concept nuclear weapon combines explosive devices in which the energy of the explosion is generated by the fission or fusion of nuclei. In a narrow sense, under nuclear weapons understand explosive devices that use the energy released during the fission of heavy nuclei. Devices that use the energy released during the fusion of light nuclei are called thermonuclear.

Nuclear weapon

The nuclear reaction, the energy of which is used in nuclear explosive devices, consists in the fission of a nucleus as a result of the capture of a neutron by this nucleus. The absorption of a neutron can lead to the fission of almost any nucleus, however, for the vast majority of elements, the fission reaction is possible only if the neutron, before being absorbed by its nucleus, had an energy exceeding a certain threshold value. The possibility of practical use of nuclear energy in nuclear explosive devices or in nuclear reactors is due to the existence of elements whose nuclei are fissioned under the influence of neutrons of any energy, including arbitrarily small ones. Substances with this property are called fissile substances.

The only fissile material found in nature in appreciable quantities is an isotope of uranium with a nucleus mass of 235 atomic units masses (uranium-235). The content of this isotope in natural uranium is only 0.7%. The rest is uranium-238. Since the chemical properties of the isotopes are exactly the same, separating uranium-235 from natural uranium requires a rather complicated isotope separation process. As a result, one can get highly enriched uranium, containing about 94% uranium-235, which is suitable for use in nuclear weapons.

Fissile substances can be obtained artificially, and the least difficult from a practical point of view is obtaining plutonium-239, resulting from the capture of a neutron by a uranium-238 nucleus (and the subsequent chain of radioactive decays of intermediate nuclei). A similar process can be carried out in one that runs on natural or low-enriched uranium. In the future, plutonium can be separated from the spent fuel of the reactor in the process of chemical processing of fuel, which is much simpler than the isotope separation process carried out in the production of weapons-grade uranium.

Other fissile substances can also be used to create nuclear explosive devices, for example uranium-233 obtained by irradiation in a nuclear reactor of thorium-232. However, practical use found only uranium-235 and plutonium-239, primarily because of the relative ease of obtaining these materials.

The possibility of practical use of the energy released during nuclear fission is due to the fact that the fission reaction can have a chain, self-sustaining character. In each fission event, approximately two secondary neutrons are produced, which, being captured by the nuclei of the fissile material, can cause their fission, which in turn leads to the formation of even more neutrons. When special conditions are created, the number of neutrons, and hence the fission acts, grows from generation to generation.

The dependence of the number of fission events on time can be described using the so-called neutron multiplication factor k, equal to the difference between the number of neutrons produced in one fission event and the number of neutrons lost due to absorption that does not lead to fission, or due to going beyond the mass of the fissile material . The parameter k, therefore, corresponds to the number of fission events that causes the decay of one nucleus. If the parameter k is less than one, then the fission reaction does not have a chain character, since the number of neutrons capable of causing fission turns out to be less than their initial number. When the value k=1 is reached, the number of neutrons that cause fission, and hence the decay acts, does not change from generation to generation. The fission reaction acquires a chain self-sustaining character. The state of matter in which it occurs chain reaction division with k=1 is called critical. When k>1, one speaks of a supercritical state.

The dependence of the number of fission events on time can be represented as follows:

N=N o *exp((k-1)*t/T)

• N is the total number of fission events that occurred during the time t from the start of the reaction
• N0 is the number of nuclei undergoing fission in the first generation, k is the neutron multiplication factor,
• T is the time of "change of generations," i.e. the average time between successive fission events, the characteristic value of which is 10 -8 sec.

If we assume that the chain reaction begins with one fission event and the value of the multiplication factor is 2, then it is easy to estimate the number of generations required to release energy equivalent to the explosion of 1 kiloton of trinitrotoluene (10 12 calories or 4.1910 12 J). Since an energy equal to approximately 180 MeV (2.910 -11 J) is released in each fission event, 1.4510 23 decay acts must occur (which corresponds to the fission of approximately 57 g of fissile material). A similar number of decays will occur within about 53 generations of fissile nuclei. The entire process will take about 0.5 microseconds, with the bulk of the energy released over the last few generations. Extending the process by just a few generations will lead to a significant increase in the released energy. Thus, to increase the energy of an explosion by a factor of 10 (up to 100 kt), only five additional generations are needed.

The main parameter that determines the possibility of a fission chain reaction and the rate of energy release during this reaction is the neutron multiplication factor. This coefficient depends both on the properties of fissile nuclei, such as the number of secondary neutrons, the cross sections for fission and capture reactions, and on external factors that determine the loss of neutrons caused by their escape from the mass of the fissile material. The probability of neutron escape depends on geometric shape sample and increases with increasing surface area. The probability of neutron capture is proportional to the concentration of the nuclei of the fissile material and the length of the path that the neutron travels in the sample. If we take a spherical sample, then as the mass of the sample increases, the probability of neutron capture leading to fission increases faster than the probability of its escape, which leads to an increase in the multiplication factor. The mass at which a similar sample reaches the critical state (k=1) is called critical mass fissile material. For highly enriched uranium, the critical mass is about 52 kg, for weapons-grade plutonium, 11 kg. The critical mass can be reduced by about half by surrounding the sample of fissile material with a layer of material that reflects neutrons, such as beryllium or natural uranium.

A chain reaction is also possible in the presence of a smaller amount of fissile material. Since the capture probability is proportional to the concentration of nuclei, an increase in the density of the sample, for example, as a result of its compression, can lead to the appearance of a critical state in the sample. It is this method that is used in nuclear explosive devices, in which the mass of fissile material that is in a subcritical state is transferred to a supercritical state using a directed explosion that subjects the charge to a high degree of compression. The minimum amount of fissile material needed to carry out a chain reaction depends mainly on the degree of compression achievable in practice.

The degree and rate of compression of the mass of fissile material determine not only the amount of fissile material needed to create an explosive device, but also explosion power. The reason for this is the fact that the energy released during the chain reaction leads to a rapid heating of the mass of fissile material and, as a result, to the expansion of this mass. After a while, the charge loses its criticality and the chain reaction stops. Since the total energy of the explosion depends on the number of nuclei that managed to undergo fission during the time during which the charge was in the critical state, in order to obtain a sufficiently large explosion power, it is necessary to keep the mass of the fissile material in the critical state for as long as possible. In practice, this is achieved by rapidly compressing the charge using a directed explosion, so that at the moment the chain reaction begins, the mass of fissile material has a very large margin of criticality.

Since the charge is in a critical state during the compression process, it is necessary to eliminate extraneous sources of neutrons that can start a chain reaction even before the charge reaches the required degree of criticality. The premature start of the chain reaction will lead, firstly, to a decrease in the rate of energy release, and secondly, to an earlier charge expansion and loss of criticality. After the mass of the fissile material was in a critical state, the beginning of a chain reaction can be given by acts of spontaneous fission of uranium or plutonium nuclei. However, the intensity of spontaneous fission turns out to be insufficient to ensure the necessary degree of synchronization of the moment of the beginning of the chain reaction with the process of matter compression and to provide a sufficiently large number of neutrons in the first generation. To solve this problem in nuclear explosive devices, a special source of neutrons is used, which provides an "injection" of neutrons into the mass of fissile material. The moment of "injection" of neutrons must be carefully synchronized with the compression process, since too early start of the chain reaction will lead to a rapid start of the expansion of the fissile material and, consequently, to a significant decrease in the energy of the explosion.

The explosion of the first nuclear explosive device was carried out by the United States on July 16, 1945 in Alamogordo, New Mexico. The device was a plutonium bomb that used a directed explosion to create criticality. The power of the explosion was about 20 kt. In the USSR, the explosion of the first nuclear explosive device, similar to the American one, was carried out on August 29, 1949.

thermonuclear weapons

In thermonuclear weapons, the energy of the explosion is generated during the fusion reactions of light nuclei, such as deuterium, tritium, which are isotopes of hydrogen or lithium. Such reactions can only occur when high temperatures, at which the kinetic energy of the nuclei is sufficient for the approach of the nuclei to a sufficiently small distance. The temperatures that in question, are about 10 7 -10 8 K.

The use of fusion reactions to increase the power of the explosion can be done in different ways. The first way is to place a container with deuterium or tritium (or lithium deuteride) inside a conventional nuclear device. The high temperatures arising at the time of the explosion lead to the fact that the nuclei of light elements enter into a reaction, due to which additional energy is released. Using this method, you can significantly increase the power of the explosion. At the same time, the power of such an explosive device is still limited by the finite time of expansion of the fissile material.

Another way is to create multi-stage explosive devices, in which, due to the special configuration of the explosive device, the energy of a conventional nuclear charge (the so-called primary charge) is used to create the necessary temperatures in a separately located "secondary" thermonuclear charge, the energy of which, in turn, can be used to detonate the third charge, etc. The first test of such a device - the Mike explosion - was carried out in the USA on November 1, 1952. In the USSR, such a device was first tested on November 22, 1955. The power of an explosive device designed in this way can be arbitrarily large. The most powerful nuclear explosion was produced with the help of a multi-stage explosive device. The power of the explosion was 60 Mt, and the power of the device was used by only one third.

Sequence of events in a nuclear explosion

The release of a huge amount of energy, which occurs during the fission chain reaction, leads to a rapid heating of the substance of the explosive device to temperatures of the order of 10 7 K. At such temperatures, the substance is an intensely radiating ionized plasma. At this stage, about 80% of the explosion energy is released in the form of electromagnetic radiation energy. The maximum energy of this radiation, called primary, falls on the X-ray range of the spectrum. The further course of events during a nuclear explosion is determined mainly by the nature of the interaction of the primary thermal radiation with the environment surrounding the epicenter of the explosion, as well as by the properties of this environment.

If the explosion is made at a low altitude in the atmosphere, the primary radiation of the explosion is absorbed by the air at distances of the order of several meters. The absorption of X-rays results in the formation of an explosion cloud characterized by a very high temperature. In the first stage, this cloud grows in size due to the radiative transfer of energy from the hot inner part of the cloud to its cold surroundings. The temperature of the gas in a cloud is approximately constant over its volume and decreases as it increases. At the moment when the temperature of the cloud drops to about 300 thousand degrees, the speed of the cloud front decreases to values ​​comparable to the speed of sound. At this moment, the formation shock wave, the front of which "breaks away" from the boundary of the explosion cloud. For an explosion with a power of 20 kt, this event occurs approximately 0.1 ms after the explosion. The radius of the explosion cloud at this moment is about 12 meters.

The intensity of the thermal radiation of the explosion cloud is entirely determined by the apparent temperature of its surface. For some time, the air heated by the passage of the shock wave masks the explosion cloud by absorbing the radiation emitted by it, so that the temperature of the visible surface of the explosion cloud corresponds to the temperature of the air behind the shock wave front, which decreases as the size of the front increases. Approximately 10 milliseconds after the start of the explosion, the temperature in the front drops to 3000°C and it again becomes transparent to the radiation of the explosion cloud. The temperature of the visible surface of the explosion cloud again begins to rise and, approximately 0.1 sec after the onset of the explosion, reaches approximately 8000°C (for an explosion with a power of 20 kt). At this moment, the radiation power of the explosion cloud is maximum. After that, the temperature of the visible surface of the cloud and, accordingly, the energy radiated by it falls rapidly. As a result, the main part of the radiation energy is emitted in less than one second.

The formation of a thermal radiation pulse and the formation of a shock wave occur at the most early stages the existence of an explosion cloud. Since the cloud contains the bulk of the radioactive substances generated during the explosion, its further evolution determines the formation of a trace of radioactive fallout. After the explosion cloud cools down so much that it no longer radiates in the visible region of the spectrum, the process of increasing its size continues due to thermal expansion and it begins to rise upwards. In the process of lifting, the cloud carries with it a significant mass of air and soil. Within a few minutes, the cloud reaches a height of several kilometers and can reach the stratosphere. The rate at which radioactive fallout falls depends on the size of the solid particles on which it condenses. If, during its formation, the explosion cloud has reached the surface, the amount of soil entrained during the rise of the cloud will be large enough and radioactive substances will settle mainly on the surface of soil particles, the size of which can reach several millimeters. Such particles fall on the surface in relative proximity to the epicenter of the explosion, and their radioactivity practically does not decrease during the fallout.

If the explosion cloud does not touch the surface, the radioactive substances contained in it condense into much smaller particles with characteristic sizes of 0.01-20 microns. Since such particles can exist for quite a long time in the upper layers of the atmosphere, they scatter over a very large area and, in the time elapsed before they fall to the surface, have time to lose a significant proportion of their radioactivity. In this case radioactive trace practically not observed. The minimum height at which an explosion does not lead to the formation of a radioactive trace depends on the power of the explosion and is approximately 200 meters for a 20 kt explosion and about 1 km for a 1 Mt explosion.

The shock wave, which is formed in the early stages of the existence of an explosion cloud, is one of the main damaging factors of an atmospheric nuclear explosion. The main characteristics of a shock wave are the peak overpressure and the dynamic pressure in the wave front. The ability of objects to withstand the impact of a shock wave depends on many factors, such as the presence of load-bearing elements, building material, orientation in relation to the front. An overpressure of 1 atm (15 psi) at a distance of 2.5 km from a ground explosion with a yield of 1 Mt is capable of destroying a multi-story reinforced concrete building. To withstand the impact of the shock wave, military installations, especially ballistic missile silos, are designed in such a way that they can withstand overpressures of hundreds of atmospheres. The radius of the area in which a similar pressure is created during an explosion of 1 Mt is about 200 meters. Accordingly, to defeat fortified targets special role plays the accuracy of attacking ballistic missiles.

At the initial stages of the existence of a shock wave, its front is a sphere centered at the explosion point. After the front reaches the surface, a reflected wave is formed. Since the reflected wave propagates in the medium through which the direct wave has passed, the speed of its propagation is somewhat higher. As a result, at some distance from the epicenter, two waves merge near the surface, forming a front characterized by approximately twice the excess pressure values. Since for an explosion of a given power, the distance at which such a front forms depends on the height of the explosion, the height of the explosion can be chosen to obtain maximum values ​​of overpressure in a certain area. If the purpose of the explosion is to destroy fortified military installations, the optimal explosion height is very small, which inevitably leads to the formation of a significant amount of radioactive fallout.

Another damaging factor of nuclear weapons is penetrating, which is a stream of high-energy neutrons and gamma quanta, formed both directly during the explosion and as a result of the decay of fission products. Along with neutrons and gamma rays, alpha and beta particles are also formed in the course of nuclear reactions, the influence of which can be ignored due to the fact that they are very effectively retained at distances of the order of several meters. Neutrons and gamma quanta continue to be released for quite a long time after the explosion, affecting the radiation environment. The actual penetrating radiation usually includes neutrons and gamma quanta appearing within the first minute after the explosion. Such a definition is due to the fact that in a time of about one minute the explosion cloud has time to rise to a height sufficient to make the radiation flux on the surface almost imperceptible.

The intensity of the penetrating flow and the distance at which its action can cause significant damage depend on the power of the explosive device and its design. obtained at a distance of about 3 km from the epicenter of a thermonuclear explosion with a yield of 1 Mt is sufficient to cause serious biological changes in the human body. A nuclear explosive device can be specially designed to increase the damage caused by penetrating radiation compared to the damage caused by other damaging factors (the so-called neutron weapons).

The processes occurring during an explosion at a considerable height, where the air density is low, are somewhat different from those occurring during an explosion at low altitudes. First of all, due to the low density of air, the absorption of primary thermal radiation occurs at much greater distances and the size of the explosion cloud can reach tens of kilometers. The processes of interaction of ionized particles of the cloud with magnetic field Earth. Ionized particles formed during the explosion also have a noticeable effect on the state of the ionosphere, making it difficult and sometimes impossible for radio waves to propagate (this effect can be used to blind radar stations).

One of the results of a high-altitude explosion is the emergence of a powerful electromagnetic pulse spread over a very large area. electromagnetic pulse also arises as a result of an explosion at low altitudes, however, the strength of the electromagnetic field in this case quickly decreases with distance from the epicenter. In the case of a high-altitude explosion, the area of ​​action of the electromagnetic pulse covers almost the entire surface of the Earth visible from the explosion point.

If the explosion is made underground, at the initial stage of the explosion, absorption environment The primary thermal radiation leads to the formation of a cavity, the pressure in which rises to several million atmospheres in less than a microsecond. Further, within fractions of a second, a shock wave is formed in the surrounding rock, the front of which overtakes the propagation of the explosion cavity. The shock wave causes destruction of the rock in the immediate vicinity of the epicenter and, weakening as it moves, gives rise to a series of seismic impulses that accompany the underground explosion. The explosion cavity continues to expand at a slightly lower rate than at the beginning, eventually reaching a significant size. Thus, the radius of the cavity formed by an explosion with a power of 150 kt can reach 50 meters. At this stage, the walls of the cavity are molten rock. At the third stage, the gas inside the cavity cools down, and the molten rock solidifies at the bottom.

During the next stage, which can last from a few seconds to several hours, the pressure of the gases in the cavity drops so that they are no longer able to withstand the load of the upper layers of the rock, which collapse down. The result is a vertical cigar-shaped structure filled with rock fragments. The dimensions of this structure depend on the nature of the rock in which the explosion was made. A cavity filled with radioactive gases remains at the upper end of this structure. If the explosion occurred at an insufficiently large depth, some of the gases may come to the surface.

Is the most destructive of all existing species weapons. The number of stocks of nuclear weapons on Earth reaches such proportions that it is enough to destroy our planet several times.

1. ATOMIC BOMB: COMPOSITION, BATTLE CHARACTERISTICS AND PURPOSE OF CREATION

Before starting to study the structure of the atomic bomb, it is necessary to understand the terminology on this issue. So, in scientific circles, there are special terms that reflect the characteristics of atomic weapons. Among them, we highlight the following:

Atomic bomb- the original name of an aviation nuclear bomb, the action of which is based on an explosive chain nuclear fission reaction. With the advent of the so-called hydrogen bomb, based on a thermonuclear fusion reaction, a common term for them was established - a nuclear bomb.

A nuclear bomb is an aerial bomb with a nuclear charge that has great destructive power. The first two nuclear bombs with a TNT equivalent of about 20 kt each were dropped by American aircraft on the Japanese cities of Hiroshima and Nagasaki, respectively, on August 6 and 9, 1945, and caused enormous casualties and destruction. Modern nuclear bombs have a TNT equivalent of tens to millions of tons.

Nuclear or atomic weapons are explosive weapons based on the use of nuclear energy released during a chain nuclear fission reaction of heavy nuclei or a thermonuclear fusion reaction of light nuclei.

Related to weapons mass destruction(WMD) along with biological and chemical.

Nuclear weapons - a set of nuclear weapons, means of their delivery to the target and controls. Refers to weapons of mass destruction; has tremendous destructive power. For the above reason, the US and the USSR invested heavily in the development of nuclear weapons. According to the power of the charges and the range of action, nuclear weapons are divided into tactical, operational-tactical and strategic. The use of nuclear weapons in war is disastrous for all mankind.

A nuclear explosion is the process of instantaneous release of a large amount of intranuclear energy in a limited volume.

The action of atomic weapons is based on the fission reaction of heavy nuclei (uranium-235, plutonium-239 and, in some cases, uranium-233).

Uranium-235 is used in nuclear weapons because, unlike the more common isotope uranium-238, it can carry out a self-sustaining nuclear chain reaction.

Plutonium-239 is also referred to as "weapon-grade plutonium" because it is intended to create nuclear weapons and the content of the 239Pu isotope must be at least 93.5%.

To reflect the structure and composition of the atomic bomb, as a prototype, we analyze the plutonium bomb "Fat Man" (Fig. 1) dropped on August 9, 1945 on the Japanese city of Nagasaki.

atomic nuclear bomb explosion

Figure 1 - Atomic bomb "Fat Man"

The layout of this bomb (typical for plutonium single-phase munitions) is approximately the following:

Neutron initiator - a beryllium ball with a diameter of about 2 cm, covered with a thin layer of yttrium-polonium alloy or polonium-210 metal - the primary source of neutrons to sharply reduce the critical mass and accelerate the onset of the reaction. It fires at the moment of transferring the combat core to a supercritical state (during compression, a mixture of polonium and beryllium occurs with the release of a large number of neutrons). At present, in addition to this type of initiation, thermonuclear initiation (TI) is more common. Thermonuclear initiator (TI). It is located in the center of the charge (similar to NI) where a small amount of thermonuclear material is located, the center of which is heated by a converging shock wave and, in the process of a thermonuclear reaction, against the background of the temperatures that have arisen, a significant amount of neutrons is produced, sufficient for the neutron initiation of a chain reaction (Fig. 2).

Plutonium. Use the purest plutonium-239 isotope, although to increase stability physical properties(density) and improve the compressibility of the charge plutonium is doped with a small amount of gallium.

A shell (usually made of uranium) that serves as a neutron reflector.

Compression sheath made of aluminium. Provides greater uniformity of compression by a shock wave, while at the same time protecting the internal parts of the charge from direct contact with explosives and hot products of its decomposition.

An explosive with a complex detonation system that ensures the detonation of the entire explosive is synchronized. Synchronicity is necessary to create a strictly spherical compressive (directed inside the ball) shock wave. A non-spherical wave leads to the ejection of the material of the ball through inhomogeneity and the impossibility of creating a critical mass. The creation of such a system for the location of explosives and detonation was at one time one of the most difficult tasks. A combined scheme (lens system) of "fast" and "slow" explosives is used.

Body made of duralumin stamped elements - two spherical covers and a belt connected by bolts.

Figure 2 - The principle of operation of the plutonium bomb

The center of a nuclear explosion is the point at which a flash occurs or the center of the fireball is located, and the epicenter is the projection of the explosion center onto the earth or water surface.

Nuclear weapons are the most powerful and dangerous type of weapons of mass destruction, threatening all mankind with unprecedented destruction and destruction of millions of people.

If an explosion occurs on the ground or fairly close to its surface, then part of the energy of the explosion is transferred to the Earth's surface in the form of seismic vibrations. A phenomenon occurs, which in its features resembles an earthquake. As a result of such an explosion, seismic waves are formed, which propagate through the thickness of the earth over very long distances. The destructive effect of the wave is limited to a radius of several hundred meters.

As a result of the extremely high temperature of the explosion, a bright flash of light occurs, the intensity of which is hundreds of times greater than the intensity sun rays falling to the earth. A flash releases a huge amount of heat and light. Light radiation causes spontaneous combustion of flammable materials and burns the skin of people within a radius of many kilometers.

A nuclear explosion produces radiation. It lasts about a minute and has such a high penetrating power that powerful and reliable shelters are required to protect against it at close distances.

A nuclear explosion is capable of instantly destroying or incapacitating unprotected people, openly standing equipment, structures and various materiel. The main damaging factors of a nuclear explosion (PFYAV) are:

shock wave;

light radiation;

penetrating radiation;

radioactive contamination of the area;

electromagnetic pulse (EMP).

During a nuclear explosion in the atmosphere, the distribution of the released energy between the PNFs is approximately the following: about 50% for the shock wave, 35% for the share of light radiation, 10% for radioactive contamination, and 5% for penetrating radiation and EMP.

Radioactive contamination of people, military equipment, terrain and various objects during a nuclear explosion is caused by fission fragments of the charge substance (Pu-239, U-235) and the unreacted part of the charge falling out of the explosion cloud, as well as radioactive isotopes formed in the soil and other materials under the influence of neutrons - induced activity. Over time, the activity of fission fragments rapidly decreases, especially in the first hours after the explosion. So, for example, the total activity of fission fragments in the explosion of a nuclear weapon with a power of 20 kT in one day will be several thousand times less than one minute after the explosion.

Analysis of the effectiveness of the integrated application of anti-jamming measures to improve the stability of the functioning of communication facilities in the conditions of enemy radio countermeasures

Given the level technical equipment, the analysis of the forces and means of electronic warfare will be carried out for the reconnaissance and electronic warfare battalion (R and EW) of the mechanized division (md) SV. Reconnaissance and electronic warfare battalion of the US Ministry of Defense includes)