Radiation, radioactivity and radio emission are concepts that even sound quite dangerous. In this article you will learn why some substances are radioactive and what that means. Why is everyone so afraid of radiation and how dangerous is it? Where can we meet radioactive substances and what does this threaten us with?
Radioactivity concept
By radioactivity I mean the “ability” of atoms of certain isotopes to split and thereby create radiation. The term “radioactivity” did not appear immediately. Initially, such radiation was called Becquerel rays, in honor of the scientist who discovered it while working with an isotope of uranium. We now call this process the term “radioactive radiation.”
In this rather complex process, the original atom is transformed into an atom of a completely different chemical element. Due to the ejection of alpha or beta particles, the mass number of the atom changes and, accordingly, this moves it along D.I. Mendeleev’s table. It is worth noting that the mass number changes, but the mass itself remains almost the same.
Relying on this information, we can rephrase the definition of the concept a little. So, radioactivity is also the ability of unstable atomic nuclei to independently transform into other, more stable and stable nuclei.
Substances - what are they?
Before we talk about what radioactive substances are, let's generally define what is called a substance. So, first of all, it is a type of matter. It is also logical that this matter consists of particles, and in our case these are most often electrons, protons and neutrons. Here we can already talk about atoms, which consist of protons and neutrons. Well, molecules, ions, crystals, and so on are made from atoms.
The concept of a chemical substance is based on the same principles. If it is impossible to isolate a nucleus in matter, then it cannot be classified as a chemical substance.
About radioactive substances
As mentioned above, in order to exhibit radioactivity, an atom must spontaneously decay and turn into an atom of a completely different chemical element. If all the atoms of a substance are unstable enough to decay in this way, then you have a radioactive substance. More technical language the definition would sound like this: substances are radioactive if they contain radionuclides, and in high concentrations.
Where are radioactive substances located in D.I. Mendeleev’s table?
Quite simple and easy way to find out whether a substance is radioactive is to look at D.I. Mendeleev’s table. Everything that comes after the lead element are radioactive elements, as well as promethium and technetium. It is important to remember which substances are radioactive, because it can save your life.
There are also a number of elements that have at least one radioactive isotope in their natural mixtures. Here is a partial list of them, showing some of the most common elements:
- Potassium.
- Calcium.
- Vanadium.
- Germanium.
- Selenium.
- Rubidium.
- Zirconium.
- Molybdenum.
- Cadmium.
- Indium.
Radioactive substances include those that contain any radioactive isotopes.
Types of radioactive radiation
Radioactive radiation comes in several types, which are now discussed we'll talk. Alpha and beta radiation have already been mentioned, but this is not the entire list.
Alpha radiation is the weakest radiation and is dangerous if particles enter directly into the human body. Such radiation is produced by heavy particles, and that is why it is easily stopped even by a sheet of paper. For the same reason, alpha rays do not travel more than 5 cm.
Beta radiation is stronger than the previous one. This is radiation from electrons, which are much lighter than alpha particles, so they can penetrate several centimeters into human skin.
Gamma radiation is realized by photons, which quite easily penetrate even further to internal organs person.
The most powerful radiation in terms of penetration is neutron radiation. It is quite difficult to hide from it, but in nature it essentially does not exist, except perhaps in close proximity to nuclear reactors.
Impact of radiation on humans
Radioactive hazardous substances can often be fatal to humans. Besides radiation exposure has an irreversible effect. If you are exposed to radiation, you are doomed. Depending on the extent of the damage, a person dies within a few hours or over many months.
At the same time, it must be said that people are continuously exposed to radioactive radiation. Thank God it's weak enough to have death. For example, watching a football match on television, you receive 1 microrad of radiation. Up to 0.2 rad per year is generally the natural radiation background of our planet. 3rd gift - your portion of radiation during dental x-rays. Well, exposure to more than 100 rads is already potentially dangerous.
Harmful radioactive substances, examples and warnings
The most dangerous radioactive substance is Polonium-210. Due to the radiation around it, you can even see a kind of glowing “aura” blue color. It is worth saying that there is a stereotype that all radioactive substances glow. This is not at all true, although there are such variants as Polonium-210. Most radioactive substances are not at all suspicious in appearance.
The most radioactive metal on this moment Livermorium is considered. Its isotope Livermorium-293 takes 61 milliseconds to decay. This was discovered back in 2000. Ununpentium is slightly inferior to it. The decay time of Ununpentia-289 is 87 milliseconds.
Also interesting fact is that the same substance can be both harmless (if its isotope is stable) and radioactive (if the nuclei of its isotope are about to collapse).
Scientists who studied radioactivity
Radioactive substances for a long time were not considered dangerous, and therefore were freely studied. Unfortunately, sad deaths have taught us that we need to be careful with such substances and increased level security.
One of the first, as already mentioned, was Antoine Becquerel. This is a great French physicist, to whom belongs the fame of the discoverer of radioactivity. For his services he was awarded membership in the London royal society. Because of his contributions to this field, he died quite young, at the age of 55. But his work is remembered to this day. The unit of radioactivity itself, as well as craters on the Moon and Mars, were named in his honor.
An equally great person was Marie Skłodowska-Curie, who worked with radioactive substances together with her husband Pierre Curie. Maria was also French, albeit with Polish roots. In addition to physics, she was engaged in teaching and even active social activities. Marie Curie - first woman laureate Nobel Prize in two disciplines at once: physics and chemistry. The discovery of such radioactive elements as Radium and Polonium is the merit of Marie and Pierre Curie.
Conclusion
As we see, radioactivity is quite difficult process, which does not always remain under human control. This is one of those cases where people can find themselves completely powerless in the face of danger. This is why it is important to remember that truly dangerous things can be very deceptive in appearance.
You can most often find out whether a substance is radioactive or not once it has been exposed to it. Therefore, be careful and attentive. Radioactive reactions help us in many ways, but we should also not forget that this is a force practically beyond our control.
In addition, it is worth remembering the contribution of great scientists to the study of radioactivity. They passed on to us an incredible amount of useful knowledge, which now saves lives, provides entire countries with energy and helps heal terrible diseases. Radioactive chemical substances is a danger and a blessing for humanity.
Essay
in the discipline "Ecology"
on the topic: “The phenomenon radioactivity in nature"
Performed:
Student of group M-081d
Kosotukhina Nadezhda
The phenomenon of radioactivity in nature
Radioactivity is the ability atomic nuclei spontaneously transform into other nuclei, emitting various types of radioactive radiation and elementary particles.
Radioactivity can be divided into two types: natural and artificial. Natural, can be observed in unstable isotopes existing in nature. Artificial radioactivity is observed in isotopes that were obtained as a result of nuclear reactions.
There are three types of radioactive radiation:
a-radiation - this radiation is characterized by electrical and magnetic fields. It has high ionizing ability. It is also characterized by low penetrating ability. At its core, it is a stream of helium nuclei.
b-radiation - just like a-radiation, this radiation is deflected by electric and magnetic fields. If we continue the comparison, its ionizing ability is much lower (by approximately two orders of magnitude), and its penetrating ability is much greater than that of a-particles. b-radiation is a stream of fast electrons.
g-radiation - unlike the previous two, is not deflected by electric and magnetic fields. Ionizing capacity is low. But the penetrating ability is simply colossal. g-radiation is short wavelength electromagnetic radiation, whose wavelength is not long. The consequence of this is pronounced corpuscular properties.
Acute and chronic radiation sickness. Radiation burns.
If nuclear weapons of mass destruction are used, then a source of nuclear destruction occurs. This territory becomes completely unsuitable for habitation. Everything will be destroyed due to the fact that factors such as air shock wave, light radiation, penetrating radiation and radioactive contamination of the area.
The most important damaging factor is the air shock wave. It is formed due to the rapid increase in the volume of the products of a nuclear explosion under the influence of a huge amount of heat and compression, and then rarefaction of the surrounding layers of air. The area affected by the blast wave is very significant! Everything living and non-living that comes in its way is destroyed.
Penetrating radiation is gamma rays and neutron flux. They're coming from the zone nuclear explosion. They have the ability to spread over many thousands of metros, they are not stopped by any medium, and they also cause the ionization of atoms and molecules. When exposed to radiation, biological processes and functions of organs and tissues are disrupted in the body. The consequence is radiation sickness.
Burns on almost the entire surface of the body occur due to exposure of the body to light radiation. For protection in open areas, special clothing and glasses are used, but in general it is advisable to take refuge in a bomb shelter.
Radioactive atoms create soil adsorption and cause radioactive contamination of the area.
The main danger for people in contaminated areas is external beta-gamma radiation and the ingress of nuclear explosion products into the body and onto the skin.
Radiation sickness (or acute radiation sickness) is an injury to all organs and systems of the body that occurs instantly. The most significant changes occur in the hereditary structures of dividing cells, mainly hematopoietic cells of the bone marrow, lymphatic system, epithelium of the gastrointestinal tract and skin, cells of the liver, lungs and other organs. This is due to the impact ionizing radiation.
Not last role plays dose rate radioactive radiation: the same amount of radiation energy absorbed by a cell causes more damage to biological structures, the shorter the irradiation period. If the exposure is extended over time, then it causes significantly less damage than the same doses absorbed over a period of time. short term.
The differences are related to the ability to restore the body damaged by radiation. As the dose rate increases, the importance of recovery processes decreases.
The absorbed dose of radiation is measured by the energy of ionizing radiation transferred to the mass of the irradiated substance. The unit of absorbed dose is the gray (Gy), equal to 1 joule absorbed by 1 kg of substance (1 Gy = 1 J/kg = 100 rad).
Organ damage and dependence of manifestations on tissue dose:
|
Clinical syndrome |
Minimum dose, rad |
|
Hematological: the first signs of cytopenia (thrombocytopenia to 10*10 4 in 1 µl on the 29th – 30th day). |
200 or more |
|
agranulocytosis (decrease in leukocytes below 1*10 3 in 1 μl), severe thrombocytopenia. |
over 250 – 300 |
|
Epilation: initial, permanent. |
500, more often 800 – 1000 |
|
Intestinal: picture of enteritis, ulcerative-necrotic changes in the mucous membranes of the oral cavity, oropharynx, nasopharynx. |
|
|
Skin lesions: erythema (initial and late), dry radioemepidermatitis, exudative radioepidermatitis, ulcerative necrotic dermatitis |
2500 or more |
To assess damage to human health due to uneven irradiation, the concept of effective equivalent dose was introduced, which is used in assessing possible stochastic effects - malignant neoplasms.
To assess damage from the stochastic effects of ionizing radiation on personnel or the population, the collective equivalent dose is used, equal to the product individual equivalent doses per number of persons exposed to radiation. The unit of collective equivalent dose is man-sievert (man-Sv).
Immediately after irradiation of a person, the clinical picture turns out to be poor, sometimes there are no symptoms at all. That is why knowledge of a person’s radiation dose plays a decisive role in the diagnosis and early prognosis of the course of acute radiation sickness, in determining therapeutic tactics before the development of the main symptoms of the disease.
In accordance with the dose of radiation exposure, acute radiation sickness is usually divided into four degrees of severity:
|
The severity of ARS, |
Lymphocytes 48 – 72 hours after irradiation (in 1 µl) |
Leukocytes on the 7th – 9th day after irradiation (in 1 µl) |
Platelets on the 20th day after irradiation (in 1 µl) |
Duration of hospitalization |
|
|
Extremely heavy |
10 – 30 min. Multiple |
Less than 80000 |
|||
|
in 30 min. – 3 hours, 2 times or more |
|||||
|
no or later than 3 hours, single dose |
More than 80000 |
Not necessary |
Differentiation of acute radiation sickness by severity depending on the manifestations of the primary reaction:
|
Severity and dose (rad) |
Indirect signs |
|||
|
weakness |
Headache state of consciousness |
Temperature |
Skin hyperemia and scleral injection |
|
|
Light (100 – 200) |
Short term headache, consciousness is clear |
Normal |
Light scleral injection |
|
|
Medium (200 – 400) |
Moderate |
Headache, clear consciousness |
Low-grade fever |
Distinct hyperemia of the skin and scleral injection |
|
Heavy (400 – 600) |
Expressed |
Severe headache at times, clear consciousness |
Low-grade fever |
Severe skin hyperemia and scleral injection |
|
Extremely heavy (more than 600) |
The sharpest |
Persistent severe headache, consciousness may be confused |
May be |
Sharp hyperemia of the skin and scleral injection |
Acute radiation sickness is an independent disease that develops as a result of the death of predominantly dividing cells of the body under the influence of short-term (up to several days) exposure to ionizing radiation on large areas of the body. The cause of acute radiation sickness can be either an accident or total irradiation of the body for therapeutic purposes - during bone marrow transplantation, in the treatment of multiple tumors.
The clinical picture of acute radiation sickness is very diverse; it depends on the radiation dose and the time elapsed after irradiation. In its development, the disease goes through several stages. In the first hours after irradiation, a primary reaction appears (vomiting, fever, headache immediately after irradiation). After a few days (the sooner, the higher the radiation dose), bone marrow depletion develops, agranulocytosis and thrombocytopenia develop in the blood. Various infectious processes, stomatitis, and hemorrhages appear. Between the primary reaction and the height of the disease, at radiation doses of less than 500 - 600 rad, a period of external well-being is observed - the latent period. The division of acute radiation sickness into periods of primary reaction, latent, height and recovery is inaccurate: purely external manifestations of the disease do not determine the true situation.
Chronic radiation sickness is a disease caused by repeated irradiation of the body in small doses, totaling more than 100 rad. The development of the disease is determined not only by the total dose, but also by its power, that is, the period of exposure during which the radiation dose was absorbed in the body. In the conditions of a well-organized radiological service in the country, cases of chronic radiation sickness are not observed. Poor control over radiation sources and violation of safety regulations by personnel when working with x-ray therapy units leads to cases of chronic radiation sickness.
The clinical picture of chronic radiation sickness is determined primarily by asthenic syndrome and moderate cytopenic changes in the blood. Changes in the blood themselves are not a source of danger for patients, although they reduce their ability to work.
With chronic radiation sickness, tumors very often arise - hemoblastosis and cancer. With a well-organized medical examination, a thorough oncological examination once a year and blood tests twice a year, it is possible to prevent the development of advanced forms of cancer, and the life expectancy of such patients approaches normal.
Along with acute and chronic radiation sickness, a subacute form can be distinguished, which occurs as a result of repeated repeated irradiation in medium doses over several months, when the total dose in a relatively short period of time reaches 500 - 600 rad. The clinical picture of this disease resembles acute radiation sickness.
Anti-radiation protection of the population. Medical prevention and first aid for radiation injuries.
According to the Civil Defense warning signals “Radiation Hazard,” the population must take shelter in protective structures. As is known, they significantly (several times) weaken the effect of penetrating radiation.
Due to the danger of radiation damage, it is impossible to begin providing first aid to the population if there are high levels of radiation in the area. In these conditions, the provision of self- and mutual assistance by the affected population itself, and strict adherence to the rules of conduct in the contaminated area are of great importance.
In areas contaminated with radioactive substances, you must not eat food, drink water from contaminated water sources, or lie down on the ground. The procedure for preparing food and feeding the population is determined by the Civil Defense authorities, taking into account the levels of radioactive contamination of the area.
When providing first aid in areas with radioactive contamination in areas of nuclear damage, first of all, you should carry out those measures on which the preservation of the life of the affected person depends. Then it is necessary to eliminate or reduce external gamma radiation, for which protective structures are used: shelters, recessed rooms, brick, concrete and other buildings. To prevent further exposure to radioactive substances on the skin and mucous membranes, partial sanitization and partial decontamination of clothing and shoes are carried out. Partial sanitization carried out by washing clean water or wiping exposed skin with damp swabs. The affected person is washed with eyes and given a mouth rinse. Then, putting a respirator, a cotton-mauve bandage on the affected person, or covering his mouth and nose with a towel, handkerchief, scarf, his clothes are partially decontaminated. At the same time, the direction of the wind is taken into account so that dust swept from clothes does not fall on others.
If radioactive substances enter the body, the stomach is washed out and adsorbents (activated carbon) are given. If nausea occurs, take an antiemetic from your personal first aid kit. In order to prevent infectious diseases to which the irradiated person becomes susceptible, it is recommended to take antibacterial agents.
Animal and plant organisms are characterized by different radiosensitivities, the reasons for which have not yet been fully elucidated. As a rule, single-celled plants, animals and bacteria are the least sensitive, and mammals and humans are the most sensitive. Differences in sensitivity to radiation occur among individuals of the same species. It depends on the physiological state of the body, the conditions of its existence and individual characteristics. Newborns and old individuals are more sensitive to radiation. Various types of diseases, exposure to other harmful factors negatively affects the course of radiation damage.
Changes that develop in the organs and tissues of the irradiated organism are called somatic. There are early somatic effects, which are characterized by a clear dose dependence, and late ones, which include an increased risk of developing tumors (leukemia), shortening life expectancy and various types of organ dysfunction. There are no specific neoplasms unique to ionizing radiation. There is a close relationship between dose, tumor yield and latency period. As the dose decreases, the incidence of tumors decreases and the latency period increases.
In the long term, genetic (congenital deformities, inherited disorders) damage can also be observed, which, along with tumor effects, are stochastic. The basis of the genetic effects of radiation is damage to the cellular structures responsible for heredity - the reproductive ovaries and testes.
The effect of radiation, as was said, depends on the magnitude of the absorbed dose and its spatiotemporal distribution in the body. Irradiation may cause damage from minor, non-invasive clinical picture, to fatal. Single acute, prolonged, fractional, chronic irradiation at a dose other than zero, according to modern concepts, can increase the risk of long-term stochastic effects - cancer and genetic disorders.
Number of deaths from tumors and hereditary defects as a result of radiation:
|
Critical organ |
Disease |
Risk, 102 Sv |
Number of cases, 10 4 people-Sv. |
|
Whole body, red bone marrow |
Leukemia |
||
|
Thyroid |
Thyroid cancer |
||
|
Mammary gland |
Mammary cancer |
||
|
Bone tumors |
|||
|
Lung tumors |
|||
|
All other organs and tissues |
Tumors of other organs |
||
|
All organs and tissues |
All malignant tumors |
||
|
Sex glands |
Hereditary defects |
||
Acute radiation injuries 131 I of severe, moderate and mild degrees can be expected when the following quantities enter the body:
The toxicity of the radionuclide during inhalation is approximately 2 times higher, which is associated with a larger area of b-irradiation.
When smaller quantities of 131 I are received, dysfunction is noted thyroid gland, as well as minor changes in the blood picture and some indicators of metabolism and immunity. Irradiation of the thyroid gland in doses of the order of tens of grays causes a decrease in its functional activity with partial recovery in the coming months and a possible subsequent new decrease. At a dose of several grays, an increase in the functional activity of the gland was detected in the immediate period, which can be replaced by a state of hypofunction. Functional disorders are manifested not only by a decrease in the secretion of hormones, but also by a decrease in their biological activity. Damage to the gland is associated not only with the direct effect of radiation on the thyroid epithelium, but also with damage to blood vessels and especially radioimmune disorders.
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An atom consists of a nucleus surrounded by clouds of particles called electrons(see picture). In the nuclei of atoms - tiny particles, from which all substances are composed, contains a significant supply. It is this energy that is released in the form of radiation during the decay of radioactive elements. Radiation is dangerous to life, but nuclear reactions can be used to produce. Radiation is also used in medicine.
Radioactivity
Radioactivity is the property of the nuclei of unstable atoms to emit energy. Most heavy atoms are unstable, but lighter atoms have radioisotopes, i.e. radioactive isotopes. The reason for radioactivity is that atoms tend to become stable (see article " "). There are three types of radioactive radiation: alpha rays, beta rays And gamma rays. They are named after the first three letters of the Greek alphabet. Initially, the nucleus emits alpha or beta rays, and if it is still unstable, the nucleus emits gamma rays as well. 
In the picture you see three atomic nuclei. They are unstable, and each of them emits one of three types of rays. Beta particles are electrons with very high energy. They arise from the decay of a neutron. Alpha particles consist of two protons and two neutrons. The nucleus of a helium atom has exactly the same composition. Gamma rays are electromagnetic radiation high energy, propagating at the speed of light.
Alpha particles move slowly, and a layer of matter thicker than a sheet of paper traps them. They are no different from the nuclei of helium atoms. Scientists believe that helium on Earth is a product of natural radioactivity. An alpha particle flies less than 10 cm, and a sheet of thick paper will stop it. A beta particle flies about 1 meter in the air. A sheet of copper 1 millimeter thick can hold it back. The intensity of gamma rays decreases by half when passing through a layer of lead of 13 millimeters or a layer of 120 meters.
Radioactive substances are transported in thick-walled lead containers to prevent radiation leakage. Exposure to radiation causes burns, cataracts, and cancer in humans. Radiation levels are measured using Geiger counter. This device makes a clicking noise when it detects radioactive radiation. Having emitted particles, the nucleus acquires a new atomic number and turns into the nucleus of another element. This process is called radioactive decay. If new element is also unstable, the decay process continues until a stable nucleus is formed. For example, when a plutonium-2 atom (its mass is 242) emits an alpha particle, the relative atomic mass which has 4 (2 protons and 2 neutrons), it turns into a uranium atom - 238 (atomic mass 238). Half life- this is the time during which half of all atoms in the sample decay of this substance. Different ones have different periods half-life The half-life of radium-221 is 30 seconds, while that of uranium is 4.5 billion years.
Nuclear reactions
There are two types nuclear reactions: nuclear fusion And fission (splitting) of the nucleus. "Synthesis" means "combination"; at nuclear fusion two cores connect and one is large. Nuclear fusion can only occur at very high temperatures. Fusion releases a huge amount of energy. In nuclear fusion, two nuclei are combined into one large one. In 1992, the KOBE satellite was discovered in space special kind radiation, which confirms the theory that it was formed as a result of the so-called big bang . From the term fission it is clear that nuclei split apart, releasing nuclear energy. This is possible when nuclei are bombarded with neutrons and occurs in radioactive substances or in a special device called particle accelerator. The nucleus divides, emitting neutrons and releasing colossal energy.
Nuclear power
The energy released from nuclear reactions can be used to produce electricity and as a power source in nuclear submarines and aircraft carriers. The operation of a nuclear power plant is based on nuclear fission in nuclear reactors. A rod made of a radioactive substance such as uranium is bombarded with neutrons. Uranium nuclei split, emitting energy. This releases new neutrons. This process is called chain reaction. The power plant produces more energy per unit mass of fuel than any other power plant, but safety precautions and disposal radioactive waste is extremely expensive.
Nuclear weapon
Action nuclear weapons based on the fact that the uncontrolled release of a huge amount of nuclear energy leads to a terrible explosion. At the end of World War II, the United States dropped atomic bombs on Japanese cities Hiroshima and Nagasaki. Hundreds of thousands of people died. Atomic bombs are based on fission reactions, hydrogen - on synthesis reactions. The picture shows atomic bomb, dropped on Hiroshima.
Radiocarbon method
The radiocarbon method determines the time that has passed since the death of an organism. Living things contain small amounts of carbon-14, a radioactive isotope of carbon. Its half-life is 5,700 years. When an organism dies, carbon-14 reserves in tissues are depleted, the isotope decays, and the remaining amount can be used to determine how long ago the organism died. Thanks to the radiocarbon dating method, you can find out how long ago the eruption occurred. To do this, they use insects and pollen frozen in lava.
How else is radioactivity used?
In industry, radiation is used to determine the thickness of a sheet of paper or plastic (see article ““). By the intensity of beta rays passing through the sheet, even slight heterogeneity in its thickness can be detected. Food products - fruits, meat - are irradiated with gamma rays to keep them fresh. Using radioactivity, doctors trace the path of a substance in the body. For example, to determine how sugar is distributed in a patient's body, a doctor might inject some carbon-14 into the sugar molecules and monitor the emission of the substance as it enters the body. Radiotherapy, that is, irradiating a patient with strictly dosed portions of radiation, kills cancer cells - overgrown cells of the body.
Currently, radiation has useful applications not only for generating electrical and thermal energy. The beneficial properties of radiation have found application in various areas natural sciences, technology, medicine:
Ø in industry:
o gamma flaw detection – monitoring the integrity of various welded metal shells (reactor vessels, submarines and surface ships, pipelines, etc.), neutron logging;
o oil and water exploration;
Ø in agriculture:
o pre-sowing seed treatment that increases yield;
o disinfection of wastewater from livestock farms;
Ø in astronautics:
o creation of nuclear power sources for satellites, orbital complexes;
Ø in forensics:
o applying special marks to stolen items to facilitate their search, identification and exposure of criminals;
Ø in archeology:
o determination of the age of geological rocks - the age of the Earth is estimated using the uranium-lead method (about 4.5 billion years);
o The radiocarbon method allows you to determine the age of objects that have biological nature, with an accuracy of 50 years in the range of 1000 - 50000 years: for example, based on the measurement of carbon content in rope sandals found in a cave in Oregon, the existence of prehistoric people in the United States 9000 years ago was confirmed;
Ø in medicine:
o diagnosis of diseases;
o treatment of cancer patients;
o sterilization of medical instruments and materials.
The discovery of radioactivity had a huge impact on the development of science and technology, it marked the beginning of an era intensive study properties and structure of substances. New perspectives emerging in energy, industry, military, medicine and other fields human activity thanks to mastery nuclear energy, were brought to life by the discovery of the ability chemical elements to spontaneous transformations. However, along with the positive factors of using the properties of radioactivity in the interests of humanity, it is still possible to give examples of their negative interference in our lives. These include sunken ships and submarines With nuclear engines And atomic weapons, disposal of radioactive waste at sea and on land, accidents at nuclear power plants and etc.
Currently, significant progress has been made in solving the problem of using atomic energy V national economy. The main energy producing unit atomic devices, using intranuclear energy, is a reactor. Created in the reactor core the necessary conditions for the emergence and maintenance of a certain level chain reaction fission of heavy nuclei. Released at the same time thermal energy accumulated by the coolant and carried outside the core.
One of most important tasks provision radiation safety in nuclear reactors is the reliable containment of huge quantities of radioactive substances generated during their operation. Retention of fission products inside the reactor is carried out using a system of three barriers (fuel cladding, primary circuit, external protection reactor).
In 1896, the French physicist A. Becquerel checked whether uranium salt (potassium uranyl sulfate) did not emit any rays when exposed to sunlight(shortly before this there were open x-ray radiation, physicists were looking for analogues). But later A. Becquerel discovered that uranium salt emits unknown radiation even without prior illumination. Becquerel established that the intensity of radiation is determined only by the amount of uranium in the preparation and is completely independent of what compounds it is included in. Thus, this property was inherent not in the compounds, but in the chemical element uranium. This phenomenon was later called radioactivity.
The phenomenon of radioactivity (Latin: I emit rays, effective) is the spontaneous transformation of unstable atomic nuclei into the nuclei of other elements, accompanied by the emission of particles or gamma quanta.
There are 4 known types of radioactivity: alpha decay, beta decay, spontaneous fission of atomic nuclei, proton radioactivity. Radioactivity is characterized by an exponential decrease in the number of nuclei over time. Radioactivity was first discovered by the French physicist A. Becquerel (1852-1908) in 1896.
A distinction is made between natural and artificial radioactivity. Natural radioactivity is observed in isotopes existing in nature, and artificial radioactivity is observed in isotopes obtained as a result of nuclear reactions. Nuclei that undergo radioactive transformations are called mother nuclei, and those formed during the process of radioactive decay are called daughter nuclei. There are stable (stable) and radioactive isotopes. 274 stable and over 700 radioactive isotopes have been found in known chemical elements. Most naturally occurring chemical elements are mixtures of isotopes.
Depending on their origin, all naturally radioactive elements of the Earth can be divided into three groups.
The first group includes elements combined into three radioactive families. In addition to the long-lived ancestors of these families - uranium, thorium and actinouranium - this also includes their decay products, including relatively short-lived ones - radium, radon, mesothorium, etc. The number of radioactive elements of this group gradually decreases in accordance with the law of radioactive decay. The most widespread elements in this group are uranium, which is found in more quantities in the earth's crust than silver or mercury, and thorium. Natural uranium is a mixture of three isotopes - uranium - 238 (99.28%), uranium - 235 (0.71%) and uranium - 234 (0.006%). Uranium - 238 and uranium - 235 (actino-uranium) are the founders of two radioactive families.
One of the decay products of uranium 238 is radium, which was already mentioned above. Despite the relatively short half-life, the content of radium in the earth's crust is relatively stable, since the decrease in its amount as a result of decay is compensated continuing education new radium due to the decay of uranium.
Radium has found wide application in medicine, not only as a source of gamma rays for irradiating patients (in this area it is being replaced by much cheaper artificial radioactive substances), but also as a source of radon for radon baths, often used by physical therapists.
The second group of radioactive elements of the Earth consists of radioactive isotopes of elements that are not part of radioactive families. They also arose during the formation of the Earth, and their number is gradually decreasing due to radioactive decay.
From the elements of this group highest value has potassium, the radioactivity of which was discovered in 1906. Potassium is one of the most common elements. Its share is 1.1% total number atoms forming earth's crust. Potassium is necessary for normal development plants, and is also an integral integral part any living organism, including humans. Natural potassium is a mixture of three isotopes K 39, K 40 and K 41, of which only one is radioactive - K 40. The amount of this isotope in the natural mixture is small - only 0.0119%; In 1 g of natural potassium, about 30 disintegrations occur per second. Despite this seemingly insignificant activity compared to radium and uranium, potassium, due to its abundance, plays a large role in nature.
Of the other radioactive elements of the second group, rubidium Rb deserves attention, as it tends to accumulate in some plants (1 liter of grape juice contains 1 mg of rubidium). However, the activity caused by it is significantly less than K 40.
The third group of naturally radioactive substances that make up the biosphere is formed by radioactive isotopes that arise in the atmosphere as a result of the action cosmic rays. Such isotopes include radioactive carbon (C 14), phosphorus (P 32) and some others. The amount of these isotopes in nature is relatively small.
After the discovery of radioactive elements, active study began physical nature their radiation. Rutherford was able to discover the complex composition of radioactive radiation.
The experience was as follows. The radioactive drug was placed at the bottom of a narrow channel of a lead cylinder, and a photographic plate was placed opposite. The radiation coming out of the channel was affected by a magnetic field. In this case, the entire installation was in a vacuum.
In a magnetic field, the beam split into three parts. Two components of the primary radiation were deflected by opposite sides, which indicated that they had charges of opposite signs. The third component preserved the linearity of propagation. Radiation having positive charge, called alpha rays, negative - beta rays, neutral - gamma rays.
While studying the nature of alpha radiation, Rutherford conducted the following experiment. In the path of the alpha particles, he placed a Geiger counter, which measured the number of emitted particles per certain time. After this, using an electrometer, he measured the charge of the particles emitted during the same time. Knowing the total charge of alpha particles and their number, Rutherford calculated the charge of one such particle. It turned out to be equal to two elementary ones.
By the deflection of particles in a magnetic field, he determined the ratio of its charge to mass. It turned out that for one elementary charge there are two atomic units masses.
Thus, it was found that with a charge equal to two elementary ones, an alpha particle has four atomic mass units. It follows from this that alpha radiation is a stream of helium nuclei.
In 1920, Rutherford proposed that there should be a particle with a mass equal mass proton, but not having electric charge- neutron. However, he was unable to detect such a particle. Its existence was experimentally proven by James Chadwick in 1932.
In addition, Rutherford refined the ratio of the electron charge to its mass by 30%.