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Thorium in lenses at Kodak

Prof_Pixel

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From today's paper in Rochester: Dead Link Removed

Try Dead Link Removed if the longer URL doesn't work.

"For many years, Kodak was a global leader in cameras as well as film. And not a few of its cameras came with lenses that made Geiger counters chatter.
As much as 30 percent of these lenses consisted of thorium, a naturally occurring radioactive metal. Added to glass, it improves the ability of a lens to refract light, or change its direction, so that it can be focused.
Other companies used thoriated glass in lenses, but the process was developed by a Kodak consultant, George W. Morey, and first patented by the company in the United States in 1936. Kodak later developed a thorium lens coating to achieve the same effect.
The use of thoriated glass ended in the 1980s."
 
I think the Japanese government outlawed Thorium Salts being added to optical glass because of health and safety issues with workers who ingested the dust from grinding the glass.
 
Radioactive glass has been discussed several times on APUG.
 
Old Pentax Takumars often had thorium in them. No news here.
 
Coleman lantern mantles, the kind you use for camping, were made using thorium nitrate into the 1990's and plenty are still out in the wild. I have a package of them stored safely away that send my geiger counter absolutely nuts. I'd be far more concerned about those things than some glass-bound thorium waste buried in a supposedly properly built landfill. With all the environment scrutiny Kodak has had to endure, I'd feel pretty confident that the landfill was built correctly.
 
Poisson Du Jour said:
Old Pentax Takumars often had thorium in them. No news here.
Click to expand...

I bought an old Spotmatic a few years ago with a 55 1.8 Super-Takumar. This was before I knew anything about the radioactive glass. It looked lile every piece of glass in it was made from melted-down 81B filters. I could have put a bulb behind it an used it as a safelight. I had never see such a sight. They say you can put it out in the sun and bleach it. That summer I'd carry it out and put it on the deck rail every day, and it did lighten up some, but not entirely. The lens was essentially ruined.
 
Takumars with thorium elements still have a cult status among collectors. I have seen only one and the rear element was the one with thorium (200mm). I think a single x-ray will expose you to far more radiation than a creaky Takumar, so nothing to panic about, and you might even strike up an interesting conversation over a Twinings!
 
There are few things that evoke more irrationality in humans than radioactivity. The naturally occurring radiation from cosmic rays, UV, man-made (X-rays etc) and even compounds inside our bodies (Potassium 40, Carbon 14) will completely overshadow any dose you may receive from your Kodak Ektar or Pentax Takumar lens. The thorium is vitrified, and the decay particles will be arrested inside the glass matrix. This incidentally is why the glass eventually turns yellowish.

There has never been proof that low doses of radiation are harmful, but it was poorly understood why. It has recently been discovered that cell repair following radiation damage happens at extraordinary efficiency up to a certain dose rate. Above that rate, the repair mechanism starts to get overloaded, and the efficiency drops to the point where permanent cell damage becomes linear with dose. Think of it as a repair shop with a single technician. If he services fewer units than his capacity, each unit can be fully repaired, but if he is overloaded, he will rush and make mistakes. The international radiation dose limits are several orders of magnitude below the linear rate, though, as is the natural radiation dose a person will receive from natural sources (other than skin exposed to UV in large doses).
 
Ben,

The title of this thread is misleading.

That article is about the environmental impact of Kodak using radioactive istopes in the process of their lensmaking and dumping them on their grounds.

The isotopes, not the lenses. The latter are watched by us using our Geiger-counters...
 
It always drives me nuts when some article jumps on the radioactivity siren, only to come up with the fact that it's about natural thorium. If it was about glow-in-the-dark bathtubs which were made from spent nuclear fuel, then I'd agree that there's a major problem here. Otherwise, no big deal.
 

I don't have any specific knowledge of thorium waste in terms of risk or proper disposal, but I have to disagree with your premise. First, disposal began in the late 50s, so the landfill was constructed when "ignorance was bliss" (though I don't know what improvements were made since then). Keep in mind the EPA wasn't even created until 1970. Second, I believe large companies that are the main economic driver in the local economy are often excluded from more critical oversight. Especially when no one can challenge their expertise.

Here's an example in Minnesota: http://www.health.state.mn.us/divs/eh/hazardous/sites/washington/3Mwoodbury.html

If 3M - a well managed, well respected, and highly competent company - can create these problems (I believe unintentionally), then any company could have done so in the 60s.

So I don't know if there is any realistic risk from thorium waste, but I would not assume the landfill was built correctly.
 
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Articles like this really set me spinning. The poorly written lead in is designed to play on peoples fears. The inflammatory statement "which will remain radioactive for billions of years" is repeated ver Betim in paragraphs two and four.

I'm in agreement with dorff about people often irrational fears about radioactivity, and the less they understand, the more irrational they are. Plus, since no one has mentioned this as far let me add this snippet from Wkikpedia ... Despite its radioactivity, thorium fluoride (ThF4) is used as an antireflection material in multilayered optical coatings. It has excellent optical transparency in the range 0.35––12 µμm, and its radiation is primarily due to alpha particles, which can be easily stopped by a thin cover layer of another material {^ Rancourt, James D. (1996). Optical thin films: user handbook. SPIE Press. p. 196. ISBN 0-8194-2285-1.}


We all contain all 91 naturally occurring elements (Technetium is derived from irradiated Molybdenum decay), that’s Hydrogen (1) through Uranium (92), plus their isotopes.

Some foods, such as brazil nuts and bananas are mildly radioactive naturally, so there is no harm in consuming them (in moderation like everything else). Some foods contain Arsenic, but you only hear quacks and TV Dr.'s looking for ratings complaining about that. It's in the soil.
 
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The amount of radiactive isotope is of importance too. There is a difference between a nanolayer coating or a whole lens element consisting of about 1/3 out of that material.
 
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