Thursday, July 7, 2022

Different types of nuclear radiation (and why they are all dangerous).

Different types of nuclear radiation and why they are all dangerous.

By Ace Hoffman

July 7, 2022

NOTE: It is presumed you are looking at my Electromagnetic Wave Spectrum graphic as you read this explanation, so here it is:

When radioactive isotopes decay, they release high-energy rays and/or particles. In this essay we examine the four types which are most significant for humans and other living things, because we inevitably are impacted (literally!) by these rays and particles. (There are several other types of emissions during radioactive decay, but these four are the most influential on human health.)

What is the difference between alpha particles, beta particles, x-rays and gamma rays? Why is each one dangerous? And why are alpha "particles" and beta "particles" also considered to have "wave-like" behavior?

This document gives a brief description of what atoms are comprised of (the three main subatomic particles: electrons, protons and neutrons). A glance at a Periodic Table of the Elements will enhance that portion of the discussion for those who need a review.

The Electromagnetic Wave Spectrum graphic is arranged in three rows For some reason, most illustrations of the Electromagnetic Wave Spectrum only show the top two rows. The top row is labeled "Frequency in Hertz."

The middle row is called the "Wavelength Equivalent."
The bottom row -- in many ways the most important, and yet the one most illustrations of the Electromagnetic Wave Spectrum ignore -- shows the "Energy Equivalent."

For the top and bottom two rows ("Frequency in Hertz" and "Energy Equivalent") the chart is arranged in exponentially increasing values from left to right. The middle row ("Wavelength Equivalent") has exponentially increasing values going from right to left.

Each row has a range of 22 orders of magnitude. 22 orders of magnitude is an enormous difference! Here it is written out:

10000000000000000000000. Or if written with commas: 10,000,000,000,000,000,000,000.

Orders of magnitude can be difficult to grasp. But as an example, consider musical tones. The lowest bass notes are about 20 Hertz, or cycles per second. The highest notes are under about 10,000 Hertz. That is a range of about three orders of magnitude, and most music is actually only within just two orders of magnitude. The limit of human hearing is under 20,000 Hertz. 22 orders of magnitude is not just 19 times broader, it is 10^19 times broader (10000000000000000000 times broader, if written out. 10,000,000,000,000,000,000 times broader, when commas are included!).

Energy, in the form of Beta particles, Alpha particles, X-rays and/or Gamma rays is released ("ejected" or "emitted" if you prefer) when a radioactive (or "unstable") atom decays. (Please see other documents for how to determine when a particular atom will decay if it is radioactive. Suffice to say here, it is at some future, unpredictable, semi-random, moment.)

One beta particle, if released by a radioactive atom (such as Tritium), can damage thousands of chemical bonds because it is thousands of times more powerful than ANY chemical bond -- and not just in living things, but ANY chemical bond. Any metal alloy made, no matter how strong, is bonded together with chemical bonds less than approximately one thousandth (<1/1000) as strong as one beta particle's energy when it is ejected during radioactive decay.

It does not even take a full electron volt to destroy a chemical bond: Many atoms have outer electrons which are only held relatively loosely to the atom's nucleus.

If an electron is knocked out of an atom's orbit, the atom will appear to other atoms as a different element unless it is able to find a replacement electron -- which it might take from another atom that is holding its outermost electrons less tightly. Thus, a "chain reaction" of sorts can let one beta decay damage perhaps 10,000 or more molecular bonds, even though it is "only" a few thousand times more powerful than a typical chemical bond.

Beta particles have another feature which can also be very damaging: They are charged particles, with a negative charge of one electron volt. (Beta particles "become" electrons when they slow down from nearly the speed of light to "terrestrial" speeds.) Other electrons are repelled by a beta particle.

Alpha particles are thousands of times more powerful than beta particles. That is why they are so damaging if released inside a living organism. They are also very large and highly charged: Plus two electron volts, because they are composed of two protons, each with a positive charge of 1 eV, and two neutrally-charged neutrons.

Electrons are attracted to alpha particles, and it will grab two from somewhere when it slows down, and that's only after doing a lot of damage along its track. (After grabbing two electrons, it becomes a stable helium atom.) Even if alpha particles just pass near something, they can do a lot of damage. Alpha particles are roughly a thousand times more powerful than a beta particle, and about a million times more powerful than ANY chemical bond.

Gamma rays are similarly powerful but since they are neutrally charged and massless, an individual gamma ray can pass completely through the body without doing any damage and often does, since atoms are mostly empty space. But if a gamma ray does hit something (a electron or a nucleus of an atom) gamma rays can be very damaging.

It has been known since the 1950s that X-rays can cause cancer. Gamma rays are thousands of times more powerful than X-rays. Both are massless, without any electrical charge, unlike beta particles, with a -1 eV charge, and alpha particles, with a +2 eV charge.

Now let's look a little more closely at the Electromagnetic Wave Spectrum.

First, let's look at the top area, to the right of the heading. A significant portion of the chart is marked as the "Ionizing" portion.

"Ionizing" means forces in that region are strong enough to knock an electron out of its shell and/or away from the atom it belongs to.

Atoms are comprised of a very small nucleus with protons and neutrons (except for one variety of hydrogen, with only one proton and no neutrons in the core). Every atom also has an outer portion outside the nucleus, which is mostly empty space, plus one or more very small subatomic particle(s), known as electrons, with an isolated atom having one electron for each proton in the nucleus (we say "isolated" because when atoms get together, they often share one or more electrons).

The shared electrons are what form bonds with other atoms to form molecules such as Oxygen (O2), Carbon Dioxide (CO2), and DNA.

DNA is the most complex molecule known to humans (our own is not even the most complicated, or at least, not the longest). Virtually every human cell has DNA except mature red blood cells. Amazingly, the body has mechanisms to repair some types of damage to DNA molecules. But repair is not always done perfectly. If an electron is knocked out of a DNA molecule, the damage might be repairable, but it might not be. If several electrons are knocked out, the damage is much less likely to be repairable. The DNA molecule might even be broken into independent strands, which are useless (or even detrimental). Every human body has trillions of cells that each have their own copy of that person's DNA. We are all susceptible to "ionizing" radiation damage.

We've been discussing what gets impacted (or "ionized") when a moving object (beta particle or alpha particle) or packet of energy (gamma ray or x-ray) impacts something. Now let's go back to the Electromagnetic Wave Spectrum itself again.

The top row lists various types of waves: Radio Waves on the left, through Microwaves, Infrared, Visible Light (expanded because it is a very tiny portion of the entire spectrum), Ultra Violet, and then, on the far right, X-rays, Gamma Rays (with a symbol for "Gamma") and Cosmic Rays.

These last four groups are powerful enough to be Ionizing, although Ultra Violet is about 100 times less powerful than X-rays, which are in turn another 100 times less powerful than Gamma Rays. Cosmic Rays are the most powerful, and may be responsible for some cancers, but unfortunately, they are unavoidable.

Lets now look at each of the three rows individually.

The top row, "Frequency in Hertz (cycles per second)" indicates how many peaks and valleys would pass by a given point in space in the span of one second.

The middle row, "Wavelength Equivalent" indicates the distance between successive peaks (or valleys). At the left, the wavelengths are as long as a blue whale. Different images that are about the size of various wavelengths are shown, getting smaller and smaller from left to right.

The bottom row is the most important. How much energy does an energy packet (x-ray, gamma) or particle (beta, alpha) have? And how does it do its damage? It breaks chemical bonds, and the particles also do physical damage as they plow through DNA and any other molecules in their way.

Along the bottom row of the Electromagnetic Wave Spectrum graphic are shown various objects: On the left is a beaker labeled "Thermal Noise" at around 12 millielectron volts (basically, "thermal noise" is background movement of everything on earth, as viewed at the atomic level. Two liquids in the beaker would tend to mix because of "thermal noise" (and perhaps for other reasons as well).

Hydrogen Bonds and Covalent Chemical Bonds at around 1 electron volt. All molecules are held together by such bonds.

Far to the right of those bonds is the energy of a beta decay, which is several thousand times more powerful than a chemical bond.

An alpha decay at another thousand times more powerful than a beta decay.

X-rays and gamma rays are also very powerful. Gamma rays can even be more powerful than an alpha particle.

At the far right is the energy released when a plutonium atom is split. This energy release is usually dissipated among several smaller particles, and results in two "fission fragments" -- smaller atoms with each having about half the protons of the plutonium atom. (Both fragments are almost always also radioactive.)

About half -- or more -- of the radiation the average person in America absorbs in a lifetime is not natural, but is the result of medical procedures, global accidents such as Fukushima and Chernobyl (and thousands of smaller accidents), and from atomic weapons testing. Even one radioactive decay, even at the lowest energy level, can be very damaging to human and other living things. This is why experts long ago declared that "any dose (of radioactivity) is an overdose." Maybe it won't result in anything serious. But then again: Maybe it will.


Nuclear Power and Nuclear Weapons: A Beginner's Guide -- in pictures and diagrams:

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