Blowing in the wind
Human beings, and all other life, have evolved, bathed in radiant energy from that great nuclear fire that is our sun. Without the benign effects of its radiation in the visible spectrum life as we know it would not exist. However, we do know that not all radiation from the sun (as with all nuclear fires) is good for us. Ultra violet light can cause skin cancer and X rays and gamma rays can damage our internal organs. Most such radiation from the sun is, fortunately, filtered out by the atmosphere.
When a nuclear bomb is detonated, energy is liberated as a massive pulse of gamma rays. This causes devastation over several miles as the energy is absorbed by people, animals, plants, the earth and the atmosphere. Free neutrons (uncharged nuclear particles) are also liberated and produce a large range of radioactive isotopes as they penetrate the nuclei of various atoms.
In the controlled conditions of a nuclear power station reactor similar processes take place. Here radioactive isotopes are created within the reactor structure and fuel rods. We note: “Because a commercial nuclear power plant holds an order of magnitude more radioactivity
than is released by exploding an atomic bomb, long term radioactive contamination from a successful attack on a power plant would be much more drastic than that from a bomb.” (1)
Radioactive isotopes in the atmosphere, whether from a nuclear bomb explosion, from a power station reactor fire or even from the impact of a depleted uranium tank shell, start life as vapor. As the vapor cools it will condense on tiny particles of dust and begin to form “fall out”
The trouble with “fall out” is that it may take many years to fall out if it ever does so at all. For a body falling in a viscous medium (eg.air) size matters. The rate at which it will fall is proportional to the ratio of mass to surface area, i.e. for a given material, proportional to the cube of the linear dimension divided by the square of the linear dimension.
In practice this means that any particle in the air of the order of one micron or less, virtually floats, subject, not to gravity, but to the four winds of heaven. We inhale and ingest billions and billions of such particles throughout our lives and most do us no harm at all.
The radioactive isotopes in particulate matter in the atmosphere are many and varied in the emissions they produce and the energy released. The damage these emissions can do to our bodies becomes greatly enhanced if these isotopes become incorporated in our tissues and especially where cells are dividing – eg. bone marrow cells, germ cells, the developing fetus.
While we can shield ourselves from particulate (i.e. Alpha and beta) radiation with comparative ease and even screen ourselves from UV light, X rays and the very high frequency, very penetrating, gamma rays of the electro magnetic spectrum, we can do nothing about such emissions once the substances producing them are within our bodies.
We have to breathe. We have to swallow the plants and animals that constitute our food. They in their turn have to exchange gasses and particulates with the atmosphere. Our atmosphere is polluted enough. The further pollution of that atmosphere with more radioactive particulates is a possibility no one should dare contemplate.
(1) Gerd Rosenkranz, Nuclear Issues Paper No 1, p.12 Nuclear Power Plants: Radioactive targets in conventional warfare. Heinrich Boll Foundation, February 2006.