How long does a nuclear explosion last

Glossary Terms

Fig. Distribution of the released energy

Heat wave
The first effect of a nuclear explosion is an intense flash of light. The temperatures rise immeasurably. Everything is evaporated in a certain radius.

The amount of thermal energy perceived at a certain distance from the nuclear explosion depends on the explosive power of the weapon and the state of the atmosphere.

The direct heat not only ignites fires in buildings and forests, it also causes extremely severe burns to people.
The heat radiation can ignite dry, flammable materials such as paper and some fabrics. For example, if a 1 megaton bomb explodes, paper still burns within a radius of 14 kilometers.
 
Blast wave
About half the energy of a nuclear explosion is released as a pressure wave. The force of the explosion is enormous. The damage is caused both by the excess air pressure at the front of the pressure wave and by the extremely strong storms. These storms continue even after the pressure wave front has long passed the area.

The fires that have started spread rapidly in the hurricane-like winds, they are effective within a radius of 10 to 20 km. It's like a gigantic bellows kindling a fire.
 
The shock wave causes damage and explosions to ovens and petrol tanks, gas boilers and oil reservoirs, heating systems and refineries. These in turn go up in flames and cause widespread secondary fires.

The fire multiplies. Firestorms break out. Lethal substances form in the atmosphere: the oxygen is withdrawn from the air, it fills with smoke, ash and combustion gases. People are being killed, be it outdoors, indoors or in a shelter.
 
radiation
The penetrating radioactive radiation leads to serious injuries in the body. The radioactive radiation emanating from an explosion can be divided into two categories: Immediate radiation, consisting of alpha, beta, gamma and neutron rays, emanates from the center of the explosion and is effective for up to one minute.

Residual radiation, part of the radiation that is still effective after one minute. It consists of radioactive fallout, also known as fallout, and so-called neutron-induced radiation.

The radioactivity in the contaminated area decreases sharply within the first 24 hours. After about a week it can drop below a life-threatening level.

The fallout slowly floats to the ground and, depending on the duration of the float, can cause more or less strong radiation. A distinction must be made between two different types, early and delayed radioactive fallout. If a nuclear explosion takes place near the surface, the earth or water is sucked into a mushroom-shaped cloud and contaminated with the remains of the radioactive weapon. The contaminated material begins to fall within a few minutes, which can last up to 24 hours. This allows an area up to thousands of square kilometers to be hit from the explosion site. There is no early rainfall in high altitude explosions. If a bomb is detonated well above the surface, the radioactive waste in the mushroom-shaped cloud rises to great heights and gradually falls over a large area.
 
The smaller warheads, such as the neutron bomb, emit a great deal of instant radiation, but have less heat and pressure. Their effect is therefore different: the destruction of buildings is much less; But the radiation effect on humans is all the worse. Your goal is to incapacitate soldiers immediately. That means more deaths and less damage to buildings: That is why the neutron bomb was often traded under the macabre keyword "clean bomb".