The concept of radioactivity. Zone of radioactive decay
Radioactive radiation is widely used in the diagnosis and treatment of diseases.
Radionuclide diagnostics or, as it is called, the method of labeled atoms is used to determine diseases of the thyroid gland (using the isotope 131 I). This method also makes it possible to study the distribution of blood and other biological fluids, to diagnose diseases of the heart and a number of other organs.
Gamma Therapy is a treatment modality oncological diseases using g-radiation. For this, most often special installations are used, called cobalt guns, in which 66 Co is used as the emitting isotope. The use of high-energy gamma radiation makes it possible to destroy deep-seated tumors, while superficially located organs and tissues are less harmful.
Radon therapy will also be used: mineral waters containing its products are used to affect the skin (radon baths), the digestive organs (drinking), and the respiratory organs (inhalation).
For the treatment of cancer, a-particles are used in combination with neutron fluxes. Elements are introduced into the tumor, the nuclei of which, under the influence of a neutron flux, cause a nuclear reaction with the formation of a-radiation:
.
Thus, a-particles and recoil nuclei are formed in the place of the organ that needs to be exposed.
In modern medicine, for diagnostic purposes, hard X-ray bremsstrahlung produced at accelerators and having high energy quanta (up to several tens of MeV).
Dosimetric instruments
Dosimetric instruments, or dosimeters, are called devices for measuring doses of ionizing radiation or quantities associated with doses.
Structurally, dosimeters consist of a nuclear radiation detector and a measuring device. They are usually graduated in units of dose or dose rate. In some cases, an alarm is provided for exceeding set value dose rate.
Depending on the detector used, dosimeters are ionization, luminescent, semiconductor, photodosimeters, etc.
Dosimeters can be designed to measure doses of a particular type of radiation or to record mixed radiation.
Dosimeters for measuring the exposure dose of X-ray and g-radiation or its power are called radiometers.
They usually use an ionization chamber as a detector. The charge flowing in the camera circuit is proportional to the exposure dose, and the current strength is proportional to its power.
The composition of the gas in the ionization chambers, as well as the substance of the walls of which they are composed, is selected in such a way that identical conditions are realized with the absorption of energy in biological tissues.
Each individual dosimeter is a miniature cylindrical chamber that is pre-charged. As a result of ionization, the chamber is discharged, which is recorded by an electrometer built into it. Its indications depend on the exposure dose of ionizing radiation.
There are dosimeters whose detectors are gas meters.
To measure the activity or concentration of radioactive isotopes, instruments called radiometers.
The general structural diagram of all dosimeters is similar to that shown in Fig.5. The role of the sensor (measuring transducer) is performed by a nuclear radiation detector. Pointer devices, recorders, electromechanical meters, sound and light signaling devices can be used as output devices.
TEST QUESTIONS
1. What is called radioactivity? Name the types of radioactivity and types radioactive decay.
2. What is called a-decay? What are the types of b-decay? What is called g-radiation?
3. Write down the basic law of radioactive decay. Explain all the quantities included in the formula.
4. What is called decay constant? half-life? Write a formula relating these quantities. Explain all the quantities included in the formula.
5. What effect do ionizing radiation on biological tissue?
7. Give definitions and formulas for absorbed, exposure and equivalent (biological) doses of radioactive radiation, their units of measurement. Explain formulas.
8. What is the quality factor? What is the quality factor? Give its values for different radiations.
9. What are the ways to protect against ionizing radiation?
The phenomenon of radioactivity and its use in science, industry and medicine Prepared by: student school number 26 Vladimir Khrupolov K. Another mystery of nature
Prepared by: student school number 26 Vladimir Khrupolov K. Another mystery of nature
Khrupolov K. Another mystery of nature
The late 19th and early 20th centuries were exceptionally rich in mind-blowing discoveries and inventions that people could only dream of. The idea of the possibility of obtaining inexhaustible energy contained in a negligible amount of matter lived in the recesses of human thought. 
A well-known scientist of that time was Becquerel, who set himself the goal of unraveling the nature of the mysterious glow of certain substances under the influence of solar radiation. Becquerel collects a huge collection of luminous chemicals and natural minerals.
Objective
The study of the concept of radioactivity, its discovery.
Find out how radioactive isotopes are used in science, industry and medicine.
Determine the value of the phenomenon of radioactivity in the world.
The phenomenon of radioactivity
Radioactivity is the ability of some atomic nuclei to spontaneously transform into other nuclei with the emission of various types of radioactive radiation and elementary particles. How to use the phenomenon of radioactivity?
The use of radioactivity in medicine
The study of the concept of radioactivity, its discovery.
Find out how radioactive isotopes are used in science, industry and medicine.
Determine the value of the phenomenon of radioactivity in the world.
How to use the phenomenon of radioactivity?
The use of radioactivity in medicine
The use of radioactivity in medicine
Radiotherapy is the use of strong radiation to kill cancer cells.
Radioactive iodine accumulates in the thyroid
gland, determines dysfunctions and
used in the treatment of Graves' disease.
Sodium-labeled saline measures the rate of blood circulation, determines the patency of the blood vessels of the extremities.
Radioactive phosphorus measures blood volume, treats erythremia. 
The use of radioactivity in industry
One example of this is the following method for monitoring piston ring wear in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine is running, particles of the ring material enter the lubricating oil. By examining the level of radioactivity of the oil after a certain time of engine operation, the wear of the ring is determined. Powerful gamma radiation of radioactive preparations is used to study the internal structure of metal castings in order to detect defects in them. 
The use of radioactivity in agriculture
Irradiation of plant seeds with small doses of gamma rays from radioactive preparations leads to a noticeable increase in yield. Application received "labeled atoms" in agricultural technology. For example, in order to find out which of the phosphorus fertilizers is better absorbed by the plant, various fertilizers are labeled with radioactive phosphorus P. By examining plants for radioactivity, one can determine the amount of phosphorus absorbed by them from different varieties of fertilizer. 
Discovery of the phenomenon of radioactivity.
The discovery of the phenomenon of radioactivity can be attributed to the most outstanding discoveries of modern science. It was thanks to him that man was able to significantly deepen his knowledge in the field of the structure and properties of matter, understand the patterns of many processes in the Universe, and solve the problem of mastering nuclear energy.
The potential of great science
Until the discovery of radioactivity, scientists believed that they knew everything physical phenomena and nothing to open. Is there a possibility that there is something else in the world that is not known to mankind?
Is there a possibility that there is something else in the world that is not known to mankind?
radiation particle exposure radon
People have learned to use radiation in peaceful purposes, With high level security, which allowed to raise almost all industries to a new level.
Getting energy with the help of nuclear power plants. From all industries economic activity human energy has the most big influence on our lives. Heat and light in houses, traffic flows and the work of industry - all this requires energy. This industry is one of the fastest growing. Over 30 years, the total capacity of nuclear power units has grown from 5,000 to 23 million kilowatts.
Few doubt that nuclear power has taken a strong position in energy balance humanity.
Consider the use of radiation in flaw detection. X-ray and gamma flaw detection is one of the most common applications of radiation in industry to control the quality of materials. The X-ray method is non-destructive, so that the material being tested can then be used for its intended purpose. Both x-ray and gamma flaw detection are based on the penetrating power of x-rays and the characteristics of its absorption in materials.
Gamma radiation is used for chemical transformations, for example, in polymerization processes.
Perhaps one of the most important emerging industries is nuclear medicine. Nuclear medicine - a branch of medicine associated with the use of advances nuclear physics, in particular, radioisotopes, etc.
Today, nuclear medicine makes it possible to study almost all human organ systems and finds application in neurology, cardiology, oncology, endocrinology, pulmonology, and other branches of medicine.
With the help of nuclear medicine methods, they study the blood supply to organs, bile metabolism, kidney function, Bladder, thyroid gland.
It is possible not only to obtain static images, but also to overlay images obtained at different points in time to study the dynamics. This technique is used, for example, in assessing the work of the heart.
In Russia, two types of diagnostics using radioisotopes are already actively used - scintigraphy and positron emission tomography. They allow you to create complete models the work of organs.
Doctors believe that at low doses, radiation has a stimulating effect, training the human biological defense system.
Many resorts use radon baths, where the level of radiation is slightly higher than in natural conditions.
It was noticed that those who take these baths improve their working capacity, calm down nervous system heal injuries faster.
Studies by foreign scientists suggest that the frequency and mortality from all types of cancer is lower in areas with a higher natural background radiation (most of the sunny countries can be included).
The effect of radioactive radiation on humans
Radioactive radiation of all types (alpha, beta, gamma, neutrons), as well as electromagnetic radiation (X-ray radiation) have a very strong biological effect on living organisms, which consists in the processes of excitation and ionization of atoms and molecules that make up living cells. Under the influence ionizing radiation complex molecules and cellular structures are destroyed, which leads to radiation damage to the body. Therefore, when working with any source of radiation, it is necessary to take all measures for the radiation protection of people who can fall into the zone of radiation.
However, a person can be exposed to ionizing radiation and living conditions. Serious danger for human health, it can represent an inert, colorless, radioactive gas radon. It is a decay product of radium and has a half-life T = 3.82 days. Radium is found in small amounts in soil, in stones, and in various building structures. Despite the relatively short lifetime, the concentration of radon is continuously replenished due to new decays of radium nuclei, so radon can accumulate in enclosed spaces. Getting into the lungs, radon emits -particles and turns into polonium, which is not a chemically inert substance. This is followed by a chain of radioactive transformations of the uranium series. According to the American Commission on Radiation Safety and Control, the average person receives 55% of ionizing radiation from radon and only 11% from medical care. The contribution of cosmic rays is approximately 8%. The total dose of radiation that a person receives in a lifetime is many times less extremely allowable dose (SDA), which is established for people of certain professions exposed to additional exposure to ionizing radiation.
The use of radioactive isotopes
One of the most outstanding studies carried out with the help of "tagged atoms" was the study of metabolism in organisms. It has been proven that in a relatively short time the body undergoes an almost complete renewal. Its constituent atoms are replaced by new ones. Only iron, as experiments on the isotopic study of blood have shown, is an exception to this rule. Iron is part of the hemoglobin in red blood cells. When radioactive iron atoms were introduced into food, it was found that the free oxygen released during photosynthesis was originally part of the water, and not carbon dioxide. Radioactive isotopes are used in medicine for both diagnosis and therapeutic purposes. Radioactive sodium, introduced in small quantities into the blood, is used to study blood circulation, iodine is intensively deposited in the thyroid gland, especially in Graves' disease. By monitoring the deposition of radioactive iodine with a counter, a diagnosis can be made quickly. Large doses of radioactive iodine cause partial destruction of abnormally developing tissues, and therefore radioactive iodine is used to treat Graves' disease. Intense cobalt gamma radiation is used in the treatment of cancer (cobalt gun).
No less extensive are the applications of radioactive isotopes in industry. One example of this is the following method for monitoring piston ring wear in internal combustion engines. By irradiating the piston ring with neutrons, they cause nuclear reactions in it and make it radioactive. When the engine is running, particles of the ring material enter the lubricating oil. By examining the level of radioactivity of the oil after a certain time of engine operation, the wear of the ring is determined. Radioactive isotopes make it possible to judge the diffusion of metals, processes in blast furnaces, etc.
Powerful gamma radiation of radioactive preparations is used to study the internal structure of metal castings in order to detect defects in them.
Radioactive isotopes are being used more and more widely in agriculture. Irradiation of plant seeds (cotton, cabbage, radish, etc.) with small doses of gamma rays from radioactive preparations leads to a noticeable increase in yield. Large doses of "radiation cause mutations in plants and microorganisms, which in some cases leads to the emergence of mutants with new valuable properties (radioselection). Thus, valuable varieties of wheat, beans and other crops have been bred, and highly productive microorganisms used in the production of antibiotics have been obtained. Gamma radiation from radioactive isotopes is also used to combat harmful insects and for conservation food products. Wide application received "labeled atoms" in agricultural technology. For example, to find out which of the phosphate fertilizers is better absorbed by the plant, various fertilizers are labeled with radioactive phosphorus 15 32P. By examining the plants for radioactivity, one can determine the amount of phosphorus absorbed by them from different varieties of fertilizer. An interesting application of radioactivity is the method of dating archaeological and geological finds by the concentration of radioactive isotopes. The most commonly used method is radiocarbon dating. An unstable carbon isotope occurs in the atmosphere due to nuclear reactions caused by cosmic rays. A small percentage of this isotope is found in air along with the usual stable isotope. Plants and other organisms consume carbon from the air and accumulate both isotopes in the same proportion as they do in air. After the death of plants, they cease to consume carbon and the unstable isotope, as a result of decay, gradually turns into nitrogen with a half-life of 5730 years. By accurately measuring the relative concentration of radioactive carbon in the remains of ancient organisms, it is possible to determine the time of their death.
The use of radioactivity.
1. Biological actions. Radioactive radiation has a disastrous effect on living cells. The mechanism of this action is associated with the ionization of atoms and the decomposition of molecules inside cells during the passage of fast charged particles. Cells that are in a state of rapid growth and reproduction are especially sensitive to the effects of radiation. This circumstance is used for the treatment of cancerous tumors.
For the purposes of therapy, radioactive preparations emitting g-radiation are used, since the latter penetrate the body without noticeable weakening. At not too high doses of radiation, cancer cells die, while the patient's body does not suffer significant damage. It should be noted that cancer radiotherapy, like X-ray therapy, is by no means a universal remedy that always leads to a cure.
Excessively large doses radioactive emissions cause severe diseases in animals and humans (the so-called radiation sickness) and can lead to death. In very small doses, radioactive radiation, mainly a-radiation, on the contrary, has a stimulating effect on the body. Associated with this is the healing effect of radioactive mineral waters containing small amounts of radium or radon.
2. Luminous compounds. Luminescent substances glow under the action of radioactive radiation (cf. § 213). By adding a very small amount of radium salt to a luminescent substance (for example, zinc sulfide), permanently luminous paints are prepared. These paints, being applied to the dials and hands of the clock, sights etc., make them visible in the dark.
3. Determining the age of the Earth. The atomic mass of ordinary lead, mined from ores that do not contain radioactive elements, is 207.2, atomic mass lead formed as a result of the decay of uranium is 206. The atomic mass of lead contained in some uranium minerals turns out to be very close to 206. It follows that these minerals at the time of formation (crystallization from a melt or solution) did not contain lead; all lead available in such minerals has accumulated as a result of the decay of uranium. Using the law of radioactive decay, it is possible to determine its age by the ratio of the amounts of lead and uranium in a mineral.
The age of minerals of various origins containing uranium, determined by this method, is measured in hundreds of millions of years. The oldest minerals are over 1.5 billion years old.
1. Biological actions. Radioactive radiation has a disastrous effect on living cells. The mechanism of this action is associated with the ionization of atoms and the decomposition of molecules inside cells during the passage of fast charged particles. Cells that are in a state of rapid growth and reproduction are especially sensitive to the effects of radiation. This circumstance is used for the treatment of cancerous tumors.
For the purposes of therapy, radioactive drugs that emit radiation are used, since the latter penetrate the body without noticeable weakening. At not too high doses of radiation, cancer cells die, while the patient's body does not suffer significant damage. It should be noted that cancer radiotherapy, like X-ray therapy, is by no means a universal remedy that always leads to a cure.
Excessively high doses of radioactive radiation cause severe diseases in animals and humans (the so-called radiation sickness) and can lead to death. In very small doses, radioactive radiation, mainly radiation, on the contrary, has a stimulating effect on the body. Related to this is the healing effect of radioactive mineral waters containing small amounts of radium or radon.
2. Luminous compositions. Luminescent substances glow under the action of radioactive radiation (cf. §213). By adding a very small amount of radium salt to a luminescent substance (for example, zinc sulfide), permanently luminous paints are prepared. These paints, when applied to clock faces and hands, sights, etc., make them visible in the dark.
3. Determining the age of the Earth. The atomic mass of ordinary lead, mined from ores that do not contain radioactive elements, is . As can be seen from fig. 389, the atomic mass of lead formed from the decay of uranium is . The atomic mass of lead contained in some uranium minerals turns out to be very close to. It follows that these minerals at the moment of formation (crystallization from a melt or solution) did not contain lead; all lead available in such minerals has accumulated as a result of the decay of uranium. Using the law of radioactive decay, it is possible to determine its age from the ratio of the amounts of lead and uranium in a mineral (see exercise 32 at the end of the chapter).
The age of minerals of various origins containing uranium, determined by this method, is measured in hundreds of millions of years. The oldest minerals are over 1.5 billion years old.
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