The biggest immediate damage from a nuclear weapon is by a blast and thermal radiation. That is basically no different from how other bombs work. The big difference is the magnitude of the effect. In addition to the magnitude of the effect achieves nuclear weapons extensive damage by radiation.
The shock wave
A nuclear explosion creates an enormous shock/blast wave that reaches the speed of many hundreds of kilometers per hour. People close to ground zero will be instantly killed by the blast alone. At a distance, the blast causes internal injuries such as lung injuries, ear damage and internal bleeding. Above all, the blast wave will result in indirect damage.
People will be buried under falling buildings or hurled against walls or objects. Debris such as glass splinters, bricks, concrete and wooden blocks will be hurled around and cause severe injuries. The shock wave and the thermal pulse are the factors causing the most immediate deaths and injuries in the event of a nuclear explosion.
In Nagasaki, 9 percent of all deaths immediately after the atomic bombing are estimated to be the result of falling glass splinters. About as many were killed by other falling debris hitting people at a high speed. In Hiroshima, the proportion of deaths caused by falling and flying debris is estimated at 30 percent of the total death toll.
The thermal pulse
Within a certain distance from the site of explosion, the heat is so intense that practically everything is vaporised. In Hiroshima, all that was left of some humans, sitting on stone benches near the centre of explosion, was their outlines. Outside the area where wounds are fatal, many people will suffer severe burns. Heat radiation on bare skin causes burns directly. The skin will also be indirectly damaged when their clothes catch fire.
The thermal radiation causes damage to the eyes so that many people will be blinded by the explosion. For most of them, sight will return within a few minutes, but some will suffer permanent damage to the eyes, due to retinal burns.
Many people will also be wounded or killed by the fires that result from the thermal radiation. These fires may combine together and become immense firestorms, spreading out from the site of explosion. Within these areas, even people in underground shelters will die because of heat, lack of oxygen or from carbon monoxide or -dioxide poisoning.
In Hiroshima, burns caused 60 percent of the immediate deaths, while the number of immediate deaths from burns in Nagasaki amounted to 95 percent. The observant reader will notice that, counting together the number of deaths caused by falling debris and by burns, the sum will exceed 100 percent. The numbers are based on estimates by the Manhattan Engineer District, who point out that many of the victims suffered from a number of deadly injuries – hence a total sum of more than 100 percent.
Initial radiation is the first radiation to appear after a nuclear weapon has detonated. It consists of gamma and neutron radiation emitted at the moment of explosion, lasting for at most a minute. This radiation causes damage to humans, animals, the environment, electronics etc. The intensity of the initial radiation decreases quickly with an increased distance from ground zero. Regarding larger nuclear weapons, with an explosive power larger than 50 kiloton, the effects of the blast and thermal wave are so grave that the health effects of the initial radiation is negligible.
The radioactive material left behind by the nuclear weapon eventually falls to the ground as particles. This is called radioactive fallout and comes in three different categories: local, regional or global fallout.
In local fallout, the radioactive particles are spread downwind and fall to the earth within days. In some of the affected areas, the radioactive doses can be directly lethal to exposed humans.
The particles destined to become regional fallout go directly into the troposphere (the layer of air closest to the earth) after the explosion and then fall down during the span of some weeks. This fall-out can lead to damage in humans and, in the long run, to an increase in the numbers of cancer cases and genetic damage. People eating food, drinking water and breathing contaminated air suffer the effects of the fallout.
Some of the radioactive particles rise at the explosion to the stratosphere where they spread around the earth to slowly fall or rain down within months or even years as global fallout. This is caused mainly by larger nuclear weapons and when the explosion happens in the atmosphere rather than on the ground. The radioactivity decays somewhat before reaching the earth, but some radioactive substances have a half-life of thousands or millions of years – that is, the time it takes for the radioactivity to decrease by half.
This means the global fallout can cause health effects for a very long time. Cesium-137 and radioactive Iodine are examples of radioactive substances that enter the food chain and hence affect people’s health.
Electromagnetic Pulse (EMP)
When gamma radiation knocks electrons out of the atoms of air molecules, these electrons combine to form a strong pulse of electric current, generating an electromagnetic field. This field then propagates as a very short-lived wave: an electromagnetic pulse. EMP causes disturbances and damage in electronic equipment.
EMP is a serious threat to our modern society, since a major part of the infrastructure depends on electronics. There are numerous items that can catch and conduct electromagnetic energy, such as antennas, telephone wires, railway tracks. This energy can surge into computers and other sensitive equipment and cause damage to vital systems, like those supplying water or electricity, or telecommunications. Without these systems, our society will stop functioning. The EMP of a hydrogen bomb detonated at a high altitude could knock out all electronic systems within a very large area (e.g., all Northern Europe).
See for yourself
With the program Nukemap you can choose the city and the strength of the nuclear weapon and then see what happens when a nuclear weapon explode.
Last update: December 30, 2015