The explosion of the nuclear bomb in Hiroshima and Nagasaki during World War II showed the whole world what a powerful weapon of mass destruction it is. How does a nuclear explosion happen, and why does it wreak so much havoc?
The nuclear bomb is the most powerful man-made weapon so far and is one of the weapons of mass destruction. The external structure is similar to a typical aerial bomb. Unlike a conventional explosion, the detonation of an atomic bomb carries several destructive consequences, including harmful radiation. It is mainly associated with the formation of a characteristic cloud – the so-called atomic mushroom. As impressive as this visual effect is, the aftermath of the explosion is dramatic.
The principle of the nuclear bomb – what causes such a powerful explosion?
What is an atomic bomb explosion? This type of explosion can be triggered in two ways: a chain fission reaction of heavy elements (uranium or plutonium) or the fusion (combination) of light elements (hydrogen or helium). The effect of the nuclear transformations taking place in both cases is the extremely rapid release of a huge amounts of energy, which is the basis of the so-called atomic and hydrogen (thermonuclear) bombs created in this way.
For the first and last time, elemental fission was used as a weapon in World War II by the United States. It was the largest bomb explosion used in an armed conflict that resulted in deaths of thousands of people. On August 6 and 9, 1945, two loads were dropped on Japanese cities: Hiroshima (Little Boy) and Nagasaki (Fat Man).
Both explosions formed a mushroom-shaped column of smoke, the height of which was several kilometers. Although Fat Man was twice as strong as Little Boy, the surrounding hills weakened the shockwave. It is estimated that the bomb dropped on Hiroshima killed about 30% of the city’s population, and both explosions claimed 110-160,000 lives. Thousands more died over the next few years from radiation sickness.
Consequences of a nuclear explosion
During the detonation of classic explosives, the vast majority of energy is transformed into a destructive shock wave and, to a small extent, also into the release of heat. In the case of a nuclear explosion, there are several glaring factors that accompany the shock wave, and their effects significantly increase its destructive effect. They are: thermal and penetrating radiation, radioactive contamination and electromagnetic impulse.
The shockwave is the main consequence of the explosion of any type of charge. In the case of a nuclear bomb, only about 50% of the total energy produced is transferred to its creation, the other half is transformed into remaining fire factors. Although the strong blast caused by the explosion is still characterized by a high destructive force (it can reach speeds of up to 1600 km/h), this is not what is the most terrifying about the nuclear weapons.
Light (thermal) radiation makes up about 30-40% of the energy produced during the explosion. It accompanies the first phase of a nuclear explosion and is emitted by the generated light impulse – a fireball. The consequence of the emission of thermal radiation in victims in the field of destruction are extensive burns and even carbonization of the skin, resulting in it falling off. Moreover, it causes numerous fires.
About 5-10% of the total energy is emitted in this form. The main difference between light and ionizing (nuclear) radiation is that the former can be observed. Nuclear radiation, although invisible, has serious destructive consequences. The main radiating components are gamma rays and neutrons, which are distinguished by their extremely harmful effect on living organisms in a wide variety of ways.
The destructive effect of radiation results from the ability to introduce changes (mutations) and destroy DNA and RNA molecules in living organisms. The occurrence of symptoms related to the harmful effects of radiation is defined as radiation sickness. Symptoms of the disease do not appear until several hours after the outbreak. Characteristic symptoms include vomiting, diarrhea, weakness and a drop in white blood cells.
They disappear for some time, only to come back in an acute form after 1-3 weeks. It is then that bleeding and ulceration, severe hair loss, fever, anemia, clouding of the eyeballs and infertility are observed. If the radiation dose was high, death occurs. Ionizing rays can also contribute to the formation of genetic mutations that, although not leading to death, are passed onto the next generations.
So how is it possible that many people managed to survive the explosion of an atomic bomb? Well, the final appearance of the effects of ionizing radiation and their degree depends on several components, including the total radiation dose, the part of the body that was exposed to radiation, and the rate of its absorption. The general condition of the body at the time of the explosion is also of great importance.
An explosion of an atomic bomb also leads to contamination of the earth’s surface with radioactive substances, and thus to radioactive contamination (10% of energy). Its main source is radioactive fallout (these are irradiated particles of earth, dust and water that were sucked into the resulting fireball as a result of the explosion). The size of the contamination will depend both on the characteristics of the bomb (for example, its size), the type of terrain, the height of the blast, and the weather at the time of the blast.
What is a mushroom?
One of the visual effects of a nuclear explosion is the formation of a so-called mushroom cloud. Fine dust, aerosols, soil particles and bomb remains, together with the heated air, create a powerful cloud in a characteristic shape resembling a mushroom. It can rise for tens of kilometers. The radioactive cloud created in this way is carried by the wind over great distances. After time, it falls to the ground in the form of radioactive fallout.
The atomic mushroom is also accompanied by the formation of a characteristic fireball that generates light radiation. Its appearance is due to the enormous temperature generated by the nuclear chain reaction. At the time of the explosion, it reaches 100 million degrees Celsius.
Starfish Prime – an explosion of an atomic bomb in space The
Dynamic development of nuclear physics in the 1940s and 1950s led to numerous nuclear tests. One of them, carried out on July 9, 1962, was the so-called Starfish Prime, which was intended to detonate a thermonuclear (hydrogen) bomb at a very high altitude – 400 kilometers from the Earth’s surface. It was made by the United States.
The explosion of an atomic bomb in space turned out to be more devastating than expected. It caused a huge magnetic pulse that damaged electrical devices (street lamps, telephone lines, burglar alarms) in Hawaii, nearly 1,500 kilometers away. In addition, the explosion created a radiation belt (rich in charged particles) in the Earth’s magnetosphere, which in turn damaged several satellites.
Underwater and underground detonations
Surface and high-altitude (air) explosions were not the only possibilities tested by the countries leading the development of nuclear technology – the USA and the USSR. Numerous tests were also carried out on underground and underwater explosions. Depending on the location of the detonation point in relation to the earth’s surface, the intensity of the consequences (shock wave, radiation, etc.) changes. The most dangerous consequences turned out to be air explosions, which are also characterized by the largest range of destruction.
What does an underground atomic bomb explosion look like? In this type of explosion, all the energy generated by the explosion is used to melt the rock, the radiation does not spread much. It looks a bit different when detonating at a shallow depth – a column of hot gases, bomb remains and a large amount of soil particles is displaced, which leads to the formation of a large crater.
Explosion of an atomic bomb underwater at great depth does not pose a radiation hazard. It is almost completely absorbed by the surrounding water, which is additionally heated strongly due to the generated energy. Of course, the magnitude of the aftermath of the explosion will vary depending on its distance from the surface. If the charge detonates at a shallow depth, a visible fireball, shock wave, water column and cauliflower-shaped radioactive cloud are created.
Nuclear winter – the potential effect of nuclear war
The theory of nuclear winter was created in response to the rapid development in this field and the danger associated with the growing arsenal of bombs in many countries around the world. This hypothesis describes the climate change that could occur in the event of a nuclear war (the simultaneous explosion of many atomic charges). Research on the potential phenomenon was started in 1981 by the American National Academy of Sciences.
The result of such explosions would be huge amounts of dust which, blown by the explosion and dispersed by the wind, would largely obscure the Sun. This would lead to a lower temperature on Earth. Insufficient sunlight would make the life of plants impossible, with the consequent lack of food and therefore death of people and animals. Although the data on the nuclear arsenal of various countries are estimates, it is assumed that its power is at least several dozen times greater than that which would result in a nuclear winter.
Operation Plumbbob – illustrating the power of a nuclear explosion
The first explosion of an atomic bomb was a test detonation and took place at a training ground in New Mexico on July 16, 1945. The operation was carried out by the United States and was called Trinity. It was the crowning moment of several years of work on the Manhattan project – a secret government program aimed at using nuclear energy to create a previously unknown weapon.
Twelve years later, the US conducted a series of tests at a test site in Nevada, called Operation Plumbbob, in which nuclear weapons were used for as many as 29 explosions. It was not only the largest and longest operation of this type in this part of the globe, but also the most controversial. Several thousand soldiers received a high dose of radiation, moreover, it is assumed that this could result in an increase in the incidence of thyroid cancer. Hundreds of pigs subjected to the experiments also suffered from extensive burns.
During one of the test explosions, it was decided to visualize the power of a nuclear explosion. For this purpose, an armored steel cover weighing 900 kilograms was launched simultaneously at a speed of over 65 km/h. According to estimates, the nuclear explosion was to increase the velocity of the cover to a value six times greater than the escape velocity – the speed that allows a given object to leave the Earth’s gravitational field (about 40,000 km/h). In the end, the cover was not found, but it was probably destroyed by the resulting high temperature.
The Comprehensive Nuclear Test Ban Treaty was signed in 1996. Earlier, in 1968, an international agreement was drawn up – the Treaty on the Non-Proliferation of Nuclear Weapons – aimed at stopping the arms race. According to its provisions, the sale of the technology of building an atomic bomb by countries that have it to those that do not have it is forbidden. The latter also undertake to stop trying to create it. By 2003, 189 countries had ratified the treaty.
There is no doubt that as a result of the fission of the element nuclei, the most destructive weapon was invented, and its possible use in armed conflicts would bring unimaginable destruction. The best example of this is the destruction of Hiroshima and Nagasaki in 1945 – and it should be noted that these were the first structures that did not yet have the greatest possible firepower. It is assumed that if World War III ever happens – it will be a nuclear war.