The use of radioactivity for peaceful purposes. The use of radioactivity
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 method of treating cancer using gamma 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 is also used: mineral water containing and its products are used to affect the skin (radon baths), the digestive organs (drinking), 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 from the detector nuclear radiation and 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 have 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?
Introduction………………………………………………………………………3
The use of radioactive sources in various
spheres of human activity………………………………………………………….3
Chemical industry
Urban economy
Medical industry
Radiation sterilization of products and materials
Production of radioisotope pacemakers
Presowing irradiation of seeds and tubers
Radioisotope diagnostics (introduction of a radioactive drug into the body)
Radioactive waste, problems of their disposal…………………..8
The undeveloped method……………………………………………………………....12
The pressure of external circumstances……………………………………………………....13
Decision making and technological complexity of the problem………………………...13
Concept uncertainty…………………………………………………………...14
References………………………………………………………….16
Introduction
At present, it is difficult to find a branch of science, technology, industry, agriculture and medicine where sources of radioactivity (radioactive isotopes) are not used. Artificial and natural radioactive isotopes are a powerful and subtle tool for creating sensitive methods of analysis and control in industry, a unique tool for medical diagnosis and treatment of malignant tumor diseases, an effective means of influencing various substances, including organic. The most important results were obtained using isotopes as radiation sources. The creation of installations with powerful sources of radioactive radiation made it possible to use it for control and management technological processes; technical diagnostics; therapy of human diseases; obtaining new properties of substances; converting the decay energy of radioactive substances into thermal and electrical energy, etc. The most commonly used isotopes for these purposes are ⁶⁰CO, ⁹⁰Sr, ¹³⁷Cs and plutonium isotopes. To prevent depressurization of sources, they are subject to strict requirements for mechanical, thermal and corrosion resistance. This provides a guarantee of tightness during the entire period of operation of the source.
The use of radioactive sources in various fields of human activity.
Chemical industry
Radiation-chemical modification of a polyamide fabric to give it hydrophilic and antistatic properties.
Modification of textile materials to obtain wool-like properties.
Obtaining cotton fabrics with antimicrobial properties.
Radiation modification of crystal to obtain crystal products of various colors.
Radiation vulcanization of rubber-fabric materials.
Radiation modification of polyethylene pipes to increase heat resistance and resistance to aggressive environments.
Hardening of paint and varnish coverings on various surfaces.
Woodworking industry
As a result of irradiation, soft wood acquires a significantly lower ability to absorb water, high stability of geometric dimensions and higher hardness (production of mosaic parquet).
Urban economy
Radiation purification and disinfection of wastewater.
Medical industry
Radiation sterilization of products and materials
The range of radiation-sterilized products includes over a thousand items, including disposable syringes, blood service systems, medical instruments, sutures and dressings, various prostheses used in cardiovascular surgery, traumatology and orthopedics. The main advantage of radiation sterilization is that it can be carried out continuously at high throughput. It is suitable for sterilization of finished products packed in transport containers or secondary packaging, and is also applicable for sterilization of heat-labile products and materials.
Production of radioisotope pacemakers with power supplies based on ²³⁸Pu. Implanted in the human body, they are used to treat various heart rhythm disorders that are not amenable to drug exposure. The use of a radioisotope power source increases their reliability, increases their service life up to 20 years, returns patients to normal life by reducing the number of repeated operations for implanting a pacemaker.
Agriculture and food industry
Agriculture is an important field of application of ionizing radiation. To date, in the practice of agriculture and scientific research agricultural profile, the following main areas of use of radioisotopes can be distinguished:
Irradiation of agricultural objects (primarily plants) with a low dose in order to stimulate their growth and development;
Application of ionizing radiation for radiation mutagenesis and plant breeding;
Using the method of radiation sterilization to combat insect pests of agricultural plants.
Presowing irradiation of seeds and tubers(wheat, barley, corn, potatoes, beets, carrots) improves the sowing qualities of seeds and tubers, accelerates the development of plants (precocity), increases the resistance of plants to adverse environmental factors.
In the area of breeding, mutagenesis research is carried out. The aim is to select macromutations for breeding high-yielding varieties. Radiation mutants of interest have already been obtained for more than 50 crops.
The use of ionizing radiation to sterilize pests in elevators and granaries can reduce crop losses by up to 20%.
Known that ionizing γ-radiation prevents the germination of potatoes and onions, is used for disinfestation of dried fruits, food concentrates, slows down microbiological spoilage and prolongs the shelf life of fruits, vegetables, meat, fish. The possibility of accelerating the aging processes of wines and cognac, changing the rate of fruit ripening, removing unpleasant odors was revealed. medicinal waters. In the canning industry (fish, meat and dairy, vegetable and fruit) wide application has sterilization of canned food. It should be noted that the study of irradiated foodstuffs showed that γ-irradiated foodstuffs are harmless.
We have considered the use of radioisotopes specific to individual industries. In addition, radioisotopes are widely used in industry for the following purposes:
Measurement of the levels of melt liquids;
Density measurement of liquids and pulps;
Count of items on the container;
Measuring the thickness of materials;
Measurement of ice thickness on aircraft and other vehicles;
Measurement of density and moisture content of soils;
Non-destructive γ-defectoscopy of product materials.
Directly in medical practice, radioisotope therapeutic devices have found clinical application, as well as clinical radioisotope diagnostics.
γ-therapeutic devices for external γ-irradiation have been mastered. These devices have significantly expanded the possibilities of remote γ-therapy of tumors through the use of static and mobile irradiation options.
Various options and methods of radiation treatment are used for individual localizations of tumors. Persistent five-year cures at stages 1, 2 and 3 were obtained, respectively, in
90-95, 75-85 and 55-60% of patients. The positive role of radiation therapy in the treatment of cancer of the breast, lung, esophagus, oral cavity, larynx, Bladder and other organs.
Radioisotope diagnostics (introduction of a radioactive drug into the body) has become an integral part of the diagnostic process at all stages of the development of the disease or the assessment of the functional state of a healthy organism. Radioisotope diagnostic studies can be summarized in the following main sections:
Determination of the radioactivity of the whole body, its parts, individual organs in order to identify the pathological condition of the organ;
Determination of the speed of movement of a radioactive drug in certain areas of the cardiovascular system;
Study of the spatial distribution of a radioactive drug in the human body for visualization of organs, pathological formations, etc.
Among the most important aspects diagnostics include pathological changes in the cardiovascular system, timely detection malignant neoplasms, assessment of the state of the bone, hematopoietic and lymphatic systems of the body, which are hard-to-reach objects for research by traditional clinical and instrumental methods.
Nay labeled with ¹³y has been introduced into clinical practice for the diagnosis of thyroid diseases; NaCe labeled with ²⁴Na to study local and general blood flow;
Na₃PO₄ labeled with ³³P to study the processes of its accumulation in skin pigment formations and other tumor formations.
The diagnostic method in neurology and neurosurgery using the isotopes ⁴⁴Tc, ¹³³Xe and ¹⁶⁹Y has gained leading importance. It is necessary for a more precise diagnosis of diseases of the brain, as well as diseases of the cardiovascular system. In nephrology and urology, radioactive preparations containing ¹³¹Y, ¹⁹⁷Hg,
¹⁶⁹Yb, ⁵¹Cr and ¹¹³Yn. Thanks to the introduction of radioisotope methods of examination, early morbidity of the kidneys and other organs has improved.
The applied scientific application of p/isotopes is very wide. Let's take a look at some:
Of practical interest is the use of radioisotope power plants (REP) with electric power from several units to hundreds of watts. Radioisotope thermoelectric generators have found the greatest practical application, in which the conversion of r / a decay energy into electrical energy is carried out using thermoelectric converters, such power plants are completely autonomous, capable of operating in any climatic conditions, long service life and reliability in operation.
Radioisotope power sources ensure operation in systems of automatic meteorological stations; in systems navigation equipment in remote and uninhabited areas (electric power for beacons, leading signs, navigation lights).
Thanks to the positive experience of using them in low temperature conditions, it became possible to use them in Antarctica.
It is also known that isotope power plants with ²¹ºPo were used on vehicles moving on the surface of the Moon (lunar rovers).
The use of r/a isotopes in scientific research cannot be overestimated, since all practices stem from positive results in research.
In addition, we should mention such very narrow specializations as pest control in ancient art objects, as well as the use of natural radioactive isotopes in radon baths and mud in spa treatment.
At the end of the operating life of the R / A, the sources must be delivered in the prescribed manner to special plants for processing (conditioning) with subsequent disposal as radioactive waste.
Radioactive waste, problems of their disposal
Problem radioactive waste is a special case of the general problem of environmental pollution by human waste. But at the same time, the pronounced specificity of RW requires the use of specific methods to ensure safety for humans and the biosphere.
The historical experience of handling industrial and household waste was formed in conditions where the awareness of the danger of waste and programs for its neutralization was based on direct sensations. The possibilities of the latter ensured the adequacy of the awareness of the connections of the influences directly perceived by the senses with the upcoming consequences. The level of knowledge made it possible to present the logic of the mechanisms of the impact of waste on humans and the biosphere, which quite accurately corresponds to real processes. The practically developed traditional ideas about the methods of waste disposal were historically joined by qualitatively different approaches developed with the discovery of microorganisms, forming not only empirically, but also scientifically based methodological ensuring the safety of humans and their environment. In medicine and social management systems, corresponding sub-sectors were formed, for example, sanitary and epidemiological affairs, communal hygiene, etc.
With the rapid development of chemistry and chemical industries in industrial and household waste in mass quantities, new, previously not included in them elements and chemical compounds, including those that do not exist in nature. In terms of scale, this phenomenon has become comparable to natural geochemical processes. Mankind has faced the need to reach a different level of problem assessment, which should take into account, for example, cumulative and delayed effects, methods for identifying dosages of effects, the need to use new methods and special highly sensitive equipment for detecting danger, etc.
A qualitatively different danger, although similar to chemical in some of the signs, brought to man "radioactivity" , as a phenomenon that is not directly perceived by the human senses, is not destroyed by methods known to mankind, and is still insufficiently studied in general: it is impossible to exclude the discovery of new properties, effects and consequences of this phenomenon. Therefore, in the formation of general and specific scientific and practical tasks “to eliminate the danger of RW” and, in particular, in solving these problems, constant difficulties arise, showing that the traditional formulation does not accurately reflect the real, objective nature of the “RW problem”. However, the ideology of such a statement is widespread in legal and non-legal documents of a national and interstate nature, which, as one might assume, cover a wide range of modern scientific views, directions, research and practical activities; take into account the developments of all well-known domestic and foreign organizations dealing with the “radiation waste problem”.
Decree of the Government of the Russian Federation of October 23, 1995 No. 1030 approved the Federal target program"Management of radioactive waste and spent nuclear materials, their utilization and disposal for 1996-2005”.
Radioactive waste is considered in it "as substances not subject to further use (in any state of aggregation), materials, products, equipment, objects of biological origin, in which the content of radionuclides exceeds the levels established regulations. The Program has a special section “State of the problem”, which contains a description of specific facilities and public areas where “radioactive waste management” takes place, as well as general quantitative characteristics of the “radiological waste problem” in Russia.
“A large amount of accumulated unconditioned radioactive waste, insufficient technical means to ensure the safe handling of these wastes and spent nuclear fuel, the lack of reliable storage facilities for their long-term storage and (or) disposal increase the risk of radiation accidents and create a real threat of radioactive contamination of the environment, overexposure of the population and personnel of organizations and enterprises whose activities are related to use of atomic energy and radioactive materials”.
The main sources of high-level radioactive waste (RW) are nuclear energy (spent nuclear fuel) and military programs (plutonium from nuclear warheads, spent fuel from transport reactors of nuclear submarines, liquid waste from radiochemical plants, etc.).
The question arises: should RW be considered simply as waste or as a potential source of energy? The answer to this question determines whether we want to store them (in an accessible form) or bury them (i.e., make them inaccessible). The generally accepted answer at present is that RW is indeed waste, with the possible exception of plutonium. Plutonium can theoretically serve as a source of energy, although the technology for obtaining energy from it is complex and quite dangerous. Many countries, including Russia and the United States, are now at a crossroads: to launch plutonium technology using disarmament plutonium, or bury this plutonium? Recently, the Russian government and Minatom announced that they want to process weapons-grade plutonium with the US; this means the possibility of developing plutonium energy.
For 40 years, scientists have been comparing options for getting rid of radioactive waste. The main idea is that they should be placed in such a place that they cannot get into environment and harm a person. This ability to harm radioactive waste is retained for tens and hundreds of thousands of years. Irradiated nuclear fuel which we extract from the reactor contains radioisotopes with half-lives from several hours to a million years (half-life is the time during which the amount of radioactive material is halved, and in some cases new radioactive substances appear). But the total radioactivity of the waste decreases significantly over time. For radium, the half-life is 1620 years, and it is easy to calculate that after 10 thousand years, about 1/50 of the original amount of radium will remain. The regulations of most countries provide for the safety of waste for a period of 10 thousand years. Of course, this does not mean that after this time RW will no longer be dangerous: we simply shift further responsibility for RW to distant offspring. For this, it is necessary that the places and form of burial of these wastes be known to posterity. Note that the entire written history of mankind is less than 10 thousand years. The tasks that arise during the disposal of radioactive waste are unprecedented in the history of technology: people have never set themselves such long-term goals.
An interesting aspect of the problem is that it is necessary not only to protect a person from waste, but at the same time protect waste from a person. During the period allotted for their burial, many socio-economic formations will change. It cannot be ruled out that in a certain situation radioactive waste may become a desirable target for terrorists, targets for strike during a military conflict etc. It is clear that, talking about millennia, we cannot rely on, say, government control and protection - it is impossible to foresee what changes can occur. It may be best to make the waste physically inaccessible to humans, although, on the other hand, this would make it difficult for our descendants to take further security measures.
It is clear that no technical solution, no artificial material can "work" for thousands of years. The obvious conclusion: isolate the waste itself natural environment. Options were considered: to bury radioactive waste in deep oceanic depressions, in the bottom sediments of the oceans, in the polar caps; send them to space; put them in deep layers of the earth's crust. It is now generally accepted that the best way is to bury waste in deep geological formations.
It is clear that RW in solid form is less prone to penetration into the environment (migration) than liquid RW. Therefore, it is assumed that liquid radioactive waste will first be converted into a solid form (vitrified, turned into ceramics, etc.). However, injection of liquid high-level radioactive waste into deep underground horizons (Krasnoyarsk, Tomsk, Dimitrovgrad) is still practiced in Russia.
At present, the so-called "multi-barrier" or "deep echeloned" concept of burial. The waste is first contained by the matrix (glass, ceramics, fuel pellets), then by the multi-purpose container (used for transport and for disposal), then by the sorbent (absorbent) fill around the containers, and finally by the geological environment.
So, we will try to bury radioactive waste in deep geological fractions. At the same time, we were given a condition: to show that our burial will work, as we plan, for 10 thousand years. Let us now see what problems we will encounter along the way.
The first problems are encountered at the stage of selecting sites for study.
In the US, for example, not a single state wants. So that a national burial place is located on its territory. This led to the fact that, through the efforts of politicians, many potentially suitable areas were deleted from the list, and not on the basis of a scientific approach, but as a result of political games.
How does it look in Russia? At present, in Russia, it is still possible to study areas without feeling significant pressure from local authorities (if one does not assume burial near cities!). I believe that as the real independence of the regions and subjects of the Federation strengthens, the situation will shift towards the US situation. Already now there is a tendency of Minatom to move its activity to military facilities, over which there is practically no control: for example, an archipelago is supposed to create a burial place New Earth(Russian polygon No. 1), although in terms of geological parameters this is far from the best place, which will be discussed further.
But suppose that the first stage is over and the site is chosen. It is necessary to study it and give a forecast of the functioning of the burial site for 10 thousand years. Here comes a new problem.
The underdevelopment of the method.
Geology is a descriptive science. Separate branches of geology are engaged in predictions (for example, engineering geology predicts the behavior of soils during construction, etc.), but never before has geology been tasked with predicting the behavior of geological systems for tens of thousands of years. From many years of research in different countries, even doubts arose whether a more or less reliable forecast for such periods is even possible.
Imagine, however, that we managed to develop a reasonable plan for exploring the site. It is clear that the implementation of this plan will take many years: for example, Mount Yaka in Nevada has been studied for more than 15 years, but the conclusion about the suitability or unsuitability of this mountain will be made no earlier than 5 years later. At the same time, the disposal program will be under increasing pressure.
The pressure of external circumstances.
In the years cold war no attention was paid to the waste; they were accumulated, stored in temporary containers, lost, etc. An example is the Hanford military facility (analogous to our Mayak), where there are several hundred giant tanks with liquid waste, and for many of them it is not known what is inside. One sample costs 1 million dollars! In the same place, in Hanford, buried and "forgotten" barrels or boxes of waste are found about once a month.
In general, over the years of development of nuclear technologies, a lot of waste has accumulated. Temporary storage facilities at many nuclear power plants are close to full, and at military facilities they are often on the verge of "old age" failure or even beyond.
So the burial problem requires urgent solutions. The awareness of this urgency is becoming more acute, especially since 430 power reactors, hundreds of research reactors, hundreds of transport reactors of nuclear submarines, cruisers and icebreakers continue to continuously accumulate radioactive waste. But people backed up against the wall don't necessarily come up with the best technical solutions, and the chances of errors increase. Meanwhile, in decisions related to nuclear technology, mistakes can be very costly.
Finally, let's assume that we spent 10-20 billion dollars and 15-20 years studying a potential site. It's time to make a decision. Obviously, ideal places does not exist on Earth, and any place will have positive and negative properties in terms of burial. Obviously, one will have to decide whether the positive properties outweigh the negative ones, and whether these positive properties provide sufficient security.
Decision making and technological complexity of the problem
The problem of burial is technically extremely complex. Therefore, it is very important to have, firstly, high-quality science, and secondly, effective interaction (as they say in America - "interface") between science and decision-makers.
The Russian concept of underground isolation of radioactive waste and spent nuclear fuel in permafrost was developed at the Institute of Industrial Technology of the Ministry of Atomic Energy of Russia (VNIPIP). It was approved by the State Ecological Expertise of the Ministry of Ecology and natural resources Russian Federation, Ministry of Health of the Russian Federation and Gosatomnadzor of the Russian Federation. Scientific support for the concept is provided by the Department of Permafrost Science of the Moscow state university. It should be noted that this concept is unique. As far as I know, no country in the world considers the issue of RW disposal in permafrost.
The main idea is this. We place heat-generating wastes in the permafrost and separate them from the rocks with an impenetrable engineering barrier. Due to the heat release, the permafrost around the burial site begins to thaw, but after some time, when the heat release decreases (due to the decay of short-lived isotopes), the rocks will freeze again. Therefore, it is sufficient to ensure the impenetrability of engineering barriers for the time when the permafrost will thaw; after freezing, the migration of radionuclides becomes impossible.
Concept uncertainty
There are at least two serious problems associated with this concept.
First, the concept assumes that frozen rocks are impervious to radionuclides. At first glance, this seems reasonable: all water is frozen, ice is usually immobile and does not dissolve radionuclides. But if you carefully work with the literature, it turns out that many chemical elements migrate quite actively in frozen rocks. Even at temperatures of -10-12ºC, non-freezing, so-called film water is present in the rocks. What is especially important, the properties of radioactive elements that make up RW, from the point of view of their possible migration in permafrost, have not been studied at all. Therefore, the assumption about the impermeability of frozen rocks for radionuclides is without any foundation.
Secondly, even if it turns out that the permafrost is indeed a good RW insulator, it is impossible to prove that the permafrost itself will last long enough: we recall that the standards provide for burial for a period of 10 thousand years. It is known that the state of permafrost is determined by the climate, and the two most important parameters are air temperature and precipitation. As you know, the air temperature is rising due to global climate change. The highest rate of warming occurs precisely in the middle and high latitudes of the northern hemisphere. It is clear that such warming should lead to thawing of ice and reduction of permafrost.
Calculations show that active thawing can begin as early as 80-100 years, and the thawing rate can reach 50 meters per century. Thus, the frozen rocks of Novaya Zemlya can completely disappear in 600-700 years, which is only 6-7% of the time required for waste isolation. Without permafrost The carbonate rocks of Novaya Zemlya have very low insulating properties with respect to radionuclides.
The problem of storage and disposal of radioactive waste (RW) is the most important and unresolved problem of nuclear energy.
No one in the world yet knows where and how to store high-level radioactive waste, although work in this direction is underway. So far, we are talking about promising, and by no means industrial technologies for confining highly active radioactive waste into refractory glass or ceramic compounds. However, it is not clear how these materials will behave under the influence of radioactive waste contained in them for millions of years. Such a long shelf life is due to the huge half-life of a number of radioactive elements. It is clear that their release to the outside is inevitable, because the material of the container in which they will be enclosed does not "live" so much.
All RW processing and storage technologies are conditional and doubtful. And if nuclear scientists, as usual, dispute this fact, then it would be appropriate to ask them: “Where is the guarantee that all existing storage facilities and burial grounds are not carriers of radioactive contamination already now, since all observations of them are hidden from the public?”
There are several burial grounds in our country, although they try to keep silent about their existence. The largest is located in the region of Krasnoyarsk under the Yenisei, where the waste of most Russian nuclear power plants and nuclear waste European states. During the research work on this repository, the results turned out to be positive, but recently observations show a violation of the ecosystem of the Yenisei River, that mutant fish have appeared, the structure of water has changed in certain areas, although the data of scientific examinations are carefully hidden.
In the world, high-level radioactive waste is not yet buried; there is only experience of their temporary storage.
Bibliography
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In book. "Proceedings of the Symposium". M., Atomizdat, 1976
2. Frumkin M. L. et al. Technological bases of radiation processing of food products. M., Food industry, 1973
3. Breger A. Kh. Radioactive isotopes as sources of radiation in radiation-chemical technology. Isotopes in the USSR, 1975, No. 44 pp. 23-29.
4. Pertsovsky E. S., Sakharov E. V. Radioisotope devices in the food, light and pulp and paper industry. M., Atomizdat, 1972
5. Vorobyov E. I., Pobedinsky M. N. Essays on the development of domestic radiation medicine. M., Medicine, 1972
6. Site selection for the construction of a storage facility for radioactive waste. E. I. M., TsNIIatominform, 1985, No. 20.
7. Current state problems of disposal of radioactive waste in the United States. Nuclear technology Abroad, 1988, No. 9.
8. Heinonen Dis, Disera F. Nuclear Waste Disposal: Underground Storage Processes: IAEA Bulletin, Vienna, 1985, Vol. 27, No. 2.
9. Geological studies of sites for the final disposal of radioactive waste: E. I. M.: TsNIIatominform, 1987, No. 38.
10. R. V. Bryzgalova, Yu. M. Rogozin, G. S. Sinitsyna, et al., “Evaluation of some radiochemical and geochemical factors that determine the localization of radionuclides during radioactive waste disposal in geological formations,” At. Materials of the 6th CMEA Symposium, vol. 2, 1985
Which nucleus in a radioactive substance will decay first, which - next, which - last? Physicists say that it is impossible to know: the decay of one or another nucleus of a radionuclide is a random event. At the same time, the behavior of a radioactive substance as a whole is subject to clear patterns.
Learn about the half-life
If we take a closed glass flask containing a certain amount of Radon-220, it turns out that after about 56 s the number of Radon atoms in the flask will decrease by half, during the next 56 s - by a further two times, etc. Thus, it is clear that why the time interval of 56 s is called the half-life of Radon-220.
the half-life T 1/2 is a physical quantity that characterizes a radionuclide and is equal to the time during which half of the available number of nuclei of a given radionuclide decays.
Half-life of some radionuclides
The unit of half-life in SI is second:
Each radionuclide has its own half-life (see table).
The sample contains 6.4 x 10 20 Iodine-131 atoms. How many atoms of Iodine-131 will be in the sample after 16 days?
We define the activity of a radioactive source
Both Uranium-238 and Radium-226 are α-radioactive (their nuclei can spontaneously decay into an α-particle and the corresponding daughter nucleus).
From what sample will more α-particles fly out in 1 s if the number of Uranium-238 and Radium-226 atoms is the same?
We hope you answered the question correctly and, given that the half-lives of these radionuclides differ by almost 3 million times, you have established that many more α-decays will occur in the same time in a radium sample than in a uranium sample.
A physical quantity numerically equal to the number of decays occurring in a radioactive source per unit time is called the activity of the radioactive source.
The activity of a radioactive source is denoted by the symbol A. The SI unit of activity is the becquerel.
Rice. 24.1. Graph of Radium-226 activity versus time. The half-life of Radium-226 is 1600 years
The history of the discovery of artificial radioactive isotopes
The first artificial radioactive isotope (15P) was obtained in 1934 by the spouses Fredericomi Irene Joliot-Curie. Irradiating aluminum with α-particles, they observed the emission of neutrons, that is, the following nuclear reaction occurred:
The Italian physicist Enrico Fermi is known for several achievements, but his the highest award — Nobel Prize- he received for the discovery of artificial radioactivity caused by the irradiation of matter with slow neutrons. Now the neutron irradiation method is widely used in industry to obtain radioactive isotopes.
1 Bq is the activity of such a radioactive source, in which 1 act of decay occurs in 1 s:
1 Bq is a very small activity, therefore, an off-system unit of activity is used - curie (Ci):
Which scientists are named after these units? What discoveries did they make?
If the sample contains atoms of only one radionuclide, then the activity of this sample can be determined by the formula:
where N is the number of radionuclide atoms in the sample at a given point in time; λ is the radioactive decay constant of a radionuclide (a physical quantity that is a characteristic of a radionuclide and is related to the half-life by the ratio:
Over time, the number of undecayed nuclei of radionuclides in a radioactive sample decreases, therefore, the activity of the sample also decreases (Fig. 24.1).
Learn about the use of radioactive isotopes
The presence of radionuclides in an object can be detected by radiation. You have already found out that the intensity of radiation depends on the type of radionuclide and its amount, which decreases over time. All this is the basis for the use of radioactive isotopes, which physicists have learned to obtain artificially. Now for everyone chemical element found in nature, artificial radioactive isotopes have been obtained.
There are two ways in which radioactive isotopes can be used.
Rice. 24.2. To find out how plants absorb phosphorus fertilizers, a radioactive isotope of Phosphorus is added to these fertilizers, then the plants are examined for radioactivity and the amount of absorbed phosphorus is determined.
Rice. 24.3. The use of γ-radiation for the treatment of cancer. To prevent γ-rays from destroying healthy cells, several weak beams of γ-rays are used, which are focused on the tumor
1. Use of radioactive isotopes as indicators. Radioactivity is a kind of label with which you can determine the presence of an element, track the behavior of an element during physical and biological processes, etc. (see, for example, Fig. 24.2).
2. The use of radioactive isotopes as sources of γ-radiation (see, for example, Fig. 24.3).
Let's look at a few examples.
Find out how radioactive isotopes are used to diagnose diseases
The human body tends to accumulate in its tissues certain chemical substances. It is known, for example, that the thyroid gland accumulates iodine, bone- phosphorus, calcium and strontium, liver - some dyes, etc. The rate of accumulation of substances depends on the state of health of the organ. For example, with Graves' disease, the activity of the thyroid gland increases dramatically.
It is convenient to monitor the amount of iodine in the thyroid gland using its γ-radioactive isotope. Chemical properties radioactive and stable iodine do not differ, so radioactive iodine-131 will accumulate in the same way as its stable isotope. If the thyroid gland is normal, then some time after the introduction of Iodine-131 into the body, γ-radiation from it will have a certain optimal intensity. But if the thyroid gland functions with a deviation from the norm, then the intensity of γ-radiation will be abnormally high or, conversely, low. A similar method is used to study the metabolism in the body, detect tumors, etc.
It is clear that, using these diagnostic methods, it is necessary to carefully dose the amount of a radioactive preparation so that internal exposure has a minimum effect. negative impact on the human body.
Determining the age of ancient objects
Rice. 24.4. Derived from young tree 1 g of carbon has an activity of 14-15 Bq (radiates 14-15 β-particles per second). 5700 years after the death of the tree, the number of β-decays per second is halved
Rice. 24.5. The most common medical products: syringes, blood transfusion systems, etc., are carefully sterilized using γ-radiation before being sent to the consumer
There is always a certain amount of β-radioactive Carbon-14 (^C) in the Earth's atmosphere, which is formed from Nitrogen as a result of a nuclear reaction with neutrons. As part of carbon dioxide this isotope is absorbed by plants, and through them - by animals. As long as an animal or plant is alive, the content of radioactive carbon in them remains unchanged. After the termination of vital activity, the amount of radioactive carbon in the body begins to decrease, and the activity of β-radiation also decreases. Knowing that the half-life of Carbon-14 is 5700 years, it is possible to determine the age of archaeological finds (Fig. 24.4).
We use γ-radiation in technology
Of particular importance in technology are gamma flaw detectors, which are used to check, for example, the quality of welded joints. If the master, while welding the hinges to the gate, made a marriage, after a while the hinges will fall off. It's annoying, but it's fixable. But if the marriage happened during the welding of structural elements of a bridge or a nuclear reactor, tragedy is inevitable. Due to the fact that γ-rays are absorbed differently by massive steel and steel with voids, the gamma-ray flaw detector "sees" cracks inside the metal, and therefore, detects defects even at the stage of manufacturing the structure.
Killing microbes with radiation
It is known that a certain dose of radiation kills organisms. But not all organisms are useful to humans. So, doctors are constantly working to get rid of pathogenic microbes. Remember: in hospitals, they wash the floor with special solutions, irradiate the room with ultraviolet light, process medical instruments, etc. Such procedures are called disinfection and sterilization.
The peculiarities of γ-radiation made it possible to put the sterilization process on an industrial basis (Fig. 24.5). Such sterilization is carried out in special installations.
with reliable protection against penetrating radiation. Artificially created isotopes of Cobalt and Cesium are used as a source of γ-rays.
Learning to solve problems
A task. Determine the mass of Radium-226 if its activity is 5 Ci. The radioactive decay constant of Radium-226 is 1.37 · 10 11 s 1 .
Analysis of a physical problem, search for a mathematical model
To solve the problem, we use the formula for determining activity: A = AN. Knowing the activity, let us find out the number N of Radium atoms. The mass of a substance can be determined by multiplying the number of atoms by the mass of one atom: m = N ■ m 0 .
From the chemistry course you know:
1 mol of a substance contains N A \u003d 6.02 10 atoms;
molar mass of a substance (mass 1 mol).
mass of an atom
Summing up
The time during which half of the available number of nuclei of a given radionuclide decays is called the half-life T 1/2. The half-life is a characteristic of a given radionuclide. The physical quantity, which is numerically equal to the number of decays occurring in a given radioactive source per unit of time, is called the activity of the radioactive source. If the source contains atoms of only one radionuclide, the activity A of the source can be determined by the formula A = AN, where N is the number of radionuclide atoms in the sample; λ is the radioactive decay constant of the radionuclide. The SI unit of activity is the becquerel (Bq).
Over time, the activity of a radioactive sample decreases, and this is used to determine the age of archaeological finds.
Artificial isotopes are used to sterilize medical devices, diagnose and treat diseases, detect defects in metals, etc.
test questions
1. Define the half-life. What characterizes this physical quantity? 2. What is the activity of a radioactive source? 3. What is the SI unit of activity? 4. How is the activity of a radionuclide related to its radioactive decay constant? 5. Does the activity of the radionuclide sample change over time? If it changes, why and how? 6. Give examples of the use of radioactive isotopes.
Exercise number 24
1. There is the same number of nuclei of Iodine-131, Radon-220 and Uranium-235. Which radionuclide has the longest half-life? Which sample is currently the most active? Explain your answer.
2. The sample contains 2 x 1020 Iodine-131 atoms. Determine how many iodine nuclei in the sample will decay within an hour. Consider the activity of Iodine-131 unchanged during this time. The radioactive decay constant of Iodine-131 is 9.98 · 10 -7 s -1 .
3. The half-life of radioactive Carbon-14 is 5700 years. How many times has the number of Carbon-14 atoms decreased in a pine cut down 17,100 years ago?
4. Determine the half-life of the radionuclide if, over a time interval of 1.2 s, the number of decayed nuclei amounted to 75% of their initial number.
5. Currently, the radioactive sample contains 0.05 mol of Radon-220. Determine the activity of Radon-220 in the sample.
6. Today, one of the most important studies of the metabolism in the human body with the help of radioactive isotopes. In particular, it turned out that in a relatively short time the body is almost completely restored. Use additional sources of information and learn more about these studies.
Physics and technology in Ukraine
National science Center"Kharkov Institute of Physics and Technology"
(KIPT) is a world-famous scientific center. Founded in 1928 on the initiative of Academician A.F. Ioffe as the Ukrainian Institute of Physics and Technology for the purpose of research in the field nuclear physics and solid state physics.
Already in 1932, an outstanding result was achieved at the institute - the fission of the nucleus of the lithium atom was carried out. Later, liquid hydrogen and helium were obtained under laboratory conditions, the first three-coordinate radar was built, the first studies of high-vacuum technology were carried out, which served as an impetus for the development of a new physical and technological direction - vacuum metallurgy. The scientists of the institute played an important role in solving the problems of using atomic energy.
AT different years outstanding physicists worked at NSC KIPT: I. V. Obreimov, L. D. Landau, I. V. Kurchatov, K. D. Sinelnikov, L. V. Shubnikov, A. I. Leipunsky, E. M. Lifshits, I. M. Lifshitz, A. K. Walter, B. G. Lazarev, D. D. Ivanenko, A. I. Akhiezer, V. E. Ivanov, Ya. B. Fainberg, D. V. Volkov, et al. institute were created scientific schools known all over the world.
The NSC KIPT houses the largest linear electron accelerator in the CIS and the complex of thermonuclear complexes "Uragan".
The general director of the center is a well-known Ukrainian physicist, academician of the National Academy of Sciences of Ukraine Mykola Fedorovich Shulga.
This is textbook material.
radiation particle exposure radon
People have learned to use radiation for 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. Of all the branches of human economic activity, energy has the greatest impact 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 people doubt that nuclear energy has taken a firm place in the energy balance of mankind.
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 is a branch of medicine associated with the use of the achievements of 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, the function of the kidneys, bladder, and 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).
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