At Saturday's gun show, I picked up one of these:MIL-SPEC compass with Tritium light source on the needle. #2 Son and I said to ourselves, "Wonder if Tritium is Radioactive?"
Just the thing to try out with an old Civil Defense Geiger Counter. So is Tritium Radioactive?
Well, I'm told that it is, but by Wikipedia, not by the Geiger counter. Even at the most sensitive setting, I don't get a reading distinguishable from noise.
The feeling of disappointment is strange, because if there were enough radioactivity to set the geiger counter off, the compass would be a health hazard.
Still, ...
Tritium is radioactive but the alpha particles it emits won't pass through the little vial holding the material.
ReplyDeleteAre you sure you got the tritium version of the compass? They make both tritium and non-tritium versions. The tritium version has a radiation warning embossed on the back.
ReplyDeleteMinor correction: yes, tritium is radioactive -- that's how it makes the glow -- but it emits beta particles, not alpha particles. Its half-life is 12.3 years. Those two facts put together mean that its radioactivity is very, very weak. A 1950s-era Civil Defense geiger counter probably is not sensitive enough to detect it.
ReplyDeleteBob, yes it's the Tritium model. It has the Biohazard symbol and "Do not open case" warnings.
ReplyDeleteWolfwalker, I think that you're right that the level of radioactivity is below the sensitivity cutoff.
BP, those civil defense geiger counters most sensitive setting is about five orders of magnitude too high for a bit of tritium.
ReplyDeleteOn most of them the lowest setting is .1 rad per hour. A small tritium source would be under .01 millirad per hour.
The industry standard for watches, compasses etc... is .1 microsieverts, and a microsievert of beta is equivalent to .1 millirad.
Chris, you're correct about my Geiger Counter - the lowest setting is in fact 0.1 rad/hr.
ReplyDeleteIt's probably A Good Thing that we haven't been able to find anything in the house that gives us a reading ...
Oh and by the by, not that I would trust one of those thigns after this long to be in any way accurate; but even .1rads per hour is a fair bit of radiation.
ReplyDeleteGenerally speaking under .2 rads per hour for short term exposure and you're OK unless you breathe contaminated dust, or eat or drink anything.
Anything more than around .2 and you'll become quite ill. Much more than .4 and you will need treatment for acute radiation poisoning. More than 1... pretty much dead no matter what.
Of course the RAD is an outdated measure. Now they want everything done in Grays and Sieverts (which is a more accurate weighted measurement based on the nature of the radiation as well as the total energy).
Looks like EVERYONE beat me to it.
ReplyDeleteTritium is a beta emitter - it is thwarted by paper and skin.
You need to get down to the level of 14C or 125I before you start tripping Geiger counters...
Just make sure that you don't open it up and drink it Borepatch, might make you glow ;-)
ReplyDeleteMy uncle (an old Tile Contractor) had a couple of alchies' that we just simply could not keep away from breaking open our level's.
Level's back then had alcohol in the bubble part to keep them from freezing in cold weather. L.O.L.
Just got the computer back up and running, and wanted to say thanks for the mention a few posts back also.
To add to what everyone else has listed:
ReplyDeleteThe meter that you have is a CDV-715. This meter is designed to detect gamma radiation, not the Beta that is emitted by tritium. In order to detect the alpha and beta particles, the CDV-715 was packaged with the CDV-700 (this is the one with the 'wand') which could do the job that the 715 couldn't.
These old civil defense meters are so old that they are no longer reliable unless refurbished. I hope you didn't spend money getting it.
Divemedic, great information. Seems I need a Gamma emitter. ;-)
ReplyDeleteAnd nyes, we did spend some money. But it was small money.
What Divemedic said. Except that the radiation class instructors tell me that those old CD Geiger Counters are the most sensitive and accurate ones out there. You can still find them new, in the box, at electronic flea markets now and then.
ReplyDelete"These old civil defense meters are so old that they are no longer reliable unless refurbished. I hope you didn't spend money getting it."
ReplyDeleteActually, that's not true. Other than calibration, these meters (made by Victoreen and Lionel) are extremely reliable. THey do have calibraion issues after many years, but they generally work to detect no matter what. If they pass the "circuit test", then they generally work.