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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