Radioactivity, nuclear stuff

I’ve always wondered about radioactivity. We produce all this radioactive waste from nuclear this and that, stuff that won’t degrade for a jillion years, will kill you, etc.

Where does it originate?? Where does plutonium come from? What other substances are used? Are they radioactive to begin with, or do we make them so by what we do to them? If they exist in nature, why aren’t we all dying from all this radioactive schmutz lying around?

What IS the deal? I gots ta know…

This is a non-smoking area. If we see you smoking, we will assume you are on fire and act accordingly.

The most dangerous stuff is also often the shortest-lived. Highly radioactive substances usually break down quickly into less radioactive substances. Thus, only the less radiactive stuff is commonly found in nature, since there has been plenty of time since the earth’s creation for the stuff to break down.

Stuff in bombs and nuclear plants is usually man-made, out of less-radioactive naturally ocurring stuff. The process is called “enriching”; enriched uranium is the stuff to worry about. Natural uranium ore isn’t so bad; you can go hiking in some parts of the U.S. and pick up some uranium decay on a Geiger counter. Radioactive barium and iodine are mild enough to be injected/injested into the body for medical purposes.

So in short, the most radioactive, most politically-relevant substance are found in nature, but only in minute quantities. So you don’t have to worry about falling into a plutonium quarry. Just be sure to do your math when mixing uranium quantities.

A&E did a “100 greatest biographies” bit last night, and mentioned in passing that Mme Curie’s journals and diaries are locked away, they’re still radioactive. She died of leukemia, brought on by exposure to the radioactivity (of course, they didn’t know about the illness relation in those days.)


That happens to be what made me ask this question.

I’ll be interested to see who the top 25 turn out to be, and I was very surprised that so many classical composers were included, not to mention the Spawn of Satan himself, Bill Gates.

This is a non-smoking area. If we see you smoking, we will assume you are on fire and act accordingly.

U-238 can capture a neutron to form U-239. This undergoes beta decay (with a half-life of about 23 minutes) to form Np-239, and THAT undergoes beta decay again (with a half-life of a little over 2 days) to make Pu-239.

Alternatively – though I don’t know if this happens “naturally” – there’s a process where U-238 can interact with an alpha particle to produce Pu-241 and a neutron.

An interesting fact is everything is slightly radioactive. I remember my Chem teacher last year bringing in a Geiger counter in and hearing it make noise as it picked up all the free radioactivity in the room.

Theres no way to escape radiation. According to my Chem text (no one would buy it off me sniff), we get background radiation from:

  • Cosmic ray showers
  • From the crust of the earth
  • Building stone (especially granite)
  • Radon Gas
  • Carbon 14 from the food we eat
  • Potassium-40 we get from just having potassium ions in our bodies
  • And everyone in the US has some residual radiation left from the nuclear tests that have been performed (in the form of strontium-90 (i believe).

Our average mrem dose per year is 360. The deadliest dose of radiation is 600 rem (so what we get per year is well within safe limits :)). Also, radiactive substances all want to decay to a stable form, which is lead .

Also, that biography special is about the most influential people of the millenium, not the most nice or whatever.

Stoidela: I had NOTHING to do with Gates. You take that back!!

Yer pal,

I think Isaac Asimov wrote something really interesting about all the sources of radioactivity humans are subjected to. I think it was titled “The Enemy Within” or someting. I read this in a SF magazine, but I’m not sure if it was fact or fiction, he seemed very serious and wasn’t making a story out of it. His conclusion was that the most significant source or radiation came from within our own body, all the rest was insignificant compared to it. Hence, our body is its own source or random mutation. Does anyone know anything about this? Fact or fiction?

Only humans commit inhuman acts.

Momotaro writes:

Well, I certainly wouldn’t call it insignificant. I haven’t read the article, and don’t recall if Asimov published before or after the large contribution of radon (strictly speaking, radon daughters) was recognized. Self-radiation accounts for about 40 mrem/year, mostly from [sup]14[/sup]C and [sup]40[/sup]K (the former is created by cosmic rays from [sup]14[/sup]N, the latter is primordial). Radon, OTOH, accounts for an average of 200 mrem/year.
In some areas, monazite (a mineral containing [sup]232[/sup]Th and its daughters) gives the locals doses of up to 5 mrad (notmrem) per hour; these doses appear to have no health effects.
Dooebieous writes

High-Z radioactive substances want to decay (largely, although not entirely, through alpha-emission) to a stable form, usually a lead isotope; IIRC, the upper limit of stability is about Z=208. Lighter isotopes decay through beta emission to a stable isotope nearby in A/Z (atomic number/atomic mass) terms.

“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”

Pretty good recollection. There’s a stable isotope of bismuth at Z=209.

I don’t think there’s anything above that which is stable… though there’s a thorium isotope at Z=232 has a half-life of about 14,000,000 years.

An interesting item, but one for which I don’t have the source, is the assertion, with figures to back it up, that a typical coal-burning plant releases more rads (from C-14) into the atmosphere than the Three Mile Island incident did, over equivalent time spans (two days was I think the figure given).

Naturally-occurring radioactive elements, like uranium, originated in supernovae. When a star becomes a supernova it undergoes a catastrophic compression which results in the creation of all sorts of elements which wouldn’t otherwise be manufactured in a star.

Our sun is a second- or third-generation star, made up of the remains of earlier stars which went through this cycle. The solar system is about 2% elements other than hydrogen and helium, which were produced in the big bang. This is what Joni Mitchell was referring to when she said “We are stardust … We are three-billion year old carbon”.

So naturally occurring radioactive elements are either 1) those elements that have half-lives long enough to have survived since the supernova, or 2) products of these elements that are renewed by the decay of these elements.

And even if there were no radioactivity on the earth there would still some radiation from cosmic rays. The atmosphere shields us from most of these: frequent flyers get higher doses than the earthbound.

Strangers have the best candy.

Polycarp writes:

Polycarp, you may want to go here for a reference on coal releasing nore more radioactivity than nukes.
I note in passing that [sup]14[/sup]C has a half-life of only 5,730 years, and would of course be long gone from fossil fuels buried in the Carboniferous. The radioactivity in (and released from) coal comes from the decay daughters of urnaium and thorium.

“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”

Thanks, Akatsukami!!

I’m now starting a campaign:

Save the world from radioactivity!! Build nuke plants!!

IIRC, when using carbon-14 for dating things you have to adjust for exposure to airborne CO2 from fossil fuels which, as was pointed out, has no carbon-14.

Strangers have the best candy.

Akatsukami: Whoops! I forgot about that. Sorry!

One thing i have never been clear about, is high radioactivity dangerous for electronics because it causes the materials to degrade?

‘The beginning calls for courage; the end demands care’

Doobieous –

Yeah, pretty much, except that rather than general degradation, the problem is a single point of failure at a critical spot. Hard radiation can ionize, dislocate or even transmutate atoms in the chips. If this happens at the right spot it can cause the electronic function (usually a transistor) at that spot to fail. And random failures of random transistors can cause random outputs from computer components. Obviously some spots are more critical than others – e.g. memory chips are generally more forgiving than arithmetic processing units – but these are not components that degrade well. They either work correctly or they don’t. Actually having them stop working altogether is preferable in some cases to working incorrectly.

After that long diatribe I should also mention that the dreaded electromagnetic pulse (EMP) caused by nuclear weapons can also have a disastrous effect on computer components. This is a little easier to protect against and some of the effects go away when the pulse subsides (in which case the computer can reset and go) but if enough current gets in it just sort of melts things.

Structural materials also degrade after exposure to radiation – metals get brittle, etc. But this is generally from long-term exposure and is important in the design of nuclear plants and waste facilities, not so much in defense from nuclear attack. If you’re close enough that radiation is having an effect on the materials around you, you probably want the building to fall on you.

Strangers have the best candy.

As I recall, the natural radiation levels in Grand Central Station are higher than the maximum permissible radiation levels inside a nuclear plant.

One of the biggest radiation exposure mechanisms is radon gas which may be trapped in your home. When the energy crisis hit in the 70’s and people started sealing up their homes, their yearly radiation exposure skyrocketed. I seem to recall that Radon may be responsible for something like 3000 cancer diagnoses a year.

On the other hand, it appears that we don’t really understand the effects of radiation on the human body. The new data coming in from Chernobyl is confusing the heck out of scientists. For instance, Lieukemia rates are much, much lower than they should be. There are also some scientists suggesting that low levels of radiation may actually be good for you.

dhanson points out:

From this I assume that GCS is made of granite. Most granite has a relatively large level of natural radioactivity because it has a tiny (but relatively large) amount of uranium in its makeup. So if you’re phobic about these things, stay away from granite.

“The inability of science to grasp Quality, as an object of enquiry, makes it impossible for science to provide a scale of values.”
Robert Pirsig