Radioactive glass???

[M9reno]

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To summarise the document's findings:

 

"Based on reported measurements of dose rates near lenses, doses to individuals during routine use of television or photographic cameras could be substantial (i.e., several hundreds of pSv/yr (tens of mrem/yr)) if the lenses contain the maximum amount of thorium allowed under this exemption. However, based on the limited information available, lenses containing thorium appear to contain about one-third of the maximum allowable amount. Therefore, the dose estimates for individuals during routine use probably should be reduced by at least a factor of 3 to represent doses for the expected amounts of thorium in lenses."

 

But the assumed time used for calculating dose rates for professional photographers is 30 days/year for six hours a day with camera held close to the body. Here:

 

"A serious outdoor photographer is assumed to spend 30 days/yr in the field (average photographers-10 days/yr) and to carry a camera next to the body for 6 hours per day during that time. This exposure time should be conservative for most photographers. Based on the assumed exposure time and the absorbed dose rate, the annual EDE would be 0.02 mSv (2 mrem). For an average photographer the EDE would be 0.007 mSv (0.7 mrem)"

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[jaapv]

I don’t know if anybody tested it on the M, but Gorilla Glass is often slightly radioactive. On the iPad it is.

[Orient XI]

Naturally occurring thorium consist solely of the radioactive isotope thorium-232. It decays to radium-228 by emitting an energetic alpha particle (3.98 MeV) and a gamma ray of energy 0.055MeV. It has a very long half-life of 1.39×10^10 years. From a radiological point of view the alpha particle is of little concern since it loses energy so rapidly when passing through matter that a sheet of paper will absorb it. As pointed out in another post it is a different matter if ingested when all its energy will be deposited in a very small volume of tissue.

The gamma-ray is much less easily absorbed and is both photographically and radiologically active. Gamma rays turn glass yellow/brown by promoting an electron in the glass to a "forbidden" energy level where it remains trapped. By absorbing blue light (hence the yellow/brown colour) the electron is promoted to a slightly higher" forbidden" energy level. It can return to original forbidden energy level by such processes as collisions with other atoms present in the glass. The colouration is remarkably long lasting and has been used in radiation dosimetry. I had a sample in a pyrex container irradiated by gamma-rays in 1968 and when I retired in 2002 the glass had lost little, if any, of its brown colour.