radioactive lenses

[Sonnar Brian]

A SN 1,21x,xxx is way past the use of Thorium. My two 1,04x,xxx are Thorium lenses. I keep a UV filter over the front elements. Thorium is primarily an Alpha emitter, easily blocked. Just do not ingest it, as I was told in Physics Lab.

The Summicron is the only Radioactive lens that I know of with a Thorium Front element. The 50/1.4 Super-Takumar and Canon 58/1.2 had Thorium glass for the inner elements, not front.

I used a UV lamp to cure the yellowing on the Pentax lens. The Summicron had been sun-cured before I got it, but that dried the lubricants. I disassembled the mount and relubed it. Good for Black and White, produces "wishy-Washy colors". I much prefer my 1,3xx,xxx Collapsible Summicrons for color work.

But- to answer your question, I used a Geiger Counter on a HUGE Thorium optic for a high-speed, 1.6MFPS framing camera that used a Helium-Turbine to spin a rotating mirror. It set off the Geiger Counter, but was not alarming.

 

[Roger Hicks]

These are common sources of home radiation hot items, but the Coleman Thorium mantles were phased out in the early 90s, replaced by Yttrium. If you inhaled these, or kept them in your pocket for an hour or so, the estimation of radiation is ~200mrem, or over half a year's total radiation dose your body just absorbed.

If you scan the obituaries, you'll see a lot of folks dying of cancer were in the scouts, the scouts used these lanterns religiously.

Another common source of hot home items are old "Fiesta Ware" plates, coated in nicely colored uranium oxides, which many budget Geiger counter buyers use to test their new gadgets.

How many gaslight mantles have you bought since the early 90s? Even since the early 1890s?

Thanks for the information, though, which was news to me.

Cheers,

R.

 

[raid]

But- to answer your question, I used a Geiger Counter on a HUGE Thorium optic for a high-speed, 1.6MFPS framing camera that used a Helium-Turbine to spin a rotating mirror. It set off the Geiger Counter, but was not alarming.

I also used a Geiger counter on a HUGE Thorium LF optic with a 1.66 max aperture. The camera weighs around 250 pounds. I decided to take it out of our home.

 

[bmattock]

How many gaslight mantles have you bought since the early 90s? Even since the early 1890s?

Thanks for the information, though, which was news to me.

Cheers,

R.

I was a scout and also went camping with my family a lot. We had Coleman gas lanterns. I cannot recall ever snorting or eating a mantel. If I ever handled one, it was for the purpose of installing it - perhaps once or twice in my life.

I suppose, though, that I should find myself a lawyer and join the class-action lawsuit. I'm sure there must be one around somewhere, after all, everyone is a victim these days.

 

[Ed S.]

It's important to determine the type of radiation involved.

Alpha particles are electron-less helum nuclei, which rarely travel more than 10" in free air before capturing a couple of electons (and becoming an inert helium atom). A sheet of notebook paper is usually enough shielding.

Beta particles are free electrons; more shielding is needed, but a metal lens body, or the glass of a non-"hot" lens is likely enough. If an external lens is hot, then there's no shielding on that side.

Gamma rays are a bit problematic as shielding by a couple of feet of lead or the equivalent is necessary.

Neutron emitters: the Americium source in many smoke detectors? No problem. Just dispose of the alarm correctly Something larger? Don't get near it (200m should be close enough), or smooch your butt goodbye (you're too close :bang: and it's too late to run 😡).


Thorium usually decays by alpha emission, but a couple of isotopes emit beta particles (half life 24-25 days). Lanthanum decays by electron capture or beta emission. Both cases have very long half-lives. In any case, most alpha- and beta-decays involve some gamma emission.

But in the case of lenses (transparent things), the concentration of the element is very low and it's dispersed in a glass matrix. As previously posted: don't eat the lens, don't inhale any glass dust, don't hold it next to your eye.


It's also important to determine the amount of radiation involved.
If the shielding contains the radiation then then the amount is of little importance. If there is exposure, then the amount matters.

If the lens is mounted on a camera with a loaded roll of ASA800 film, how long does it take the "hot" lens to fog the film behind the shutter? This is an indicator.

400x the background radiation level (WW average: 2.4mSv) calculates to 0.96Sv.

As per wiki:
"0.5–1 Sv (50–100 rem)
Mild radiation sickness with headache and increased risk of infection due to disruption of immunity cells. Temporary male sterility is possible."

This event would make the news.

The old Coleman Gas mantles (but not since the late '80s), and some of the current imported non-Coleman ones (check the label) did/do contain thorium in some form. The chief danger is inhaling or ingesting the ash from a used mantle.

The link between "a lot of folks dying of cancer were in the scouts, the scouts used these lanterns religiously." is weak; many of those former scouts grew up to smole, drink, sork in industries with carcinogenic chemicals, etc.

Then there's radon exposure, frequently found in houses with basements (little airflow to disperse the gas) and with a lot of concrete/rock construction. IIRC, the Northeast US (New England, south to Pennsylvania), and running east and north to Minnesota, had radon problems more than the South, the Plains States and the West Coast. Radon has accounted for more than a few people.

 

[Roger Hicks]

But in the case of lenses (transparent things), the concentration of the element is very low and it's dispersed in a glass matrix. As previously posted: don't eat the lens, don't inhale any glass dust, don't hold it next to your eye.

Thanks for an excellent summary. The problem with the eye, as I understand it, is that some people do use these things (especially old Takumars) as telescope eyepieces!

I got an autoradiograph from an Aero Ektar on Polaroid 3000 in less than 24 hours (rear element down on the film pack). Hence my suggestion you don't store 'em under the bed. Otherwise I'll leave the inverse square law to deal with it at more than about 3-4m.

Cheers,

R.

 

[JohnTF]

My understanding on the Coleman et.al. mantles, had to do with the advice to not breathe the smoke generated when they were burned during installation. US Military used to buy quite a few and am sure surplus are still available. Great lanterns.

I live in a "Nuclear Free Zone", a suburb which passed a law prohibiting basically, bringing in anything radioactive, and it is proudly posted, yet has a law requiring smoke detectors.

I have friends who will not eat food from a microwave, out of fear of health, not taste.

Of course, I also recall the X ray burn treatment some got for acne, and those machines for fitting shoes that were really not shielded.

Many of the early workers credited with discoveries involving radioactive elements, or using X Ray diffraction had shorter lives than they might have. A former professor evidently had stolen some uranium from Oak Ridge, and kept it in the back of his classroom in a small lead bottle. He dropped it in my hand, it was very dense and warm to the touch. Density 22 or so. NRC guys eventually showed up to collect it.

Roger you probably have access to the long storage milk, is that sterilized by radiation?

 

[ampguy]

yes I know

yes I know

This is a great site for determining what you have - http://www.sky.sannet.ne.jp/seven-ss/camera/summicron50.htm

A SN 1,21x,xxx is way past the use of Thorium. My two 1,04x,xxx are Thorium lenses. I keep a UV filter over the front elements. Thorium is primarily an Alpha emitter, easily blocked. Just do not ingest it, as I was told in Physics Lab.

The Summicron is the only Radioactive lens that I know of with a Thorium Front element. The 50/1.4 Super-Takumar and Canon 58/1.2 had Thorium glass for the inner elements, not front.

I used a UV lamp to cure the yellowing on the Pentax lens. The Summicron had been sun-cured before I got it, but that dried the lubricants. I disassembled the mount and relubed it. Good for Black and White, produces "wishy-Washy colors". I much prefer my 1,3xx,xxx Collapsible Summicrons for color work.

But- to answer your question, I used a Geiger Counter on a HUGE Thorium optic for a high-speed, 1.6MFPS framing camera that used a Helium-Turbine to spin a rotating mirror. It set off the Geiger Counter, but was not alarming.

 

[ampguy]

half life varies

half life varies

depending on the specific isoptope of Thorium, but can be from hours to 75,000 years. If all of the isotopes used in these lenses have short half lives, we wouldn't see them as "hot" 50 years later.

The total of 400x equaling a ~ 1 Sievert is unlikely, as one would need to put their body in contact with the front of that lens, where the detector was when measuring 400x. Basically wearing that lens on their eye, gonads, or wherever.

But the point is, if the 400x reading off the front of the lens was accurate for this flickr user's lens, you probably don't want to put that up to your eye even a few times, maybe not even be 1m away from it for long periods of time. At least I wouldn't want to.

Here's the guy's flickr link: http://www.flickr.com/photos/focuslight/311156800/

It's important to determine the type of radiation involved.

Alpha particles are electron-less helum nuclei, which rarely travel more than 10" in free air before capturing a couple of electons (and becoming an inert helium atom). A sheet of notebook paper is usually enough shielding.

Beta particles are free electrons; more shielding is needed, but a metal lens body, or the glass of a non-"hot" lens is likely enough. If an external lens is hot, then there's no shielding on that side.

Gamma rays are a bit problematic as shielding by a couple of feet of lead or the equivalent is necessary.

Neutron emitters: the Americium source in many smoke detectors? No problem. Just dispose of the alarm correctly Something larger? Don't get near it (200m should be close enough), or smooch your butt goodbye (you're too close :bang: and it's too late to run 😡).


Thorium usually decays by alpha emission, but a couple of isotopes emit beta particles (half life 24-25 days). Lanthanum decays by electron capture or beta emission. Both cases have very long half-lives. In any case, most alpha- and beta-decays involve some gamma emission.

But in the case of lenses (transparent things), the concentration of the element is very low and it's dispersed in a glass matrix. As previously posted: don't eat the lens, don't inhale any glass dust, don't hold it next to your eye.


It's also important to determine the amount of radiation involved.
If the shielding contains the radiation then then the amount is of little importance. If there is exposure, then the amount matters.

If the lens is mounted on a camera with a loaded roll of ASA800 film, how long does it take the "hot" lens to fog the film behind the shutter? This is an indicator.

400x the background radiation level (WW average: 2.4mSv) calculates to 0.96Sv.

As per wiki:
"0.5–1 Sv (50–100 rem)
Mild radiation sickness with headache and increased risk of infection due to disruption of immunity cells. Temporary male sterility is possible."

This event would make the news.

The old Coleman Gas mantles (but not since the late '80s), and some of the current imported non-Coleman ones (check the label) did/do contain thorium in some form. The chief danger is inhaling or ingesting the ash from a used mantle.

The link between "a lot of folks dying of cancer were in the scouts, the scouts used these lanterns religiously." is weak; many of those former scouts grew up to smole, drink, sork in industries with carcinogenic chemicals, etc.

Then there's radon exposure, frequently found in houses with basements (little airflow to disperse the gas) and with a lot of concrete/rock construction. IIRC, the Northeast US (New England, south to Pennsylvania), and running east and north to Minnesota, had radon problems more than the South, the Plains States and the West Coast. Radon has accounted for more than a few people.

 

[Sonnar Brian]

The use of Thorium Glass was not permitted in eyepieces. The body of the lens and outer glass elements stops the radiation. There were regulations ragarding its use. I was surprised that the Summicrons had it in the front element.

 

[ampguy]

yeah

yeah

I'm surprised too. I think the first thing I do, and maybe other RFFers do upon getting lenses is checking the front and backs close up for how the glass looks, cleaning marks, what the blades look like, etc.

This is definitely the one lens you probably don't want to put up to the eyes for close examination...

The use of Thorium Glass was not permitted in eyepieces. The body of the lens and outer glass elements stops the radiation. There were regulations ragarding its use. I was surprised that the Summicrons had it in the front element.

 

[Freakscene]

I've visited Chernobyl. I don't worry about my radioactive Takumars or Leitz glass.

Marty

 

[hiromu]

No alpha or beta particles come through the camera body hitting your eye. They are stopped by the camera body metal part (unless you camera is made of plastic).

Gamma/x rays will penetrate the camera body, but also travel through your body without having much interaction with you.

You have a lot more radioactive materials in your body, named potassium-40, which also emits gamma rays.

But if you are concerned, you can send me the lens, and I can measure it for you. Yes, I am a radiochemist.

Having medical exams or flying will have a lot more effect on you than using those radioactive lens (but don't eat them).

Hiromu

 

[degruyl]

I have a slightly different question: does it fog film left in the camera when the lens in left on it? (I don't have one of these lenses, as far as I know. I also spend way to much time around actual nuclear sources to worry about a bit of thorium glass).

 

[Frontman]

I have a couple old thorium lenses, a Zuiko 55/1.2, and a Canon 35/2. The Zuiko is clear enough (other than the gold-colored lens coating), but the Canon lens looks very warm (through the viewfinder) compared to the other lenses in my collection.

Which Summicrons came with thorium glass? I have an old screw-mount, collapsible Summicron somewhere...

 

[Sonnar Brian]

The screw mount Summicrons with SN under 105xxxx. Lenses in the 104xxxx range are "mixed". Lenses under 104xxxx are Thorium glass. I have two of them.

 

[ampguy]

Thanks Hiromu

Thanks Hiromu

I'm going to test myself, but I might have questions for you later. Thanks for the offer.

No alpha or beta particles come through the camera body hitting your eye. They are stopped by the camera body metal part (unless you camera is made of plastic).

Gamma/x rays will penetrate the camera body, but also travel through your body without having much interaction with you.

You have a lot more radioactive materials in your body, named potassium-40, which also emits gamma rays.

But if you are concerned, you can send me the lens, and I can measure it for you. Yes, I am a radiochemist.

Having medical exams or flying will have a lot more effect on you than using those radioactive lens (but don't eat them).

Hiromu

 

[JohnTF]

I have a Geiger counter, never thought to use it around my lenses.

The Geology Department at CWRU is a bit higher in radiation, probably the stone in the building--

Always an interesting topic.

John

 

[George S.]

Two thoughts/questions...

If flying exposes you to more radiation than these lenses do,
a: shouldn't airline pilots and flight attendants be dying early deaths from cancers? I don't see that.
and b: hence there should be no worries with regard to the lenses.

Wouldn't an extreme example of a radioactive lens left mounted on a film camera loaded with film, fog that film?

 

[Ed S.]

It depends on which lens element is "hot". As I suggested in post 25, load some fast film and find out. The hot lens element will work like a radioactive flashlight. A hot front lens is unlikely to fog loaded film (alternatively, there will be other, obvious effects).

A hot rear lens might fog film, but it depends on the camera type and shutter material. A metal-shuttered SLR with auto-return mirror may give no indication. Ditto for an RF with a fan metal shutter. A Kiev 4 with metal curtains might leave bands. Cameras with cloth shutters and SLRs with no auto-return mirror are most likely to show fogging. Enough gamma/neutron emissions and the other problems will take precedence.

From what I gather, the thorium/lanthanum lenses were discovered after the fact. I suppose that thorium and lanthanum were known to have radioactive isotopes, but it was their chemistry that made them useful. Perhaps the glassmakers/optical designers were unaware of the radioactive isotopes, or unaware that they form a substantial portion of the available elements. Even lead-214 and lead-210 are radioactive. Fortunately, there's more lead-206 on this planet.

400x background seems unusually high, but assuming a 2.4mSv average value, the math indicates 0.96Sv. Red alert. Perhaps the owner of the lens made a bad reading, or missed a decimal point (40.0x), or perhaps lives in a heavily wooded area with a very low background (0.2mSv). But perhaps he got an unusually hot lens; it's entirely possible that his lens got a higher proportion of one of the magic isotopes ...

I worked in the nuclear industry once upon a time. No matter how low-level, never show contempt for hot things (or power tools, or ...). If your lens is hot, get it tested.

R. Hicks: Thanks for the vote. I have a Turist lens adapter for M42 lenses (about 5"long and works well with 50mm lenses), but I've never heard of camera lenses used as telescope eyepieces. It seems either an expensive solution or an expedient one.

Perhaps my Vega-11U will double as an excellent wide angle eyepiece