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Radon from thoriated glass
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PostPosted: Mon May 23, 2022 9:18 pm    Post subject: Radon from thoriated glass Reply with quote

This is purely a scientific question, please correct my thinking here....

Today I was reminded that the radioactive decay chain of thorium 232 as used in some camera lenses runs through radon. However this is the radon 220 isotope with a half life of 55 seconds. When discussing radon gas problems in houses this is (usually?) radon 222 from the uranium 238 decay chain, with a longer half life of 3.8 days.

I presume that with the shorter half life of 55 seconds, radon 220 is less of a problem and consequently not a major concern when storing radioactive lenses? Or does the shorter half life indicate that the 220 isotope is more radioactive than the 222 isotope? I assume that quantity would also be a factor; I cannot imagine that thoriated camera lenses give off relevant amounts of radon? It might even in part remain trapped inside the glass?

Regards, C.


PostPosted: Mon May 23, 2022 10:37 pm    Post subject: Reply with quote

It's still alpha radiation, stopped by a sheet of paper. It is only dangerous when breathing it in. The chances of that happening within 55 seconds are next to nothing. It will probably decay still inside the lens.


PostPosted: Tue May 24, 2022 8:33 am    Post subject: Re: Radon from thoriated glass Reply with quote

connloyalist wrote:
This is purely a scientific question, please correct my thinking here....

Today I was reminded that the radioactive decay chain of thorium 232 as used in some camera lenses runs through radon. However this is the radon 220 isotope with a half life of 55 seconds. When discussing radon gas problems in houses this is (usually?) radon 222 from the uranium 238 decay chain, with a longer half life of 3.8 days.

I presume that with the shorter half life of 55 seconds, radon 220 is less of a problem and consequently not a major concern when storing radioactive lenses? Or does the shorter half life indicate that the 220 isotope is more radioactive than the 222 isotope? I assume that quantity would also be a factor; I cannot imagine that thoriated camera lenses give off relevant amounts of radon? It might even in part remain trapped inside the glass?

Regards, C.


I'm no expert in this area, but I would assume that the measurable amounts of radon gas in some houses built from granite etc. (a known issue in e.g. trad. Cornish houses in the UK https://www.cornwall.gov.uk/environment/environmental-protection/radon/), stems from the relatively large exposed surface area of the stone materials involved. I would hazard a guess that most of the Radon produced inside the lens' glass stays trapped inside the glass and only a truly minute amount of it may escape where it is produced in the first few atomic layers on the polished surface.

Perhaps an expert can confirm (or correct if my assumption is wrong)


PostPosted: Tue May 24, 2022 8:58 am    Post subject: Re: Radon from thoriated glass Reply with quote

RokkorDoctor wrote:
connloyalist wrote:
This is purely a scientific question, please correct my thinking here....

Today I was reminded that the radioactive decay chain of thorium 232 as used in some camera lenses runs through radon. However this is the radon 220 isotope with a half life of 55 seconds. When discussing radon gas problems in houses this is (usually?) radon 222 from the uranium 238 decay chain, with a longer half life of 3.8 days.

I presume that with the shorter half life of 55 seconds, radon 220 is less of a problem and consequently not a major concern when storing radioactive lenses? Or does the shorter half life indicate that the 220 isotope is more radioactive than the 222 isotope? I assume that quantity would also be a factor; I cannot imagine that thoriated camera lenses give off relevant amounts of radon? It might even in part remain trapped inside the glass?

Regards, C.


I'm no expert in this area, but I would assume that the measurable amounts of radon gas in some houses built from granite etc. (a known issue in e.g. trad. Cornish houses in the UK https://www.cornwall.gov.uk/environment/environmental-protection/radon/), stems from the relatively large exposed surface area of the stone materials involved. I would hazard a guess that most of the Radon produced inside the lens' glass stays trapped inside the glass and only a truly minute amount of it may escape where it is produced in the first few atomic layers on the polished surface.

Perhaps an expert can confirm (or correct if my assumption is wrong)


I'm not an expert but I am a chemist and have some experience in radioactivity Smile. I would also expect any radon produced to be trapped within the glass. Rocks are typically considerable more porous than glass, and the elements in glass are all bonded to each other.


PostPosted: Sun May 29, 2022 1:17 am    Post subject: Reply with quote

It's a non-issue, don't sleep with your lens, don't grind the lens to dust or smash it and you'll be fine, the background radiation will have more impact.