Radioactive rain

Radioactive rain. It is defined as the deposition of radioactive particles, released into the atmosphere by nuclear explosions or leaks from nuclear facilities and plants, on the Earth’s surface .


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  • 1 Harmful effects
  • 2 Composition
  • 3 Biological effects of radiation
  • 4 Genetic effects
  • 5 See also
  • 6 Sources

Damaging effects

Public interest has focused primarily on the effects of fallout since the period of large-scale atmospheric nuclear testing in the 1950s and early 1960s .

Its harmful effects were discussed for many years, but it was not until 1984 that a decision was made, when a Utah federal judge ruled that 10 people had become ill with cancer because the government had failed to take adequate measures regarding the exposure of citizens to radioactive fallout in that state.

In 1985 the England and Wales Pension Appeals Court reached a similar conclusion in the case of a British nuclear testing veteran on the Christmas Islands during the 1950s. Since the signing of the nuclear testing limitation treaty in 1963 Radioactive fallout levels have decreased worldwide. The Chernobyl nuclear accident produced a certain amount of radioactive fallout.


The material of which radioactive fallout is made is produced by nuclear fission and by the activation of soil , air , water and other materials in the immediate vicinity of the detonation site.

The individual radioactive particles are invisible, and so light that they could circle around the planet over and over again without ever descending to the surface. However, this situation would only occur if a nuclear bomb were detonated at a considerable distance from the atmosphere. When a nuclear weapon is detonated near the Earth ‘s surface, the violence of the explosion sprayed large amounts of material, much of which is absorbed into the ball fire and thus to the hot mass that rises forming the characteristic cloud shaped of fungus. Inside the fireball and on the stem of the bomb cloud, the radioactive particles adhere to heavier particles, which act as a ballast.

The highest mass particles of matter fall back to Earth in a matter of minutes, forming a very localized radioactive fallout. The smaller, but easily visible, windblown particles fall to the Earth’s surface after several hours, and are called local radioactive fallout. The nature and extent of this depend on the type and power of the explosion, the altitude of the detonation and the speed and direction of the wind.

The microscopic particles remain suspended for longer periods. If the explosion is underpowered or medium powered, the bomb cloud may not reach the tropopause, that is, the atmospheric layer between the troposphere and the stratosphere . In cases like this, so-called tropospheric radioactive rain occurs, and the bomb fragments move around the Earth following the latitude where the detonation occurred, falling to the surface when rain and other forms of precipitation carry the foreign matter of the atmosphere.

If the power of the explosion is sufficient to introduce debris from the pump into the stratosphere, many of the small particles remain in it, and are subject to the action of stratospheric winds. The rain produced in this case is called stratospheric or global atomic rain. Since there is no precipitation in the stratosphere, these particles remain in suspension for considerable periods. They disperse horizontally, so that some particles, after having circled the planet several times, end up distributed throughout the stratosphere. Vertical mixing, especially in the polar regions in winter and early spring , returns the material to the troposphere, where it behaves like tropospheric radioactive fallout.

Biological effects of radiation

Still, long-lived radioisotopes, such as 90Sr, do not appreciably decay for as long as they remain in the stratosphere , and therefore may remain a potential risk for many years, particularly through contaminated and intended food. for human consumption.

The long-term retention of radioactive waste in the atmosphere allows some of the short-lived products to dissipate in the atmosphere. In the case of tropospheric radioactive fallout, some degree of radioactive decay occurs in the atmosphere, somewhat reducing the dose of radioactivity to which the Earth’s surface is exposed.


Genetic effects

When evaluating the long-term effects of fallout, it is essential to consider those of radiation. Radiation can produce mutations, that is, genetic changes in reproductive cells that transmit inherited characteristics from one generation to the next. Almost all radiation-induced mutations are harmful, and their deleterious effects persist for successive generations.

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