[Test-Equipment] Radioactive Tube Stamp (was: re: Nixie project)

[WA5CAB at cs.com]

I was reading an article in Analog recently with some bearing on the 
subject.  One could say that the problem is that refining processes, by and large, 
are isotope insensitive.  If the refining process for Thorium could be 
easily set to extract only Thoium-232, there would be essentially no problem, as 
it has a half-life of some 14 billion years.  However, Thorium-230 (AKA 
Ionium) has a half-life of 7700 years.  And Thorium-228 (AKA Radiothorium) a 
half-life of under two years.

FWIW, Th-230 is in the decay chain of U-238, not Th-232.

In a message dated 7/3/2010 2:26:25 PM Central Daylight Time, 
dickburk at ix.netcom.com writes: 
>      There are a lot of tubes with thoriated tungsten 
> filaments, I think most of the Eimac triode and tetrode 
> transmitting tubes have them.
>      Thorium was used in some types of optical glass 
> especially for aerial photography lenses during WW-2. Some 
> of these had enough radiation to cause "browning" of the 
> glass over a period of many years. Thorium lends some 
> desirable optical qualities to the glass but it was 
> discontinued after the degree of radiation was discovered. 
> Some sources claim that the thorium was an accidental 
> ingredient, included as an impurity particularly to 
> lanthanum, but that is not the case: thorium was delibrately 
> used and is included in the formulas shown in the patents 
> issued to the National Bureau of Standards, where rare-earth 
> optical glass was developed. Even some high-performance 
> lenses for domestic rather than military use contained some 
> thorium elements. I don't know what the radiation levels of 
> these lenses are but I understand that the decay products of 
> thorium may be more hazardous than the thorium.
> 

Robert Downs - Houston
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