Traser GlowRing - so cool - but you can't buy one in the U.S.A.

I was aimlessly wandering around online earlier today, and happened on the Traser GlowRing.

It's a small luminous keychain attachment, containing a tiny vial of tritium gas.

As I looked for a place to buy one, I kept running up against notices that GlowRings could not be shipped to the U.S. or Canada.

They're sold in the U.K. without any problem.

Now, you'll recall my fascination with what I've termed "intellectual arbitrage" - where something has different values/rules attached to it, depending on the country or place.

And you may, for background and reference, want to refer to last month's post on U.S. government-issue navigator/pilot watches, also with tritium vial watch face technology.

So, why can't I buy a keychain attachment with tritium?

Here's what I learned:

The active part of the technology is a 1-millimeter diameter hollow borosilicate glass tube, whose internal layer is covered with fluorescent (phosphor) powder.

The tube is then filled with tritium (radioactive hydrogen) gas.

Tritium emits beta particles, which are essentially low speed electrons.

When a beta ray hits the powder-coated walls of the tube, a photon is emitted.

Light is produced.

The glass tubes were given the name "Trasers" in 1968, when they were patented.

The word Traser is a contraction of the words "tritium" and "laser"; the laser part refers to the fact that the tube is sealed with a CO2 laser after being injected with tritium gas.

The half-life of tritium is 12 years, so in 12 years, the tube will glow half as brightly as when new.

Thus, they're said to last for 10 years.

What makes the GlowRing different from other luminous devices is that it does not ever need to be placed in front of a light source in order to emit its own light.

It is, if you will, self-powered.

It will be just as bright after a year in a dark room as if it had been in direct sunlight all that time.

The light is said to be almost unnoticeable in daylight, so much so that some who've bought them think they got a dud.

At night, though,

the soft glow is said to illuminate a radius of about 18".

Rob Reeve, a U.S. Navy nuclear reactor operator, commented on this site that the beta particles are incapable of penetrating human skin due to their low energy.

Mark Ford, a nuclear engineer commenting on the same site, wrote that there is a very small amount of higher energy gamma radiation emitted from these devices.

However, to put things in perspective, he notes that this dose is 600 times less than that coming from a luminous watch, and "completely safe."

Of note is that there are two versions of the GlowRing.

The older, original version (just above) is a solid piece of plastic enclosing the tritium-filled vial.

The new one, called the X2 (below),

has metal caps on the top and bottom.

A number of comments on various sites indicated that these caps are prone to coming off,

and that the old version is thus more durable.

Personally, at least looking at the pictures online, I think the old one, without the metal caps, looks a lot nicer as well.

Also, the old version costs less.

Another thing: one owner pointed out that the GlowRing may trigger radiation detectors, so taking one to the airport might not be the best idea.

Also, the writer noted that the Washington, D.C. Metro system now has radiation detectors, so again, carrying one there could lead to all sorts of unpleasantness.

The reason these devices cannot be imported into the U.S. is that they - unlike watches with tritium dials - are considered "frivolous" uses of technology involving nuclear radiation.

If, however, you don't live in the U.S. or Canada, this is a good place to buy one.