Last time when it came to the failure of the cobalt bomb, many friends left messages wondering how the radioactivity generated by the explosion of the nuclear bomb caused deadly pollution. So today, let's talk about the radioactive fall ash after the explosion of nuclear weapons.
Simply put, if the radioactive falling ash is mixed with the rainfall of the explosion site, it will form a commonly known "black rain", which is elaborated below:
When it comes to nuclear explosions, many people will immediately form the impression of mushroom clouds in their minds, after all, this is a business card of nuclear explosions.
However, it should be noted that the production of mushroom clouds is not directly related to the size of energy in nature. The mere presence of a cloud of low-density gas in the air has a high probability of producing a mushroom cloud.
It's just that when the nuclear bomb exploded, the huge energy heated the gas around the explosion fireball, resulting in a decrease in the density of the gas.
We can simply think of the reduced density gas around the nuclear explosion fireball as a huge hot air balloon without borders. Just like the principle of the hot air balloon, this hot air balloon without boundaries will also rise under the buoyancy of the air.
As the ascent process, since the nuclear bomb has released most of the energy, the "hot air balloon" will begin to cool gradually, so that the cold air around it will fill the space occupied by the "hot air balloon", forming an umbrella-like part of the mushroom cloud. The air on the ground is also sucked into the low-pressure area of the "hot air balloon" to form the stalk-like part of the mushroom cloud.
Since the air is also mass, under the action of inertia, the mushroom cloud will appear cloud rolling and swirling.
In the mushroom cloud of the GIF, we will also see the process of forming a white cloud of water vapor condensation by high pressure.
However, these phenomena do not form the so-called "black rain".
What is formed is the "radioactive falling ash", which is partly composed of vaporized and gradually condensed nuclear bomb parts, as well as ground objects vaporized in the ground explosion (if it is) fireballs, and the other components are the ground dust and dirt in the "mushroom handle" that are sucked into the sky at low pressure. These substances are mixed in the mushroom cloud with the radioactive material of the nuclear bomb explosion, and some of the materials that are not originally radioactive will be fully activated under the action of neutrons to form new radioactive materials.
Most of these activated radioactive materials have a half-life of several hours, and a small fraction will have a half-life of up to several years. Falling on a human body can cause beta radiation damage. If the measurement is too large, people will not live more than 24 hours.
Theoretically, mushroom clouds as a whole are extremely radioactive. The soot in the mushroom cloud will return to the ground within minutes of the explosion if the particles are larger, while most of the smaller particles of soot will be driven by the wind and fall within a few hundred kilometers in the downwind direction of the explosion for a day or two.
Let's take an example:
In 1953, during the U.S. nuclear test Operation Castle Inspection, a 15-megaton hydrogen bomb exploded at Bikini Atoll.
Data were collected on radioactive falling dust during the explosion.
The chart shows that radioactive fallen dust has been detected at a location of 300 miles (482 kilometers) after 16 hours. The radiation dose reaches 100 rad/hour, which is equivalent to 12 X-rays an hour.
At greater distances, the radiation dose was detected to drop significantly, and it did not form a short-term fatal injury.
However, in Operation Castle, although 15 million tons of hydrogen bombs exploded, no black rain was generated.
The production of "black rain" is heavily dependent on meteorological conditions, and only a large amount of radioactive rain combined with cumulonimbus clouds to cause radioactive rainfall can form a "black rain". If you rely only on the nuclear bomb explosion, the little water vapor cloud on the mushroom cloud handle will not form a truly effective rainfall.
Therefore, the black rain under the nuclear explosion is actually a small probability behavior, and the emergence of black rain mainly depends on "hitting the big luck".
W. Jun recently wrote a collection of nuclear bomb-related articles:
It's funny, a non-existent weapon that has panicked the world until now
Nuclear winter? pull!
Successively, W Jun will also write some content related to nuclear weapons, if everyone is interested in nuclear weapons, then pay more attention to it.