The concept of the explosion and explosives. What is an explosion? The concept and classification of explosions What is an explosion definition by fire

What is an explosion? This is a process of instantaneous transformation of the state in which a significant amount of thermal energy and gases are released, forming a shock wave.

Explosives are compounds that have the ability to undergo changes in the physical and chemical state as a result of external influences with the formation of an explosion.

Classification of explosion types

1. Physical - the energy of an explosion is the potential energy of a compressed gas or steam. Depending on the magnitude of the internal energy pressure, an explosion of different power is obtained. The mechanical impact of the explosion is due to the action of the shock wave. Fragments of the shell cause an additional damaging effect.

2. Chemical - in this case, the explosion is due to the almost instantaneous chemical interaction of the substances that make up the composition, with the release of a large amount of heat, as well as gases and steam with a high degree of compression. Explosions of these types are typical, for example, for gunpowder. Substances arising as a result of a chemical reaction acquire high pressure when heated. The explosion of pyrotechnics also belongs to this species.

3. Nuclear explosions are lightning-fast reactions of nuclear fission or fusion, characterized by a huge power of released energy, including heat. The colossal temperature at the epicenter of the explosion leads to the formation of a zone of very high pressure. The expansion of the gas leads to the appearance of a shock wave, which is the cause of mechanical damage.

The concept and classification of explosions allow you to act correctly in an emergency.

Action type

Distinctive features

Explosions differ depending on the chemical reactions taking place:

Decomposition is characteristic of a gaseous medium.
Redox processes imply the presence of a reducing agent with which the oxygen in the air will react.
Reaction of mixtures.

Volumetric explosions include dust explosions, as well as explosions of steam clouds.

dust explosions

They are typical for closed dusty structures, such as mines. A dangerous concentration of explosive dust appears during mechanical work with bulk materials that give a large amount of dust. Working with explosives requires full knowledge of what an explosion is.

For each type of dust, there is a so-called maximum permissible concentration, above which there is a danger of spontaneous explosion, and this amount of dust is measured in grams per cubic meter of air. The calculated concentration values are not constant values and must be corrected depending on humidity, temperature and other environmental conditions.

Of particular danger is the presence of methane. In this case, there is an increased probability of detonation of dust mixtures. Already a five percent content of methane vapor in the air threatens with an explosion, due to which the ignition of a dust cloud follows and an increase in turbulence. A positive feedback occurs, leading to an explosion of great energy. Scientists are attracted by such reactions, the explosion theory still haunts many.

Safety when working in confined spaces

When working in closed rooms with a high content of dust in the air, it is imperative to adhere to the following safety rules:

Dust removal by ventilation;

Fight against excessive dryness of air;

Dilution of the air mixture to reduce the concentration of explosives.

Dust explosions are typical not only for mines, but also for buildings and granaries.

Steam cloud explosions

They are reactions of a lightning-fast change of state, generating the formation of a blast wave. Occur outdoors, in a confined space due to the ignition of a combustible vapor cloud. This usually happens when there is a leak.

Refusal to work with combustible gas or steam;

Refusal of ignition sources that can cause a spark;

Avoiding closed spaces.

You need to have a sound understanding of what an explosion is, what danger it carries. Failure to comply with safety rules and the illiterate use of some items leads to disaster.

Gas explosions

The most common accidents in which a gas explosion occurs occur as a result of improper handling of gas equipment. Timely elimination and characteristic definition are important. What does gas explosion mean? It occurs due to improper operation.

In order to prevent such explosions, all gas equipment must undergo regular preventive technical inspection. All residents of private households, as well as apartment buildings, are recommended an annual maintenance of the VDGO.

To reduce the consequences of an explosion, the structures of the premises in which gas equipment is installed are made not capital, but, on the contrary, lightweight. In the event of an explosion, there is no major damage and blockages. Now you imagine what an explosion is.

In order to make it easier to determine the leakage of household gas, the aromatic additive ethyl mercaptan is added to it, which causes a characteristic smell. If there is such a smell in the room, it is necessary to open the windows to ensure the supply of fresh air. Then you should call the gas service. At this time, it is better not to use electrical switches that can cause a spark. It is strictly forbidden to smoke!

The explosion of pyrotechnics can also become a threat. The storage of such items must be equipped in accordance with the standards. Poor quality products can harm the person who uses it. All this should definitely be taken into account.

General information about the explosion

CHARACTERISTIC FEATURES OF THE EXPLOSION:

High rate of chemical transformation of explosives;
a large number of gaseous explosion products;
strong sound effect (rumble, loud sound, noise, strong bang);
powerful crushing action.

Depending on the environment in which explosions occur, they are underground, ground, air, underwater and surface.

The scale of the consequences of explosions depends on their power and the environment in which they occur. The radii of the affected zones during explosions can reach up to several kilometers.

There are three blast zones.

3she I- zone of action of the detonation wave. It is characterized by an intense crushing action, as a result of which the structures are destroyed into separate fragments, flying away at high speeds from the center of the explosion.

Zone II- the area of action of the products of the explosion. In it, the complete destruction of buildings and structures occurs under the action of expanding explosion products. At the outer boundary of this zone, the resulting shock wave separates from the explosion products and moves independently from the center of the explosion. Having exhausted their energy, the products of the explosion, having expanded to a density corresponding to atmospheric pressure, no longer produce a destructive effect.

Zone III- zone of action of an air shock wave - includes three subzones: III a - strong destruction, III b - medium destruction, III c - weak destruction. At the outer boundary of zone 111, the shock wave degenerates into a sound wave, which is still audible at considerable distances.

EXPLOSION EFFECTS ON BUILDINGS, STRUCTURES, EQUIPMENT .

Buildings and structures of large sizes with light load-bearing structures, which rise significantly above the earth's surface, are subjected to the greatest destruction by explosion products and a shock wave. Underground and underground structures with rigid structures have significant resistance to destruction.

Damage is divided into full, strong, medium and weak.

Complete destruction. Ceilings in buildings and structures collapsed and all the main load-bearing structures were destroyed. Recovery is not possible. Equipment, means of mechanization and other equipment are not subject to restoration. In utility and energy networks, there are breaks in cables, destruction of sections of pipelines, supports of overhead power lines, etc.

Strong destruction. There are significant deformations of load-bearing structures in buildings and structures, most of the ceilings and walls are destroyed. Restoration is possible, but impractical, as it practically boils down to new construction using some of the surviving structures. The equipment and mechanisms are mostly destroyed and deformed.

In communal and energy networks, there are breaks and deformations in certain sections of underground networks, deformations of overhead power lines and communications, breaks in technological pipelines.

Medium destruction. In buildings and structures, it was mainly not load-bearing, but secondary structures (light walls, partitions, roofs, windows, doors) that were destroyed. Possible cracks in the outer walls and falls in some places. Ceilings and cellars are not destroyed, part of the structures is suitable for operation. In utility and energy networks, destruction and deformation of elements are significant, which can be eliminated by major repairs.

Weak destruction. Part of the internal partitions, windows and doors were destroyed in buildings and structures. The equipment has significant deformations. There are minor damages and breakdowns of structural elements in utility and energy networks.

General information about the fire

FIRE AND ITS BEGINNING .

A fire is an uncontrolled burning that causes material damage, harm to the life and health of citizens, the interests of society and the state.

Essence of burning was discovered in 1756 by the great Russian scientist M. V. Lomonosov. By his experiments, he proved that combustion is a chemical reaction of the combination of a combustible substance with oxygen in the air. Therefore, in order for the combustion process to proceed, the following are necessary terms:

The presence of a combustible substance (in addition to combustible substances used in production processes and combustible materials used in the interior of residential and public buildings, a significant amount of combustible substances and combustible materials is contained in building structures);
the presence of an oxidizing agent (usually, oxygen in the air is an oxidizing agent during combustion of substances; in addition to it, chemical compounds containing oxygen in the composition of molecules can be oxidizing agents: nitrates, perchlorates, nitric acid, nitrogen oxides and chemical elements: fluorine, bromine, chlorine);
the presence of an ignition source (open flame candles, matches, lighters, fires or sparks).

It follows that the fire can be stopped if one of the first two conditions is excluded from the combustion zone.

The possibility of fires in buildings and structures, and in particular the spread of fire in them, depends on what parts, structures and materials they are made of, what are their sizes and layout. As can be seen from Scheme 2, substances and materials are divided into flammability groups:

On non-combustible substances, unable to burn;
for slow-burning substances capable of burning under the influence of an ignition source, but unable to burn independently after its removal;
for combustible substances capable of burning after the ignition source is removed:
a) hardly flammable, capable of igniting only under the influence of a powerful ignition source;
b) flammable, capable of igniting from short-term exposure to low-energy ignition sources (flames, sparks).

For the first time, the task of studying the physical essence of an explosion was set by M.V. Lomonosov. In his work "On the Nature and Birth of Saltpeter", written in 1748, he defines an explosion as a very rapid release of a significant amount of energy and a large volume of gases.

Explosion is the process of a very fast (supersonic) physical or chemical transition of a substance or group of substances from one state to another, accompanied by a very rapid transition of the potential energy of the original substance into kinetic energy capable of doing mechanical work.

The phenomenon of an explosion in its manifestations such as a lightning discharge, a volcanic eruption has been known to mankind since time immemorial. Somewhat later, people learned how to make explosive compositions and use the explosion for their own purposes. However, to form a correct idea of the essence of the phenomenon called an explosion, significant progress was required in the development of the natural sciences.

A characteristic sign of an explosion is the extremely rapid appearance or, more precisely, the manifestation of the action of pressure, as a rule, very large.

According to the nature of the process of the flow of explosions, they are usually classified into:

PHYSICAL- in which only a physical transformation of matter occurs (flameless explosion with the help of liquid carbon dioxide and compressed air, explosions of steam boilers, cylinders with liquefied gas, electrical discharges), i.e. during a physical explosion, energy is released as a result of a physical process.

Physical explosion finds use in the coal mining industry in the form of cartridges airdox, in which the energy of compressed air is used to destroy the medium.

CHEMICAL- in which there is an extremely rapid change in the chemical composition of substances involved in the reaction with the release of heat and gases (explosion of methane, coal dust, explosives).

In a chemical explosion, energy is released as a result of a rapid chemical reaction. This type of explosion can be given the following definition: explosion called the rapid chemical transformation of an explosive, proceeding with the release of heat and the formation of gases.

From this definition follow four basic conditions that a chemical reaction must satisfy in order for it to proceed in the form of an explosion:

Exothermicity (heat release)

formation of gases

high speed of reaction

the ability to self-propagate.

If at least one of these conditions is not met, the explosion will not occur.

The chemical transformation of explosives and mixtures can take place in various forms, the main of which are :

· slow chemical transformation (decomposition of a substance);

· combustion;

· detonation.

With a slow chemical transformation, the decomposition reaction proceeds simultaneously in the entire volume of the substance, which is at the same temperature, almost equal to the ambient temperature. The reaction rate corresponds to this temperature and the explosive mass is the same at all points. When the explosive is heated, its temperature increases not only due to external heating, but also due to the heat released during the chemical decomposition reaction. Under certain conditions, this reaction can become self-accelerating, as a result of which explosives quickly turn into compressed gases almost simultaneously throughout the entire volume. A thermal explosion of explosives will occur, which can serve as an example of a homogeneous (homogeneous) explosion. However, a practically homogeneous explosion is not feasible due to uneven heat removal from explosives, since one or more combustion centers always occur in the substance, from which combustion then spreads to the rest of the explosive mass.

The basis of modern explosive technology is the use self-propagating explosive transformation. With this form of explosion, the chemical transformation, which began at any point in the charge, spontaneously propagates to its boundaries. The ability of a chemical reaction to propagate itself is a characteristic feature of this form of explosion.

Self-propagating explosive transformation is possible during combustion and detonation of explosives. In both cases, there is a chemical transformation front - a relatively narrow zone in which an intense chemical reaction occurs, propagating through the substance at a certain speed. Ahead of this zone is the original BB, behind her- conversion products

The temperatures ahead of the front, behind it, and in the chemical reaction zone itself differ significantly; there is also an inequality of pressures and density.

The reaction rate, more precisely, the linear speed of movement of the process front, depends mainly not on the initial temperature of the substance, but on the amount of energy released during the reaction, the conditions for its transfer to the unreacted substance, and the kinetic characteristics of the chemical transformation that occurs in it during this transfer. Since the mechanism of energy transfer during combustion and detonation is different (during combustion, thermal energy is transferred due to heat conduction, during detonation, the shock wave plays the main role), the propagation velocity of the process also differs and during combustion does not exceed several centimeters per second for condensed explosives, and during detonation is kilometers per second.

In accordance with the difference in the rate of propagation of the process, the destructive effect in different forms of the transformation of explosives differs significantly.

Slow transformation only in a closed volume can lead to an increase in pressure up to the rupture of the shell.

Combustion It is also capable of significantly increasing the pressure only in a closed or semi-closed volume. Accordingly, this process is used in cases where too much pressure is undesirable (missile chambers, firearms, etc.).

NUCLEAR- in which chain reactions of nuclear fission occur with the formation of new elements. Currently, two types of atomic energy release during an explosion are being implemented:

transformation of heavy nuclei into lighter ones (radioactive decay and fission of atomic nuclei of uranium and plutonium);

formation of heavier nuclei from light nuclei (fusion of atomic nuclei).

In blasting in industry, chemical explosions are used.

An explosion is a common physical phenomenon that has played a significant role in the fate of mankind. It can destroy and kill, as well as be useful, protecting a person from threats such as flooding and asteroid attack. Explosions differ in nature, but in the nature of the process they are always destructive. This strength is their main distinguishing feature.

The word "explosion" is familiar to everyone. However, the question of what an explosion is can only be answered on the basis of what this word is used for. Physically, an explosion is a process of extremely rapid release of energy and gases in a relatively small volume of space.

The rapid expansion (thermal or mechanical) of a gas or other substance, such as when a grenade explodes, creates a shock wave (high pressure zone) that can be destructive.

In biology, an explosion means a rapid and large-scale biological process (for example, an explosion in numbers, an explosion in speciation). Thus, the answer to the question of what an explosion is depends on the subject of study. However, as a rule, it is precisely the classic explosion that is meant by it, which will be discussed further.

Classification of explosions

Explosions can have a different nature, power. Occur in various environments (including vacuum). According to the nature of occurrence, explosions can be divided into:

physical (explosion of a burst balloon, etc.);
chemical (for example, an explosion of TNT);
nuclear and thermonuclear explosions.

Chemical explosions can occur in solid, liquid or gaseous substances, as well as air suspensions. The main ones in such explosions are redox reactions of the exothermic type, or exothermic decomposition reactions. An example of a chemical explosion is a grenade explosion.

Physical explosions occur when the tightness of containers with liquefied gas and other substances under pressure is violated. They can also be caused by thermal expansion of liquids or gases in the composition of a solid body, followed by a violation of the integrity of the crystal structure, which leads to a sharp destruction of the object and the appearance of an explosion effect.

Explosion power

The power of explosions can be different: from the usual loud pop due to a burst balloon or an exploded firecracker to giant cosmic explosions of supernovae.

The intensity of the explosion depends on the amount of energy released and the rate of its release. When evaluating the energy of a chemical explosion, such an indicator as the amount of heat released is used. The amount of energy in a physical explosion is determined by the amount of kinetic energy of the adiabatic expansion of vapors and gases.

man-made explosions

At an industrial enterprise, explosive objects are not uncommon, and therefore such types of explosions as air, ground and internal (inside a technical structure) can occur there. In coal mining, methane explosions are not uncommon, which is especially typical for deep coal mines, where, for this reason, there is a lack of ventilation. Moreover, different coal seams have different methane content, and therefore the level of explosive danger in the mines is different. Methane explosions are a big problem for the deep mines of Donbass, which requires increased control and monitoring of its content in the mine air.

Explosive objects are containers with liquefied gas or steam under pressure. Also military warehouses, containers with ammonium nitrate and many other objects.

The consequences of an explosion at work can be unpredictable, including tragic ones, among which the possible release of chemicals occupies a leading position.

The use of explosions

The explosion effect has long been used by mankind for various purposes, which can be divided into peaceful and military. In the first case, we are talking about the creation of directed explosions for the destruction of buildings to be demolished, ice jams on rivers, in the extraction of minerals, in construction. Thanks to them, the labor costs necessary for the implementation of the tasks set are significantly reduced.

An explosive is a chemical mixture that, under the influence of certain, easily achieved conditions, enters into a violent chemical reaction, leading to the rapid release of energy and a large amount of gas. By its nature, the explosion of such a substance is similar to combustion, only it proceeds at a tremendous speed.

External influences that can provoke an explosion are as follows:

mechanical impacts (for example, impact);
a chemical component associated with the addition of other components to the explosive that provoke the start of an explosive reaction;
temperature effects (heating of the explosive or sparks on it);
detonation from a nearby explosion.

The degree of response to external influences

The degree of reaction of an explosive to any of the influences is exclusively individual. So, some types of gunpowder ignite easily when heated, but remain inert under the influence of chemical and mechanical influences. TNT explodes from the detonation of other explosives, and it is not very sensitive to other factors. Mercury fulminate is undermined by all kinds of impacts, and some explosives can even explode spontaneously, making such compounds very dangerous and unsuitable for use.

How does an explosive detonate?

Different explosives explode in slightly different ways. For example, gunpowder is characterized by a rapid ignition reaction with the release of energy over a relatively long period of time. Therefore, it is used in military affairs to give speed to cartridges and projectiles without breaking their shells.

In another type of explosion (detonation), the explosive reaction propagates through the substance at supersonic speed, and it is also the cause. This leads to the fact that energy is released in a very short period of time and at a tremendous speed, so the metal capsules are torn apart from the inside. This type of explosion is typical for such dangerous explosives as RDX, TNT, ammonite, etc.

Explosive types

Features of sensitivity to external influences and indicators of explosive power make it possible to divide explosives into 3 main groups: propelling, initiating and blasting. Throwing powders include various types of gunpowder. This group includes low-power explosive mixtures for firecrackers and fireworks. In military affairs, they are used for the manufacture of lighting and signal rockets, as a source of energy for cartridges and shells.

A feature of initiating explosives is sensitivity to external factors. At the same time, they have low explosive power and heat dissipation. Therefore, they are used as a detonator for blasting and propellant explosives. They are carefully packaged to prevent self-destruction.

High explosives have the highest explosive power. They are used as fillings for bombs, shells, mines, rockets, etc. The most dangerous of them are hexogen, tetryl, and PETN. Less powerful explosives are TNT and plastid. Among the least powerful is ammonium nitrate. Brisant substances with high explosive power are also more sensitive to external influences, which makes them even more dangerous. Therefore, they are used in combination with less powerful or other components that lead to a decrease in sensitivity.

Explosive parameters

In accordance with the volumes and rate of energy and gas release, all explosives are evaluated according to such parameters as brisance and explosiveness. Brisatness characterizes the rate of energy release, which directly affects the destructive ability of the explosive.

Explosiveness determines the magnitude of the release of gases and energy, and hence the amount of work produced during the explosion.

In both parameters, hexogen is the leader, which is the most dangerous explosive.

So, we tried to answer the question of what an explosion is. And also considered the main types of explosions and methods of classification of explosives. We hope that after reading this article, you have got a general idea of what an explosion is.

An explosion is a fast-flowing process of physical and chemical transformations of substances, accompanied by the release of a significant amount of energy in a limited volume, as a result of which a shock wave is formed and propagates in the surrounding space, capable of leading or leading to an emergency of a man-made nature. As a result of the explosion, the substance filling the volume turns into a highly heated gas or plasma with a very high pressure, which causes the formation and propagation of a shock wave in the environment. An explosion occurs during chemical reactions, an electric discharge, exposure to a beam of light (from a quantum generator) on various materials, nuclear fission and fusion reactions.

The explosion is used in military (when conducting hostilities) and mining (when mining), in construction (when creating foundations and destroying old structures), mechanical engineering (explosive welding, explosive stamping), petrochemical industry (when performing technological operations, creating underground storage facilities), when destroying chemically and biologically hazardous substances, etc.

Recently, explosions have become one of the main types of terrorist attacks. The damaging factors of explosions are shock light, heat and radiation waves that can create a threat to human life and health, damage economic and other facilities and become a source of emergency situations.

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There are several types of explosions:

physical explosion - caused by a change in the physical state of matter. As a result of such an explosion, the substance turns into a gas with high pressure and temperature;
chemical explosion - caused by the rapid chemical transformation of substances, in which the potential chemical energy is converted into thermal and kinetic energy of expanding explosion products;
nuclear explosion - a powerful explosion caused by the release of nuclear energy either by a rapidly developing chain reaction of fission of heavy nuclei, or by a thermonuclear fusion reaction of helium nuclei from lighter nuclei;
- occurred as a result of a violation of production technology, errors of maintenance personnel or errors made during the design;
dust explosion - when the initial initiating pulse contributes to the perturbation of dust or gas, which leads to a subsequent powerful explosion;
pressure vessel explosion - an explosion of a vessel in which gases or liquids compressed under high pressure are stored in working condition, or an explosion in which the pressure increases as a result of external heating or self-ignition of the resulting mixture inside the vessel;
volume explosion - detonation or deflagration explosion of gas-air, dust-air and dust-gas clouds.

As a result of the explosion. the resulting highly heated gas or plasma with very high pressure with great force acts on the environment, causing it to move. The movement generated by the explosion, in which there is a sharp increase in pressure, density and temperature of the medium, is called a blast wave. The blast wave front propagates through the medium at high speed, as a result of which the area covered by the movement expands rapidly. The occurrence of a blast wave is a characteristic consequence of an explosion in various media.

If there is no medium, i.e. the explosion takes place in a vacuum, the energy is converted into kinetic energy of the explosion products flying in all directions at high speed. By means of a blast wave (or flying products in a vacuum), an explosion produces a mechanical effect on objects located at various distances from the explosion site.

As you move away from the explosion site, the mechanical effect of the blast wave weakens. Various types of explosions differ in the physical nature of the energy source and the way it is released. Typical examples are explosions of chemical explosives. They have the ability for rapid chemical decomposition, in which the energy of intermolecular bonds is released in the form of heat. They are characterized by an increase in the rate of chemical decomposition with increasing temperature. At a relatively low temperature, chemical decomposition proceeds very slowly, so that explosive substances may not undergo a noticeable change in their state for a long time. In this case, a thermal equilibrium is established between the explosives and the environment, in which continuously released small amounts of heat are removed outside the substance through heat conduction.

If conditions are created under which the released heat does not have time to be removed outside the explosive, then due to an increase in temperature, a self-accelerating process of chemical decomposition develops, which is called a thermal explosion. Due to the fact that heat is removed through the outer surface of the explosive, and its release occurs in the entire volume of the substance, thermal equilibrium can also be disturbed with an increase in the total mass of the explosive. This circumstance is taken into account when storing explosives.

Another process for the implementation of the explosion is possible, in which the chemical transformation propagates through the explosive substance sequentially, from layer to layer in the form of a wave. The leading front of such a wave moving at high speed is a shock wave - a sharp (jump-like) transition of a substance from its initial state to a state with very high pressure and temperature. An explosive substance compressed by a shock wave is in a state in which chemical decomposition proceeds very quickly.

As a result, the region in which the energy is released is concentrated in a thin layer adjacent to the surface of the shock wave. The release of energy ensures that the high pressure in the shock wave is maintained at a constant level. The process of chemical transformation of an explosive substance, which is introduced by a shock wave and is accompanied by a rapid release of energy, is called detonation. Detonation waves propagate through explosives at a very high speed, always exceeding the speed of sound in the original substance. For example, the detonation wave velocities in solid explosives are several km/s. A ton of solid explosive can be converted in this way into a dense gas at very high pressure in 10-4 seconds. The pressure in the resulting gases exceeds atmospheric pressure by several hundred thousand times. The effect of a chemical explosive explosion can be enhanced in a certain direction by the application of specially shaped explosive charges.

Nuclear transformations are associated with more fundamental transformations of substances. In a nuclear explosion, the transformation of atomic nuclei of the initial substance into the nuclei of other elements occurs, which is accompanied by the release of the binding energy of elementary particles (protons and neutrons) that make up the atomic nucleus.

It is based on the ability of certain isotopes of heavy elements of uranium or plutonium to fission, in which the nuclei of the original substance decay, forming nuclei of lighter elements. The fission of all the nuclei contained in 50 g of uranium or plutonium releases the same amount of energy as the detonation of 1000 tons of trinitrotoluene, so that nuclear transformation is capable of producing an explosion of enormous force. The fission of the nucleus of an atom of uranium or plutonium can occur as a result of the capture of one neutron by the nucleus. It is significant that as a result of fission, several new neutrons are produced, each of which can cause the fission of other nuclei.

As a result, the number of divisions will increase very quickly (according to the law of geometric progression). If we assume that with each fission event the number of neutrons capable of causing the fission of other nuclei doubles, then in less than 90 fission events such a number of neutrons is formed that is sufficient to fission the nuclei contained in 100 kg of uranium or plutonium. The time required for the division of this amount of matter will be ~ 10-6 s. This self-accelerating process is called a chain reaction. In reality, not all neutrons produced in fission cause the fission of other nuclei. If the total amount of fissile matter is small, then most of the neutrons will escape the matter without causing fission. There is always a small amount of free neutrons in fissile matter, but a chain reaction develops only when the number of newly formed neutrons exceeds the number of neutrons that do not produce fission. Such conditions are created when the mass of fissile material exceeds the so-called. critical mass. An explosion occurs when separate parts of a fissile material (the mass of each part is less than the critical mass) quickly join together with a total mass exceeding the critical mass, or with strong compression, which reduces the surface area of the substance and thereby reduces the number of neutrons escaping. To create such conditions, an explosion of a chemical explosive is usually used.

There is another type of nuclear reaction - the fusion of light nuclei, accompanied by the release of a large amount of energy. The repulsive forces of similar electric charges (all nuclei have a positive electric charge) prevent the fusion reaction from proceeding, therefore, for an effective nuclear transformation of this type, the nuclei must have high energy. Such conditions can be created by heating substances to very high temperatures. In this regard, the fusion process occurring at high temperature is called a thermonuclear reaction. During the fusion of deuterium nuclei (an isotope of hydrogen 2H), almost 3 times more energy is released than during the fission of the same mass of uranium. The temperature required for fusion is reached in a nuclear explosion of uranium or plutonium. Thus, if a fissile substance and isotopes of hydrogen are placed in the same device, a fusion reaction can be carried out, the result of which will be an explosion of enormous force. In addition to a powerful blast wave, a nuclear explosion is accompanied by intense emission of light and penetrating radiation.

In the types of explosions described above, the released energy was initially contained in the form of molecular or nuclear bond energy in matter. There are explosions in which the released energy is supplied from an external source. An example of such an explosion is a powerful electric discharge in any medium. Electrical energy in the discharge gap is released in the form of heat, turning the medium into an ionized gas with high pressure and temperature. A similar phenomenon occurs when a powerful electric current flows through a metal conductor, if the current strength is sufficient to quickly turn the metal conductor into steam. The explosion phenomenon also occurs when a substance is exposed to focused laser radiation. As one of the types of explosion, one can consider the process of rapid release of energy resulting from the sudden destruction of the shell that held the high pressure gas (for example, the explosion of a cylinder with compressed gas). An explosion can occur when solid bodies collide, moving towards each other at high speed, for example, with space speed. During a collision, the kinetic energy of bodies is converted into heat as a result of the propagation of a powerful shock wave through the substance that occurs at the moment of collision. The velocities of the relative approach of solid bodies, necessary for the substance to completely turn into vapor as a result of a collision, are measured in tens of km / s, and the pressures developing in this case amount to millions of atmospheres.

In nature, there are many phenomena that are accompanied by explosions: powerful electrical discharges in the atmosphere during a thunderstorm (lightning), sudden volcanic eruptions, large meteorites falling to the Earth's surface. As a result of the fall of the Tunguska meteorite (1907), an explosion occurred, equivalent in terms of the amount of energy released from the explosion to ~ 107 tons of trinitrotoluene.

V. have found wide application in scientific research and in industry. They made it possible to achieve significant progress in the study of the properties of gases, liquids and solids at high pressures and temperatures. The study of explosions plays an important role in the development of the physics of nonequilibrium processes, which studies the phenomena of mass, momentum, and energy transfer in various media, the mechanisms of phase transitions of matter, the kinetics of chemical reactions, and so on. Under the influence of an explosion, such states of substances can be achieved that are inaccessible with other methods of research. Powerful compression of the electric discharge channel by means of an explosion of a chemical substance makes it possible to obtain, within a short period of time, magnetic fields of enormous intensity [up to 1.1 Ga/m (up to 14 million Oe)]. The intense emission of light during the explosion of a chemical explosive in a gas can be used to excite an optical quantum generator (laser). Under the action of high pressure, which is created during the detonation of an explosive, explosive stamping, explosive welding and explosive hardening of metals are carried out.

Explosions are widely used in mineral exploration. Seismic waves reflected from different layers (elastic waves in the earth's crust) are recorded by seismographs. The analysis of seismograms makes it possible to draw a conclusion about the occurrence of oil, natural gas, and other minerals. Explosions are also widely used in the opening and development of mineral deposits. Almost no construction of dams, roads and tunnels in the mountains can do without blasting.

However, uncontrolled and unauthorized explosions of any nature are sources of emergency and catastrophic situations at most potentially dangerous civil and defense facilities, when hazardous natural processes occur on the Earth, the Sun, or other space objects.

The main methods of prevention and prevention of explosion. are many of the methods of emergency protection that provide increased explosion resistance of buildings, structures, pressure vessels, pipelines, mining facilities, military depots, granaries, tailings, production of chemical and nuclear explosives.

The basis for the justification of explosion resistance is the general theory of explosion, which gives an idea of all the damaging factors that accompany them.

Sufficiently reliable means of protection against explosions include bunkers, containments, spacesuits that create barriers to shock, thermal, light waves and radiation, as well as special systems with oriented multifocal destruction that dampen shock waves.

The issues of liquidation of the consequences of an explosion of various nature and in various environments are an extensive area of scientific research and practical development of the leading departments of the country (the Ministry of Defense of Russia, the Ministry of Emergency Situations of Russia, the Ministry of Transport of Russia, the Ministry of Natural Resources of Russia, etc.), as well as academic and industry research institutes, design and technology bureaus , government oversight bodies.