10 shameful questions about nuclear weapons: physicist Dmitry Pobedinsky answers

In the new article series experts answer questions that are usually embarrassing to ask: it seems that everyone already knows about it, and the questioner will look stupid.

Before the premiere of Oppenheimer, we talked with the physicist Dmitry Pobedinsky about atomic bombs. We hope the film will be clearer now.

1. How is an atomic bomb different from a conventional one?

A bomb, in principle, is a projectile stuffed with an explosive that can enter into a chemical reaction very quickly. When this happens, an explosion occurs - that is, a large amount of energy is released in a short time.

Prior to the activation of the bomb, this energy is stored in a “sleeping state”, as it were. In ordinary bombs, it is stored in the form of bonds between the atoms of molecules. In a nuclear bomb - in the form of links between the particles of the nucleus, protons and neutrons. The connections between the latter are much stronger, so the energy that will be released when the bomb is activated will be more - ceteris paribus - about a million times.

2. What is the difference between atomic, nuclear and thermonuclear bombs?

The concepts of an atomic and nuclear bomb are most often interchangeable and in our context mean the same thing: for their explosion, the nuclear fission reaction is used heavy elementssuch as uranium or plutonium.

Thermonuclear bombs use a different principle - thermonuclear fusion, in which such lungs elements like hydrogen or lithium merge into heavier ones, due to which the energy necessary for explosion.

In terms of energy release, thermonuclear bombs, unlike nuclear bombs, can be made very large. It is quite difficult to multiply the power of a nuclear charge, but it is relatively easy to increase the power of a thermonuclear bomb.

Even thermonuclear bombs do not have such a damaging factor as radiation. But when a nuclear bomb explodes, many unstable elements are formed and radiation contamination of the area occurs.

However, often a thermonuclear bomb contains a nuclear bomb, which leads to radiation pollution, albeit less.

To summarize:

• atomic bomb and nuclear bomb are the same
• atomic bombs use reactions of heavy elements, thermonuclear bombs use light ones,
• it is easier to increase the power of thermonuclear bombs than atomic bombs,
• with a nuclear and thermonuclear explosion of the same power, less radiation pollution will be in the second case.

3. How are nuclear weapons activated and guided towards a target?

In the radioactive substance contained inside the atomic bomb, the fission reaction goes on constantly in a smoldering mode. However, the energy released in this case is not enough for a big explosion to occur.

It is possible to make the process go more actively. For this, the fission reaction must be chain and self-sustaining - that is, so that the breaking of one bond between the particles of the nucleus provokes the breaking of another, and so on in increasing order. Then this avalanche-like impact in micro fractions of a second will lead to the release of a large amount of energy and, accordingly, an explosion.

There is such a thing as critical mass - the minimum mass of a substance necessary to start a fission chain reaction. That is, in order for the bomb to explode, it is necessary to exceed the critical mass. This is done in two ways:

1. Connect together two identical bars with the same substance inside and compress them for a while. That is, if the critical mass is 10 kg, and each bar weighs 6 kg, then by connecting them, we get a bar weighing 12 kg, which will exceed the critical mass, and a nuclear chain reaction will begin. So, for example, did the creators of the first bomb "Baby", which was dropped on Hiroshima.
2. A ball that has a mass less than the critical one is surrounded by explosives and creates a directed explosion. The shock wave compresses this ball, its density increases. The mass for this new density becomes higher than the critical one, and the reaction starts. This method is called implosion, it was used to activate the Fat Man dropped on Nagasaki, as well as for the Gadget, the very first bomb detonated in the US desert. The movie Oppenheimer shows this moment.

How the bomb is directed to the target is a matter of aerodynamics and space ballistics. Now there are ballistic missiles with nuclear or thermonuclear warheads that are launched into the air like space rockets, but they do not go into orbit. Instead, they begin to fall towards the target along a certain, pre-calculated trajectory.

4. What happens after the explosion?

After the bomb explodes, a lot of light radiation is first released, which burns everything in a certain radius. This flash is so powerful that it can be compared to the radiation from a star in space. Therefore, everything that is in the epicenter instantly burns out.

Then comes the shock wave. It moves at a speed above the speed of sound, but below the speed of light, sweeping away everything in its path: destroying buildings, uprooting trees, overturning cars.

In parallel with this, the area is contaminated with radiation. People get sick with radiation sickness, they and their descendants increase the growth of oncological diseases. Plants and animals mutate. Agricultural fields become unusable.

5. Do nuclear presidents really have a red button?

I do not know that. I think it's a figurative title. In an airplane, for example, there are devices on which flight parameters and pilots' conversations are recorded. They are called black boxes, although they are actually painted orange. The same is true here - it is unlikely that the "red button" describes the physical embodiment.

But the fact that there are strategic nuclear weapons that are on alert and, relatively speaking, ready for use at any moment is true. It can be used when there is a direct threat to the state - from a nuclear strike to an alien attack, for example. In this case, the first person of the state, the president, gives a personal order to launch it.

In addition, there are tactical nuclear weapons that are not prepared for direct use. It is stored in a “mothballed” state in military units.

6. Do nuclear weapons have an expiration date?

Nuclear bombs use an unstable radioactive substance that undergoes a natural decay process. Because of this, the active properties of nuclear bombs become smaller and smaller over time. But the account goes not for years, but for tens of thousands of years.

For example, the half-life of plutonium-239 is 24,000 years, and that of uranium-235 is 700,000,000 years. What does it mean? This means that only after this time the active substance in the bomb will become half as much. That is, on the horizon of hundreds of years, a nuclear bomb remains dangerous.

However, in addition to this, there are additional elements in the bomb, each of which has its own expiration date. These elements also become obsolete. For example, the most common explosives can become damp, electronics can become unusable. Therefore, the shelf life of each particular bomb depends on its design.

7. Can an atomic bomb explode on its own?

Extremely unlikely. The explosion of a nuclear or thermonuclear bomb is a process in which something can easily go wrong. If, for example, a bomb accidentally falls out of an airplane onto the pavement, then something in it can move, click, the process of starting the explosion will begin, but, most likely, it will not be fully completed and will not lead to a giant energy release. There will be just a small "zilch".

For example, in 1966, during the Cold War, the US Air Force conducted Operation Chrome Dome. Several bombers with atomic bombs on board were constantly in the air and were ready at any moment to strike at the USSR.

Several accidents occurred during this operation. Once, an atomic bomb fell out of their hatch, and its fragments fell on the Spanish village of Palomares. There was a fire, but, fortunately, there was no explosion, and none of the residents were injured. Also, the bomb fell into the sea, and it was pulled out with the involvement of divers. Each of these cases, despite other negative consequences, did not lead to the activation of a nuclear bomb.

8. Can nuclear weapons be bought?

It is almost impossible to acquire or produce nuclear weapons - it is difficult, expensive and illegal.

In 1968, most of the countries that existed at that time signed the Treaty on the Non-Proliferation of Nuclear Weapons. It restricts the production and sale of such weapons. However, some countries are now suspected of violating it. For example, there have been reports that Iran wants to join the club of nuclear powers. Allegedly, the development of an atomic bomb is underway on its territory.

What can be said for sure is that private enterprises can hardly develop nuclear weapons. Most often these are national projects available only to countries with large economies. Indeed, in order to create an atomic bomb from scratch, you must first enrich the ore so that the desired isotope is obtained from ordinary uranium. In addition, very accurate instruments are needed to measure the presence of explosives in weapons.

In addition, a special “radioactive police” monitors the circulation of radioactive elements. After all, radiation always leaves traces. Therefore, it is hardly possible to make sure that a large amount of radioactive material is transported somewhere imperceptibly.

9. How is an explosion at a nuclear power plant different from an explosion of an atomic bomb?

When a nuclear bomb explodes, a chain reaction occurs, and the energy stored in the nucleus of the atom is released. And in the event of an accident at a nuclear power plant, a large pressure arises inside a nuclear reactor with a radioactive substance, which leads to a rupture. Imagine that you are boiling condensed milk: if you boil a jar, it will explode.

Yes, in both cases, radioactive contamination of the area occurs, but it may differ in scale. For example, Hiroshima and Nagasaki were repopulated only a few years after the bombing. But around the Chernobyl nuclear power plant, the exclusion zone is still preserved, although the accident occurred a long time ago - in 1986. Why?

Firstly, the fact is that the atomic bomb in Japan was detonated at a height of several hundred meters above the ground, so the radiation “weathered” faster. The reactor at Chernobyl exploded at ground level, making the soil radioactive for many years. Only recently have they begun to meet wild animals and plants without signs of mutations.

Secondly, the “Kid” bomb contained only about 65 kg of uranium, while the “Fat Man” contained about 6 kg of plutonium. The Chernobyl reactor released 180 tons of nuclear fuel. That is, during the accident, an order of magnitude more harmful substances were released into the atmosphere.

10. How many atomic bombs does it take to destroy the earth? What happens if a nuclear war breaks out?

The world's nuclear arsenal now has about 13,000 nuclear warheads. This reserve is not enough to, for example, move the Earth out of its orbit and thereby possibly destroy life on it.

However, if a nuclear war breaks out, most of the world's population will suffer. If we take into account that every fifth person lives in a million-plus city, then strikes against them will lead to a significant reduction in the human population.

Then, fires will start all over the Earth, which will affect the climate. So the survivors will face massive drought, acid rain and famine.