Radiation, and especially its effects on us, is difficult to understand and difficult to explain. Oh, we all know that it’s not good for us. It can kill us outright; it can cause a variety of cancers and mutations; it can cause sterility, weaken the immune system, and other degrees of malaise that are not fatal. But when it comes to questions of “how much radiation?” and “What type of radiation?” and such – it’s just complicated. Anyone who has simple answers is simply wrong.
One of the reasons for confusion is that the word “radiation” is accurately used for infra-red radiation from anything that has a temperature above absolute zero; for radio waves; for the light that we need to see anything; for ultra-violet radiation that gives us a sun tan or sunburn; and finally, for the ionizing radiation of various types that comes from nuclear explosions and nuclear reactors.
Anyone who warns us of the harm from nuclear technology should, to be technically correct, always speak of “ionizing radiation.” That would at least distinguish the types of radiation that can directly break chemical bonds (like the bonds that keep the strands of DNA in our cells together and functioning) from those that have no such power.
This is not to say that the other lower-energy types of radiation from infra-red to ultra-violet are entirely harmless. In sufficient amounts, they can cause heating (microwaves), blindness (a laser in the eyes, or staring at the sun), even skin cancer (following a bad sunburn, or multiple sunburns). But there are several things about these lower-energy levels of electromagnetic radiation that distinguish them from ionizing radiation.
The lower-energy radiation is so common that we are exposed to it continuously of at least daily. It’s not particularly harmful at the normal levels we encounter. We can directly detect much of it with our senses, so we get immediate warning when something is too hot or too bright.
Ionizing radiation is harmful even in very small doses. here, I’ll quote directly from Wikipedia, because I don’t know how to express the idea any better than this:
The linear no-threshold model (LNT) is a model used in radiation protection to quantify radiation exposure and set regulatory limits. It assumes that the long term, biological damage caused by ionizing radiation (essentially the cancer risk) is directly proportional to the dose. This allows the summation by dosimeters of all radiation exposure, without taking into consideration dose levels or dose rates. In other words, radiation is always considered harmful with no safety threshold, and the sum of several very small exposures are considered to have the same effect as one larger exposure (response linearity).
It’s a good thing that ionizing radiation is not a common part of our environment, because not only is it harmful at any dosage, our senses are not able directly to detect it. We may notice the symptoms of exposure to ionizing radiation hours, days or years later, but we are just not equipped to notice the ionizing radiation itself. Just think of when you have had a dental X-ray. (This is on the lower-energy end of ionizing radiation.) You probably heard a buzzing, which is a deliberate warning sound indicating the device is producing X-rays, but you felt nothing different than when the machine was not buzzing.
X-rays were not even known to science until they were discovered by Wilhelm Röntgen in 1895. In the previous decade, several scientists noticed that photographic plates be fogged when placed near an operating Crookes tube, but Röntgen was the first to investigate and determine the reason.
There is some discussion in the scientific community about whether X-rays should be classified as gamma radiation or not. This is similar to the so-called controversy over whether Pluto is a planet or not. Some people want to define a planet so that Pluto is considered to be one, and some people want to define it so Pluto is not one.
X-rays and gamma rays are both electromagnetic radiation. Both are for some purposes treated as waves and both are sometimes treated as particles (photons). Both x-rays and gamma rays are forms of high-frequency ionizing radiation, which means they have enough energy to remove an electron from (ionize) an atom or molecule.
Ionized molecules are unstable and quickly undergo chemical changes. Gamma rays are at the higher-energy, higher frequency and shorter wavelength end of the electromagnetic spectrum. X-rays are lower energy, lower frequency and longer wavelength compared to gamma rays, and X-rays are also higher energy, higher frequency and shorter wavelength than ultraviolet light. For a more detailed and technical explanation, you might look at David Terr’s website or similar sources.
For all this sort of ionizing electromagnetic radiation, the best defenses are distance and shielding. Let’s say the source of radiation is a reactor meltdown. The further away you are, even if there is nothing between it and you but clear air, the less radiation will reach you and the less affected you will be. At any given distance, the more heavy shielding such as lead, steel and concrete are between the source and you, still less radiation will reach you and you will be less affected.
The alpha and beta radiation which are also produced in a meltdown can travel only short distances. These are not electromagnetic radiation. They are particles; pieces of broken atoms. Beta radiation is simply an electron knocked loose from its normal orbit around an atomic nucleus and traveling with some considerable energy.
The highest-energy beta electron might travel up to 12 yards in air, or about an inch through water. The alpha particle is more than 7000 times as massive as a beta electron, and travels only a few inches through air or a negligible distance through water. Unless you are right at a nuclear reactor during a meltdown, you don’t have to worry about alpha and beta radiation from outside your body.
The problem with radioactive fallout is there are many ways for it to get inside your body. With radioactive isotopes, each unstable atom can be the source of alpha, beta and gamma radiation. If any of these unstable atoms get inside your body, then your cells are at point blank range and no shielding is possible.
A meltdown, nuclear bomb or other “criticality event” produces many varieties of radioactive isotopes. There’s uranium and plutonium of course, because there are in the nuclear fuel to begin with and most are not consumed in the nuclear reaction. The atoms that are consumed break down into radioactive iodine, cesium, strontium and more.
There’s a tremendous amount of detailed information available about all of this. There are college courses on the subject, and yet there is much that is not yet known about how cells work and how the various types of radiation affect them. if you want to know more, you might start with the Wikipedia article on ionizing radiation and continue with the many references at the bottom of the page.
With just a little technical knowledge or a lot, the conclusion we soon reach is that it is dangerous to operate a nuclear reactor, because the danger of disaster is both real and very much greater than the risk assessment experts at the Nuclear Regulatory Commission (NRC) would have us believe. In 1954, the head of the Atomic Energy Commission (now the NRC) predicted that electricity would become “too cheap to meter.” We see how that worked out. They are as trustworthy as the Michigan Department of Environmental Quality was when it said the water in Flint was safe to drink.