Atomic weapons. What is the difference between atomic, nuclear and hydrogen bombs? What nuclear weapons look like

But this is something we often do not know. And why does a nuclear bomb explode, too ...

Let's start from afar. Every atom has a nucleus, and the nucleus consists of protons and neutrons - everyone knows this, perhaps. In the same way, everyone saw the periodic table. But why are the chemical elements located in it exactly like this and not otherwise? Certainly not because Mendeleev so wanted. The ordinal number of each element in the table indicates how many protons are in the nucleus of an atom of this element. In other words, iron is number 26 in the table, because the iron atom has 26 protons. And if there are not 26 of them, this is no longer iron.

But the number of neutrons in the nuclei of the same element can be different, which means that the mass of the nuclei is different. Atoms of the same element with different masses are called isotopes. Uranium has several such isotopes: the most widespread in nature is uranium-238 (in its nucleus there are 92 protons and 146 neutrons, together it turns out 238). It is radioactive, but you cannot make a nuclear bomb from it. But the isotope uranium-235, a small amount of which is found in uranium ores, is suitable for a nuclear charge.

The reader may have come across the expressions "enriched uranium" and "depleted uranium". Enriched uranium contains more uranium-235 than natural uranium; in depleted, respectively - less. Enriched uranium can be used to obtain plutonium, another element suitable for a nuclear bomb (it hardly occurs in nature). How uranium is enriched and how plutonium is obtained from it is a topic for another conversation.

So why does a nuclear bomb explode? The fact is that some heavy nuclei tend to decay if a neutron hits them. And you won't have to wait long for a free neutron - there are a lot of them flying around. So, such a neutron gets into the uranium-235 nucleus and thereby breaks it into "fragments". This releases a few more neutrons. Can you guess what happens if there are nuclei of the same element around? That's right, a chain reaction will happen. This is how it goes.

In a nuclear reactor, where uranium-235 is "dissolved" in the more stable uranium-238, an explosion does not occur under normal conditions. Most of the neutrons that are emitted from decaying nuclei fly away "into milk", not finding uranium-235 nuclei. In the reactor, the decay of nuclei is "sluggish" (but this is enough for the reactor to give energy). Here in a single piece of uranium-235, if it is of sufficient mass, neutrons are guaranteed to break nuclei, the chain reaction will go like an avalanche, and ... Stop! After all, if you make a piece of uranium-235 or plutonium of the mass necessary for an explosion, it will immediately explode. This is not the case.

And if you take two pieces of subcritical mass, and push them against each other using a remote control mechanism? For example, place both in a tube and attach a powder charge to one in order to shoot one piece, like a projectile, into another at the right time. Here is the solution to the problem.

You can do otherwise: take a spherical piece of plutonium and fix explosive charges over its entire surface. When these charges detonate on command from the outside, their explosion will squeeze the plutonium from all sides, squeeze it to a critical density, and a chain reaction will occur. However, accuracy and reliability are important here: all explosive charges must work at the same time. If some of them work, and some do not, or some of them work with a delay, no nuclear explosion will emerge: plutonium will not be compressed to a critical mass, but will dissipate in the air. Instead of a nuclear bomb, you get the so-called "dirty" one.

This is what an implosion-type nuclear bomb looks like. The charges, which should create a directed explosion, are made in the form of polyhedrons in order to cover the surface of the plutonium sphere as closely as possible.

The device of the first type was called cannon, of the second type - implosion.
The bomb "Malysh" dropped on Hiroshima had a charge of uranium-235 and a cannon-type device. The Fat Man bomb detonated over Nagasaki carried a plutonium charge, and the explosive device was implosive. Nowadays, cannon-type devices are almost never used; implosion is more complicated, but at the same time they allow regulating the mass of a nuclear charge and spending it more rationally. And plutonium replaced uranium-235 as a nuclear explosive.

Quite a few years passed, and physicists offered the military an even more powerful bomb - thermonuclear, or, as it is also called, hydrogen. So hydrogen explodes stronger than plutonium?

Hydrogen is really explosive, but not that explosive. However, there is no "ordinary" hydrogen in a hydrogen bomb, it uses its isotopes - deuterium and tritium. The nucleus of "ordinary" hydrogen has one neutron, deuterium has two, and tritium has three.

In a nuclear bomb, the nuclei of the heavy element are divided into nuclei of the lighter ones. In a thermonuclear one, the reverse process is going on: light nuclei merge with each other into heavier ones. The nuclei of deuterium and tritium, for example, combine to form helium nuclei (otherwise called alpha particles), and the "extra" neutron is sent into "free flight." In this case, much more energy is released than during the decay of plutonium nuclei. By the way, it is this process that takes place on the Sun.

However, the fusion reaction is possible only at ultra-high temperatures (which is why it is called THERMONUCLEAR). How to get deuterium and tritium to react? It's very simple: you need to use a nuclear bomb as a detonator!

Since deuterium and tritium are themselves stable, their charge in a thermonuclear bomb can be arbitrarily huge. This means that a thermonuclear bomb can be made incomparably more powerful than a "simple" nuclear one. The "Kid" dropped on Hiroshima had a TNT equivalent within 18 kilotons, and the most powerful hydrogen bomb (the so-called "Tsar Bomba", aka "Kuz'kina's Mother") was already 58.6 megatons, more than 3255 times more powerful "Baby"!


The “mushroom” cloud from the Tsar Bomba rose to a height of 67 kilometers, and the blast wave circled the globe three times.

However, such a gigantic capacity is clearly excessive. Having "played enough" with megaton bombs, military engineers and physicists took a different path - the path of miniaturization of nuclear weapons. In its usual form, nuclear weapons can be dropped from strategic bombers, like aerial bombs, or launched with ballistic missiles; if you miniaturize them, you get a compact nuclear charge that does not destroy everything for kilometers around, and which can be placed on an artillery shell or an air-to-ground missile. Mobility will increase, the range of tasks to be solved will expand. In addition to strategic nuclear weapons, we will get tactical ones.

A variety of delivery vehicles have been developed for tactical nuclear weapons - nuclear cannons, mortars, recoilless weapons (for example, the American Davy Crockett). The USSR even had a project for a nuclear bullet. True, they had to abandon it - nuclear bullets were so unreliable, so complex and expensive to manufacture and store, that there was no point in them.

Davy Crockett. A number of these nuclear weapons were in service with the US Armed Forces, and the West German Defense Minister unsuccessfully sought to equip the Bundeswehr with them.

Speaking of small nuclear weapons, it is worth mentioning another type of nuclear weapon - the neutron bomb. The plutonium charge in it is small, but this is not necessary. If the thermonuclear bomb goes along the path of increasing the force of the explosion, then the neutron bomb relies on another damaging factor - radiation. To amplify radiation in a neutron bomb there is a reserve of beryllium isotope, which, when exploded, gives a huge amount of fast neutrons.

As conceived by its creators, the neutron bomb should kill the enemy's manpower, but leave intact the equipment, which can then be captured during the offensive. In practice, it turned out a little differently: the irradiated equipment becomes unusable - anyone who dares to pilot it will very soon "earn" radiation sickness. This does not negate the fact that the explosion of a neutron bomb is capable of hitting the enemy through tank armor; neutron ammunition was developed by the United States precisely as a weapon against Soviet tank formations. However, tank armor was soon developed, providing some kind of protection from the flux of fast neutrons.

Another type of nuclear weapon was invented in 1950, but never (as far as is known) was produced. This is the so-called cobalt bomb - a nuclear charge with a cobalt shell. In an explosion, cobalt, irradiated by a flux of neutrons, becomes an extremely radioactive isotope and scatters over the area, contaminating it. Just one such bomb of sufficient power could cover the entire globe with cobalt and destroy all of humanity. Fortunately, this project remained a project.

What can be said in conclusion? The nuclear bomb is indeed a terrible weapon, and at the same time it (what a paradox!) Helped to maintain relative peace between the superpowers. If your opponent has nuclear weapons, you will think ten times before attacking him. No country with a nuclear arsenal has yet been attacked from outside, and since 1945 there have been no wars between major states in the world. Let's hope there won't be any.

World science does not stand still. Penetration into the secrets of the structure of the atomic nucleus has given humanity effective and cheap energy, new diagnostic technologies. However, research in this area has led to the creation of nuclear weapons and terrible catastrophes, resulting in a huge number of deaths, the destruction of cities and the contamination of many kilometers of the earth's surface.

The debate about the pros and cons of scientific discoveries in this area continues to this day.

History of creation

Prerequisites

The military-political situation and the powerful development of scientific theories in the 20th century created real preconditions for the emergence of weapons of mass destruction.

However, the first brick in the construction of an atomic bomb can be considered the discovery (in 1896) by Antoine Henri Becquerel of the radioactivity of uranium. Maria Sklodowska-Curie and Pierre Curie conducted their research in the same vein. Already in 1913 they created their own scientific institution (Radium Institute) to study radioactivity.

Two more important discoveries in this area: the planetary model of the atom and the successful experiments on nuclear fission, significantly accelerated the emergence of new weapons.

In 1934, the first patent was issued, which described a nuclear reactor (Leo Szilard), and in 1939, a uranium bomb was patented by Frederic Joliot-Curie.

Three countries of the world began their struggle for the palm in the production of nuclear weapons.

German program

Start

In 1939-1945, scientists from Nazi Germany were engaged in the creation of the atomic bomb. This program was called the "Uranium Project" and was highly classified. Her plans included the creation of weapons within nine to twelve months. The project brought together about 22 scientific organizations, which included the most famous institutions of the country.

Albert Speer and Erich Schumann were appointed at the head of the secret company.

To create a superweapon, the production of uranium fluoride was launched, from which uranium-235 could be obtained, and a special device for isotope separation using the Clusius-Dickel method was developed. This installation consisted of two pipes, one of which was to be heated and the other cooled. Between them, uranium hexafluoride in a gaseous state was supposed to move, which would make it possible to separate the lighter uranium -235 and heavy uranium-238.

Based on the theoretical calculations for the design of a nuclear reactor, provided by Werner Heisenberg, Auerge received an order to produce a certain amount of uranium. Norwegian Norsk Hydro provided deuterium oxide (heavy hydrogen water).

In 1940, the Physics Institute, which dealt with atomic energy, was taken over by the armed forces.

Failures

However, despite the fact that a huge number of scientists worked on the project during the year, the assembled device for separating isotopes did not work. About five more options for uranium enrichment were developed, which also did not lead to success.

It is believed that the reasons for the failed experiments are the lack of heavy hydrogen water and insufficiently purified graphite. Only at the beginning of 1942, the Germans were able to build the first reactor, which exploded after a while. Subsequent experiments were hampered by the destruction of a deuterium oxide plant in Norway.

The latest data on conducting experiments that make it possible to obtain a chain reaction was dated January 1945, but at the end of the month the installation had to be dismantled and sent further from the front line to Haigerloch. The last trial of the device was scheduled for March - April. It is believed that scientists could get a positive result in a short time, but this was not destined to happen as the Allied troops entered the city.

At the end of World War II, the German reactor was exported to America.

American program

Prerequisites

The first developments related to atomic energy were carried out by America, together with Canada, Germany and England. The program was called the "Uranium Committee". The project was led by two people - a scientist and a military man, physicist Robert Oppenheimer and General Leslie Groves. Especially to cover the work, a special part of the troops was formed - the Manhattan Engineering District, of which Groves was appointed commander.

In mid-1939, President Roosevelt received a letter signed by Albert Einstein stating that Germany was developing the latest superweapon. A special organization, the Uranium Committee, was appointed to find out how real Einstein's words were. Already in October, the news about the possibility of creating weapons was confirmed and the committee began its active work.

Gadget

"Project Manhattan"

In 1943, the Manhattan Project was created in the United States, whose goal was to create nuclear weapons. Famous scientists from allied countries, as well as a huge number of construction workers and military personnel, participated in the development.

Uranium was the main raw material for experiments, but the composition of the natural fossil contains only 0.7% of the uranium-235 required for the production. Therefore, it was decided to conduct research on the separation and enrichment of this element.

For this, technologies of thermal and gas diffusion, as well as electromagnetic separation were used. At the end of 1942, the construction of a special installation for producing gas diffusion was approved.

Fact. Despite the fact that scientists from England, Canada, America and Germany worked in the project, the United States refused to share the research results with England, which served to develop some tension between the allied countries.

The main goal of the research was set: to create a nuclear bomb in 1945, which was achieved by scientists who were part of the Manhattan Project.

Implementation

The result of the activities of this organization was the creation of three bombs:

• Gadget based on plutonium-239;
• Little Boy (Kid) uranium;
• Fat Man (Fat Man) based on the decay of plutonium-239.

Little Boy and Fat Man were dropped into Japan in August 1945, causing irreparable damage to the country's population.

Nuclear bomb kid and fat man

Theory and development

Back in 1920, the Radium Institute was established in the USSR, which was engaged in fundamental research on radioactivity. Already in the middle of the 20th century (from 1930 to 1940), active work was carried out in the Soviet Union related to the production of nuclear energy.

In 1940, prominent Russian scientists appealed to the government, speaking of the need to develop a practical base in the atomic field. Thanks to this, a special organization (Commission on the Uranium Problem) was created, and V.G. Khlopin was appointed its chairman. During the year, a tremendous amount of work was done to organize and coordinate the institutions that were part of it. However, the war broke out, and most of the scientific institutes had to be evacuated to. Kazan. In the rear, theoretical work on the development of this industry continued.

In September 1942, almost immediately after the start of the American Manhattan project, the USSR government decided to begin work on the study of uranium. For this, special premises were allocated for the laboratory in Kazan. The research report was scheduled for April 1943. And in February 1943, practical work began on the creation of an atomic bomb.

Practical developments

After the return of the Radium Institute to Leningrad (1944), the scientists began the practical implementation of their projects. It is believed that December 5, 1945 is the start date of work on the development of atomic energy.

Research was carried out in the following areas:

• study of radioactive plutonium;
• plutonium separation experiments;
• development of technology for obtaining plutonium from uranium.

After the bombing of Japan, the State Defense Committee issued a decree establishing a Special Committee on the Use of Atomic Energy. The First Main Directorate was established to manage this project. A huge amount of human and material resources was thrown into the solution of the task. Stalin's directive ordered the creation of uranium and plutonium bombs no later than 1948.

Development

The primary tasks of the project were the opening of the production of industrial plutonium and uranium and the construction of a nuclear reactor. To separate isotopes, it was decided to use the diffusion method. Secret enterprises needed to resolve these issues began to be built with great speed. The technical documentation for this weapon was supposed to be ready by July 1946, and the assembled structures already in 1948.

Thanks to the colossal human resource and powerful material base, the transition from theory to practical experiments took place in a short time. The first reactor was built and successfully launched in December 1946. And already in August 1949, the first atomic bomb was successfully tested.

The first test of the atomic bomb in the Soviet Union

Bomb device

Main components:

• body;
• automatic system;
• nuclear charge.

The hull is made of durable and reliable metal that can protect the warhead from negative external factors. In particular, from temperature changes, mechanical damage or other influences that can cause an unplanned explosion.

Automation controls the following functions:

• safety devices;
• cocking mechanism;
• emergency blasting device;
• nutrition;
• subversive system (charge detonation sensor).

A nuclear charge is a device that contains a supply of certain substances and provides the release of energy directly for an explosion.

Operating principle

At the heart of any nuclear weapon is a chain reaction - a process in which a chain fission of atomic nuclei occurs and powerful energy is released.

Criticality can be reached by a variety of factors. There are substances capable of or not capable of a chain reaction, in particular Uranium-235 and Plutonium-239, which are used in the manufacture of this type of weapon.

In uranium-235, the fission of a heavy nucleus can be excited by one neutron, and as a result of the process, 2 to 3 neutrons appear. Thus, a branched chain reaction is generated. In this case, neutrons are its carriers.

Natural uranium consists of 3 isotopes - 234, 235 and 238. However, the content of Uranium-235 required to maintain a chain reaction is only about 0.72%. Therefore, for industrial purposes, isotope separation is carried out. An alternative is the use of Plutonium-239. This element is obtained artificially, in the process of irradiation of Uranus - 238 neutrons.

When a uranium or plutonium bomb explodes, two key points can be distinguished:

• the immediate center of the explosion, where the chain reaction takes place;
• the explosion projection onto the surface is the epicenter.

RDS-1 in section

Damage factors in a nuclear explosion

Types of atomic bomb damage:

• shock wave;
• light and heat radiation;
• electromagnetic influence;
• radioactive contamination;
• penetrating radiation.

The shock blast wave destroys buildings and equipment, damages people. This is facilitated by the sharp pressure drop and high air velocity.

The explosion releases a huge amount of light and heat energy. Damage by this energy can spread over several thousand meters. The brightest light hits the visual apparatus, and the high temperature ignites flammable substances and causes burns.

Electromagnetic impulses damage electronics and damage radio communications.

Radiation infects the surface of the earth in the focus of damage and causes neutron activation of substances in the soil. Penetrating radiation destroys all systems of the human body and causes radiation sickness.

Classification of nuclear weapons

There are two classes of warheads:

• atomic;
• thermonuclear.

The first are devices of the single-stage (single-phase) type, the generation of energy in which occurs during the fission of heavy nuclei (using uranium or plutonium) to obtain lighter elements.

The second - devices with a two-stage (two-phase) mechanism of action, there is a sequential development of two physical processes (chain reaction and thermonuclear fusion).

Another important indicator of nuclear weapons is their power, which is measured in TNT equivalent.

Today there are five such groups:

• less than 1 kt (kilotons) - ultra-low power;
• from 1 to 10 kt - small;
• from 10 to 100 kt - medium;
• 100 to 1 Mt (megatons) - large;
• more than 1 Mt - extra large.

Fact. It is believed that the explosion at the Chernobyl nuclear power plant had a capacity of about 75 tons.

Detonation options

Detonation can be provided by connecting two main circuits or a combination of them.

Ballistic or cannon scheme

Its use is possible only in charges containing uranium. To carry out an explosion, one block is fired, containing a fissile substance with a subcritical mass, into another block, which is motionless.

Implosive scheme

An inward-directed explosion is produced by compressing the fuel, during which the subcritical mass of the fissile material becomes supercritical.

Delivery vehicles

Nuclear warheads can deliver almost modern missiles to the target, which can be placed inside the ammunition.

There is a division of delivery vehicles into the following groups:

• tactical (means of destruction of air, sea and space targets), designed to destroy military equipment and human resources of the enemy on the front line and in the immediate rear;
• strategic - the defeat of strategic targets (in particular, administrative units and industrial enterprises located in the rear of the enemy);
• operational-tactical destruction of targets that are in the range of operational depth.

The most powerful bomb in the world

The so-called Tsar Bomba (AN602 or Ivan) is considered such a warhead. The weapon was developed in Russia by a group of nuclear physicists. Academician I. V. Kurchatov supervised the project. It is the most powerful thermonuclear explosive device in the world that has been successfully tested. The charge power is about 58.6 megatons (in TNT equivalent), which exceeded the design characteristics by almost 7 Mt. Testing mega-weapons were carried out on October 30, 1961.

Bomb AN602

The AN602 bomb is included in the Guinness Book of Records.

The atomic bombings of Hiroshima and Nagasaki

At the end of World War II, the United States decided to demonstrate the presence of weapons of mass destruction. This was the only military use of nuclear bombs in history.

In August 1945, nuclear warheads were dropped on Japan, which fought on the side of Germany. The cities of Hiroshima and Nagasaki were almost completely razed to the ground. Records indicate that about 166,000 people died in Hiroshima, and 80,000 in Nagasaki. However, a huge number of Japanese victims of the explosion died some time after the bombing or continued to get sick for many years. This is due to the fact that penetrating radiation causes disturbances in all systems of the human body.

At that time, the concept of radioactive contamination of the earth's surface did not exist, so people continued to be in the area exposed to radiation. High mortality, genetic deformities in newborns and the development of oncological diseases were not then associated with explosions.

Danger of war and disaster associated with the atom

Nuclear power and weapons have been and remain the subject of the most heated debate. Since it is impossible to realistically assess security in this area. The presence of super-powerful weapons, on the one hand, is a deterrent, however, on the other hand, its use can cause a large-scale global catastrophe.

The danger of any nuclear industry is primarily associated with the disposal of waste, which for a long time still emit a high background radiation. And also with the safe and efficient operation of all production compartments. There are more than 20 cases when the “peaceful atom” got out of control and caused colossal losses. One of the biggest disasters is considered the accident at the Chernobyl nuclear power plant.

Conclusion

Nuclear weapons are considered one of the most powerful tools in world politics in the arsenal of some countries. On the one hand, this is a serious argument for preventing military clashes and strengthening peace, but on the other, it is the cause of possible large-scale accidents and disasters.

On the day of the 70th anniversary of the testing of the first Soviet atomic bomb, Izvestia publishes unique photographs and memoirs of eyewitnesses of the events that took place at the Semipalatinsk test site. New materials shed light on the situation in which scientists created a nuclear device - in particular, it became known that Igor Kurchatov used to hold secret meetings on the banks of the river. Also very interesting are the details of the construction of the first reactors for producing weapons-grade plutonium. The role of intelligence in accelerating the Soviet nuclear project should also be noted.

Young but promising

The need for the early development of Soviet nuclear weapons became apparent when, in 1942, intelligence reports revealed that scientists in the United States were far advanced in nuclear research.Indirectly, this was also indicated by the complete cessation of scientific publications on this topic back in 1940. Everything indicated that work on the creation of the most powerful bomb in the world was in full swing.

On September 28, 1942, Stalin signed a secret document "On the organization of work on uranium."

The leadership of the Soviet atomic project was entrusted to the young and energetic physicist Igor Kurchatov, who, as his friend and colleague Academician Anatoly Aleksandrov later recalled, "has long been perceived as the organizer and coordinator of all work in the field of nuclear physics." However, the scale of the works mentioned by the scientist was still small at that time - in the USSR, in the specially created in 1943 Laboratory No. 2 (now the Kurchatov Institute), only 100 people were engaged in the development of nuclear weapons, while in the USA about 50 thousand specialists worked on a similar project.

Therefore, the work in Laboratory No. 2 was carried out at an urgent pace, which required both the supply and creation of the latest materials and equipment (and this in wartime!), And the study of intelligence data, which managed to get some information about American research.

“Intelligence helped speed up the work and cut our efforts by about a year,” said Andrei Gagarinsky, advisor to the director of the Kurchatov Institute. - In Kurchatov's "reviews" about intelligence materials, Igor Vasilyevich essentially gave scouts assignments, which scientists would like to know about.

Not existing in nature

Scientists from Laboratory No. 2 transported a cyclotron from the newly liberated Leningrad, which was launched back in 1937 - then it became the first in Europe. This facility was necessary for neutron irradiation of uranium.So it was possible to accumulate the initial amount of plutonium that does not exist in nature, which later became the main material for the first Soviet atomic bomb RDS-1.

Then the production of this element was established with the help of the first in Eurasia atomic reactor F-1 on uranium-graphite blocks, which was built in Laboratory No. 2 in the shortest possible time (in just 16 months) and launched on December 25, 1946 under the leadership of Igor Kurchatov.

The physicists achieved industrial volumes of plutonium release after the construction of a reactor under the letter A in the city of Ozersk, Chelyabinsk region (scientists also called it "Annushka") - the installation reached its design capacity on June 22, 1948, which has already brought the project to create a nuclear charge very close.

In the sphere of compression

The first Soviet atomic bomb had a charge of plutonium with a capacity of 20 kilotons, which was located in two hemispheres separated from each other.Inside them was the initiator of a chain reaction from beryllium and polonium, when combined, neutrons are released, starting a chain reaction. For powerful compression of all these components, a spherical shock wave was used, which appeared after the detonation of a round shell of explosives surrounding the plutonium charge. The outer case of the resulting product had a teardrop shape, and its total mass was 4.7 tons.

They decided to test the bomb at the Semipalatinsk test site, which was specially equipped in order to assess the impact of the explosion on a variety of buildings, equipment and even animals.

Photo: RFNC-VNIIEF Museum of Nuclear Weapons

–– In the center of the landfill there was a high iron tower, and around it, like mushrooms, a variety of buildings and structures grew: brick, concrete and wooden houses with different types of roofing, cars, tanks, ship gun turrets, a railway bridge and even a swimming pool, - notes in Nikolai Vlasov, a participant in those events, in his manuscript "First Trials". - So, in terms of the variety of objects, the polygon resembled a fair - only without people who were almost invisible here (with the exception of the rare lonely figures who completed the installation of the equipment).

There was also a biological sector on the territory, where there were pens and cages with experimental animals.

Shore meetings

Remained with Vlasov and memories of the attitude of the team to the project manager during the testing period.

“At this time, Kurchatov's nickname Beard was already firmly established (he changed his appearance in 1942), and his popularity encompassed not only the learned fraternity of all specialties, but also officers and soldiers,” writes an eyewitness. –– The team leaders were proud to meet with him.

Some highly secret interviews Kurchatov conducted in an informal setting - for example, on the river bank, inviting the right person for a swim.

A photo exhibition dedicated to the history of the Kurchatov Institute, which celebrates its 75th anniversary this year, has opened in Moscow. A selection of unique archival footage depicting the work of both ordinary employees and the most famous physicist Igor Kurchatov - in the gallery of the portal site

Igor Kurchatov, a physicist, was one of the first in the USSR to study the physics of the atomic nucleus, he is also called the father of the atomic bomb. In the photo: a scientist at the Physics and Technology Institute in Leningrad, 1930s

Photo: Archive of the National Research Center "Kurchatov Institute"

The Kurchatov Institute was founded in 1943. At first it was called Laboratory No. 2 of the Academy of Sciences of the USSR, whose employees were engaged in the creation of nuclear weapons. Later the laboratory was renamed into the Institute of Atomic Energy named after I.V. Kurchatov, and in 1991 - to the National Research Center

Photo: Archive of the National Research Center "Kurchatov Institute"

Today the Kurchatov Institute is one of the largest research centers in Russia. Its specialists are engaged in research in the field of safe development of nuclear power. Photo: accelerator "Fakel"

Photo: Archive of the National Research Center "Kurchatov Institute"

The end of the monopoly

The scientists calculated the exact time of the tests in such a way that the wind carried away the radioactive cloud formed as a result of the explosion in the direction of uninhabited territories.and the impact of harmful rainfall on humans and livestock was minimal. As a result of such calculations, the historic explosion was scheduled for the morning of August 29, 1949.

–– In the south, a glow broke out and a red semicircle appeared, similar to the rising sun, –– Nikolay Vlasov recalls. –– And three minutes after the glow died down and the cloud dissolved in the predawn haze, we heard the roaring roar of the explosion, similar to the distant thunder of a mighty thunderstorm.

Arriving at the place of operation of the RDS-1, (see help), scientists could assess all the destruction that followed.According to them, there were no traces left of the central tower, the walls of the nearest houses collapsed, and the water in the pool completely evaporated from the high temperature.

But this destruction, paradoxically, helped to establish a global balance in the world. The creation of the first Soviet atomic bomb ended the US monopoly on nuclear weapons.This made it possible to establish a parity of strategic arms, which still keeps countries from using military weapons capable of destroying an entire civilization.

Alexander Koldobsky, Deputy Director of the Institute of International Relations, NRNU MEPhI, veteran of nuclear energy and industry:

The abbreviation RDS in relation to prototypes of nuclear weapons first appeared in the decree of the USSR Council of Ministers of June 21, 1946 as an abbreviation of the wording "Jet engine C". In the future, this designation in official documents was assigned to all pilot designs of nuclear charges at least until the end of 1955. Strictly speaking, RDS-1 is not really a bomb, it is a nuclear explosive device, a nuclear charge. Later, for the RDS-1 charge, a ballistic body of an aerial bomb ("product 501") was created, adapted to the Tu-4 bomber. The first serial samples of nuclear weapons based on the RDS-1 were manufactured in 1950. However, these products were not tested in the ballistic case, they were not accepted into service with the army and were stored disassembled. And the first test with the release of an atomic bomb from the Tu-4 took place only on October 18, 1951. It used a different charge, much more perfect.

Hundreds of books have been written about the history of nuclear confrontation between superpowers and the construction of the first nuclear bombs. But there are many myths about modern nuclear weapons. Popular Mechanics decided to clarify this issue and tell how the most destructive weapon invented by man works.

Explosive nature

The uranium nucleus contains 92 protons. Natural uranium is basically a mixture of two isotopes: U238 (with 146 neutrons in its nucleus) and U235 (143 neutrons), the latter being only 0.7% in natural uranium. The chemical properties of isotopes are absolutely identical, and therefore it is impossible to separate them by chemical methods, but the difference in masses (235 and 238 units) allows this to be done by physical methods: a mixture of uranium is converted into gas (uranium hexafluoride), and then pumped through countless porous partitions. Although uranium isotopes are indistinguishable neither in appearance nor chemically, they are separated by a chasm in the properties of nuclear characters.

The fission process of U238 is paid: a neutron arriving from outside must bring with it an energy of 1 MeV or more. And U235 is disinterested: nothing is required from the incoming neutron to excite and then decay, its binding energy in the nucleus is quite enough.

When neutrons hit, the uranium-235 nucleus easily fissions, forming new neutrons. Under certain conditions, a chain reaction begins.

When a neutron enters a nucleus capable of fission, an unstable compound is formed, but very quickly (after 10−23−10−22 s) such a nucleus falls apart into two fragments that are not equal in mass and "instantly" (within 10−16−10− 14 s) emitting two or three new neutrons, so that over time, the number of fissioning nuclei can multiply (this reaction is called a chain reaction). This is possible only in U235, because greedy U238 does not want to divide from its own neutrons, whose energy is an order of magnitude less than 1 MeV. The kinetic energy of particles - fission products by many orders of magnitude exceeds the energy released during any act of a chemical reaction in which the composition of the nuclei does not change.

Metallic plutonium exists in six phases, with densities ranging from 14.7 to 19.8 kg / cm 3. At temperatures below 119 degrees Celsius, there is a monoclinic alpha phase (19.8 kg / cm 3), but such plutonium is very fragile, and in the cubic face-centered delta phase (15.9) it is plastic and well processed (it is this phase that they try save with alloying additions). There can be no phase transitions during detonation compression - plutonium is in a quasi-liquid state. Phase transitions are dangerous during production: with large parts, even with a slight change in density, a critical state can be reached. Of course, this will happen without an explosion - the workpiece will simply heat up, but nickel plating may be dumped (and plutonium is very toxic).

Critical build

Fission products are unstable and “come to life” for a long time, emitting various radiation (including neutrons). Neutrons that are emitted after a considerable time (up to tens of seconds) after fission are called delayed, and although their proportion is small compared to instantaneous ones (less than 1%), the role they play in the operation of nuclear facilities is the most important.

The explosive lenses created a converging wave. Reliability was provided by a pair of detonators in each unit.

The fission products in numerous collisions with surrounding atoms give them their energy, increasing the temperature. After neutrons have appeared in the assembly with fissile matter, the heat release power can increase or decrease, and the parameters of the assembly, in which the number of fissions per unit time is constant, are called critical. The criticality of the assembly can be maintained at both a large and a small number of neutrons (at a correspondingly higher or lower heat release power). The thermal power is increased either by pumping additional neutrons into the critical assembly from outside, or by making the assembly supercritical (then more and more generations of fissile nuclei supply additional neutrons). For example, if it is necessary to increase the thermal power of the reactor, it is brought to such a regime when each generation of prompt neutrons is slightly less numerous than the previous one, but thanks to the delayed neutrons, the reactor barely passes the critical state. Then it does not go into acceleration, but picks up power slowly - so that its growth can be stopped at the right time by introducing neutron absorbers (rods containing cadmium or boron).

The plutonium assembly (a globular layer in the center) was surrounded by a uranium-238 hull and then a layer of aluminum.

The neutrons produced by fission often fly past the surrounding nuclei without causing repeated fission. The closer to the surface of the material a neutron is born, the more chances it has to fly out of the fissile material and never come back. Therefore, the shape of the assembly that saves the largest amount of neutrons is a sphere: for a given mass of matter, it has a minimum surface. An unenclosed (solitary) ball of 94% U235 with no cavities inside becomes critical with a mass of 49 kg and a radius of 85 mm. If an assembly of the same uranium is a cylinder with a length equal to the diameter, it becomes critical with a mass of 52 kg. The surface also decreases with increasing density. Therefore, explosive compression, without changing the amount of fissile material, can bring the assembly to a critical state. It is this process that underlies the common design of a nuclear charge.

The first nuclear charges used polonium and beryllium (center) as a neutron source.

Ball assembly

But most often not uranium is used in nuclear weapons, but plutonium-239. It is produced in reactors by irradiating uranium-238 with powerful neutron fluxes. Plutonium costs about six times more expensive than U235, but during fission, the Pu239 nucleus emits an average of 2.895 neutrons - more than U235 (2.452). Moreover, the probability of fission of plutonium is higher. All this leads to the fact that the solitary ball of Pu239 becomes critical at almost three times less mass than the ball of uranium, and most importantly, at a smaller radius, which makes it possible to reduce the dimensions of the critical assembly.

A layer of aluminum was used in order to reduce the rarefaction wave after detonation of the explosive.

The assembly is carried out from two carefully fitted halves in the form of a spherical layer (hollow inside); it is deliberately subcritical - even for thermal neutrons and even after being surrounded by a moderator. A charge is mounted around the assembly of very precisely fitted blocks of explosives. In order to save neutrons, it is necessary to preserve the noble shape of the ball during the explosion - for this, the layer of explosive must be detonated simultaneously over its entire outer surface, pressing the assembly evenly. It is widely believed that this requires a lot of electric detonators. But this was only at the dawn of "bombing": to trigger many tens of detonators required a lot of energy and considerable dimensions of the initiation system. In modern charges, several detonators selected according to a special method, similar in characteristics, are used, from which a highly stable (in terms of detonation speed) explosive is triggered in grooves milled in a polycarbonate layer (the shape of which on a spherical surface is calculated using the methods of Riemann geometry). Detonation at a speed of about 8 km / s will run along the grooves absolutely equal distances, at the same time it will reach the holes and detonate the main charge - simultaneously at all required points.

The figures show the first moments of the life of a fireball of a nuclear charge - radiation diffusion (a), expansion of hot plasma and the formation of "blisters" (b) and an increase in radiation power in the visible range when the shock wave is detached (c).

Explosion inward

An inward explosion squeezes the assembly at over a million atmospheres. The surface of the assembly decreases, the internal cavity in plutonium almost disappears, the density increases, and very quickly - in a dozen microseconds, the compressible assembly jumps through the critical state on thermal neutrons and becomes significantly supercritical on fast neutrons.

After a period determined by the negligible time of insignificant deceleration of fast neutrons, each of their new, more numerous generation adds 202 MeV energy by fission into the already bursting with monstrous pressure of the material of the assembly. On the scale of the phenomena taking place, the strength of even the best alloy steels is so scanty that no one even thinks of taking it into account when calculating the dynamics of an explosion. The only thing that prevents the assembly from scattering is inertia: in order to expand the plutonium ball by only 1 cm in a dozen nanoseconds, it is required to give the substance an acceleration that is tens of trillions of times higher than the acceleration of gravity, and this is not easy.

In the end, the matter still scatters, fission stops, but the process does not end there: the energy is redistributed between the ionized fragments of separated nuclei and other particles emitted during fission. Their energy is on the order of tens and even hundreds of MeV, but only electrically neutral high-energy gamma quanta and neutrons have a chance to avoid interaction with matter and "escape". Charged particles quickly lose energy in collisions and ionizations. At the same time, radiation is emitted - it is true, no longer a hard nuclear, but softer, with an energy three orders of magnitude lower, but still more than sufficient to knock out electrons from atoms - not only from the outer shells, but everything in general. A hodgepodge of naked nuclei, electrons stripped from them and radiation with a density of grams per cubic centimeter (try to imagine how well you can sunbathe under a light that has acquired the density of aluminum!) - everything that was a charge a moment ago - comes into a kind of equilibrium ... In a very young fireball, a temperature of the order of tens of millions of degrees is established.

Fire ball

It would seem that even soft, but moving at the speed of light, radiation should leave far behind the substance that gave rise to it, but this is not so: in cold air, the range of quanta of keV energies is centimeters, and they do not move in a straight line, but change the direction of motion, re-emitting with each interaction. The quanta ionize the air, spread in it, like cherry juice poured into a glass of water. This phenomenon is called radiation diffusion.

A young fireball of explosion with a power of 100 kt a few tens of nanoseconds after the completion of the fission flash has a radius of 3 m and a temperature of almost 8 million kelvin. But after 30 microseconds, its radius is 18 m, however, the temperature drops below a million degrees. The sphere devours space, and the ionized air behind its front hardly moves: radiation cannot transfer a significant momentum to it during diffusion. But it pumps enormous energy into this air, heating it, and when the radiation energy dries up, the ball begins to grow due to the expansion of hot plasma, bursting from the inside with what was previously a charge. Expanding, like an inflated bubble, the plasma envelope becomes thinner. Unlike a bubble, of course, nothing inflates it: there is almost no substance left on the inside, it all flies from the center by inertia, but 30 microseconds after the explosion, the speed of this flight is more than 100 km / s, and the hydrodynamic pressure in the substance - more than 150,000 atm! It is not destined to become too thin a shell, it bursts, forming "blisters".

In a vacuum neutron tube between the tritiated target (cathode) 1 and the anode unit 2, a pulse voltage of one hundred kilovolts is applied. When the voltage is maximum, it is necessary that deuterium ions appear between the anode and the cathode, which must be accelerated. An ion source serves for this. An ignition pulse is applied to its anode 3, and the discharge, passing over the surface of the ceramic 4 saturated with deuterium, forms deuterium ions. Having accelerated, they bombard a target saturated with tritium, as a result of which an energy of 17.6 MeV is released and neutrons and helium-4 nuclei are formed. In terms of the composition of particles and even in terms of energy yield, this reaction is identical to synthesis - the process of fusion of light nuclei. In the 1950s, many believed so, but later it turned out that a "breakdown" occurs in the tube: either a proton or a neutron (of which the deuterium ion accelerated by an electric field is composed) "gets stuck" in the target nucleus (tritium). If a proton binds, then the neutron is torn off and becomes free.

Which of the mechanisms of transferring the energy of the fireball to the environment prevails depends on the explosion power: if it is large, radiation diffusion plays the main role, if it is small, the expansion of the plasma bubble. It is clear that an intermediate case is also possible when both mechanisms are effective.

The process captures new layers of air, there is no longer enough energy to strip all electrons from atoms. The energy of the ionized layer and fragments of the plasma bubble is running out, they are no longer able to move a huge mass in front of them and slow down noticeably. But what was air before the explosion moves, breaking away from the ball, absorbing new layers of cold air ... The formation of a shock wave begins.

Shock Wave and Atomic Mushroom

When the shock wave is detached from the fireball, the characteristics of the emitting layer change and the radiation power in the optical part of the spectrum increases sharply (the so-called first maximum). Further, the processes of illumination and changes in the transparency of the surrounding air compete, which leads to the realization of a second maximum, less powerful, but much longer - so much so that the output of light energy is greater than in the first maximum.

Near the explosion, everything around evaporates, farther away it melts, but even further away, where the heat flux is no longer sufficient to melt solids, soil, rocks, houses flow like liquid under the monstrous pressure of gas that destroys all strength bonds, heated to intolerable for the eyes shine.

Finally, the shock wave goes far from the point of explosion, where a loose and weakened, but expanded many times cloud remains of condensed vapors that have turned into the smallest and very radioactive dust of the vapors that have been the plasma of the charge, and that in their terrible hour was close to a place from which one should keep as far as possible. The cloud begins to rise upward. It cools down, changing its color, "puts on" a white cap of condensed moisture, dust from the surface of the earth stretches behind it, forming a "leg" of what is commonly called an "atomic mushroom".

Neutron initiation

Attentive readers can, with a pencil in hand, estimate the energy release from an explosion. When the assembly is in the supercritical state of the order of microseconds, the age of neutrons is of the order of picoseconds, and the multiplication factor is less than 2, about a gigajoule of energy is released, which is equivalent to ... 250 kg of TNT. And where are the kilo and megatons?

Neutrons - slow and fast

In non-fissile matter, "bouncing" from nuclei, neutrons transfer to them a part of their energy, the greater the lighter (closer to them in mass) the nuclei. The more collisions the neutrons take part in, the more they slow down, and, finally, they come into thermal equilibrium with the surrounding matter - they thermalize (it takes milliseconds). Thermal neutron velocity - 2200 m / s (energy 0.025 eV). Neutrons can escape from the moderator, are captured by its nuclei, but with a slowdown their ability to enter into nuclear reactions increases significantly, so the neutrons that are not "lost" more than compensate for the decrease in numbers.
So, if a ball of fissile matter is surrounded by a moderator, many neutrons will leave the moderator or be absorbed in it, but there will also be those that will return to the ball (“reflected”) and, having lost their energy, are much more likely to cause fission. If the ball is surrounded by a layer of beryllium 25 mm thick, then 20 kg of U235 can be saved and still reach the critical state of the assembly. But such savings are paid in time: each successive generation of neutrons must first slow down before causing fission. This delay reduces the number of neutron generations produced per unit time, which means that the energy release is delayed. The less fissile matter in the assembly, the more moderator is required for the development of a chain reaction, and the fission proceeds with increasingly low-energy neutrons. In the limiting case, when criticality is achieved only on thermal neutrons, for example, in a solution of uranium salts in a good moderator - water, the mass of the assemblies is hundreds of grams, but the solution simply boils periodically. The released vapor bubbles reduce the average density of the fissile substance, the chain reaction stops, and when the bubbles leave the liquid, the fission flash repeats (if the vessel is plugged, the steam will rupture it - but it will be a thermal explosion devoid of all typical "nuclear" signs).

The fact is that the chain of fissions in an assembly does not begin with one neutron: in the required microsecond, millions of them are injected into the supercritical assembly. In the first nuclear charges, for this purpose, isotope sources were used, located in a cavity inside the plutonium assembly: polonium-210 at the moment of compression combined with beryllium and caused neutron emission with its alpha particles. But all isotopic sources are rather weak (in the first American product less than a million neutrons were generated per microsecond), and polonium is already very perishable - in just 138 days it reduces its activity by half. Therefore, isotopes were replaced by less dangerous (not emitting in an unplugged state), and most importantly, more intensely emitting neutron tubes (see inset): in a few microseconds (this is how long the pulse generated by the tube lasts), hundreds of millions of neutrons are born. But if it doesn’t work or doesn’t work on time, the so-called cotton will happen, or “zilch” - a low-power thermal explosion.

Neutron initiation not only increases the energy release of a nuclear explosion by many orders of magnitude, but also makes it possible to regulate it! It is clear that, having received a combat mission, in the formulation of which the power of a nuclear strike is necessarily indicated, no one disassembles the charge in order to equip it with a plutonium assembly that is optimal for a given power. In ammunition with switchable TNT equivalent, it is enough to simply change the supply voltage of the neutron tube. Accordingly, the neutron yield and energy release will change (of course, when the power is reduced in this way, a lot of expensive plutonium is wasted).

But they began to think about the need to regulate energy release much later, and in the first post-war years there could be no talk of reducing power. More powerful, more powerful and more powerful! But it turned out that there are nuclear-physical and hydrodynamic restrictions on the permissible dimensions of the subcritical sphere. The TNT equivalent of a hundred kilotons explosion is close to the physical limit for single-phase munitions, in which only fission occurs. As a result, they abandoned fission as the main source of energy, and relied on reactions of another class - synthesis.

Great Britain Romania Germany Saudi Arabia Egypt Syria Israel USA India Norway Iraq Ukraine Iran France Canada Kazakhstan Sweden China South Africa DPRK Japan Poland

When a nuclear weapon is detonated, a nuclear explosion occurs, the damaging factors of which are:

People who have been directly exposed to the damaging factors of a nuclear explosion, in addition to physical damage, experience a powerful psychological effect from the terrifying appearance of the explosion and destruction pattern. The electromagnetic pulse does not have a direct effect on living organisms, but it can disrupt the operation of electronic equipment.

Classification of nuclear weapons

All nuclear weapons can be divided into two main categories:

• "Atomic" - single-phase or single-stage explosive devices, in which the main energy output comes from the nuclear fission reaction of heavy nuclei (uranium-235 or plutonium) with the formation of lighter elements.

• Thermonuclear weapons (also "hydrogen") are two-phase or two-stage explosive devices in which two physical processes localized in different regions of space develop sequentially: at the first stage, the main source of energy is the fission reaction of heavy nuclei, and at the second, fission and thermonuclear fusion reactions are used in various proportions, depending on the type and setting of the ammunition.

The fusion reaction, as a rule, develops inside a fissile assembly and serves as a powerful source of additional neutrons. Only early nuclear devices in the 40s of the XX century, a few cannon bombs in the 1950s, some nuclear artillery shells, as well as products of nuclear-technologically underdeveloped states (South Africa, Pakistan, North Korea) do not use thermonuclear fusion as a power amplifier nuclear explosion. Contrary to the persistent stereotype, in thermonuclear (i.e., two-phase) munitions, most of the energy (up to 85%) is released due to the fission of uranium-235 / plutonium-239 and / or uranium-238 nuclei. The second stage of any such device can be equipped with a tamper made of uranium-238, which is effectively fissioned from the fast neutrons of the fusion reaction. This achieves a manifold increase in the power of the explosion and a monstrous increase in the amount of radioactive fallout. With the light hand of R. Jung, the author of the famous book Brighter than a Thousand Suns, written in 1958 hot on the heels of the Manhattan Project, this kind of "dirty" ammunition is usually called FFF (fusion-fission-fusion) or three-phase. However, this term is not entirely correct. Almost all "FFF" refers to two-phase and differ only in the tamper material, which in a "clean" ammunition can be made of lead, tungsten, etc. The exception is Sakharov's "Sloika" devices, which should be classified as single-phase, although they have layered explosive structure (plutonium core - lithium-6 deuteride layer - uranium 238 layer). In the United States, such a device is called the Alarm Clock. The scheme of sequential alternation of fission and fusion reactions is implemented in two-phase ammunition, in which up to 6 layers can be counted at a very "moderate" power. An example is the relatively modern W88 warhead, in which the first section (primary) contains two layers, the second section (secondary) has three layers, and another layer is the uranium-238 shell common to the two sections (see figure).

• Sometimes a separate category is allocated to a neutron weapon - a two-phase ammunition of low power (from 1 kt to 25 kt), in which 50-75% of the energy is obtained through thermonuclear fusion. Since the main carrier of energy in fusion is fast neutrons, then in the explosion of such an ammunition the neutron yield can be several times higher than the neutron yield in the explosion of single-phase nuclear explosive devices of comparable power. Due to this, a significantly greater weight of the damaging factors of neutron radiation and induced radioactivity (up to 30% of the total energy yield) is achieved, which can be important from the point of view of the task of reducing radioactive fallout and reducing destruction on the ground with a high efficiency of use against tanks and manpower. It should be noted that the mythical nature of the notion that neutron weapons only hit people and leave buildings intact. In terms of its destructive impact, the explosion of a neutron munition is hundreds of times superior to any non-nuclear munition.

Cannon scheme

The "cannon scheme" was used in some of the first generation nuclear weapons. The essence of the cannon scheme consists in firing a charge of gunpowder from one block of fissile material of subcritical mass ("bullet") into another - motionless ("target"). The blocks are designed so that when combined, their total mass becomes supercritical.

This method of detonation is possible only in uranium munitions, since plutonium has a neutron background by two orders of magnitude, which sharply increases the likelihood of a premature development of a chain reaction before the blocks are connected. This leads to incomplete energy output (fizzle or "zilch"). To implement the cannon scheme in plutonium ammunition, an increase in the speed of connection of the charge parts to a technically unattainable level is required. In addition, uranium can withstand mechanical overloads better than plutonium.

A classic example of such a scheme is the "Little Boy" bomb dropped on Hiroshima on August 6th. Uranium for its production was mined in the Belgian Congo (now the Democratic Republic of the Congo), in Canada (Big Bear Lake) and in the USA ( Colorado). For this purpose, the Little Boy bomb used a 16.4 cm naval gun barrel shortened to 1.8 m, while the uranium "target" was a cylinder 100 mm in diameter, onto which a cylindrical "bullet" of a supercritical mass (38.5 kg) with the corresponding internal channel. Such an "intuitively incomprehensible" design was made to reduce the neutron background of the target: it was not located in it close, but at a distance of 59 mm from the neutron reflector ("tamper"). As a result, the risk of a premature start of a fission chain reaction with incomplete energy release was reduced to several percent.

Implosive scheme

This detonation scheme involves obtaining a supercritical state by compressing fissile material with a focused shock wave created by an explosion of a chemical explosive. To focus the shock wave, so-called explosive lenses are used, and detonation is performed simultaneously at many points with precision accuracy. The creation of such a system for placing explosives and detonation was at one time one of the most difficult tasks. The formation of a converging shock wave was ensured by the use of explosive lenses made of "fast" and "slow" explosives - TATB (Triaminotrinitrobenzene) and Baratol (a mixture of TNT with barium nitrate), and some additives) (see animation).

The first nuclear charge (the nuclear device "Gadget" (eng. gadget - device), blown up on the tower for testing purposes during tests with the expressive name "Trinity" ("Trinity") on July 16, 1945 at a test site near the town of Alamogordo in the state of New Mexico), and the second of the atomic bombs used as intended - "Fat Man" dropped on Nagasaki. In fact, the Gadget was a stripped-down prototype of the Fat Man bomb. In this first atomic bomb, the so-called "hedgehog" was used as a neutron initiator. urchin). (For technical details, see the article "Fat Man.") Subsequently, this scheme was found to be ineffective, and the uncontrolled type of neutron initiation was hardly used in the future.

In nuclear charges based on the fission reaction, a small amount of thermonuclear fuel (deuterium and tritium) is usually placed in the center of a hollow assembly, which is heated and compressed during the fission of the assembly to such a state that a thermonuclear fusion reaction begins in it. This gas mixture must be continuously renewed in order to compensate for the continually occurring spontaneous decay of tritium nuclei. The additional neutrons released in this case initiate new chain reactions in the assembly and compensate for the loss of neutrons leaving the core, which leads to a manifold increase in the energy yield from the explosion and a more efficient use of fissile matter. By varying the content of the gas mixture in the charge, ammunition is obtained with a wide range of explosion power.

It should be noted that the described scheme of spherical implosion is archaic and has hardly been used since the mid-1950s. Really applied Swan design (eng. swan - swan), is based on the use of an ellipsoidal fissile assembly, which, in the process of two-point, that is, implosion initiated at two points, is compressed in the longitudinal direction and turns into a supercritical sphere. As such, no explosive lenses are used. The details of this design are still classified, but, presumably, the formation of the converging shock wave is carried out due to the ellipsoidal shape of the imploding charge, so that there is an air-filled space between it and the nuclear assembly inside. Then uniform compression of the assembly is carried out due to the fact that the detonation velocity of the explosive exceeds the velocity of the shock wave in the air. A much lighter tamper is made not of uranium-238, but of beryllium, which reflects neutrons well. It can be assumed that the unusual name of this design - "Swan" (first test - Inca in 1956) was inspired by the image of a swan flapping its wings, which is partly associated with a shock wave front, smoothly covering the assembly on both sides. Thus, it turned out to be possible to abandon spherical implosion and, thereby, reduce the diameter of an implosive nuclear weapon from 2 m for the Fat Man bomb to 30 cm or less. For self-destruction of such a munition without a nuclear explosion, only one of the two detonators is initiated, and the plutonium charge is destroyed by an asymmetric explosion without any risk of its implosion.

The power of a nuclear charge, operating exclusively on the principle of fission of heavy elements, is limited to tens of kilotons. Power output (eng. yield) of a single-phase munition, reinforced with a thermonuclear charge inside a fissile assembly, can reach hundreds of kilotons. It is practically impossible to create a single-phase device of the megaton class; an increase in the mass of fissile matter does not solve the problem. The fact is that the energy released as a result of the chain reaction inflates the assembly at a speed of about 1000 km / s, so it quickly becomes subcritical and most of the fissile matter does not have time to react. For example, in the "Fat Man" bomb dropped on the city of Nagasaki, no more than 20% of the 6.2 kg of plutonium charge managed to react, and in the "Malysh" bomb with a cannon assembly that destroyed Hiroshima, only 1.4% of 64 kg enriched to about 80% disintegrated. uranium. The most powerful single-phase (British) ammunition in history, detonated during the Orange Herald tests in the city, reached a power of 720 kt.

Two-phase ammunition can increase the power of nuclear explosions to tens of megatons. However, MIRV missiles, the high precision of modern delivery vehicles, and satellite reconnaissance have made megaton-class devices virtually unnecessary. Moreover, carriers of super-powerful ammunition are more vulnerable to missile defense and air defense systems.

Teller-Ulam design for a two-phase munition ("thermonuclear bomb").

In a two-phase device, the first stage of the physical process ( primary) is used to start the second stage ( secondary), during which the largest part of the energy is released. This scheme is commonly called the Teller-Ulam design.

Energy from detonation primary transmitted through a special channel ( interstage) in the process of radiation diffusion of X-ray quanta and provides detonation secondary by means of radiation implosion of a tamper / pusher, which contains lithium-6 deuteride and a plutonium ignition rod. The latter also serves as an additional source of energy together with a pusher and / or tamper made of uranium-235 or uranium-238, and together they can provide up to 85% of the total energy yield of a nuclear explosion. In this case, thermonuclear fusion serves to a greater extent as a source of neutrons for nuclear fission. Under the action of neutrons from fission into Li nuclei, tritium is formed in the composition of lithium deuteride, which immediately enters into a thermonuclear fusion reaction with deuterium.

In the first two-phase experimental device Ivy Mike (10.5 Mt in the test of 1952), liquefied deuterium and tritium were used instead of lithium deuteride, but subsequently the extremely expensive pure tritium was not used directly in the second stage thermonuclear reaction. It is interesting to note that only thermonuclear fusion provided 97% of the main energy yield of the experimental Soviet Tsar Bomba (aka Kuz'kina Mother), which was detonated in 1961 with an absolutely record energy output of about 58 Mt. The most effective in terms of power / weight ratio of two-phase ammunition was the American "monster" Mark 41 with a capacity of 25 Mt, which was mass-produced for deployment on B-47, B-52 bombers and in a monoblock version for Titan-2 ICBMs. The tamper of this bomb is made of uranium-238, so it has never been fully tested. When the tamper was replaced with lead, the power of this device was reduced to 3 Mt.

Delivery vehicles

Almost any heavy weapon can be a means of delivering a nuclear weapon to a target. In particular, tactical nuclear weapons have existed since the 1950s in the form of artillery shells and mines - ammunition for nuclear artillery. The carriers of nuclear weapons can be MLRS rockets, but so far there are no nuclear missiles for MLRS. However, the dimensions of many modern MLRS missiles make it possible to place in them a nuclear charge similar to that used by barreled artillery, while some MLRS, for example, the Russian Smerch, are almost equal in range to tactical missiles, while others (for example, the American MLRS system) are capable launch tactical missiles from their installations. Tactical and long-range missiles are carriers of nuclear weapons. The Arms Limitation Treaties consider ballistic missiles, cruise missiles and aircraft as delivery vehicles for nuclear weapons. Historically, aircraft were the first means of delivering nuclear weapons, and it was with the help of aircraft that the only one in history was carried out combat nuclear bombing:

1. To a Japanese city Hiroshima on August 6, 1945. At 08:15 local time, the B-29 "Enola Gay" under the command of Colonel Paul Tibbets, at an altitude of over 9 km, dropped the "Little Boy" atomic bomb on the center of Hiroshima. The fuse was installed 600 meters above the surface; the explosion, equivalent to 13 to 18 kilotons of TNT, occurred 45 seconds after the discharge.
2. To a Japanese city Nagasaki on August 9, 1945. At 10:56 the B-29 "Bockscar" aircraft under the command of pilot Charles Sweeney arrived at Nagasaki. The explosion occurred at 11:02 local time at an altitude of about 500 meters. The explosion power was 21 kilotons.

The development of air defense systems and missile weapons has highlighted missiles.

The "old" nuclear powers USA, Russia, Great Britain, France and China are the so-called. the nuclear five - that is, the states that are considered "legitimate" nuclear powers under the Treaty on the Non-Proliferation of Nuclear Weapons. The rest of the countries with nuclear weapons are called "young" nuclear powers.

In addition, US nuclear weapons are or may be located on the territory of several states that are NATO members and other allies. Some experts believe that in certain circumstances, these countries can use it.

Test of a thermonuclear bomb at Bikini Atoll, 1954. Explosion power 11 Mt, of which 7 Mt was released from the fission of a tamper from uranium-238

The explosion of the first Soviet nuclear device at the Semipalatinsk test site on August 29, 1949. 10 hours 05 minutes.

the USSR tested its first nuclear device with a capacity of 22 kilotons on August 29, 1949 at the Semipalatinsk test site. Testing of the world's first thermonuclear bomb - in the same place on August 12, 1953. Russia became the only internationally recognized heir to the Soviet Union's nuclear arsenal.

Israel does not comment on the information that he possesses nuclear weapons, however, according to the unanimous opinion of all experts, he has owned nuclear warheads of his own design since the late 1960s - early 1970s.

South Africa had a small nuclear arsenal, but all six assembled nuclear charges were voluntarily destroyed when the apartheid regime was dismantled in the early 1990s. It is believed that South Africa conducted its own or jointly with Israel nuclear tests in the Bouvet Island area in 1979. South Africa is the only country that independently developed nuclear weapons and at the same time voluntarily renounced them.

For various reasons, Brazil, Argentina and Libya voluntarily abandoned their nuclear programs. Over the years, it was suspected that several more countries could develop nuclear weapons. It is currently assumed that Iran is closest to creating its own nuclear weapons. Also, according to many experts, some countries (for example, Japan and Germany) that do not possess nuclear weapons, by their scientific and production capabilities, are able to create them within a short time after a political decision and funding.

Historically, Nazi Germany had the potential to create nuclear weapons second or even first. However, the Uranium Project was not completed before the defeat of the Third Reich for a number of reasons.

The world's nuclear stockpiles

Number of warheads (active and in reserve)

	1947	1952	1957	1962	1967	1972	1977	1982	1987	1989	1992	2002	2010
USA	32	1005	6444	≈26000	>31255	≈27000	≈25000	≈23000	≈23500	22217	≈12000	≈10600	≈8500
USSR / Russia	-	50	660	≈4000	8339	≈15000	≈25000	≈34000	≈38000		≈25000	≈16000	≈11000
Great Britain	-	-	20		270							512	≈225