I’ve been thinking a lot about how to explain the dangers of radioactivity and I just read something that I think is a totally misleading description of what radiation is.  The non-scientist writing about science described the dangerous stuff in a reactor as fundamentally the same as sunlight or heat.  I guess that might be true at some level but it’s not helpful in understanding radioactivity.

Back in the 1950s we had the same problem and the misunderstanding that so many people suffered from manifested itself as Godzilla and gigantic mutated ants in the movies.  The scientists didn’t explain things in an understandable way and people filled in the gaps with monsters. I thought I’d try to explain some of it here.

While in grad school I worked in the accelerator lab and learned a good bit from my professor who was the university’s radiation safety officer.  We operated a particle accelerator; when the particles hit something, the sudden deceleration causes energy to be radiated so I always wore a film badge.  We had to learn a little about this stuff to get to work there and this is what I learned, more or less.

First, the term ‘radiation’ is misused often.  Radiation means any energy that is radiated; that is, it travels from its source by radiating into space.  Heat is the best example of this.  Light is another good example.  You feel the warmth of the campfire when you stand next to it; you read a book by standing next to a light.  Both these things radiate energy from their sources to you.  That’s why the thing in old houses was called a ‘radiator’. But when we start talking about ‘radiation’ in the nuclear reactor sense, we are usually talking about radioactivity which is a very similar word.  This is an unfortunate mashing together of two different usages although it is true than when anything starts at some point and travels out in all direction it is said to ‘radiate’ so what I’m about to write about is certainly ‘radiation’ but I think it’s best to separate the two usages.

So what is radioactivity? It’s when a large atom (one with a large number of protons and neutrons) is too large to stay that way and it splits into two or more pieces.  I don’t remember the details of why a large atom would become unstable but I do remember that with both the nucleus and with the cloud of electrons there is nice neat arrangement of things that occurs naturally. If you get above a certain size (or stick in an extra neutron or two) then things get unstable and tend to fall apart. Usually there are other things besides the two new atoms that are produced too – like X-rays and/or gamma rays. In addition, usually the fragments of such an event are themselves unstable in some way and they will also split into fragments creating more X-rays, gamma rays, and such.  Lots of these X-rays and gamma rays are absorbed by other atoms nearby and this ultimately manifests itself as heat which is why radioactive compounds are often hot.  But lots of X-rays and gamma rays get out.  These are the problem.

There are other fragments.  There are beta particles; this is nothing more than extra electrons.  The same thing that makes up electricity.  Then there are alpha particles; this is the nucleus of a helium atom.  In other words two protons and two neutrons floating freely.  If you could force them into the same general vicinity as the beta particles, they would combine and make a helium atom and you’d have no trouble.  These aren’t very much trouble anyway; they don’t penetrate very far into anything.  Enough of them will cause first degree burns to the skin but little else.  They are sometimes called beta rays and alpha rays but this is just a misnomer left over from the earliest days of nuclear physics before the particles were completely understood.  The other things: X-rays and gamma rays, I’ll discuss later. There can also be extra neutrons floating around.  These tend to get lodged in the nuclei of other atoms and contribute to more instability and more decaying atoms.  Some materials like Boron are neutron absorbers – I don’t know how they get absorbed or where they go when they’re absorbed.  I suspect that some atoms have nuclei that can take on another neutron and still be nice and stable.  Others can’t.  This stability is probably easiest to visualize by thinking of Jenga blocks.  They stand up pretty well when everything is arranged just right but if you knock out one in just the right place, the whole stack falls apart.

We used the term ‘ionizing radiation’ in the lab. That is kind of a catch-all phrase that describes anything coming out of an atom or molecule that will cause damage.  There are many mechanisms for such damage but one stands out.  Basically, if an X-ray or gamma ray collides with an atom or molecule, it will knock off an electron which creates an ion.

So what?

If you ionize an atom, its chemical properties change.  Biological processes are so complex that if you ionize one of the atoms in one of the molecules, you’ll usually screw up the whole chain of events.  If this happens enough (if you have enough X-rays for example) you can cause an entire organ to stop functioning.  Furthermore, if you ionize one of the molecules in a chromosome, then the next time that chromosome is duplicated during cell division, the process might get screwed up depending on what that particular damaged gene does in the human genome.  Usually the process just fails to complete and that cell dies.  If not, the change might do nothing (that we are aware of so far) or it might control something important.  If it happens to be a switch that controls cell division then cellular division might continue without stopping which is what cancer is.

Or whatever chemical chain of events that makes an organ function might stop and that organ would cease to perform its function.  Sometimes all this stuff: the X-rays, beta particles, alpha particles, and gamma rays all together will cause enough damage to look like a first degree burn.  This is sometimes called ‘beta burn’ or ‘gamma burns’.  Usually you see this when someone inadvertently carries a radioactive material in their hands or pockets or some such accidental exposure.

Some of this damage happens all the time. The human body is set up to deal with a few events of random molecular damage but if you get too much of this ionizing radiation, the body can’t deal with it.  This cumulative ionization affects the body in many strange ways but usually manifests itself as cancer or organ shutdown.  In extreme cases, this tissue damage will show up as hemorrhaging, diarrhea, or vomiting because so many of the cells have died. This usually happens because you get a radioactive compound on you through some accident (or oversight).

This is complicated further by the fact that the body needs several elements in trace amounts.  Iodine for example is one of the atoms in a hormone produced in the thyroid gland.  Iodine has an isotope (that is, a nucleus that has an extra neutron which makes it unstable) that is radioactive and it’s a by-product of nuclear reactors that produce power.  The thyroid will absorb whatever iodine it encounters, radioactive or not, and if it gets flooded with the radioactive kind, the damage cause by X-rays ionizing everything will cause the thyroid to stop working.  It may even die.  This is why they give iodine tablets to people who have been exposed to radioactive material; they flood the thyroid with normal iodine so that it won’t absorb any of the radioactive stuff.  This only works if you take the iodine tablets before you’re exposed to the radioactive stuff.  And by the way, the table salt that we all buy in the grocery store has iodine in it already as a nutritional supplement so iodine tablets aren’t really necessary for most people.  If a reactor melts down in Japan, you don’t need to start taking iodine tablets.  This radioactive Iodine has a very short lifetime anyway.  In a few days it’s all gone.

Another example is calcium.  The body needs calcium to build bones with.  One of the byproducts of a reactor is Strontium-90 which is an isotope that is chemically very similar to calcium, in fact, the body likes to build bones with this more than calcium.  So the body will absorb Strontium-90 and incorporate into its bones.  But Strontium-90 is radioactive with a very long half life.  Your body itself then becomes radioactive and the resultant onslaught of X-rays (from the radioactive splitting) causes damage over time. Even worse, if your body stores the Strontium-90 in your bones then it tends to damage the bone marrow and cause cancer of the bone marrow; or leukemia.

So there you have both the immediate effects and the long term effects.  If there isn’t too much exposure to radioactivity, your body can deal with it and heal although because of the few random chromosomes damaged here and there, you always have an elevated risk of cancer from that point on. As far as I know, there haven’t been many cases of this chromosomal damage resulting in a genetic mutation that was obvious in children of victims.  Monstrosities are pretty much limited to the movies. Cases of people with extra fingers and freaky stuff like that do exist but as far as I know those aren’t due to radioactivity; more from inbreeding or simply randomness I think.

Back to the atoms again, radioactive elements exist in nature – in fact that’s where we get them.  Uranium and Plutonium are two elements that are just at that special sweet spot in the periodic table.  They have a definite number of protons in their nuclei but can have a few extra neutrons on occasion.  Those extra neutrons make them unstable and prone to falling apart; in other words, prone to radioactive decay.  This is why we use them for nuclear reactor fuel (and bombs).  We can make this decay process go faster by concentrating the number of radioactive atoms together and when there are enough and they are close enough then the fireworks start.  (You’ve probably seen the demonstration of a chain reaction with a roomful of mousetraps.)  This is done by separating the radioactive uranium atoms from the non-radioactive ones. This gives you the concentrated radioactive stuff that you need for the power plants  but the process is never perfect and so the stuff that should be totally non-radioactive (what is called ‘depleted uranium’) is never pure and always has some radioactive atoms in it. This isn’t good for much but has been used in armor-piercing bullets and in counterweights due to its extreme density. (It’s denser than lead but is harder. It’s also about the same color as lead although most metals are about the same color no matter what they are.)  It also has the curious property that when mixed with other chemicals can impart an intense orange color and so at one time was used in Fiestaware dishware back in the 1950s.  The water pitchers were noticeably radioactive; my professor had one such pitcher around for demonstrations and I once put a Geiger counter down into it and it clicked like crazy.  I should point out that the dishware was not all that radioactive; only barely detectable above what occurs in nature but we had a sensitive detector and with the pitcher, you could completely surround the Geiger tube by putting in inside the pitcher and so the effect was more pronounced.

So that’s kind of what happens.  I could be wrong; I could be remembering what I learned in a distorted way or I could have not learned it right to begin with.  But I’m mostly right I think.  The world is much more complicated than this but this is about all I could put down without getting overly complicated.

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