Radioactive fallout is divided into two types: early (local) and late. Radioactive fallout How is rainfall measured?

Fallout

radioactive substances released into the environment, formed as a result of a nuclear explosion or releases during accidents of radiation hazardous objects and falling onto land and water areas. The rate of deposition of these substances depends on the size of the solid particles on which they condense, forming radioactive dust. There are three types of radioactive particles: near (local) - consist mainly of large and medium particles larger than 100 microns in size, falling within a few hours after a nuclear explosion and covering an area of ​​up to several hundred kilometers; intermediate (tropospheric) - consist of particles with a diameter of up to several tens of micrometers that fall into the upper troposphere and fall for several months, creating weak radioactive contamination over a large area; global (stratospheric) - consist of particles up to tenths of a micrometer in size falling from the stratosphere over several years across the globe. In case of radiation accidents, the propagation range of R.o. depending on the height of the rise of radioactive substances, it ranges from hundreds of meters to thousands of km.

EdwART. Glossary of terms of the Ministry of Emergency Situations, 2010

See what “Radioactive fallout” is in other dictionaries:

Solid or liquid particles containing radioactive substances that have fallen to the surface of water (earth) that were formed as a result of nuclear explosions, technological or emergency emissions from nuclear industry enterprises. The greatest... ...Marine Dictionary

fallout- Radioactive substances falling from the atmosphere onto the surface of the Earth along with rain or snow, or in dry form, especially dangerous after nuclear explosions in the atmosphere... Dictionary of Geography

FALLOUT- solid or liquid particles containing radioactive (see), fallen onto the surface of the earth, water, structures and other objects and leading to their radioactive (see) ... Big Polytechnic Encyclopedia

fallout- — EN radioactive fallout The material that descends to the earth or water well beyond the site of a surface or subsurface nuclear explosion. (Source: MGH)… … Technical Translator's Guide

Fallout- * radioactive fallout * radioactive fallout solid or liquid particles deposited on the surface of the earth from the atmosphere that contain radionuclides (). R. o., as a rule, fall out as a result of accidents accompanied by explosions on... ... Genetics. encyclopedic Dictionary

Radioactive fall out radioactive fallout. Solid or liquid particles deposited from the atmosphere onto the earth's surface (often associated with precipitation) containing radioactive substances (radionuclides); as a rule, R.o. are... ... Molecular biology and genetics. Dictionary.

fallout- radioaktyvieji krituliai statusas T sritis chemija apibrėžtis Radioaktyviosiomis medžiagomis užteršti krituliai. atitikmenys: engl. radioactive precipitation rus. radioactive fallout... Chemijos terminų aiškinamasis žodynas

fallout- radioaktyviosios nuosėdos statusas T sritis apsauga nuo naikinimo priemonių apibrėžtis Kritulių pavidalu iškritusi atmosferoje esanti radioaktyvioji medžiaga. Radioaktyviosios nuosėdos gali būti vietinės (per kelias valandas iškrintančios maždaug … Apsaugos nuo naikinimo priemonių enciklopedinis žodynas

fallout- radioaktyvieji krituliai statusas T sritis ekologija ir aplinkotyra apibrėžtis Radioaktyviosiomis medžiagomis užteršti atmosferos krituliai. Jeigu radioaktyvieji krituliai nusėda smarkiai lyjant arba sningant, vietovėje gali susidaryti plotai,… … Ekologijos terminų aiškinamasis žodynas

Radioactive aerosols formed after a nuclear explosion or as a result of emissions from enterprises and falling out of the atmosphere ... Large medical dictionary

Radioactive fallout is radioactive aerosols deposited from the atmosphere resulting from nuclear weapons testing. Radioactive fallout is distinguished: local, tropospheric and stratospheric.

Local radioactive fallout is large, predominantly fused particles that fall under the influence of gravity near the explosion site. Their main sanitary significance is determined as sources. Tropospheric radioactive fallout is radioactive particles of micron and submicron size that enter the troposphere during a nuclear explosion. Over the course of 2-6 weeks, they are transported by air currents around the globe, gradually settling on the earth's surface. They contain predominantly short-lived isotopes, of which radioactive iodine poses the greatest sanitary hazard. Atmospheric precipitation (especially drizzle) plays a decisive role in cleansing the troposphere. Stratospheric (or global) radioactive fallout is radioactive particles injected during a nuclear explosion into the upper atmosphere (stratosphere) and slowly settling on the ground. Their stay in the stratosphere ranges from 2 to 5 years. They contain predominantly long-lived isotopes (, cesium-137, cerium-144, etc.).

The density of global radioactive fallout is uneven at different latitudes. Maximum fallout after the cessation of mass nuclear weapons testing in 1963 occurred between 20-60° N. w. Due to the peculiarities of the transfer of air masses, there are seasonal fluctuations in the density of precipitation with a maximum in spring - early summer. Further migration of radioactive isotopes deposited on the surface of the earth along the biological chain is determined by their biological availability. In contrast to local fallout, consisting mainly of large fused insoluble particles, stratospheric radioactive fallout, consisting of fine fractions, has a high degree of bioavailability (strontium-90, cesium-137). The solubility of these particles can reach 100%. In the first years after nuclear weapons testing, contamination of terrestrial vegetation occurred everywhere due to the direct deposition of radioactive fallout on the surface of plants. Subsequently, their migration into the plant by roots from the soil becomes increasingly important. The highest density of radioactive fallout occurred in 1963, as a result of which the maximum radiation doses to the population caused by stratospheric fallout occurred in 1963-1964. However, even during this period they did not exceed the dose limit established for the population. Due to the decrease in the density of radioactive fallout and radioactive decay, the supply of radioactive isotopes decreases every year. Accordingly, the absolute values ​​of the radiation dose to people are reduced. For example, radiation doses to bone tissue in adult residents of Moscow in 1968 due to incorporated strontium-90 were 2.6 mrad/year, i.e., less than 10% of the dose limit.

The absence of a real health hazard from such doses eliminates the need for any preventive or health measures.

However, monitoring of the radiation situation caused by global fallout on the territory of Russia is carried out continuously in order to study the corresponding patterns. The objects of observation are atmospheric air, open water bodies, vegetation, etc. Constant monitoring is also carried out of the content of radioactive substances in the body of various age groups of the population and the population dose due to global radioactive fallout.

Radioactive fallout is fallout from a radioactive cloud resulting from the explosion of a nuclear device.

There are local, delayed and global radioactive fallout. Local radioactive fallout has particles of the order of tens of microns or more in size; fall out during ground explosions over several tens of hours and spread in the direction of the wind 500-550 km from the center of the explosion. Delayed (semi-global, tropospheric, continental) radioactive fallout has particles of the order of 1-5 μm in size; fall out within a few weeks from the moment of the explosion (usually up to 5 months) and spread in the latitudinal direction. Global, stratospheric fallout has particles smaller than 1 μm; fall out over a number of years, usually more intensely in the spring.

The nature of the formation and fallout of radioactive fallout depends on the nature of the explosion (ground, air, surface), TNT equivalent, nuclear device, the nature of the soil in the area of ​​the explosion and meteorological factors.

During a ground explosion of a nuclear device with a TNT equivalent of about 1 Mt, about 20,000 units of evaporated soil are added to the usual substances that make up the fireball (fission products, charge shell and other parts heated to a temperature of several million degrees). In addition, air currents accompanying the explosion raise a significant amount of dust and other solid particles that make up the “leg” of the specific “mushroom” of a nuclear explosion.

Radioactive contamination as a result of such an explosion covers an area of ​​about 28 thousand km 2 an hour after it. Local precipitation accounts for approximately 90% of the total soil mass raised during a ground explosion.

The finely dispersed part of the soil raised into the air passes into the stratosphere, subsequently forming the basis for the formation of global radioactive fallout. During air explosions (the fireball does not touch the surface of the earth), the formation of local precipitation does not occur, and the bulk of radioactive fragments raised into the stratosphere subsequently forms global precipitation.

Thus, as a result of explosions of nuclear devices, a large number of different radioactive isotopes enter the atmosphere, which are carried by air currents, contaminating the areas most remote from the explosion site.

For many years, Sr 90, Cs 137 and other radioactive isotopes formed during the explosion will be carried by air currents. The highest density of radioactive contamination is created by local radioactive fallout, the isotopic composition of which is represented mainly by short-lived radioactive fragments, primarily radioactive J 131.

The decline in radioactivity in the first period after a nuclear explosion (up to 100 days) obeys the law t -1.2. The isotopic composition of delayed radioactive fallout is less diverse, however, J 131 plays a fairly significant role in them. As part of global fallout, radioactivity is represented by long-lived fragments - Sr 90, Cs 137, Ce 144, Pr 144, Pm 147 and some others, but biological significance is mainly represented by Sr 90 and Cs 137.

Falling onto the surface of soil and plants, radioactive fallout enters into cycles of biological processes continuously occurring on Earth, migrating in complex ways along various links of the ecological chain (see Ecology, radiation). A study of the mechanism of penetration of Sr 90 - a component of global radioactive fallout - showed that up to 80% of it is concentrated in the surface layer of uncultivated land 5 cm thick. In arable lands it is distributed over the entire plowing depth. With ongoing radioactive fallout, the amount of Sr 90 entering the human diet depends to a greater extent on direct contamination of the leaves, inflorescences and lower parts of perennial plants than on its absorption by roots from the soil. If the rate of radioactive fallout decreases, absorption by roots begins to dominate.

A number of radioactive substances produced during explosions of nuclear devices enter the human body and accumulate in it. Sr 90 is of especially great biological importance, having a 28-year half-life and accumulating in the human skeleton. The main accumulation of strontium occurs in the rapidly growing parts of the bone - the epiphyses, which turn into a kind of strontium “depots”, from where nearby areas of the bone and bone marrow are constantly irradiated (see Radiation toxicology).

In connection with the biological significance of radioactive fallout, a system for monitoring the levels of radioactive fallout, migration and entry into the human body of the most important radioactive fragments of nuclear fission has been developed and is being implemented in the USSR and a number of other countries.

As a result of the Triple Nuclear Test Ban Treaty, the amount of radioactive fallout has decreased significantly and continues to decrease. See also Radiation hygiene.

Dust that rises into the air as a result of a nuclear explosion - a nuclear weapons test or a nuclear power plant accident - and then falls to the ground is called radioactive fallout. This dust contaminates everything around precisely because it is radioactive. This means that it contains certain types of atoms that undergo spontaneous decay. When each of these atoms decays, a small amount of energy and matter is released - a phenomenon called radiation.

During a nuclear explosion, a strong blast wave is generated, a large amount of heat is released and many radioactive atoms are formed. These atoms mix with soil particles, which, being lifted into the air by the force of the explosion, form a multi-ton radioactive dust cloud. After some time, this dust settles on the ground in the form of radioactive fallout. The heaviest particles from this cloud fall to the ground in the first minutes or hours after the explosion. However, the lungs linger in the atmosphere for a longer time. The wind can carry them around the globe for months or even years. In the end, they inevitably return to the surface of the earth along with snow, rain or fog.

Radioactive fallout that gets on human skin can be washed off with water. However, if particles of radioactive dust enter the body, they can remain there for many years. They enter the body along with air, water and food. Moreover, the last path is the most common. Radioactive dust settles on leaves and fruits and contaminates the soil, from which radioactive atoms enter the plants through the roots. Even if these plants are not eaten by humans, they can be eaten by animals, whose meat, in turn, is eaten by people or other animals. Once inside the body, radioactive atoms emit radiation that destroys living cells or, at least, weakens their defenses against all kinds of diseases.

What is gypsum?

Human use of gypsum is growing at such a rate that global production has doubled in recent years. Due to the fact that gypsum perfectly resists fire and water, and also does not allow cold and heat to pass through, it is used in large quantities in construction for wall cladding. By the way, gypsum blocks and bricks can be sawn and nailed like wooden boards. A mixture of gypsum with a small amount of cement and some other components forms a lightweight building material called plaster. It is widely used in the construction of modern buildings. What is gypsum? Gypsum is a mineral that is calcium sulfate mixed with water.

There is a translucent variety of gypsum called selenite, and another with a special luster known as alabaster. Gypsum is mined from thick layers that lie underground at varying depths: some near the surface, others much deeper. In the US state of Texas, layers of gypsum more than 100 meters thick were found, covering an area of ​​hundreds of square kilometers. Gypsum has been used as a building material and for plastering walls and ceilings since ancient Egypt.

Used alone or mixed with sand or lime, gypsum is made into moldings, tiles or finishing plaster. You can use it to make bricks or even entire blocks for walls. Gypsum is used to create scenery for films and plays; sculptors and dental surgeons use it in their work. Gypsum is a cheap raw material and its reserves are found almost everywhere in the world.

What is slate?

Millions of years ago, particles of fine-grained clay settled to the bottom of lakes and inland seas, forming soft silt. Then it hardened, turning into clay shales. At that time, constant movements occurred in the earth's crust, as a result of which folds appeared in the layers of shale covered with other rocks. The pressure of the upper layers on those layers was so significant that it compressed them into a material we know as slate. Clay particles settled to the bottom of lakes and seas in even layers, which continued to persist even after the shales turned into slate. Thanks to this, today we can divide it into thin wide plates.

Typically, slate is dark gray and black in color, although it can also be red, green or light grey. The predominantly black color is explained by the fact that the living organisms that existed in the original silt, dying, decomposed, forming inclusions in the clay layers in the form of fine crumbs of coal dust. Slate can only be found in those areas of the globe where rock-forming pressure and shifts in the earth's crust have had an active influence on ancient layers of shale. Slate is used quite widely by humans. Its main area of ​​application is construction, where it serves as a roofing material for the roofs of houses and buildings of all types.

What is dust?

Dust is formed by tiny solid particles suspended in the air. Dust, as a rule, rises from the ground by the wind, then floats in the air under the influence of air currents until it settles again on the surface under the influence of gravity or along with rain and snow. Dust sources can be very different. It appears as a result of soil weathering, is released from volcanic craters during eruptions, is found in the exhaust fumes of cars and other vehicles, and even in ocean spray. Perhaps the last of the listed sources - the ocean - will seem dubious to you. Indeed, how can ocean water serve as a source of dust?

However, did you know that every year 2,000,000,000 tons of various salts enter the earth's atmosphere from the ocean? Water evaporates into water vapor, and the chemical elements contained in ocean salt remain in the air. Surely each of you has heard the expression dust storm. It occurs in areas where natural vegetation has died due to drought. During such a storm, thousands of tons of dust rise into the air and are transported over a distance of up to 3000 km, or even more!

For example, during a dust storm that raged in the southwestern United States in 1933, about 10 tons of dust fell per square kilometer in New England (the northeastern region of the United States). The dust raised by a storm in the great African Sahara Desert has reached London and other European cities! In general, the atmosphere constantly contains a huge amount of dust. About 43,000,000 tons of dust fall into the United States annually, about 13,000,000 tons of which is due to human activities.

Air pollution from dust is one of the causes of mud clouds - smog - hanging over large cities. Currently, in all developed countries there are special systems to combat this evil, which causes damage to human health and the environment.

What is milk made from?

Many people consider milk to be perhaps the best product we eat. Once you find out how many substances that are beneficial for your body are contained in it, you will understand why this is so. One of the main components of milk is protein, which is necessary to strengthen muscles and restore them after hard work. The other is fat, which supplies energy to your body. This fat, as you might guess, is called milk fat. If milk contains globules (small, ball-shaped particles of fat), then butter can be made from it. Milk also contains sugar, a hydrocarbon that is another source of energy. It's called lactose. It does not taste as sweet as sugar obtained from cane or sugar beets, but it is easier than all others that are absorbed by the human body.

Milk also supplies the body with important mineral salts. Humans need them to strengthen bones and produce fresh blood. Milk contains especially a lot of phosphorus and calcium, and it contains more of the latter than any other food. In addition, milk contains iron, copper, manganese, magnesium, sodium, potassium, chlorine, iodine, cobalt and zinc. And this list is by no means complete! Milk also provides us with many vitamins. It contains a high content of vitamins B2, A, B1 and, in addition, C and D in minimal quantities. Of course, milk contains a lot of water. However, it is noteworthy that despite the fact that milk is a liquid product, it contains 110 g of solid matter for every liter.

What is carbon?

Carbon is a chemical element that is extremely important for any living thing. Of all the matter that exists on Earth, it accounts for less than one percent, but it is found in any organism, living or dead. The body of any living creature is built from substances containing carbon, and its presence in one place or another on earth, even in small quantities, may indicate that life once existed there. Plants extract carbon from carbon dioxide - carbon dioxide - in the atmosphere and use it as building material for roots, stems and leaves. Animals get it by eating these plants. Both of them release it into the air in the form of the same carbon dioxide during respiration, and it accumulates in the soil during the decomposition of the bodies of dead creatures.

Of all the forms of pure carbon, the best known, and perhaps the most valuable to humans, is coal. It is approximately 4/5 carbon, with the remainder being hydrogen and other elements. The value of coal stems from the chemical properties of carbon, the main one being that it readily reacts with oxygen. This process occurs when coal is burned in air, releasing a large amount of thermal energy that can be used for a variety of purposes.

However, carbon in inanimate nature can be found not only in the form of coal. Two other forms of its existence in its pure form, sharply different from each other, are graphite and diamond. Graphite is very soft and greasy to the touch. It serves as an excellent lubricant for many mechanisms. And, as you know, pencil leads are made from it. In this case, graphite is mixed with clay to reduce its softness. Diamonds, on the other hand, are the hardest substances known to man. They are used to create especially durable cutters, as well as jewelry.

Carbon atoms can form bonds with each other and with atoms of other elements. The result is a huge variety of carbon compounds. One of the simplest is the already mentioned carbon dioxide, which is formed when carbon is burned in oxygen or in air. Carbon monoxide, or carbon dioxide, which is poisonous to humans and animals, is formed when carbon burns in an atmosphere where there is a lack of oxygen. Carbon reacts with great difficulty with other elements or substances. As a rule, this occurs at a fairly high temperature.

What is nitrogen?

All living things need nitrogen, because it plays an important role in the body of plants, humans and animals. Nitrogen is part of proteins, which are building materials for the human body. Without these substances, no one can grow, heal wounds or replace dying tissue. The air we breathe contains 78 percent nitrogen; for every square kilometer of the Earth's surface there are about 12,500,000 tons of nitrogen. Nitrogen is a gas without color, taste or odor. It dissolves only slightly in water. At very low temperatures or high pressures, it turns into a liquid. Under normal atmospheric pressure, nitrogen becomes liquid at a temperature of -210 °C. It would seem that with such an amount of nitrogen in the air, living creatures should not have problems obtaining it.

However, in reality, in nature, only plants from the legume family are able to absorb nitrogen from the air. All other living organisms, including humans, cannot absorb pure nitrogen. To obtain the necessary nitrogen, people eat protein foods made from certain types of plants or herbivores. When we breathe, we inhale nitrogen contained in the air. But nitrogen, unlike oxygen, is not absorbed at all by our lungs, and we simply exhale it back.

However, the presence of nitrogen in the atmosphere helps ensure that we do not absorb too much oxygen. An excess of the latter is no less dangerous than its deficiency. As for other living beings, they also receive nitrogen in the form of compounds with other elements: plants - from the soil, animals - from plants or from other animals. Nitrogen interacts with other elements with great difficulty. For example, it reacts with oxygen in nature only during lightning flashes during a thunderstorm, which create exceptionally high temperatures.

What is uranium?

Uranium has existed on earth for billions of years, but most people only learned about it after the creation of nuclear weapons and nuclear power plants. Uranium is one of the heaviest chemical elements. It is a metal and its content in the earth's crust is higher than such long-known elements as mercury and silver. Deposits of uranium ores have been discovered in many regions of the globe. Their deposits are especially large in Russia, Canada, the USA, Zaire and some other countries. Pure uranium metal shines just like silver. However, if you hold it in the air for several minutes, the surface of the piece of metal becomes dull and acquires a brown tint. A film of uranium oxide forms on it - a compound of uranium with oxygen, and the process of its formation is called oxidation. A film formed on the surface of the metal prevents the penetration of oxygen into the sample and the further development of the oxidation process.

The main difference between uranium and the vast majority of other elements is that it has natural radioactivity. This means that the uranium atoms themselves gradually change, emitting certain types of rays invisible to the eye. These rays come in three types, called alpha, beta and gamma radiation. As uranium atoms undergo changes, they transform into another radioactive element. The same thing happens with the new element, and a new portion of radiation is released. This continues until a new element is formed that is not radioactive. There are 14 stages in this chain of transformations. One of them produces the well-known element radium, and the last one produces lead.

Lead is a non-radioactive element, and therefore the chain of transformations ends with it. The complete process of turning uranium into lead takes billions of years. Uranium has several isotopes. Isotopes are atoms of the same element that have different atomic weights, which are indicated by numbers after the name of the element. Uranium-235 is used as a material for atomic bombs and fuel for nuclear power plants. Another element - plutonium, used for the same purposes - does not exist in nature, and is obtained from uranium using special devices.

(global). Early precipitation falls on a limited area of ​​the earth's surface during the first 24 hours after the explosion. Global precipitation occurs over a long period of time

time on the surface of the entire globe.

An area is considered contaminated if the dose rate of ionizing radiation

is 0.5 R/h or more. Over time, the dose rate gradually decreases and

reaches values ​​that are safe for humans. For example, the dose rate

ionizing radiation after a ground-based nuclear explosion decreases after 1 hour

almost doubled, after 7 hours - 10 times, and after 2 days - 100 times. Every 7 times

an increase in time after the explosion leads to a 10-fold decrease in dose rate

ionizing radiation.

The leading radiation factor of damage is external gamma irradiation,

leading to the development of an acute form of radiation sickness. High pollution density

exposure of the skin to radioactive substances can lead to radiation burns. Once in the gastrointestinal tract or lungs, radioactive substances are absorbed into the blood and distributed by the blood stream to organs and tissues. Some radioactive isotopes (cesium, tellurium, molybdenum, etc.) are distributed relatively evenly in the body and are quickly eliminated from it, others

accumulate in certain organs and tissues (iodine isotope is deposited in

thyroid gland, strontium and barium - in bone tissue, the lanthanide group - in liver tissue). In order of decreasing sensitivity to radiation, tissues are distributed as follows: lymphatic tissue, lymph nodes, spleen, thymus, bone marrow, germ cells.

The main sources of radioactive contamination are:

1.group– radioactive isotopes formed during a nuclear explosion

as a result of fission of uranium or plutonium nuclei. The half-life of these isotopes is from

a few minutes to tens of years. In the contaminated area, in the first hours and days, short-lived isotopes (bromine-90 -16 s., rubidium-90 -2.74 min.) are of greatest importance; then, within 1-3 weeks, iodine isotopes (125,130,131,133, etc.) prevail, and subsequently remain long-lived isotopes of strontium-90 - period 28 years, cesium-137 - 33 years. This group poses the greatest danger because it has a huge gamma

activity.

2.group– induced radioactivity – occurs under the influence of neutron radiation

flow. Neutrons interact with the nuclei of various elements (air, soil), in

As a result, they become radioactive and emit beta and gamma radiation.

The most important isotopes are silicon, sodium, and calcium. Induced

radioactivity occupies a small area (maximum 2-3 km) and isotopes have a short half-life (from minutes to days).

3.group– unreacted part of the nuclear charge (90% of the total

quantities of uranium and plutonium. The most dangerous ingestion of these substances is

body and skin contamination. The damaging effect of radioactive contamination of an area is determined by external radiation, depending on the level of radioactivity - this is the dose rate of gamma radiation at a height of 1 m from the contaminated surface of the earth. An area with a radiation level above 0.5 R/hour is considered contaminated. Radiation levels on a contaminated surface are continually reduced by converting isotopes into non-radioactive, stable substances according to the rule: for a sevenfold increase in the time elapsed after the explosion, the radiation level decreases by a factor of 10. Contact of radioactive substances on the skin or inside can slightly increase the damaging effect of external radiation and is determined by the degree of infection.

Electromagnetic pulse represents a short-term strong

electromagnetic field arising at the moment of a nuclear explosion, operating for

a few seconds; induces electromotive force in conductors up to several thousand

volts, disables radio-electronic equipment. Seismic explosion waves occur in the ground during nuclear explosions and are one of the main damaging factors for buried structures during underground explosions.

In case of explosions of low and medium power nuclear weapons in the structure

sanitary losses are expected mainly to be a combination of traumatic injuries,

burns and radiation sickness, and in high-power explosions - a combination of injuries and burns.

The source of nuclear destruction (NSD)) is the territory within which

As a result of the impact of the damaging factors of a nuclear explosion, massive

damage to people, farm animals, destruction or damage to buildings and structures.

The fission of heavy uranium and plutonium nuclei produces hundreds of different radionuclides with different half-lives. The distribution of daughter products by mass numbers has two maxima, located in the ranges 85-105 and 130-150. The radionuclides cesium-137 and strontium-90 are formed with high yield. They have relatively long half-lives (about 30 years) and therefore pose a particular danger to human health. In the first weeks after the explosion, iodine-131 (half-life 8 days) is of particular importance, as it can accumulate in the thyroid gland and thereby create high local doses of radiation.

Neutrons produced during a nuclear or thermonuclear explosion interact with the nuclei of atoms that make up the atmosphere, soil, and structural materials. Thus, their interaction with atmospheric nitrogen nuclei leads to the formation of radioactive carbon 14 C.

Sources of radioactive substances can be fission products of nuclear fuel, the part of the nuclear charge that has not reacted, and radioactive isotopes formed in soil and other materials under the influence of neutrons (induced activity).

A ground or low explosion draws many grains of soil dust into a fiery cloud containing radioactive fission products of uranium and plutonium nuclei. The dust particles melt from the surface and at the same time absorb (dissolve) radioactive substances. When an atomic cloud moves in one direction or another under the influence of the prevailing upper (stratospheric) winds, dust grains gradually fall to the ground - first larger ones, then smaller and smaller ones. A long radioactive strip is formed - a “trace” - the result of a significant amount of radioactive substances falling out of a cloud raised into the air. The shape of the trace can be very diverse, depending on the surrounding conditions.

Local (local) radioactive fallout is fallout that falls within the first few hours, but not more than a day after the explosion. They form a radioactive trace of an explosion cloud on the ground with fairly high levels of contamination. Such local traces can be formed mainly after ground explosions in the area immediately adjacent to the explosion crater.

Global radioactive fallout is those products of nuclear explosions that have been in the stratosphere for quite a long time, i.e. above the tropopause. Then, about 4-6 months after the nuclear explosion, they begin to fall onto the Earth's surface in the form of very small particles, spreading almost throughout the entire globe. The fallout of global radioactive particles is facilitated by ordinary precipitation - rain, snow, fog.

In addition, after airborne nuclear explosions of medium and large calibers, the formation of radioactive contamination in the intermediate zone due to tropospheric fallout is possible, especially when ground-level dust formation is drawn into the explosion cloud. This is semi-global radioactive fallout, the fall of which begins approximately 10-20 hours after the explosion at distances of about 500-1000 km from the explosion site and can continue for 2-4 weeks. The radioactive particles that make up this fallout are easily carried by winds.

The scale and degree of radiation pollution of the environment as a result of the use of nuclear weapons depend on the type and power of the explosion.

An air nuclear explosion is an explosion produced at an altitude of up to 10 km, when the luminous area does not touch the ground (water). Severe radioactive contamination of the area occurs mainly near the epicenters of low air explosions. Their characteristic feature is that, despite the connection of the dust column with the explosion cloud, soil particles raised from the surface of the earth do not interact with radioactive products - fission fragments of nuclear fuel. In this regard, the formation of a source of radioactive contamination occurs due to the condensation of vapors only from the structural materials of the bomb. Radioactive products are localized in droplets of the resulting liquid. The size of the radioactive particles formed in this way is about 10 microns. These particles spread and fall to the ground at distances of up to several hundred and even thousands of kilometers from the site of the explosion. In addition, particles of the surface layer of soil exposed to neutron radiation are drawn into the disturbed region of the atmosphere and subsequently fall out of the dust column at close distances from the epicenter of the explosion.

During high air explosions, mineral (soil) particles are practically not involved in the explosion cloud. Radioactive contamination of the area occurs in the zone of propagation of neutrons of penetrating radiation in the area of ​​the epicenter, and radioactive particles formed mainly from structural materials of nuclear weapons become one of the components of global radionuclide fallout.

During a high-altitude nuclear explosion (explosion height of more than 10 km), radioactive products reach the surface of the earth long after it has occurred and only in the form of global fallout.

During an underwater explosion, instantaneous gamma rays and neutrons are absorbed by water, and radioactive products are distributed between the air and sea water. A hollow column of water appears with a cloud at the top. After the collapse of the water column, a base wave is formed at its base, which is a driving cloud consisting of small radioactive drops of water and fog. After some time, this cloud breaks away from the surface of the water, moves with the wind, and radioactive rain falls out of it, forming a local trace. The length of the trace and the density of radioactive contamination of the area when precipitation falls on a hard surface after an underwater explosion are significantly less than after a land explosion.

A surface nuclear explosion is an explosion carried out on the surface of water, in which the luminous area formed during the explosion touches the surface of the water. The cloud of a surface explosion is similar in height and appearance to a cloud of a ground explosion, but the size of the local trace and the density of contamination, although significant, are smaller than after a ground explosion, but larger than after an underwater explosion of a nuclear charge of approximately the same power.