[lug] glowing key ring

David Anselmi anselmi at anselmi.us
Mon Dec 13 15:52:28 MST 2004

Jason Davis wrote:
> Hello,
>  Does anyone know where I can order one of these key rings ... and  have
> it shipped to the US?

Google says the NRC doesn't allow this.  Take with a grain of salt:


I had been taught that beta radiation (the tritium decay product) is 
blocked by the skin (so your only real worry is exposure to the lens of 
the eye, unless taken internally).  But I'd seen a geiger counter 
register radiation from a tritium watch with the tritium behind the 
crystal.  Seems that you need something like .5" of plastic to block 
beta radiation (is that a tenth-thickness, or something more?):


so that explains it.  Interesting that light elements are better for 
blocking beta.


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