral atom of any substance, including the human body, and turn it into a positively charged ion with all the ensuing consequences, which will be discussed later. Thus, an alpha particle with an energy of 5 MeV forms 150,000 pairs of ions.
Characteristics of the penetrating power of various types of ionizing radiation
The quantitative content of radioactive material in the human body or substance is defined by the term "radioactive source activity" (radioactivity). The unit of radioactivity in the SI system is the becquerel (Bq), which corresponds to one decay in 1 s. Sometimes in practice the old unit of activity, the curie (Ci), is used. This is the activity of such a quantity of a substance in which 37 billion atoms decay in 1 second. For translation, the following dependence is used: 1 Bq = 2.7 x 10 Ci or 1 Ki = 3.7 x 10 Bq.
Each radionuclide has an invariable, unique half-life (the time required for the substance to lose half of its activity). For example, for uranium-235 it is 4,470 years, while for iodine-131 it is only 8 days.
Sources of radiation hazard
1. The main cause of danger is a radiation accident. A radiation accident is a loss of control over a source of ionizing radiation (RSR) caused by equipment malfunction, improper actions of personnel, natural disasters or other reasons that could lead or have led to exposure of people above the established norms or to radioactive contamination of the environment. In case of accidents caused by the destruction of the reactor vessel or the melting of the core, the following are emitted:
1) Fragments of the core;
2) Fuel (waste) in the form of highly active dust, which can stay in the air for a long time in the form of aerosols, then, after passing through the main cloud, fall out in the form of rain (snow) precipitation, and if it enters the body, cause a painful cough, sometimes similar in severity to an asthma attack;
3) lava, consisting of silicon dioxide, as well as concrete molten as a result of contact with hot fuel. The dose rate near such lavas reaches 8000 R/hour, and even a five-minute stay nearby is detrimental to humans. In the first period after precipitation of RV, the greatest danger is iodine-131, which is a source of alpha and beta radiation. Its half-life from the thyroid gland is: biological - 120 days, effective - 7.6. This requires the fastest possible iodine prophylaxis of the entire population in the accident zone.
2. Enterprises for the development of deposits and enrichment of uranium. Uranium has an atomic weight of 92 and three natural isotopes: uranium-238 (99.3%), uranium-235 (0.69%), and uranium-234 (0.01%). All isotopes are alpha emitters with negligible radioactivity (2800 kg of uranium are equivalent in activity to 1 g of radium-226). The half-life of uranium-235 = 7.13 x 10 years. The artificial isotopes uranium-233 and uranium-227 have half-lives of 1.3 and 1.9 minutes. Uranium is a soft metal that looks like steel. The content of uranium in some natural materials reaches 60%, but in most uranium ores it does not exceed 0.05-0.5%. In the process of mining, upon receipt of 1 ton of radioactive material, up to 10-15 thousand tons of waste is formed, and during processing from 10 to 100 thousand tons. From the waste (containing a small amount of uranium, radium, thorium and other radioactive decay products), a radioactive gas is released - radon-222, which, when inhaled, causes irradiation of lung tissues. When ore is enriched, radioactive waste can get into nearby rivers and lakes. During the enrichment of uranium concentrate, some leakage of gaseous uranium hexafluoride from the condensation-evaporation plant into the atmosphere is possible. Some uranium alloys, shavings, sawdust obtained during the production of fuel elements can ignite during transportation or storage, as a result, significant amounts of burnt uranium waste can be released into the environment.
3. Nuclear terrorism. Cases of theft of nuclear materials suitable for the manufacture of nuclear weapons, even by handicraft, have become more frequent, as well as threats to disable nuclear enterprises, ships with nuclear installations and nuclear power plants in order to obtain a ransom. The danger of nuclear terrorism also exists at the everyday level.
4. Tests of nuclear weapons. Recently, miniaturization of nuclear charges for testing has been achieved.
The device of ionizing radiation sources
According to the device, IRS are of two types - closed and open.
Sealed sources are placed in sealed containers and pose a danger only if there is no proper control over their operation and storage. Military units also make their contribution, transferring decommissioned devices to sponsored educational institutions. Loss of decommissioned, destruction as unnecessary, theft with subsequent migration. For example, in Bratsk, at the building construction plant, IRS, enclosed in a lead sheath, was stored in a safe along with precious metals. And when the robbers broke into the safe, they decided that this massive lead blank was also precious. They stole it, and then honestly divided it, sawing a lead “shirt” in half and an ampoule with a radioactive isotope sharpened in it.
Working with open IRS can lead to tragic consequences in case of ignorance or violation of the relevant instructions on the rules for handling these sources. Therefore, before starting any work using IRS, it is necessary to carefully study all job descriptions and safety regulations and strictly comply with their requirements. These requirements are set out in the Sanitary Rules for the Management of Radioactive Waste (SPO GO-85). The Radon enterprise, upon request, performs individual control of persons, territories, objects, checks, dosages and repairs of devices. Works in the field of IRS handling, radiation protection means, production, production, transportation, storage, use, maintenance, disposal, disposal are carried out only on the basis of a license.
Ways of penetration of radiation into the human body
To correctly understand the mechanism of radiation damage, it is necessary to have a clear understanding of the existence of two ways in which radiation penetrates into the tissues of the body and affects them.
The first way is external irradiation from a source located outside the body (in the surrounding space). This exposure may be due to X-rays and gamma rays, as well as some high-energy beta particles that can penetrate the superficial layers of the skin.
The second way is internal exposure caused by the ingress of radioactive substances into the body in the following ways:
In the first days after a radiation accident, radioactive isotopes of iodine that enter the body with food and water are the most dangerous. There are a lot of them in milk, which is especially dangerous for children. Radioactive iodine accumulates mainly in the thyroid gland, which weighs only 20 g. The concentration of radionuclides in this organ can be 200 times higher than in other parts of the human body;
Through injuries and cuts on the skin;
Absorption through healthy skin during prolonged exposure to radioactive substances (RS). In the presence of organic solvents (ether, benzene, toluene, alcohol), the permeability of the skin to RV increases. Moreover, some RVs that enter the body through the skin enter the bloodstream and, depending on their chemical properties, are absorbed and accumulated in critical organs, which leads to high local doses of radiation. For example, the growing bones of the limbs absorb radioactive calcium, strontium, radium well, and the kidneys absorb uranium. Other chemical elements, such as sodium and potassium, will be distributed throughout the body more or less evenly, as they are found in all cells of the body. At the same time, the presence of sodium-24 in the blood means that the body was additionally subjected to neutron irradiation (i.e., the chain reaction in the reactor was not interrupted at the time of irradiation). It is especially difficult to treat a patient exposed to neutron irradiation, so it is necessary to determine the induced activity of the body's bioelements (P, S, etc.);
Through the lungs while breathing. The penetration of solid radioactive substances into the lungs depends on the degree of dispersion of these particles. From tests conducted on animals, it was found that dust particles smaller than 0.1 micron behave in the same way as gas molecules. When you inhale, they enter the lungs with air, and when you exhale, they are removed with air. Only a small fraction of solid particles may remain in the lungs. Large particles larger than 5 microns are retained by the nasal cavity. Inert radioactive gases (argon, xenon, krypton, etc.) that have entered the blood through the lungs are not compounds that make up tissues, and are eventually removed from the body. Do not stay in the body for a long time and radionuclides, the same type with the elements that make up the tissues and consumed by humans with food (sodium, chlorine, potassium, etc.). They are completely removed from the body over time. Some radionuclides (for example, radium, uranium, plutonium, strontium, yttrium, zirconium deposited in bone tissues) enter into a chemical bond with bone tissue elements and are hardly excreted from the body. During a medical examination of the inhabitants of the areas affected by the Chernobyl accident at the All-Union Hematological Center of the Academy of Medical Sciences, it was found that with a general irradiation of the body with a dose of 50 rads, some of its cells were irradiated with a dose of 1,000 and more rads. At present, standards have been developed for various critical organs that determine the maximum permissible content of each radionuclide in them. These standards are set out in Section 8 "Numerical Values of Permissible Levels" of the NRB Radiation Safety Standards - 76/87.
Internal exposure is more dangerous and its consequences more severe for the following reasons:
The radiation dose increases sharply, determined by the time the radionuclide stays in the body (radium-226 or plutonium-239 throughout life);
The distance to the ionized tissue is practically infinitely small (the so-called contact irradiation);
Irradiation involves alpha particles, the most active and therefore the most dangerous;
Radioactive substances do not spread evenly throughout the body, but selectively, they concentrate in individual (critical) organs, increasing local exposure;
It is not possible to use any protection measures used for external exposure: evacuation, personal protective equipment (PPE), etc.
Measures of ionizing influence
The measure of the ionizing effect of external radiation is exposure dose, determined by air ionization. For a unit of exposure dose (De) it is customary to consider X-ray (P) - the amount of radiation at which in 1 cc. air at a temperature of 0 C and a pressure of 1 atm, 2.08 x 10 pairs of ions are formed. According to the guidelines of the International Company for Radiological Units (ICRU) RD - 50-454-84 after January 1, 1990, it is not recommended to use such values as the exposure dose and its rate in our country (it is accepted that the exposure dose is the absorbed dose in air). Most of the dosimetric equipment in the Russian Federation is calibrated in roentgens, roentgens / hours, and these units are not yet abandoned.
The measure of the ionizing effect of internal exposure is absorbed dose. The rad is taken as the unit of absorbed dose. This is the dose of radiation transferred to the mass of the irradiated substance in 1 kg and measured by the energy in joules of any ionizing radiation. 1 rad = 10 J/kg. In the SI system, the unit of absorbed dose is the gray (Gy), equal to an energy of 1 J/kg.
1 Gy = 100 rad.
1 rad = 10 Gr.
To convert the amount of ionizing energy in space (exposure dose) into that absorbed by the soft tissues of the body, the coefficient of proportionality K = 0.877 is used, i.e.:
1 x-ray \u003d 0.877 rad.
Due to the fact that different types of radiation have different efficiencies (with equal energy costs for ionization, they produce different effects), the concept of “equivalent dose” has been introduced. Its unit of measurement is rem. 1 rem is a dose of radiation of any kind, the effect of which on the body is equivalent to the effect of 1 rad of gamma radiation. Therefore, when assessing the overall effect of exposure to radiation on living organisms with total exposure to all types of radiation, a quality factor (Q) equal to 10 for neutron radiation (neutrons are about 10 times more effective in terms of radiation damage) and 20 for alpha radiation is taken into account. In the SI system, the unit of equivalent dose is the sievert (Sv), equal to 1 Gy x Q.
Along with the amount of energy, type of irradiation, material and mass of the organ, an important factor is the so-called biological half-life radioisotope - the length of time required for excretion (with sweat, saliva, urine, feces, etc.) from the body of half of the radioactive substance. Already 1-2 hours after the RV enters the body, they are found in its secretions. The combination of the physical half-life with the biological half-life gives the concept of "effective half-life" - the most important in determining the resulting amount of radiation to which the body is exposed, especially critical organs.
Along with the concept of "activity" there is the concept of "induced activity" (artificial radioactivity). It occurs when slow neutrons (products of a nuclear explosion or nuclear reaction) are absorbed by the nuclei of atoms of non-radioactive substances and turn them into radioactive potassium-28 and sodium-24, which are formed mainly in the soil.
Thus, the degree, depth and form of radiation injuries that develop in biological objects (including humans) when exposed to radiation depend on the amount of absorbed radiation energy (dose).
The mechanism of action of ionizing radiation
The fundamental feature of the action of ionizing radiation is its ability to penetrate biological tissues, cells, subcellular structures and, causing simultaneous ionization of atoms, damage them due to chemical reactions. Any molecule can be ionized, and hence all structural and functional destruction in somatic cells, genetic mutations, effects on the fetus, illness and death of a person.
The mechanism of this effect is the absorption of ionization energy by the body and the breaking of the chemical bonds of its molecules with the formation of highly active compounds, the so-called free radicals.
The human body is 75% water, therefore, the indirect effect of radiation through the ionization of the water molecule and subsequent reactions with free radicals will be of decisive importance in this case. When a water molecule is ionized, a positive HO ion and an electron are formed, which, having lost energy, can form a negative HO ion. Both of these ions are unstable and decompose into a pair of stable ions, which recombine (reduce) to form a water molecule and two free OH radicals and H, characterized by exceptionally high chemical activity. Directly or through a chain of secondary transformations, such as the formation of a peroxide radical (hydrated water oxide), and then hydrogen peroxide H O and other active oxidants of the OH and H groups, interacting with protein molecules, they lead to tissue destruction mainly due to vigorous processes oxidation. At the same time, one active molecule with high energy involves thousands of molecules of living matter in the reaction. In the body, oxidative reactions begin to prevail over reduction ones. There comes a retribution for the aerobic method of bioenergy - saturation of the body with free oxygen.
The impact of ionizing radiation on humans is not limited to changes in the structure of water molecules. The structure of the atoms that make up our body is changing. The result is the destruction of the nucleus, cell organelles and rupture of the outer membrane. Since the main function of growing cells is the ability to divide, its loss leads to death. For mature non-dividing cells, destruction causes the loss of certain specialized functions (production of certain products, recognition of foreign cells, transport functions, etc.). Radiation-induced cell death occurs, which, unlike physiological death, is irreversible, since the implementation of the genetic program of terminal differentiation in this case occurs against the background of multiple changes in the normal course of biochemical processes after irradiation.
In addition, the additional supply of ionization energy to the body disrupts the balance of energy processes occurring in it. After all, the presence of energy in organic substances depends primarily not on their elemental composition, but on the structure, arrangement and nature of the bonds of atoms, i.e. those elements that are most easily amenable to energy impact.
Consequences of irradiation
One of the earliest manifestations of irradiation is the mass death of lymphoid tissue cells. Figuratively speaking, these cells are the first to take the impact of radiation. The death of lymphoids weakens one of the main life support systems of the body - the immune system, since lymphocytes are cells that are able to respond to the appearance of antigens foreign to the body by producing strictly specific antibodies to them.
As a result of exposure to radiation energy in small doses, changes in the genetic material (mutations) occur in cells that threaten their viability. As a result, degradation (damage) of chromatin DNA (breaks of molecules, damage) occurs, which partially or completely block or distort the function of the genome. There is a violation of DNA repair - its ability to restore and heal cell damage with an increase in body temperature, exposure to chemicals, etc.
Genetic mutations in germ cells affect the life and development of future generations. This case is typical, for example, if a person was exposed to small doses of radiation during exposure for medical purposes. There is a concept - when a dose of 1 rem is received by the previous generation, it gives an additional 0.02% of genetic anomalies in the offspring, i.e. in 250 babies per million. These facts and long-term studies of these phenomena have led scientists to the conclusion that there are no safe doses of radiation.
The impact of ionizing radiation on the genes of germ cells can cause harmful mutations that will be passed from generation to generation, increasing the "mutation load" of humanity. Life-threatening conditions are those that double the “genetic load”. Such a doubling dose is, according to the conclusions of the UN Scientific Committee on Atomic Radiation, a dose of 30 rad for acute exposure and 10 rad for chronic exposure (during the reproductive period). With increasing dose, it is not the severity that increases, but the frequency of possible manifestations.
Mutational changes also occur in plant organisms. In the forests affected by radioactive fallout near Chernobyl, as a result of a mutation, new absurd plant species have arisen. Rust-red coniferous forests appeared. In a wheat field located near the reactor, two years after the accident, scientists discovered about a thousand different mutations.
Impact on the fetus and fetus due to maternal exposure during pregnancy. The radiosensitivity of a cell changes at different stages of the process of division (mitosis). The most sensitive cell is at the end of dormancy and the beginning of the first month of division. The zygote, the embryonic cell that is formed after the fusion of the spermatozoon with the egg, is especially sensitive to radiation. In this case, the development of the embryo during this period and the influence of radiation, including X-ray, radiation on it can be divided into three stages.
Stage 1 - after conception and until the ninth day. The newly formed embryo dies under the influence of radiation. Death in most cases goes unnoticed.
Stage 2 - from the ninth day to the sixth week after conception. This is the period of formation of internal organs and limbs. At the same time, under the influence of an irradiation dose of 10 rem, a whole range of defects appears in the embryo - a splitting of the palate, a halt in the development of limbs, a violation of the formation of the brain, etc. At the same time, growth retardation of the body is possible, which is expressed in a decrease in body size at birth. The result of exposure of the mother during this period of pregnancy can also be the death of a newborn at the time of delivery or some time after them. However, the birth of a live child with gross defects is probably the greatest misfortune, much worse than the death of an embryo.
Stage 3 - pregnancy after six weeks. Doses of radiation received by the mother cause a persistent lag in the body in growth. In an irradiated mother, the child is undersized at birth and remains below average height for life. Pathological changes in the nervous, endocrine systems, etc. are possible. Many radiologists suggest that the high probability of having a defective child is the basis for terminating a pregnancy if the dose received by the embryo during the first six weeks after conception exceeds 10 rads. Such a dose was included in the legislative acts of some Scandinavian countries. For comparison, with fluoroscopy of the stomach, the main areas of the bone marrow, the abdomen, and the chest receive a radiation dose of 30-40 rad.
Sometimes a practical problem arises: a woman undergoes a series of x-rays, including images of the stomach and pelvis, and is subsequently found to be pregnant. The situation is aggravated if the exposure occurred in the first weeks after conception, when pregnancy may go unnoticed. The only solution to this problem is not to expose the woman to radiation during this period. This can be achieved if a woman of reproductive age undergoes an X-ray of the stomach or abdomen only during the first ten days after the onset of the menstrual period, when there is no doubt about the absence of pregnancy. In medical practice, this is called the ten-day rule. In an emergency, X-ray procedures may not be postponed for weeks or months, but it is prudent for a woman to tell her doctor about her possible pregnancy before taking an X-ray.
In terms of sensitivity to ionizing radiation, the cells and tissues of the human body are not the same.
The testes are among the most sensitive organs. A dose of 10-30 rads can reduce spermatogenesis within a year.
The immune system is highly sensitive to radiation.
In the nervous system, the retina of the eye turned out to be the most sensitive, since visual impairment was observed during irradiation. Taste sensitivity disorders occurred during radiation therapy of the chest, and repeated irradiation with doses of 30-500 R reduced tactile sensitivity.
Changes in somatic cells can contribute to the development of cancer. A cancerous tumor occurs in the body at the moment when the somatic cell, having gone out of control of the body, begins to rapidly divide. The root cause of this is mutations in genes caused by repeated or strong single irradiation, leading to the fact that cancer cells lose their ability to die by physiological, or rather programmed, death even in the event of an imbalance. They become, as it were, immortal, constantly dividing, increasing in number and dying only from a lack of nutrients. This is how the tumor grows. Especially rapidly develops leukemia (blood cancer) - a disease associated with the excessive appearance in the bone marrow, and then in the blood of defective white cells - leukocytes. However, in recent years it has become clear that the relationship between radiation and cancer is more complex than previously thought. So, in a special report of the Japanese American Association of Scientists, it is said that only some types of cancer: tumors of the mammary and thyroid glands, as well as leukemia, develop as a result of radiation damage. Moreover, the experience of Hiroshima and Nagasaki showed that thyroid cancer is observed with irradiation of 50 or more rads. Breast cancer, from which about 50% of patients die, is observed in women who have repeatedly undergone x-ray examinations.
A characteristic of radiation injuries is that radiation injuries are accompanied by severe functional disorders and require complex and lengthy (more than three months) treatment. The viability of irradiated tissues is significantly reduced. In addition, complications occur many years and decades after the injury. Thus, there were cases of the occurrence of benign tumors 19 years after irradiation, and the development of radiation skin and breast cancer in women after 25-27 years. Often, injuries are detected against the background or after exposure to additional factors of a non-radiation nature (diabetes, atherosclerosis, purulent infection, thermal or chemical injuries in the irradiation zone).
It should also be taken into account that people who survived a radiation accident experience additional stress for several months and even years after it. Such stress can turn on the biological mechanism that leads to the emergence of malignant diseases. Thus, in Hiroshima and Nagasaki, a major outbreak of thyroid cancer was observed 10 years after the atomic bombing.
Studies conducted by radiologists based on the data of the Chernobyl accident indicate a decrease in the threshold of consequences from exposure to radiation. Thus, it has been established that exposure to 15 rem can cause disturbances in the activity of the immune system. Even when receiving a dose of 25 rem, the liquidators of the accident showed a decrease in blood lymphocytes - antibodies to bacterial antigens, and at 40 rem, the likelihood of infectious complications increases. Under the influence of constant irradiation with a dose of 15 to 50 rem, cases of neurological disorders caused by changes in the structures of the brain were often noted. Moreover, these phenomena were observed in the long term after irradiation.
Radiation sickness
Depending on the dose and time of exposure, three degrees of the disease are observed: acute, subacute and chronic. In the lesions (when receiving high doses), as a rule, acute radiation sickness (ARS) occurs.
There are four degrees of ARS:
Light (100 - 200 rad). The initial period - the primary reaction, as in ARS of all other degrees - is characterized by bouts of nausea. There is a headache, vomiting, general malaise, a slight increase in body temperature, in most cases - anorexia (lack of appetite, up to disgust for food), infectious complications are possible. The primary reaction occurs 15-20 minutes after irradiation. Its manifestations gradually disappear after a few hours or days, or may be absent altogether. Then comes a latent period, the so-called period of imaginary well-being, the duration of which is determined by the dose of radiation and the general condition of the body (up to 20 days). During this time, erythrocytes exhaust their life span, ceasing to supply oxygen to the cells of the body. Mild ARS is curable. Negative consequences are possible - blood leukocytosis, reddening of the skin, decreased efficiency in 25% of those affected 1.5 - 2 hours after exposure. There is a high content of hemoglobin in the blood within 1 year from the moment of exposure. The recovery period is up to three months. Of great importance in this case are the personal attitude and social motivation of the victim, as well as his rational employment;
Average (200 - 400 rad). Short bouts of nausea, passing in 2-3 days after irradiation. The latent period is 10-15 days (may be absent), during which the leukocytes produced by the lymph nodes die and stop rejecting the infection that enters the body. Platelets stop clotting blood. All this is the result of the fact that the bone marrow, lymph nodes and spleen killed by radiation do not produce new red blood cells, white blood cells and platelets to replace the spent ones. Skin edema, blisters develop. This state of the body, called "bone marrow syndrome", leads to 20% of those affected to death, which occurs as a result of damage to the tissues of the hematopoietic organs. Treatment consists in isolation of patients from the external environment, the introduction of antibiotics and blood transfusion. Young and elderly men are more susceptible to moderate ARS than middle-aged men and women. Disability occurs in 80% of those affected 0.5 - 1 hour after irradiation and after recovery remains reduced for a long time. Development of a cataract of eyes and local defects of extremities is possible;
Heavy (400 - 600 rad). Symptoms characteristic of gastrointestinal upset: weakness, drowsiness, loss of appetite, nausea, vomiting, prolonged diarrhea. The hidden period can last 1 - 5 days. After a few days, there are signs of dehydration of the body: weight loss, exhaustion and complete exhaustion. These phenomena are the result of the death of the villi of the intestinal walls, which absorb nutrients from incoming food. Their cells under the influence of radiation are sterilized and lose the ability to divide. There are foci of perforation of the walls of the stomach, and bacteria enter the bloodstream from the intestines. There are primary radiation ulcers, purulent infection from radiation burns. Loss of ability to work 0.5-1 hour after irradiation is observed in 100% of the victims. In 70% of those affected, death occurs a month later from dehydration of the body and poisoning of the stomach (gastrointestinal syndrome), as well as from radiation burns during gamma irradiation;
Extremely heavy (more than 600 rad). In a matter of minutes after irradiation, severe nausea and vomiting occur. Diarrhea - 4-6 times a day, in the first 24 hours - impaired consciousness, skin edema, severe headaches. These symptoms are accompanied by disorientation, loss of coordination, difficulty swallowing, upset stools, seizures, and eventually death. The immediate cause of death is an increase in the amount of fluid in the brain due to its release from small vessels, which leads to an increase in intracranial pressure. This condition is called "syndrome of violation of the central nervous system."
It should be noted that the absorbed dose, which causes damage to individual parts of the body and death, exceeds the lethal dose for the whole body. Lethal doses for individual parts of the body are as follows: head - 2000 rad, lower abdomen - 3000 rad, upper abdomen - 5000 rad, chest - 10000 rad, limbs - 20000 rad.
The level of effectiveness of ARS treatment achieved today is considered to be the limit, as it is based on a passive strategy - the hope for an independent recovery of cells in radiosensitive tissues (mainly bone marrow and lymph nodes), for supporting other body systems, transfusion of platelet mass to prevent hemorrhage, erythrocyte - to prevent oxygen starvation. After that, it remains only to wait until all the cellular renewal systems start working and the disastrous consequences of radiation exposure are eliminated. The outcome of the disease is determined by the end of 2-3 months. In this case, the following may occur: complete clinical recovery of the victim; recovery, in which his ability to work in one way or another will be limited; poor outcome with progression of the disease or the development of complications leading to death.
The transplantation of a healthy bone marrow is hampered by an immunological conflict, which is especially dangerous in an irradiated organism, as it depletes the already undermined immunity forces. Russian scientists-radiologists offer a new way of treating patients with radiation sickness. If part of the bone marrow is taken away from the irradiated person, then in the hematopoietic system, after this intervention, the processes of earlier recovery begin than in the natural course of events. The extracted part of the bone marrow is placed in artificial conditions, and then after a certain period of time it is returned to the same organism. Immunological conflict (rejection) does not occur.
Currently, scientists are working, and the first results have been obtained on the use of pharmaceutical radioprotectors, which allow a person to endure radiation doses that are approximately twice the lethal dose. These are cysteine, cystamine, cystophos and a number of other substances containing sulfidehydryl groups (SH) at the end of a long molecule. These substances, like "scavengers", remove the resulting free radicals, which are largely responsible for enhancing oxidative processes in the body. However, a major disadvantage of these protectors is the need to introduce it into the body intravenously, since the sulfidehydryl group added to them to reduce toxicity is destroyed in the acidic environment of the stomach and the protector loses its protective properties.
Ionizing radiation also has a negative effect on fats and lipoeds (fat-like substances) contained in the body. Irradiation disrupts the process of emulsification and promotion of fats in the cryptal region of the intestinal mucosa. As a result, droplets of non-emulsified and coarsely emulsified fat, absorbed by the body, enter the lumen of the blood vessels.
An increase in fatty acid oxidation in the liver leads, in insulin deficiency, to increased liver ketogenesis, i.e. An excess of free fatty acids in the blood reduces the activity of insulin. And this, in turn, leads to the widespread disease of diabetes mellitus today.
The most characteristic diseases associated with damage from radiation are malignant neoplasms (thyroid gland, respiratory organs, skin, hematopoietic organs), metabolic and immune disorders, respiratory diseases, pregnancy complications, congenital anomalies, and mental disorders.
Recovery of the body after irradiation is a complex process, and it proceeds unevenly. If the restoration of erythrocytes and lymphocytes in the blood begins after 7-9 months, then the restoration of leukocytes - after 4 years. The duration of this process is influenced not only by radiation, but also by psychogenic, social, social, professional and other factors of the post-radiation period, which can be combined into one concept of "quality of life" as the most capaciously and fully expressing the nature of human interaction with biological environmental factors, social and economic conditions.
Ensuring safety when working with ionizing radiation
When organizing work, the following basic principles for ensuring radiation safety are used: selection or reduction of source power to minimum values; reducing the time of work with sources; increasing the distance from the source to the worker; shielding of radiation sources with materials that absorb or attenuate ionizing radiation.
In rooms where work is carried out with radioactive substances and radioisotope devices, the intensity of various types of radiation is monitored. These rooms should be isolated from other rooms and equipped with supply and exhaust ventilation. Other collective means of protection against ionizing radiation in accordance with GOST 12.4.120 are stationary and mobile protective screens, special containers for the transportation and storage of radiation sources, as well as for the collection and storage of radioactive waste, protective safes and boxes.
Stationary and mobile protective screens are designed to reduce the level of radiation in the workplace to an acceptable level. Protection against alpha radiation is achieved by using Plexiglas a few millimeters thick. To protect against beta radiation, screens are made of aluminum or plexiglass. Water, paraffin, beryllium, graphite, boron compounds, and concrete protect against neutron radiation. Lead and concrete protect against X-ray and gamma radiation. Lead glass is used for viewing windows.
When working with radionuclides, protective clothing should be used. In case of contamination of the working room with radioactive isotopes, film clothing should be worn over cotton overalls: a dressing gown, a suit, an apron, trousers, sleeves.
Film clothing is made from plastics or rubber fabrics that are easily cleaned from radioactive contamination. In the case of film clothing, it is necessary to provide for the possibility of supplying air under the suit.
Workwear sets include respirators, air helmets and other personal protective equipment. To protect the eyes, goggles with glasses containing tungsten phosphate or lead should be used. When using personal protective equipment, it is necessary to strictly follow the sequence of putting on and taking off, and dosimetric control.
More from the Life Safety section:
- Abstract: Ensuring the safety of general ship and loading and unloading operations
- Test: Designing and creating safe working conditions at the enterprise
- Coursework: Assessment of the chemical situation after an accident at a chemical-unsafe facility with a twist of unsafe chemical speeches
- Summary: Legal, regulatory, technical and organizational framework for ensuring the safety of society
Radiation in the 20th century represents a growing threat to all mankind. Radioactive substances processed into nuclear energy, getting into building materials and finally used for military purposes, have a harmful effect on human health. Therefore, protection from ionizing radiation ( radiation safety) is becoming one of the most important tasks for ensuring the safety of human life.
radioactive substances(or radionuclides) are substances capable of emitting ionizing radiation. The reason for it is the instability of the atomic nucleus, as a result of which it undergoes spontaneous decay. Such a process of spontaneous transformations of the nuclei of atoms of unstable elements is called radioactive decay, or radioactivity.
Ionizing radiation - radiation that is created during radioactive decay and forms ions of various signs when interacting with the environment.
The act of decay is accompanied by the emission of radiation in the form of gamma rays, alpha, beta particles and neutrons.
Radioactive radiation is characterized by different penetrating and ionizing (damaging) ability. Alpha particles have such a low penetrating power that they are retained by a sheet of plain paper. Their range in the air is 2-9 cm, in the tissues of a living organism - fractions of a millimeter. In other words, these particles, when externally exposed to a living organism, are unable to penetrate the skin layer. At the same time, the ionizing ability of such particles is extremely high, and the danger of their impact increases when they enter the body with water, food, inhaled air or through an open wound, since they can damage those organs and tissues into which they have penetrated.
Beta particles are more penetrating than alpha particles, but less ionizing; their range in the air reaches 15 m, and in the tissues of the body - 1-2 cm.
Gamma radiation travels at the speed of light, has the greatest penetration depth, and can only be weakened by a thick lead or concrete wall. Passing through matter, radioactive radiation reacts with it, losing its energy. Moreover, the higher the energy of radioactive radiation, the greater its damaging ability.
The amount of radiation energy absorbed by a body or substance is called absorbed dose. As a unit of measurement of the absorbed radiation dose in the SI system, Gray (Gr). In practice, an off-system unit is used - glad(1 rad = 0.01 Gy). However, with an equal absorbed dose, alpha particles have a much greater damaging effect than gamma radiation. Therefore, to assess the damaging effect of various types of ionizing radiation on biological objects, a special unit of measurement is used - rem(biological equivalent of X-ray). The SI unit for this equivalent dose is sievert(1 Sv = 100 rem).
To assess the radiation situation on the ground, in a working or residential area, due to exposure to X-ray or gamma radiation, use exposure dose. The unit of exposure dose in the SI system is a coulomb per kilogram (C/kg). In practice, it is most often measured in roentgens (R). The exposure dose in roentgens quite accurately characterizes the potential hazard of exposure to ionizing radiation with a general and uniform exposure of the human body. An exposure dose of 1 R corresponds to an absorbed dose approximately equal to 0.95 rad.
Under other identical conditions, the dose of ionizing radiation is the greater, the longer the exposure, i.e. dose accumulates over time. The dose related to the unit of time is called the dose rate, or radiation level. So, if the level of radiation in the area is 1 R / h, this means that for 1 hour of being in this area a person will receive a dose of 1 R.
The roentgen is a very large unit of measurement, and radiation levels are usually expressed in fractions of an roentgen - thousandths (milliroentgen per hour - mR / h) and millionths (micro roentgen per hour - microR / h).
Dosimetric instruments are used to detect ionizing radiation, measure their energy and other properties: radiometers and dosimeters.
Radiometer is a device designed to determine the amount of radioactive substances (radionuclides) or radiation flux.
Dosimeter- a device for measuring the exposure or absorbed dose rate.
A person is exposed to ionizing radiation throughout his life. This is first of all natural radiation background Earths of cosmic and terrestrial origin. On average, the exposure dose from all natural sources of ionizing radiation is about 200 mR per year, although this value in different regions of the Earth can vary between 50-1000 mR / year and more.
Natural radiation background– radiation generated by cosmic radiation, natural radionuclides naturally distributed in the earth, water, air, and other elements of the biosphere (for example, food products).
In addition, a person encounters artificial sources of radiation. (technogenic radiation background). It includes, for example, ionizing radiation used for medical purposes. A certain contribution to the technogenic background is made by enterprises of the nuclear fuel cycle and coal-fired thermal power plants, aircraft flights at high altitudes, watching TV programs, using clocks with luminous dials, etc. In general, the technogenic background ranges from 150 to 200 mrem.
Technogenic radiation background - natural radiation background, modified as a result of human activity.
Thus, each inhabitant of the Earth annually on average receives radiation dose of 250-400 mrem. This is the normal state of the human environment. The adverse effect of this level of radiation on human health has not been established.
A completely different situation arises during nuclear explosions and accidents at nuclear reactors, when vast zones of radioactive contamination (contamination) with a high level of radiation are formed.
Any organism (plant, animal or person) does not live in isolation, but in one way or another is connected with all animate and inanimate nature. In this chain, the path of radioactive substances is approximately as follows: plants assimilate them with leaves directly from the atmosphere, roots from the soil (soil water), i.e. accumulate, and therefore the concentration of RS in plants is higher than in the environment. All farm animals receive RS from food, water, and from the atmosphere. Radioactive substances, entering the human body with food, water, air, are included in the molecules of bone tissue and muscles and, remaining in them, continue to irradiate the body from the inside. Therefore, human safety in conditions of radioactive contamination (contamination) of the environment is achieved by protection from external radiation, contamination by radioactive fallout, as well as protection of the respiratory and gastrointestinal tract from the ingress of radioactive substances into the body with food, water and air. In general, the actions of the population in the area of infection are mainly reduced to the observance of the relevant rules of conduct and the implementation of sanitary and hygienic measures. When reporting a radiation hazard, it is recommended that the following be carried out immediately:
1. Take shelter in residential buildings or office space. It is important to know that the walls of a wooden house attenuate ionizing radiation by 2 times, and a brick house by 10 times. Deep shelters (basements) weaken the radiation dose even more: with a wooden coating - by 7 times, with brick or concrete - by 40-100 times.
2. Take measures to protect against penetration into the apartment (house) of radioactive substances with air: close the windows, ventilation hatches, vents, seal the frames and doorways.
3. Create a supply of drinking water: collect water in closed containers, prepare the simplest sanitary products (for example, soap solutions for hand treatment), turn off the taps.
4. Carry out emergency iodine prophylaxis (as soon as possible, but after a special notification!). Iodine prophylaxis consists in taking stable iodine preparations: potassium iodide tablets or a water-alcohol solution of iodine. Potassium iodide should be taken after meals with tea or water once a day for 7 days, one tablet (0.125 g) at a time. A water-alcohol solution of iodine should be taken after meals 3 times a day for 7 days, 3-5 drops per glass of water.
You should know that an overdose of iodine is fraught with a number of side effects, such as an allergic condition and inflammatory changes in the nasopharynx.
5. Start preparing for a possible evacuation. Prepare documents and money, essentials, pack medicines that you often turn to, a minimum of linen and clothes (1-2 shifts). Gather a supply of canned food you have for 2-3 days. All this should be packed in plastic bags and bags. Turn on the radio to listen to the information messages of the Commission for Emergency Situations.
6. Try to follow the rules of radiation safety and personal hygiene, namely:
Eat only canned milk and food products that have been stored indoors and have not been exposed to radioactive contamination. Do not drink milk from cows that continue to graze in contaminated fields: radioactive substances have already begun to circulate through the so-called biological chains;
Do not eat vegetables that grew in the open field and are plucked after the release of radioactive substances into the environment;
Eat only in enclosed spaces, wash hands thoroughly with soap before eating, and rinse your mouth with a 0.5% solution of baking soda;
Do not drink water from open sources and running water after the official announcement of the radiation hazard; cover the wells with foil or covers;
Avoid long-term movement on the contaminated area, especially on a dusty road or grass, do not go to the forest, refrain from swimming in the nearest body of water;
Change shoes when entering the premises from the street (“dirty” shoes should be left on the landing or on the porch);
7. In the case of movement in open areas, it is necessary to use improvised means of protection:
Respiratory organs - cover your mouth and nose with a gauze bandage moistened with water, a handkerchief, a towel or any part of clothing;
Skin and hairline - cover yourself with any items of clothing - hats, scarves, capes, gloves. If you absolutely must go outside, we recommend that you wear rubber boots.
The following are precautions in conditions of increased radiation, recommended by the famous American doctor Gale - a specialist in radiation safety.
NECESSARY:
1. Good nutrition.
2. Daily stool.
3. Decoctions of flax seeds, prunes, nettles, laxative herbs.
4. Drink plenty of water, sweat more often.
5. Juices with coloring pigments (grape, tomato).
6. Chokeberry, pomegranates, raisins.
7. Vitamins P, C, B, beet juice, carrots, red wine (3 tablespoons daily).
8. Grated radish (grate in the morning, eat in the evening and vice versa).
9. 4-5 walnuts daily.
10. Horseradish, garlic.
11. Buckwheat, oatmeal.
12. Bread kvass.
13. Ascorbic acid with glucose (3 times a day).
14. Activated charcoal (1-2 pieces before meals).
15. Vitamin A (no more than two weeks).
16. Quademite (3 times a day).
Of dairy products, it is best to eat cottage cheese, cream, sour cream, butter. Peel vegetables and fruits up to 0.5 cm, remove at least three leaves from cabbage heads. Onions and garlic have an increased ability to absorb radioactive elements. From meat products, there are mainly pork and poultry. Avoid meat broths. Cook the meat in this way: drain the first broth, refill it with water and cook until tender.
PRODUCTS WITH ANTI-RADIOACTIVE ACTION:
1. Carrot.
2. Vegetable oil.
3. Curd.
4. Calcium tablets.
DO NOT EAT:
2. Aspic, bones, bone fat.
3. Cherries, apricots, plums.
4. Beef: This is the most likely to be contaminated.
"INSTITUTE OF MANAGEMENT"
(Arkhangelsk)
Volgograd branch
Department "_______________________________"
Test
by discipline: " life safety »
topic: " ionizing radiation and protection against them »
Is done by a student
gr. FK - 3 - 2008
Zverkov A.V.
(FULL NAME.)
Checked by teacher:
_________________________
Volgograd 2010
Introduction 3
1. The concept of ionizing radiation 4
2. Main AI detection methods 7
3. Radiation doses and units of measurement 8
4. Sources of ionizing radiation 9
5. Means of protection of the population 11
Conclusion 16
List of used literature 17
Humanity got acquainted with ionizing radiation and its features quite recently: in 1895, the German physicist V.K. Roentgen discovered rays of high penetrating power arising from the bombardment of metals with energetic electrons (Nobel Prize, 1901), and in 1896 A.A. Becquerel discovered the natural radioactivity of uranium salts. Soon this phenomenon became interested in Marie Curie, a young chemist, a Pole by birth, who coined the word "radioactivity". In 1898, she and her husband Pierre Curie discovered that uranium is converted into other chemical elements after radiation. The couple named one of these elements polonium in memory of the birthplace of Marie Curie, and another - radium, since in Latin this word means "emitting rays". Although the novelty of acquaintance lies only in how people tried to use ionizing radiation, and radioactivity, and the ionizing radiation accompanying it, existed on Earth long before the birth of life on it and were present in space before the appearance of the Earth itself.
There is no need to talk about the positive that the penetration into the structure of the core, the release of the forces hidden there, brought into our life. But like any potent agent, especially on such a scale, radioactivity has made a contribution to the human environment that cannot be classified as beneficial.
The number of victims of ionizing radiation also appeared, and it itself began to be recognized as a danger that could bring the human environment into a state unsuitable for further existence.
The reason is not only in the destruction that ionizing radiation produces. Worse, it is not perceived by us: none of the human senses will not warn him about approaching or approaching a source of radiation. A person can be in the field of radiation that is deadly for him and not have the slightest idea about it.
Such dangerous elements, in which the ratio of the number of protons and neutrons exceeds 1 ... 1.6. Currently, of all the elements of the table D.I. Mendeleev, more than 1500 isotopes are known. Of this number of isotopes, only about 300 are stable and about 90 are naturally occurring radioactive elements.
The products of a nuclear explosion contain more than 100 unstable primary isotopes. A large number of radioactive isotopes are contained in the fission products of nuclear fuel in nuclear reactors of nuclear power plants.
Thus, the sources of ionizing radiation are artificial radioactive substances, medical and scientific preparations made on their basis, products of nuclear explosions during the use of nuclear weapons, and waste from nuclear power plants during accidents.
The radiation hazard for the population and the entire environment is associated with the appearance of ionizing radiation (IR), the source of which is artificial radioactive chemical elements (radionuclides) that are formed in nuclear reactors or during nuclear explosions (NU). Radionuclides can enter the environment as a result of accidents at radiation hazardous facilities (NPPs and other facilities of the nuclear fuel cycle - NFC), increasing the radiation background of the earth.
Ionizing radiation is radiation that is directly or indirectly capable of ionizing the medium (creating separate electric charges). All ionizing radiations by their nature are divided into photon (quantum) and corpuscular. Photon (quantum) ionizing radiation includes gamma radiation, which occurs when the energy state of atomic nuclei changes or particle annihilation, bremsstrahlung, which occurs when the kinetic energy of charged particles decreases, characteristic radiation with a discrete energy spectrum, which occurs when the energy state of atomic electrons changes, and X-ray radiation. radiation consisting of bremsstrahlung and/or characteristic radiation. Corpuscular ionizing radiation includes α-radiation, electron, proton, neutron and meson radiation. Corpuscular radiation, consisting of a stream of charged particles (α-, β-particles, protons, electrons), whose kinetic energy is sufficient to ionize atoms in a collision, belongs to the class of directly ionizing radiation. Neutrons and other elementary particles do not directly produce ionization, but in the process of interaction with the medium they release charged particles (electrons, protons) that are capable of ionizing the atoms and molecules of the medium through which they pass. Accordingly, corpuscular radiation, consisting of a stream of uncharged particles, is called indirectly ionizing radiation.
Neutron and gamma radiation is commonly referred to as penetrating radiation or penetrating radiation.
Ionizing radiation according to its energy composition is divided into monoenergetic (monochromatic) and non-monoenergetic (non-monochromatic). Monoenergetic (homogeneous) radiation is radiation consisting of particles of the same type with the same kinetic energy or of quanta of the same energy. Non-monoenergetic (inhomogeneous) radiation is radiation consisting of particles of the same type with different kinetic energies or of quanta of different energies. Ionizing radiation, consisting of particles of various types or particles and quanta, is called mixed radiation.
Reactor accidents produce a+ ,b± particles and g-radiation. During nuclear explosions, neutrons -n° are additionally formed.
X-ray and g-radiation have a high penetrating and sufficiently ionizing ability (g in air can propagate up to 100m and indirectly create 2-3 pairs of ions due to the photoelectric effect per 1 cm path in air). They represent the main hazard as sources of external exposure. Significant thicknesses of materials are required to attenuate g-radiation.
Beta particles (electrons b- and positrons b+) are short-lived in air (up to 3.8 m/MeV), and in biological tissue - up to several millimeters. Their ionizing ability in the air is 100-300 pairs of ions per 1 cm of the path. These particles can act on the skin remotely and by contact (when clothing and body are contaminated), causing "radiation burns". Dangerous if ingested.
Alpha - particles (helium nuclei) a + are short-lived in air (up to 11 cm), in biological tissue up to 0.1 mm. They have a high ionizing capacity (up to 65,000 pairs of ions per 1 cm of path in the air) and are especially dangerous if they enter the body with air and food. Irradiation of internal organs is much more dangerous than external exposure.
The consequences of radiation exposure for people can be very different. They are largely determined by the magnitude of the radiation dose and the time of its accumulation. Possible consequences of exposure of people during long-term chronic exposure, the dependence of the effects on the dose of a single exposure are given in the table.
Table 1. Consequences of human exposure.
| Table 1. | ||
| Radiation Effects of Irradiation | ||
| 1 | 2 | 3 |
| Bodily (somatic) | Probabilistic corporal (somatic - stochastic) | Gynetic |
| 1 | 2 | 3 |
affect the irradiated. They have a dose threshold. | Conditionally do not have a dose threshold. | |
| Acute radiation sickness | Reducing life expectancy. | Dominant gene mutations. |
| Chronic radiation sickness. | Leukemia (latent period 7-12 years). | recessive gene mutations. |
| Local radiation damage. | Tumors of various organs (latent period up to 25 years or more). | Chromosomal aberrations. |
2. Main AI detection methods
To avoid the terrible consequences of AI, it is necessary to carry out strict control of radiation safety services using instruments and various techniques. In order to take measures to protect against the impact of AI, they must be detected and quantified in a timely manner. Influencing various environments, AIs cause certain physico-chemical changes in them that can be registered. Various AI detection methods are based on this.
The main ones are: 1) ionization, which uses the effect of ionization of the gaseous medium caused by exposure to AI, and as a result, a change in its electrical conductivity; 2) scintillation, which consists in the fact that in some substances, under the influence of IR, flashes of light are formed, which are recorded by direct observation or using photomultipliers; 3) chemical, in which IR are detected using chemical reactions, changes in acidity and conductivity that occur during irradiation of liquid chemical systems; 4) photographic, which consists in the fact that under the action of IR on a photographic film on it in the photolayer, silver grains are released along the particle trajectory; 5) a method based on the conductivity of crystals, i.e. when, under the influence of AI, a current arises in crystals made of dielectric materials and the conductivity of crystals made of semiconductors changes, etc.
3. Radiation doses and units of measurement
The action of ionizing radiation is a complex process. The effect of irradiation depends on the magnitude of the absorbed dose, its power, the type of radiation, and the volume of irradiation of tissues and organs. For its quantitative assessment, special units have been introduced, which are divided into non-systemic and units in the SI system. Currently, SI units are predominantly used. Table 10 below lists the units of measurement of radiological quantities and compares the units of the SI system and non-SI units.
Table 2. Basic radiological quantities and units
Table 3. Dependence of effects on the dose of a single (short-term) human exposure.
It should be borne in mind that radioactive exposure received during the first four days is usually called single, and for a long time - multiple. The dose of radiation that does not lead to a decrease in the efficiency (combat capability) of the personnel of formations (personnel of the army during the war): single (during the first four days) - 50 rads; multiple: during the first 10-30 days - 100 rad; within three months - 200 glad; during the year - 300 rad. Do not confuse, we are talking about the loss of performance, although the effects of exposure persist.
4. Sources of ionizing radiation
Distinguish between ionizing radiation of natural and artificial origin.
All inhabitants of the Earth are exposed to radiation from natural sources of radiation, while some of them receive larger doses than others. Depending, in particular, on the place of residence. So the level of radiation in some places of the globe, where radioactive rocks are especially deposited, turns out to be much higher than the average, in other places - respectively, lower. The radiation dose also depends on the lifestyle of people. The use of certain building materials, the use of cooking gas, open charcoal braziers, airtight spaces, and even air travel all increase exposure from natural sources of radiation.
Terrestrial sources of radiation together are responsible for most of the exposure to which a person is exposed due to natural radiation. The rest of the radiation comes from cosmic rays.
Cosmic rays mainly come to us from the depths of the Universe, but some of them are born on the Sun during solar flares. Cosmic rays can reach the Earth's surface or interact with its atmosphere, generating secondary radiation and leading to the formation of various radionuclides.
Over the past few decades, man has created several hundred artificial radionuclides and learned how to use the energy of the atom for a variety of purposes: in medicine and to create atomic weapons, to produce energy and detect fires, to search for minerals. All this leads to an increase in the radiation dose of both individuals and the population of the Earth as a whole.
Individual doses received by different people from artificial sources of radiation vary greatly. In most cases, these doses are very small, but sometimes exposure due to man-made sources is many thousand times more intense than due to natural sources.
Currently, the main contribution to the dose received by man from man-made sources of radiation is made by medical procedures and methods of treatment associated with the use of radioactivity. In many countries, this source is responsible for almost the entire dose received from man-made sources of radiation.
Radiation is used in medicine both for diagnostic purposes and for treatment. One of the most common medical devices is the X-ray machine. New complex diagnostic methods based on the use of radioisotopes are also becoming more widespread. Paradoxically, one of the ways to fight cancer is radiation therapy.
Nuclear power plants are the source of the most intensely debated exposures, although they currently make a very small contribution to the total exposure of the population. During the normal operation of nuclear installations, releases of radioactive materials into the environment are very small. Nuclear power plants are only part of the nuclear fuel cycle, which begins with the extraction and enrichment of uranium ore. The next stage is the production of nuclear fuel. Spent nuclear fuel is sometimes reprocessed to extract uranium and plutonium from it. The cycle ends, as a rule, with the disposal of radioactive waste. But at each stage of the nuclear fuel cycle, radioactive substances enter the environment.
5. Means of protection of the population
1. Collective means of protection: shelters, prefabricated shelters (BVU), anti-radiation shelters (PRU), simple shelters (PU);
2. Individual respiratory protective equipment: filtering gas masks, insulating gas masks, filtering respirators, insulating respirators, self-rescuers, hose-type, self-contained, cartridges for gas masks;
3. Individual means of skin protection: filtering, insulating;
4. Devices for dosimetric reconnaissance;
5. Devices for chemical reconnaissance;
6. Devices - determinants of harmful impurities in the air;
7. Photos.
6. Radiation control
Radiation safety is understood as the state of protection of the present and future generation of people, material resources and the environment from the harmful effects of AI.
Radiation control is the most important part of ensuring radiation safety, starting from the design stage of radiation hazardous facilities. It aims to determine the degree of compliance with the principles of radiation safety and regulatory requirements, including not exceeding the established basic dose limits and permissible levels during normal operation, obtaining the necessary information to optimize protection and make decisions on intervention in the event of radiation accidents, contamination of the area and buildings with radionuclides, and also in areas and buildings with high levels of natural exposure. Radiation control is carried out for all sources of radiation.
Radiation control is subject to: 1) radiation characteristics of radiation sources, emissions into the atmosphere, liquid and solid radioactive waste; 2) radiation factors created by the technological process at workplaces and in the environment; 3) radiation factors in contaminated areas and in buildings with an increased level of natural exposure; 4) levels of exposure of personnel and the public from all sources of radiation to which these Standards apply.
The main controlled parameters are: annual effective and equivalent doses; the intake of radionuclides into the body and their content in the body to assess the annual intake; volumetric or specific activity of radionuclides in air, water, food, building materials; radioactive contamination of the skin, clothing, footwear, work surfaces.
Therefore, the administration of the organization can introduce additional, more stringent numerical values of the controlled parameters - administrative levels.
Moreover, state supervision over the implementation of the Radiation Safety Standards is carried out by the bodies of the State Sanitary and Epidemiological Supervision and other bodies authorized by the Government of the Russian Federation in accordance with the current regulations.
Control over compliance with the Norms in organizations, regardless of the form of ownership, is assigned to the administration of this organization. Control over the exposure of the population is assigned to the executive authorities of the constituent entities of the Russian Federation.
Control over the medical exposure of patients is assigned to the administration of health authorities and institutions.
A person is exposed to radiation in two ways. Radioactive substances can be outside the body and irradiate it from the outside; in this case, one speaks of external irradiation. Or they can be in the air that a person breathes, in food or in water and get inside the body. This method of irradiation is called internal.
Alpha rays can be protected by:
Increasing the distance to IRS, because alpha particles have a short range;
Use of overalls and special footwear, tk. the penetrating power of alpha particles is low;
Exclusion of alpha-particle sources from getting into food, water, air and through mucous membranes, i.e. the use of gas masks, masks, glasses, etc.
As protection against beta radiation, use:
Fences (screens), taking into account the fact that a sheet of aluminum with a thickness of several millimeters completely absorbs the flow of beta particles;
Methods and methods that exclude the ingress of beta radiation sources into the body.
Protection against X-rays and gamma radiation must be organized taking into account the fact that these types of radiation are characterized by high penetrating power. The following measures are most effective (usually used in combination):
Increasing the distance to the radiation source;
Reducing the time spent in the danger zone;
Shielding of the radiation source with high-density materials (lead, iron, concrete, etc.);
Use of protective structures (anti-radiation shelters, basements, etc.) for the population;
Use of personal protective equipment for respiratory organs, skin and mucous membranes;
Dosimetric control of the environment and food.
For the population of the country, in case of declaring a radiation hazard, there are the following recommendations:
Take shelter in houses. It is important to know that the walls of a wooden house attenuate ionizing radiation by 2 times, and a brick house by 10 times. Cellars and basements of houses weaken the radiation dose from 7 to 100 or more times;
Take protective measures against penetration into the apartment (house) of radioactive substances with air. Close the windows, seal the frames and doorways;
Make a supply of drinking water. Draw water into closed containers, prepare the simplest sanitary products (for example, soap solutions for hand treatment), turn off the taps;
Carry out emergency iodine prophylaxis (as early as possible, but only after special notification!). Iodine prophylaxis consists in taking stable iodine preparations: potassium iodide or a water-alcohol solution of iodine. This achieves a 100% degree of protection against the accumulation of radioactive iodine in the thyroid gland. Water-alcohol solution of iodine should be taken after meals 3 times a day for 7 days: a) children under 2 years old - 1-2 drops of 5% tincture per 100 ml of milk or nutrient mixture; b) children over 2 years old and adults - 3-5 drops per glass of milk or water. Apply tincture of iodine in the form of a grid to the surface of the hands once a day for 7 days.
Start preparing for a possible evacuation: prepare documents and money, essentials, pack medicines, a minimum of linen and clothes. Gather a supply of canned food. All items should be packed in plastic bags. Try to follow the following rules: 1) accept canned food; 2) do not drink water from open sources; 3) avoid long-term movements on the contaminated territory, especially on a dusty road or grass, do not go to the forest, do not swim; 4) when entering the premises from the street, take off your shoes and outerwear.
In the case of movement in open areas, use improvised means of protection:
Respiratory organs: cover your mouth and nose with a gauze bandage moistened with water, a handkerchief, a towel or any part of clothing;
Skin and hairline: cover with any items of clothing, hats, scarves, capes, gloves.
Conclusion
And since only ionizing radiation and its harmful effects on living organisms were discovered, it became necessary to control human exposure to these radiations. Everyone should be aware of the dangers of radiation and be able to protect themselves from it.
Radiation is inherently harmful to life. Small doses of radiation can “start” a not yet fully understood chain of events leading to cancer or genetic damage. At high doses, radiation can destroy cells, damage organ tissues and cause the death of an organism.
In medicine, one of the most common devices is an x-ray machine, and new sophisticated diagnostic methods based on the use of radioisotopes are also becoming more widespread. Paradoxically, one of the ways to fight cancer is radiation therapy, although radiation is aimed at healing the patient, but often the doses are unreasonably high, since the doses received from radiation for medical purposes make up a significant part of the total radiation dose from man-made sources.
Huge damage is also caused by accidents at facilities where radiation is present, a vivid example of this is the Chernobyl nuclear power plant.
Thus, it is necessary for all of us to reflect so that it does not turn out that what is lost today may turn out to be completely irreparable tomorrow.
Bibliography
1. Nebel B. Science of the environment. How the world works. In 2 volumes, M., Mir, 1994.
2. Sitnikov V.P. Fundamentals of life safety. –M.: AST. 1997.
3. Protection of the population and territories from emergencies. (ed. M.I. Faleev) - Kaluga: State Unitary Enterprise "Oblizdat", 2001.
4. Smirnov A.T. Fundamentals of life safety. Textbook for 10, 11 grades of secondary school. - M .: Education, 2002.
5. Frolov. Fundamentals of life safety. Textbook for students of educational institutions of secondary vocational education. – M.: Enlightenment, 2003.
Department of BJD
Test
discipline: Life safety
on the topic: Ionizing radiation
Perm, 2004
Introduction
Ionizing radiation is called radiation, the interaction of which with the environment leads to the formation of electric charges of various signs.
Ionizing radiation is the radiation that radioactive substances possess.
Under the influence of ionizing radiation, a person develops radiation sickness.
The main goal of radiation safety is to protect the health of the population, including personnel, from the harmful effects of ionizing radiation by observing the basic principles and norms of radiation safety without unreasonable restrictions on useful activities when using radiation in various areas of the economy, in science and medicine.
Radiation safety standards (NRB-2000) are used to ensure human safety under the influence of ionizing radiation of artificial or natural origin.
Main characteristics of ionizing radiation
Ionizing radiation is called radiation, the interaction of which with the environment leads to the formation of electric charges of various signs. The sources of these radiations are widely used in engineering, chemistry, medicine, agriculture and other areas, for example, in measuring soil density, detecting leaks in gas pipelines, measuring the thickness of sheets, pipes and rods, antistatic treatment of fabrics, polymerization of plastics, radiation therapy of malignant tumors, etc. However, it should be remembered that sources of ionizing radiation pose a significant threat to the health and life of people using them.
There are 2 types of ionizing radiation:
corpuscular, consisting of particles with a rest mass other than zero (alpha and beta radiation and neutron radiation);
electromagnetic (gamma radiation and x-rays) with a very short wavelength.
alpha radiation is a stream of helium nuclei with high speed. These nuclei have a mass of 4 and a charge of +2. They are formed during the radioactive decay of nuclei or during nuclear reactions. Currently, more than 120 artificial and natural alpha-radioactive nuclei are known, which, emitting an alpha particle, lose 2 protons and 2 neurons.
The energy of alpha particles does not exceed a few MeV (mega-electron-volt). The emitted alpha particles move almost in a straight line at a speed of about 20,000 km/s.
Under the path length of a particle in air or other media, it is customary to call the greatest distance from the radiation source at which it is still possible to detect a particle before it is absorbed by a substance. The path length of a particle depends on the charge, mass, initial energy, and the medium in which the motion occurs. With an increase in the initial energy of the particle and a decrease in the density of the medium, the path length increases. If the initial energy of the emitted particles is the same, then heavy particles have lower velocities than light ones. If the particles move slowly, then their interaction with the atoms of the substance of the medium is more efficient and the particles quickly waste their energy reserve.
The path length of alpha particles in air is usually less than 10 cm. Due to their large mass, alpha particles quickly lose their energy when interacting with matter. This explains their low penetrating power and high specific ionization: when moving in air, an alpha particle forms several tens of thousands of pairs of charged particles - ions per 1 cm of its path.
beta radiation is a stream of electrons or positrons resulting from radioactive decay. About 900 beta radioactive isotopes are currently known.
The mass of beta particles is several tens of thousands of times less than the mass of alpha particles. Depending on the nature of the source of beta radiation, the speed of these particles can lie within 0.3 - 0.99 of the speed of light. The energy of beta particles does not exceed several MeV, the path length in air is approximately 1800 cm, and in the soft tissues of the human body ~ 2.5 cm. The penetrating power of beta particles is higher than that of alpha particles (due to their smaller mass and charge).
neutron radiation is a stream of nuclear particles that do not have an electric charge. The mass of a neutron is approximately 4 times less than the mass of alpha particles. Depending on the energy, slow neutrons are distinguished (with an energy of less than 1 KeV (kilo-electron-Volt) \u003d 10 3 eV), neutrons of intermediate energies (from 1 to 500 KeV) and fast neutrons (from 500 KeV to 20 MeV). During the inelastic interaction of neutrons with the nuclei of atoms of the medium, secondary radiation arises, consisting of charged particles and gamma quanta (gamma radiation). During elastic interactions of neutrons with nuclei, the usual ionization of matter can be observed. The penetrating power of neutrons depends on their energy, but it is much higher than that of alpha or beta particles. Neutron radiation has a high penetrating power and represents the greatest danger to humans of all types of corpuscular radiation. The neutron flux power is measured by the neutron flux density.
Gamma radiation It is electromagnetic radiation with high energy and short wavelength. It is emitted during nuclear transformations or the interaction of particles. High energy (0.01 - 3 MeV) and short wavelength determines the high penetrating power of gamma radiation. Gamma rays are not deflected in electric and magnetic fields. This radiation has a lower ionizing power than alpha and beta radiation.
x-ray radiation can be obtained in special X-ray tubes, in electron accelerators, in the environment surrounding the source of beta radiation, etc. X-ray radiation is one of the types of electromagnetic radiation. Its energy usually does not exceed 1 MeV. X-ray radiation, like gamma radiation, has a low ionizing ability and a large penetration depth.
To characterize the effect of ionizing radiation on a substance, the concept of radiation dose has been introduced. The dose of radiation is the part of the energy transferred by radiation to the substance and absorbed by it. The quantitative characteristic of the interaction of ionizing radiation and matter is absorbed radiation dose(E), equal to the ratio of the average energy dE transferred by ionizing radiation to a substance in an elementary volume, to the mass of the irradiated substance in this volume dm:
Until recently, only X-ray and gamma radiation, based on their ionizing effect, was taken as a quantitative characteristic. exposure dose X is the ratio of the total electric charge dQ of ions of the same sign, arising in a small volume of dry air, to the mass of air dm in this volume, i.e.
To assess the possible damage to health during chronic exposure to ionizing radiation of arbitrary composition, the concept equivalent dose(H). This value is defined as the product of the absorbed dose D and the average radiation quality factor Q (dimensionless) at a given point in the tissue of the human body, i.e.:
There is another characteristic of ionizing radiation - dose rate X (respectively absorbed, exposure or equivalent) representing the dose increment over a small period of time dx divided by this period dt. Thus, the exposure dose rate (x or w, C / kg s) will be:
X \u003d W \u003d dx / dt
The biological effect of the considered radiations on the human body is different.
Alpha particles, passing through matter and colliding with atoms, ionize (charge) them, knocking out electrons. In rare cases, these particles are absorbed by the nuclei of atoms, transferring them to a state of higher energy. This excess energy contributes to the flow of various chemical reactions that do not proceed without irradiation or proceed very slowly. Alpha radiation has a strong effect on the organic substances that make up the human body (fats, proteins and carbohydrates). On the mucous membranes, this radiation causes burns and other inflammatory processes.
Under the action of beta radiation, radiolysis (decomposition) of water contained in biological tissues occurs, with the formation of hydrogen, oxygen, hydrogen peroxide H 2 O 2, charged particles (ions) OH - and HO - 2. The decomposition products of water have oxidizing properties and cause the destruction of many organic substances that make up the tissues of the human body.
The action of gamma and X-ray radiation on biological tissues is mainly due to the free electrons formed. Neutrons passing through matter produce the strongest changes in it in comparison with other ionizing radiations.
Thus, the biological effect of ionizing radiation is reduced to a change in the structure or destruction of various organic substances (molecules) that make up the human body. This leads to a violation of the biochemical processes occurring in the cells, or even to their death, resulting in damage to the body as a whole.
Distinguish between external and internal irradiation of the body. External exposure is understood as the effect on the body of ionizing radiation from sources external to it. Internal exposure is carried out by radioactive substances that have entered the body through the respiratory organs, the gastrointestinal tract or through the skin. Sources of external radiation - cosmic rays, natural radioactive sources in the atmosphere, water, soil, food, etc., sources of alpha, beta, gamma, X-ray and neutron radiation used in engineering and medicine, charged particle accelerators, nuclear reactors (including accidents at nuclear reactors) and a number of others.
Radioactive substances that cause internal irradiation of the body enter it when eating, smoking, drinking contaminated water. The entry of radioactive substances into the human body through the skin occurs in rare cases (if the skin has damage or open wounds). Internal irradiation of the body lasts until the radioactive substance decays or is removed from the body as a result of physiological metabolic processes. Internal exposure is dangerous because it causes long-term non-healing ulcers of various organs and malignant tumors.
When working with radioactive substances, the hands of operators are exposed to significant radiation. Under the influence of ionizing radiation, a chronic or acute (radiation burn) damage to the skin of the hands develops. Chronic lesion is characterized by dry skin, cracking, ulceration and other symptoms. In acute lesions of the hands, edema, tissue necrosis, ulcers occur, at the site of formation of which the development of malignant tumors is possible.
Under the influence of ionizing radiation, a person develops radiation sickness. There are three degrees of it: the first (light), second and third (severe).
Symptoms of radiation sickness of the first degree are weakness, headaches, sleep disturbance and appetite, which increase in the second stage of the disease, but they are additionally accompanied by disturbances in the activity of the cardiovascular system, metabolism and blood composition change, and digestive organs are upset. At the third stage of the disease, hemorrhages are observed, hair loss, the activity of the central nervous system and sex glands is disrupted. In people who have undergone radiation sickness, the likelihood of developing malignant tumors and diseases of the hematopoietic organs increases. Radiation sickness in an acute (severe) form develops as a result of irradiation of the body with large doses of ionizing radiation in a short period of time. The impact on the human body and small doses of radiation is dangerous, since in this case a violation of the hereditary information of the human body can occur, mutations occur.
A low level of development of a mild form of radiation sickness occurs at an equivalent radiation dose of approximately 1 Sv, a severe form of radiation sickness, in which half of all exposed people die, occurs at an equivalent radiation dose of 4.5 Sv. A 100% lethal outcome from radiation sickness corresponds to an equivalent radiation dose of 5.5–7.0 Sv.
Currently, a number of chemical preparations (protectors) have been developed that significantly reduce the negative effect of ionizing radiation on the human body.
In Russia, the maximum permissible levels of ionizing radiation and the principles of radiation safety are regulated by the "Radiation Safety Standards" NRB-76, "Basic Sanitary Rules for Working with Radioactive Substances and Other Sources of Ionizing Radiation" OSP72-80. In accordance with these regulatory documents, exposure standards are established for the following three categories of persons:
For category A persons, the main dose limit is the individual equivalent dose of external and internal radiation per year (Sv / year) depending on the radiosensitivity of organs (critical organs). This is the maximum allowable dose (MAD) - the highest value of the individual equivalent dose per year, which, with uniform exposure for 50 years, will not cause adverse changes in the health of personnel detected by modern methods.
For category A personnel, the individual equivalent dose ( H, Sv) accumulated in the critical organ over time T(years) from the beginning of professional work, should not exceed the value determined by the formula:
H = SDA ∙ T. In addition, the dose accumulated by the age of 30 should not exceed 12 SDA.
For category B, a dose limit per year (PD, Sv/year) is set, which is understood as the highest average value of the individual equivalent dose per calendar year for a critical group of people, at which uniform exposure for 70 years cannot cause adverse changes in the state of health, detected by modern methods. Table 1 shows the main dose limits of external and internal exposures depending on the radiosensitivity of organs.
Table 1 - Basic values of dose limits for external and internal exposure
Ionizing radiation is a phenomenon associated with radioactivity.
Radioactivity is the spontaneous transformation of the nuclei of atoms of one element into another, accompanied by the emission of ionizing radiation.
The degree, depth and form of radiation injuries that develop among biological objects when exposed to ionizing radiation, primarily depend on the amount of absorbed radiation energy. To characterize this indicator, the concept of absorbed dose is used, i.e., the radiation energy absorbed by a unit mass of the irradiated substance.
Ionizing radiation is a unique environmental phenomenon, the effects of which on the body at first glance are not at all equivalent to the amount of absorbed energy.
The most important biological reactions of the human body to the action of ionizing radiation are conditionally divided into two groups:
1) acute lesions;
2) long-term effects, which in turn are divided into somatic and genetic effects.
At radiation doses of more than 100 rem, acute radiation sickness develops, the severity of which depends on the radiation dose.
Long-term consequences of a somatic nature include a variety of biological effects, among which the most significant are leukemia, malignant neoplasms, and reduced life expectancy.
Regulation of exposure and principles of radiation safety. Since January 1, 2000, exposure of people in the Russian Federation has been regulated by radiation safety standards (NRB-96), hygienic standards (GN) 2.6.1.054-96. The main dose exposure limits and permissible levels are established for the following categories of exposed persons:
1) personnel - persons working with man-made sources (group A) or who, due to the conditions of work, are in the area of impact (group B);
2) the population, including persons from the staff, outside the scope and conditions of their production activities.
Three classes of standards are provided for the indicated categories of exposed persons:
1) basic dose limits (maximum allowable dose - for category A, dose limit - for category B);
2) acceptable levels;
3) control levels set by the administration of the institution in agreement with the State Sanitary and Epidemiological Supervision at a level below the permissible level.
Basic principles for ensuring radiation safety:
1) reducing the power of sources to minimum values;
2) reducing the time of work with sources;
3) increasing the distance from sources to workers;
4) shielding of radiation sources with materials that absorb ionizing radiation.
-
ionizing radiation and security radiation security. ionizing radiation is a phenomenon associated with radioactivity. Radioactivity is the spontaneous transformation of the nuclei of atoms of one element into another ... -
ionizing radiation and security radiation security. ionizing radiation -
ionizing radiation and security radiation security. ionizing radiation is a phenomenon associated with radioactivity. Radioactivity is spontaneous. -
ionizing radiation and security radiation security. ionizing radiation is a phenomenon associated with radioactivity. Radioactivity - spontaneous ... more ». -
Norms radiation security. The human body is constantly exposed to cosmic rays and natural radioactive elements present in the air, soil, and in the tissues of the body itself.
For ionizing radiation SDA is set at 5 rem per year. -
In accordance with the above, the Ministry of Health of Russia in 1999 approved the norms radiation security(NRB-99)
Exposure dose - based on ionizing action radiation, this is a quantitative characteristic of the field ionizing radiation. -
Currently, radiation injury to people may be associated with violation of rules and regulations. radiation security when working with sources ionizing radiation, during accidents at radiation-hazardous objects, during nuclear explosions, etc. -
5) multiple sources ionizing radiation both closed and open types
Legislation on nuclear and radiation security unites legal acts of different legal force. -
security
Radiation shelters are structures that protect people from ionizing radiation, contamination with radioactive substances, drops of AOHV and ... -
It is enough to download cheat sheets for security life - and you are not afraid of any exam!
noise, infrasound, ultrasound, vibration level - increased or decreased barometric pressure - increased level ionizing radiation-increased...
Found similar pages:10
