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Re: [OM] Radioactive glass

Subject: Re: [OM] Radioactive glass
From: Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 7 Aug 2003 08:58:03 +0100
In article , Joe Gwinn <joegwinn@xxxxxxxxxxx> writes
At 12:40 AM +0000 8/7/03, olympus-digest wrote:
Date: Wed, 6 Aug 2003 18:47:23 +0100
From: Kennedy McEwen <rkm@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: [OM] Radioactive glass

In article , Joe Gwinn <joegwinn@xxxxxxxxxxx> writes
>
>Whoa!  It's not nearly that dangerous, as it's very difficult to get
>the thorium out of the glass, even if the glass is reduced to powder.
>
Its not an issue of getting the radioactive elements out of the glass.
It is what happens to the alpha emission once you have ingested any of
the fine glass particles or dust.  Alpha radiation, not the decaying
element, is then absorbed by LIVE tissue and that is the danger and the
case of carcinogenic mutation.

Given the relative density of skin and glass, how much of the alpha radiation will in fact escape the glass, even if it's been crushed? In practice, the danger comes from chemically disolved material, not powder, as the range of the alpha radiation in glass and in water is very short.

That is the point - once ingested it has no skin to penetrate. This is the major danger with all alpha emitters. Outside of the body they are relatively harmless because the radiation is effectively stopped by the layer of dead skin cells - that doesn't exist to provide any protection once the material is ingested. The radiation is absorbed directly by living cells in your lungs, liver, blood, intestine or other internal organs. Absorption means they are stopped by the cells themselves, and that means cell damage with the usual probability of that damage being mutation.

Do we know the actual amount of thorium in the glass, as a mass percentage?

Depending on the glass used, the radioactive material can be up to 10% of the mass.

Americium is *much* hotter than an equal mass of thorium.

That is not an issue since it only determines how fast the material decays. Eventually it all decays and, providing that a significant proportion of that occurs within your lifetime (and in the case of the radioactive materials used in glass this is true) then all of that emission will be absorbed if the material is retained in the body.

I wonder what happened to the folk that ground the glass into lenses for a living. Given that they did this all day every day, they would be the first to go, not us duffers. I don't recall ever reading stories about them dying like rabbits from this or anything else associated with lens manufacture.

Certainly here in our optics facility, where we used thorium containing coatings for many years, the protection measures taken for the workforce were extreme. The cost of that and the cleanup operations when optics were damaged in the factory or in the field, was one of the main drivers for an alternative coating material. We never used radioactive glass, however I would expect that similar precautions were also required at manufacture and just as costly if not more so. Coating tends to be a fairly sterile environment in the first place, leading to relatively simple safety precautions. Glass polishing is generally messy with a lot of waste slurry produced. Of course they were probably made in 3rd world countries where the dangers were probably ignored and life expectancy was short in any case. That doesn't mean you should make yours equally short by being irresponsible with the product.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers

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