2-62. It Glows


I’m in the fortunate position of having people come up to me and say, “Hey, have you ever seen one of these before?” Hmm, usually it’s not as creepy as that sounds.

Last week, my good friend Mark Graunke came over and handed me something for the curiosity collection. It’s a very small metal cage, with a pale yellow tube in it. It looks all the world like some sort of nano-bot capsule that you would swallow to gain super powers. And that impression didn’t go away when I learned what it was.

He told me to take it somewhere dark, so into the bathroom I went and it was there I discovered how cool this thing was. The vial was giving off a steady green glow. Certainly not bright, but definitely strong. It was the kind of glow you’d expect from something radioactive.

Which it was.

Keys found!

Keys found!

He had given me a vial of tritium gas. Tritium is H3, a radioactive isotope of hydrogen. It has a half-life of about 12 years, and as such, this thing can be expected to glow for about 25 years. As it decays, it will form He3, which is the substance being mined in the film “Moon.”

Though it’s sold ostensibly as a keychain finder (it glows!), there’s a lot to learn from it. Our perception of radioactive things “glowing” has more to do with us watching too many episodes of the Simpsons than our experience with radiation. In most case, radiation doesn’t glow.

The complete concept of “radiation” is too complex for this short piece. There are many different kinds of radiation, including some you’re familiar with such as light and radio waves, but this device is radioactive in the same way the fuel in a nuclear power plant is.

The basic concept of ionizing radiation is this: a radioactive element emits a particle at a regular rate. This is called “decay,” and that particle can do things, like detect smoke, show what your bones look like, boil water for a turbine, or excite phosphor on a glass tube.

This little vial of tritium is actually a fluorescent light bulb. Electrons from the decaying tritium gas hit the phosphor coated glass causing it to glow. This seems like “magic” since we’re so used to electricity being needed for such things, but because the tritium is supplying electrons, the electricity is integral to the device. At least for the next 25 years or so.

Green is the most common color because it’s the brightest glow. You can find bulbs of red, blue, purple etc, but in general, white will be the dimmest, and green will be the brightest.

So yes, if you see me on the street, it’s very likely that I’ll have a vial of a radioactive substance in my pocket. And that substance can be used in the making of nuclear weapons. And this may have you wondering… is this safe?

Yes, by every measure, this is safe. The radiation is leaving the vial only in the form of visible light. That’s it. If this tiny vial somehow broke (it’s in a cage of titanium), the amount is so small that a few minutes of airing would remove the slightest danger. Even if I intentionally broke the vial and inhaled the gas, there’s little risk as the biologic half-life is only a few days, and can be reduced by drinking a lot of water.

Radiation isn’t evil or even inherently dangerous. It’s just something that exists, and the more we understand it, the more we can use it for important things.

If the word “radiation” fills you with fear, there’s a known cure for that. It’s curiosity.

Hmm... looks radioactive.

Hmm… looks radioactive.

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One Comment

  1. Tritium has replaced radium for things like illuminated watch hands, instrument dials and exit markers, which is a good thing- Radium can be pretty nasty if it get inside you. Tritium is a weak beta source and clears the body rather fast if ingested. (Perhaps an urban legend but there were stories of nuclear workers who accidentally got tritium into their system being sent home to drink beer or tea to more quickly clear it out of their bodies.)
    It’s radioactive enough that a spill can cause serious cleanup actions however- That happened at the University of Vermont when someone broke a tritium illuminated exit sign. But the risk of not having an exit sign you can see in the dark when there’s an emergency far outweighs any possible tritium risk. Same idea for not getting your potassium because you won’t eat bananas (which are quite radioactive as food goes).

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