Tritium tubes have radioactive tritium gas and a phosphor which glows constantly. Tritium is hydrogen with two neutrons. It is radioactive with a half life of 12.3 years.
“Continue reading” for radiation count and information about beta radiation from tritium plus links.
It emits beta radiation of a low energy of 18.6 keV. It is used where a long term glow is needed such as in “Exit” signs or (expensive) watches. This is not the same as the glowing hands on many cheaper watches. These are phosphorescent and emit light after exposure to light. Also emitted is an electron antineutrino. Cool really, generating antimatter in your pocket.
There is a photo on Wikipedia showing what appears to be the same sized radioluminescent tube given as 1.8 curies (67 GBq) 6 by 0.2 inches (150 mm × 5.1 mm). This is 1.8 million times the radioactivity of my americium smoke detector sample which is 1 microcurie. Of course, very little of the low energy beta radiation would pass through the glass and much is low level x rays that are generated by bremsstrahlung radiation.
The Geiger counter graph above shows the 3 tritium tubes over the detector reading 600 CPM. Background radiation here is around 50 so it is around 12 times background levels.
This glowing key ring attachment, above left, has the same tritium in a tube with phosphor. It can be bought on eBay for about $10. Search in eBay for “Tritium keyring”.
Total US production has been 225 kg and cost is $30,000/g.
The Geiger counter graph shows a few hours of background radiation of around 50 counts per minute (CPM) which jumps to around 4 times that when the tritium keyring is placed on the pancake Geiger detector (added to the background). Hence it gives 3 times background levels on its own.
BTW, I have had my children so this works in lieu of a vasectomy when I have it in my pocket.
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Photo Date: 2006; June 7, 2013