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Delicate subject: radioactive lenses
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PostPosted: Wed Sep 01, 2021 11:24 am    Post subject: Delicate subject: radioactive lenses Reply with quote
Hi All,

I would like to carefully discuss a subject that can cause quite a bit of controversy: radioactive lenses. Please be polite.

In my opinion each of us must decide for themselves what to do with radioactive lenses. That is not the question here. I for myself have decided I try to avoid them. I picked up a cheap beta-gamma detector (Radex RD1503+) on Amazon and I test every used lens that comes into my house. Anything that exceeds 0.20 µSv/hr on the front or rear lens is labeled as "radioactive" and put into a storage unit elsewhere in the building where I live.

I have weeded out one or two unexpected lenses this way that are not on the list at https://camerapedia.fandom.com/wiki/Radioactive_lenses. These were between 0.20µSv and 0.30µSv/hr if memory serves. I haven't yet come across anything that is "screaming hot".

For today I have two questions:

1. Looking at the decay chain of thorium (https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Decay_Chain_Thorium.svg/1310px-Decay_Chain_Thorium.svg.png) I see Radon in there. It looks like it has a short half life, but is there a risk of radon gas build-up in the room where such lenses are stored?

2. I own a Radex RD1503+ (a beta-gamma detector; note that it does not detect alpha's, which apparently are stopped by as little as a sheet of paper) When using my RD1503+ it runs through a detection cycle. Visually it encloses four sides of a square. What happens on some (!) lenses is that on the first leg of the cycle it beeps several times (warning signal) and throws up numbers exceeding my personal 0.20µSv/hr limit, but at the end of the cycle settles down to "safe" (again, personal) levels. This leaves me in doubt: it ends the detection cycle on "safe" levels, but what is the beeping about at first? Is there something going on I should be concerned about? Why does this happen on some lenses but not on others? I realize this is vague, but anyone have any ideas or suggestions what might be happening here?

Regards, C.


PostPosted: Wed Sep 01, 2021 11:59 am    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
...

Last edited by Blazer0ne on Tue Feb 22, 2022 5:07 pm; edited 2 times in total


PostPosted: Wed Sep 01, 2021 12:32 pm    Post subject: Reply with quote
The two lenses I have "weeded out" as being radioactive over the full cycle are:

1. Carl Zeiss Jena Flektogon 35mm f/2.8 - 0.27 µSv/hr (don't remember front or rear). This is one of the earlier bare metal / aluminum versions.

2. Komuranon 75-150mm f/4.5 - 0.25µSv/hr on the front lens. This one surprised me. A third-party zoom lens, and not a fast one either.

The ones that beep in an unexplained manner as I described previously are:

- Olympus Pen-F 50-90mm f/3.5. I have read somewhere that many 1960's PEN-F lenses are radioactive (such as the 38mm 1.Cool, but this one ends the cycle "OK", but with the described beeping.

- Sun 38-90mm f/3.5. This is perhaps a bit of an uncommon lens. Picked it up because Sun was an OEM for quite a few lenses and I was curious. Same unexplained beeping that settles down to "OK".

I have whole bunches of other lenses that don't react at all in this way which gives me the uneasy feeling that "somethin's up".

Regards, C.


PostPosted: Wed Sep 01, 2021 12:46 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:07 pm; edited 1 time in total


PostPosted: Wed Sep 01, 2021 1:01 pm    Post subject: Reply with quote
Blazer0ne wrote:
Unfortunately, I don’t own those. Do you have any others?


No, none that come to mind. But I do thank you for the thought and effort Smile

Regards, C.


PostPosted: Wed Sep 01, 2021 1:15 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:12 pm; edited 1 time in total


PostPosted: Wed Sep 01, 2021 4:31 pm    Post subject: Reply with quote
Radioactive gasses like radon and thoron also emit from concrete and brick and the ground (depending on source material) Since you house will probably contain concrete or brick or it is build on ground, radon or thoron will be in your house anyway, in higher concentrations than you could ever get from your lenses. Smokers are in more danger of getting cancer from radon exposure than non smokers. If you are worried about it, ventilate your house well. A sheet of paper will stop any direct radiation from a lens.


PostPosted: Wed Sep 01, 2021 4:48 pm    Post subject: Reply with quote
D1N0 wrote:
Radioactive gasses like radon and thoron also emit from concrete and brick and the ground (depending on source material) Since you house will probably contain concrete or brick or it is build on ground, radon or thoron will be in your house anyway, in higher concentrations than you could ever get from your lenses. Smokers are in more danger of getting cancer from radon exposure than non smokers. If you are worried about it, ventilate your house well.


Good point! Actually I live in an apartment building that is built entirely from concrete so I am surrounded by concrete walls. And every wall that isn't concrete is gypsum block. And decent ventilation is always a good idea. Smile

D1N0 wrote:
A sheet of paper will stop any direct radiation from a lens.


My understanding (but correct me if I am wrong, I am not a physicist) is that only alpha particles are blocked by a sheet of paper. Beta particles are stopped by thin sheet of metal, and gamma rays need more substantial shielding?

Regards, C.


PostPosted: Wed Sep 01, 2021 5:20 pm    Post subject: Reply with quote
As a child I've been consuming radioactive powdered milk from Poland (after a well known event in 1986.). I know about that product now, but I can only imagine things I don't know.
"Radioactive" is a powerful word, but I'm more interested in the actual effect and how to avoid it. Most radioactive lenses won't cause any harm, except if one intentionally tries
to provoke his own fate. If rear glass element is radioactive, but the lens cap blocks it (or the camera when the lens is mounted), or if there are no negative effects except if we
keep the exposed glass element extremely close to our body for many, many days non-stop, honestly I wouldn't care at all. Why should I, if I get more exposed to all sorts of radiation
whenever I leave home on a sunny day for more than a few seconds? At the same time I won't be eating radioactive lenses to prove the point. It's good to want to be informed in any case.
For example, my Sonnar 180mm "Olympia" has a funny smell and it makes me wonder what kind of grease did they use back then. Perhaps it could be more poisonous than 20 radioactive lenses combined,
or it could be perfectly fine to inhale for hours a day (beside the dizziness it would cause), I've no idea.


PostPosted: Wed Sep 01, 2021 5:37 pm    Post subject: Reply with quote
D1N0 wrote:
Radioactive gasses like radon and thoron also emit from concrete and brick and the ground (depending on source material) Since you house will probably contain concrete or brick or it is build on ground, radon or thoron will be in your house anyway, in higher concentrations than you could ever get from your lenses. Smokers are in more danger of getting cancer from radon exposure than non smokers. If you are worried about it, ventilate your house well. A sheet of paper will stop any direct radiation from a lens.


Like 1 Like 1 (beat me to the reply! Thanks D1N0!)

https://en.wikipedia.org/wiki/Radon
https://www.epa.gov/radon


PostPosted: Wed Sep 01, 2021 5:44 pm    Post subject: Reply with quote
Dejan wrote:
As a child I've been consuming radioactive powdered milk from Poland (after a well known event in 1986.). I know about that product now, but I can only imagine things I don't know.
"Radioactive" is a powerful word, but I'm more interested in the actual effect and how to avoid it. Most radioactive lenses won't cause any harm, except if one intentionally tries
to provoke his own fate. If rear glass element is radioactive, but the lens cap blocks it (or the camera when the lens is mounted), or if there are no negative effects except if we
keep the exposed glass element extremely close to our body for many, many days non-stop, honestly I wouldn't care at all. Why should I, if I get more exposed to all sorts of radiation
whenever I leave home on a sunny day for more than a few seconds? At the same time I won't be eating radioactive lenses to prove the point. It's good to want to be informed in any case.
For example, my Sonnar 180mm "Olympia" has a funny smell and it makes me wonder what kind of grease did they use back then. Perhaps it could be more poisonous than 20 radioactive lenses combined,
or it could be perfectly fine to inhale for hours a day (beside the dizziness it would cause), I've no idea.


Another major concern is level of polychlorinated biphenyls in milk from cows downwind from coal-burning power plants...for those in USA, that's east of the Rocky Mountains...

https://en.wikipedia.org/wiki/Polychlorinated_biphenyl
https://www.epa.gov/pcbs/learn-about-polychlorinated-biphenyls-pcbs


PostPosted: Wed Sep 01, 2021 6:05 pm    Post subject: Reply with quote
Exactly, we're exposed to so many harmful factors in our environment. Radioactive lenses are probably not a major concern.


PostPosted: Wed Sep 01, 2021 7:06 pm    Post subject: Reply with quote
The threshold figures you have chosen are well within the range of typical background radioactivity. 1.5 to 3.5 mSv/Yr is typical but background in some places is very much higher. Your 0.2uSv/hr lower trigger is close to 2 mSv/yr.
If you are not correcting for background then probably all you are measuring is the local background, but even if these values are above local background they are extremely low.

If radioactivity at these levels worries you do not fly (at cruising altitude jumbo jet passengers are exposed to over 20x as much from cosmic rays) & do not go on holiday to places with granite rock around (again having high background).

Paranoia about such low dosage levels is quite uncalled for.

With respect for your questions
1. There would be no chance of building up a dangerous level of radon gas even if the entirety of your lens was made of pure thorium. There are quite a few other daughter nucleotides between Thorium & Radon. Each atom present will eventually decay past but it will be many millions of years before half the material has got as far as radon & due to it's short life any that gets to raydon becomes something else quite quickly.

2, All radioactive decay is random. Readings will always jump around, it's only when you get very high levels of radionucleotides that the readings start to appear more consistent. When measuring around background levels it is usual to get some readings that are double others, an increased time averaging period will be needed to reduce the effect. When we used to measure staff exposure to the naturally occurring radioactive material that concentrates up in our processes, the measurements had to be done in a lead castle (to reduce background effects) & we had to measure for at least an hour to get realistic results. The results you are recording are lower than we used to measure.

Last edited by DConvert on Wed Sep 01, 2021 7:43 pm; edited 1 time in total


PostPosted: Wed Sep 01, 2021 7:16 pm    Post subject: Reply with quote
connloyalist wrote:

My understanding (but correct me if I am wrong, I am not a physicist) is that only alpha particles are blocked by a sheet of paper. Beta particles are stopped by thin sheet of metal, and gamma rays need more substantial shielding?

Regards, C.


Your understanding on this is roughly right, paper (or the layer of dead skin that covers your body will stop practically all alpha particles. A few inches of air is also sufficient.
Beta particles will be stopped by thin metal but a 1cm thickness of perspex is the usual sheilding used for handling radioactive chemicals, as this also stops betas while allowing vision.
Some gamma rays travel right through the earth, so I guess that counts as substantial sheilding...


PostPosted: Wed Sep 01, 2021 9:35 pm    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:08 pm; edited 1 time in total


PostPosted: Thu Sep 02, 2021 2:39 am    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
connloyalist wrote:
Hi All,

I would like to carefully discuss a subject that can cause quite a bit of controversy: radioactive lenses. Please be polite.

In my opinion each of us must decide for themselves what to do with radioactive lenses. That is not the question here. I for myself have decided I try to avoid them. I picked up a cheap beta-gamma detector (Radex RD1503+) on Amazon and I test every used lens that comes into my house. Anything that exceeds 0.20 µSv/hr on the front or rear lens is labeled as "radioactive" and put into a storage unit elsewhere in the building where I live.

I have weeded out one or two unexpected lenses this way that are not on the list at https://camerapedia.fandom.com/wiki/Radioactive_lenses. These were between 0.20µSv and 0.30µSv/hr if memory serves. I haven't yet come across anything that is "screaming hot".

For today I have two questions:

1. Looking at the decay chain of thorium (https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Decay_Chain_Thorium.svg/1310px-Decay_Chain_Thorium.svg.png) I see Radon in there. It looks like it has a short half life, but is there a risk of radon gas build-up in the room where such lenses are stored?

2. I own a Radex RD1503+ (a beta-gamma detector; note that it does not detect alpha's, which apparently are stopped by as little as a sheet of paper) When using my RD1503+ it runs through a detection cycle. Visually it encloses four sides of a square. What happens on some (!) lenses is that on the first leg of the cycle it beeps several times (warning signal) and throws up numbers exceeding my personal 0.20µSv/hr limit, but at the end of the cycle settles down to "safe" (again, personal) levels. This leaves me in doubt: it ends the detection cycle on "safe" levels, but what is the beeping about at first? Is there something going on I should be concerned about? Why does this happen on some lenses but not on others? I realize this is vague, but anyone have any ideas or suggestions what might be happening here?

Regards, C.

My guess at what's happening is that the source of radiation will emit particles in a random pattern, this can cause clusters of particle releases, if it happens at the beginning of the sampling, the first sample could be high but as time goes on the average rate becomes clear the warning should automatically clear it self.


PostPosted: Thu Sep 02, 2021 3:06 am    Post subject: Reply with quote
Converting this discussion to the standard to bananas, (1 banana = 0.1uSv) 0.2-0.3uSv, that's only 2 or 3 delicious bananas!

I eat on average 3 x bananas or I suppose 3 x Zeis Flecktons worth of radiation a day.

Actually I'm nearly out, best pop off too the shops.


PostPosted: Thu Sep 02, 2021 12:56 pm    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
connloyalist wrote:
Hi All,

In my opinion each of us must decide for themselves what to do with radioactive lenses. That is not the question here. I for myself have decided I try to avoid them. I picked up a cheap beta-gamma detector (Radex RD1503+) on Amazon and I test every used lens that comes into my house. Anything that exceeds 0.20 µSv/hr on the front or rear lens is labeled as "radioactive" and put into a storage unit elsewhere in the building where I live.


0.2 µS/h corresponds to 1.75 mS/y (or 175 mR/y). That's pretty much the natural background here in Switzerland.

I guess you're measuring these values at the surface of the lens. At a distance of 2-3 m this radiation will drop to meaningless levels.

Of course there are lenses which have a much higher radiation. If you happen to have one - try and measure its radiation as a function of the distance (0 cm - 25 cm - 50 cm - 100 cm - 200 cm - 400 cm). Doing so you'll see at which point the "lens radioactivity" starts being masked by the "natural" radiation of your surroundings. That should give you a good idea about the "safe" distance to store your really radioactive lenses (not talking about 0.2 µS/h here!!). From whar I've been reading elsewhere, the radiation of even the most radioactive lenses is "lower than the background" at distances >1-2 m.


connloyalist wrote:

Looking at the decay chain of thorium (https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Decay_Chain_Thorium.svg/1310px-Decay_Chain_Thorium.svg.png) I see Radon in there. It looks like it has a short half life, but is there a risk of radon gas build-up in the room where such lenses are stored?

No. The Radon will remain trapped inside the glass. That's precisely the reason why so much money and research was put into processing really hot radioactive waste (say 10 S/h) into a glass. BTW 10 S/h is 50'000'000 times the amount you consider as "dangerous".


connloyalist wrote:

2. I own a Radex RD1503+ (a beta-gamma detector; note that it does not detect alpha's, which apparently are stopped by as little as a sheet of paper) When using my RD1503+ it runs through a detection cycle. Visually it encloses four sides of a square. What happens on some (!) lenses is that on the first leg of the cycle it beeps several times (warning signal) and throws up numbers exceeding my personal 0.20µSv/hr limit, but at the end of the cycle settles down to "safe" (again, personal) levels. This leaves me in doubt: it ends the detection cycle on "safe" levels, but what is the beeping about at first? Is there something going on I should be concerned about? Why does this happen on some lenses but not on others? I realize this is vague, but anyone have any ideas or suggestions what might be happening here?


Apparently your detector is avearging the measured radiation over time. Since the detector is measuring single decays (those famous "clicks" on a Geiger counter), you may have three "counts" in the first second, zero counts in the second, and one in the third second, and so one. So while in some seconds the detected decays are "above average", this doesn't mean that you are in danger.


Being a chemist who specifically has been trained in the detection of smalldst amounts of poisonous substances i would like to add a few remarks concerning measuring.

1) Your strict "decision level" of 0.20 µSv/h doesn't make sense ("0.18 µSv/h = OK" and "0.22 µSv/h = not OK"). Changing your distance from the lens has a much bigger influence on how much radiation you get on your body: measuring your "0.22 µSv/h" lens at a distance of 5 cm will probably bring it down to 0.18 µSv/h ... let alone putting it atr a distance of 1 m !

2) Being a chemist, i'm much more concerned about ingested / inhaled radioactivity (such as "hot particles" from a burning reactor core or the former nuclear testing). You won't detect them at all with your detector since their danger comes from the plutonium (alpha radiation). Alpha radiation causes constant trouble in the close vicinity (maybe 100 µm) of such hot particles (e. g. inside the lungs). There's some evidence that these particles are at least partially responsible for lung cancer in smokers. In the aftermath of Fukushima we had roughly 100 hot particles per m3 (or 10 particles per cubic foot) in the San Francisco area (!!).

3) That said, i'm even more concerned about the mix of trace chemicals we inhale in our flats, offices and sleeping rooms. They not only interfere with our well-being and sleep, but also with the delicate regulation system within our body. I usually have much more trouble with those trace chemicals than with small amounts of radioactivity (I have been in places with up to 2 mS/h which is 10'000 times more intense than your personal "decision level").

All that said I'm not using radioactive glass for photography, and I'm storing the stuff at least 5 m away from where I work or sleep. Doing so, I'm sure the effect is neglectable comparing to the natural radiation.

S


PostPosted: Thu Sep 02, 2021 1:06 pm    Post subject: Reply with quote
Thank you, very helpful answer Smile You have definitely made me feel more comfortable about this.

Regards, Christine


PostPosted: Thu Sep 02, 2021 1:17 pm    Post subject: Reply with quote
As an aside to your remarks about hot particles, smoking etc. Not related to photography.

My mother died in 1986 at the age of 58 (do the math) of lung cancer and brain tumors. My father smoked all his life, so my Mom (and I) inhaled all of that for almost 20 years. Additionally, I have long suspected that in the 1950's she might have been "in the wrong place at the wrong time" with respect to the (literal) fallout from certain "tests" being conducted in Nevada at the time. It is my understanding that a few of those were pretty dirty. None of this can be proven of course. My father lived to the age of 87 so go figure.

Regards, C.


PostPosted: Thu Sep 02, 2021 6:05 pm    Post subject: Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:08 pm; edited 1 time in total


PostPosted: Thu Sep 02, 2021 6:56 pm    Post subject: Reply with quote
I'd say it's Kryptonite. Wink


PostPosted: Fri Sep 03, 2021 5:11 pm    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
Blazer0ne wrote:
Any recent Godzilla sightings in your area?
Laugh 1


PostPosted: Fri Sep 03, 2021 8:53 pm    Post subject: Re: Delicate subject: radioactive lenses Reply with quote
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Last edited by Blazer0ne on Tue Feb 22, 2022 5:08 pm; edited 1 time in total


PostPosted: Sat Sep 04, 2021 7:28 pm    Post subject: Reply with quote
Here's a series of 3 YT videos about radioactive lenses. The fellow who made them investigated for his own edification and shared his results. I found them to be quite thoughtful and informative.

https://www.youtube.com/watch?v=LjPTI5j0W4g
https://www.youtube.com/watch?v=ZaAOMPvlTaU
https://www.youtube.com/watch?v=pUuoZhoT0L8


Just in case anyone wants to see something with some real data.
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