Vintage radioactive wrist watches - Is Radium really nasty?

[jebem]

We live in an era where nuclear power makes the economy rolling in many countries.
Nowadays we all are aware of the dangerous health issues related to exposure to excessive radiation accumulated levels.

However in the 20 century up the 1950's, people were really not concerned at all with radiation.
In fact they believed that radioactive materials added to consumer products would give huge benefits.



Some time ago I ordered some nice vintage watch hands, guaranteed to have Radium paint.
I wanted to discover how dangerous can it be for human health by comparing the safety accumulated radiation annual dose against what these Radium painted hands can emit.



GM tube counter quest.
So my next step was looking to a GM counter able to detect at very least Beta and Gama particles.
Buying one ready built was out of question - too expensive and no fun at all - I wanted to build it myself in my spare time!

Ex-Soviet republics came to rescue by selling me cheap GM tubes.
I selected the SBM-20 tube as it is easy to work with and it has a large exposed surface when compared with other more compact detectors.

Next I wanted a system able to not only counting particles but also able to do the math to calculate (*) the radiation dose in normalized Sieverts
(*) see? this is why I posted this subject here in MoHPC!.
Instead of reinventing the wheel, I just ordered on kit from existing diy projects.

While the kit works fine, I'm not happy with the 500VDC high voltage DC-DC converter circuit because it consumes about 20mA from the 9V batteries.
This is too much. I have built my own high voltage DC-DC converter circuit consuming only about 4 mA under load.
But I'm too lazy to redraw the PCB to replace the circuit. So it will stay as it is for a while.


Assembling the Kit mainboard PCB.
Regulated 5VDC power supply, high voltage DC-DC converter, pulse detection and amplification, analog monitoring (visual and audible), and digital calculator based on a arduino open source project.
Following the electronics best practices, place the components as you like best (just kidding).






Assembling the Kit LCD display piggyback PCB.
This particular kit offers not only the digital monitoring on Sieverts, but it can also offers a data logger interface, two different menu readings selected by a press button, and at last a menu driven setup invoked using a IR TV like command set (so there is no need to connect the arduino to a PC).





At last, the watch hands radiation emitting testing...
Considering the current safety standards, what would be the risk level for someone using that watch for a full year, accepting the monitored value of 39uSv/h?

[Thomas Klemm]

(01-18-2015 11:19 AM)jebem Wrote:  Considering the current safety standards, what would be the risk level for someone using that watch for a full year, accepting the monitored value of 39uSv/h?

XKCD: Radiation Dose Chart

That would be about 340 mSv per year. Compare this to:

Quote:Maximum yearly dose permitted for US radiation workers (50 mSv).

Be careful!
Thomas

PS: Cool project!

[Bill (Smithville NJ)]

(01-18-2015 11:19 AM)jebem Wrote:  At last, the watch hands radiation emitting testing...
Considering the current safety standards, what would be the risk level for someone using that watch for a full year, accepting the monitored value of 39uSv/h?

The biggest risk with Radium Watches was to the girls that worked in the factory painting the watch faces. Just do a Google search for "Radium Girls" and you can read about the suffering done by these workers just so we could read the watch faces and hands in the dark.

Bill

[rprosperi]

(01-18-2015 01:44 PM)Thomas Klemm Wrote:  XKCD: Radiation Dose Chart

The warning note at the very bottom of the chart is great. Not sure it would hold up in court, after all, it's only in tiny print...

[walter b]

(01-18-2015 01:44 PM)Thomas Klemm Wrote:  ... about 340 mSv per year. Compare this to:

Quote:Maximum yearly dose permitted for US radiation workers (50 mSv).

And: Lowest one-year dose clearly linked to increased cancer risk = 100 mSv.

Watch it!

([:-(

P.S.: Radium decays emitting alpha particles. So a sheet of paper is sufficient for shielding. Once the watch hands are mounted and the cover glass is fixed, there should be no risk anymore. BUT avoid ANY direct contact of that material to your body!!

Radium is almost entirely 226Ra, decaying into 222Rn which is a gaseous alpha emitter, decaying into 218Po which is an alpha emitter again decaying into 214Pb. The lifetimes of 222Rn and 218Po are far shorter than the one of 226Ra. Since it's a noble gas, 222Rn can be inhaled, so after some days contemplating over open watch hands you have some Polonium in your lung where it must not be!!

BTW, German Wikipedia tells:

Quote:Die maximale erlaubte Jahresdosis für beruflich strahlenexponierte Personen beträgt 20 mSv, über ein Berufsleben dürfen jedoch nicht mehr als 400 mSv zusammenkommen.

(~ max. dose per year for professionals exposed to radioactivity is 20 mSv; they shall not receive more than 400 mSv in their professional life.) Compare the value stated above and you see that US radiation workers are more robust (as usual ).

[Paul Berger (Canada)]

(01-18-2015 11:19 AM)jebem Wrote:  Some time ago I ordered some nice vintage watch hands, guaranteed to have Radium paint.
I wanted to discover how dangerous can it be for human health by comparing the safety accumulated radiation annual dose against what these Radium painted hands can emit.

You may be interested in this article about vintage watches with radium paint dials, you will note that the author states there is a significant danger of radioactive dust being present inside such watches dues to the radioactivity breaking down the binder in the paint.
http://www.vintagewatchstraps.com/luminous.htm

[Katie Wasserman]

(01-18-2015 11:19 AM)jebem Wrote:  While the kit works fine, I'm not happy with the 500VDC high voltage DC-DC converter circuit because it consumes about 20mA from the 9V batteries.
This is too much. I have built my own high voltage DC-DC converter circuit consuming only about 4 mA under load.
But I'm too lazy to redraw the PCB to replace the circuit. So it will stay as it is for a while.

Very nice work (and great pictures, as usual)!

I've made some tiny little GM tube detectors/counters too and did a little better on my home made high voltage supply specs (under 100 ua at 6 volts input). However that's still not good enough for me.

I prefer to use the LND-712 tube as it has a mica window to allow in alpha particles, but it's much more expensive (and fragile) than the Russian tubes.

For the power supply I've been using these incredibly tiny, efficient modules:

http://www.ebay.com/itm/Geiger-counter-p...257eaa7ce3

Which will power the tube for over a year on a single CR2032. You can ask the seller to customize the voltage for the tube you're using.

[jebem]

(01-18-2015 01:44 PM)Thomas Klemm Wrote:  

(01-18-2015 11:19 AM)jebem Wrote:  Considering the current safety standards, what would be the risk level for someone using that watch for a full year, accepting the monitored value of 39uSv/h?

That would be about 340 mSv per year. Compare this to:

Quote:Maximum yearly dose permitted for US radiation workers (50 mSv).

Thanks, Thomas!
It is better to be safe than sorry. I have to put these two watch hands away in the cellar. Just in case!

(01-18-2015 02:28 PM)walter b Wrote:  

(01-18-2015 01:44 PM)Thomas Klemm Wrote:  ... about 340 mSv per year. Compare this to:

Lowest one-year dose clearly linked to increased cancer risk = 100 mSv.

Clearly these radioactive compound products should be banned from the market for safety reasons. The true is that I bought these vintage watch hands from the eBay, legally, about two years ago.

I believe I took the minimum safety precautions handling it. I never opened the hands plastic bag container, and this package is going to a safer place away from me in my garage/cellar for the next 1600 years
Is that the Radium half-life I'm reading in Google? Really? How come we mortals spend at most 100 years on earth and a tiny heavy atom in excess of neutrons lives as much as 16 times more only to lose half of its material? Not fair!

And thank you for the excellent explanation on the Radium disintegration!

It reminds me of my professor Campos at Maputo University Physics Department (Mozambique) when he spent time to explain me the mysteries of Universe at a coffee table after school. He used to drive a nice 60's Porsche, I think it was the Speedster.
He used to express some extravagant ideas at the time, and some of them came true today.

(01-18-2015 05:40 PM)Katie Wasserman Wrote:  

(01-18-2015 11:19 AM)jebem Wrote:  I have built my own high voltage DC-DC converter circuit consuming only about 4 mA under load.

I've made some tiny little GM tube detectors/counters too and did a little better on my home made high voltage supply specs (under 100 ua at 6 volts input). However that's still not good enough for me.

I prefer to use the LND-712 tube as it has a mica window to allow in alpha particles, but it's much more expensive (and fragile) than the Russian tubes.

For the power supply I've been using these, tiny, incredibly efficient modules:

http://www.ebay.com/itm/Geiger-counter-p...257eaa7ce3

Which will power the tube for over a year on a single CR2032.

Thank you so much for your extra information, Katie!

Yes, I have been looking to build something to detect Alfa particles as well, and the LND-712 with mica ending seems to be a good candidate.

Now, that HV power supply is amazing!
Expensive, but it looks really efficient!

[Manolo Sobrino]

Jebem, I think no one really needs (nor really wants) to own any amount of radium just for the fun of it. Maybe you can keep it somehow safely now, but can you expect that it will be handled properly in the future?

Alpha emitters when inhaled or ingested become a "fully-blown" ionization source sitting within your living tissue, that's why they are powerful mutagens and even small amounts are dangerous (don't judge these things for their size, but for their activity). This radium paint can produce some nasty powder. The idea of radiological protection is to prevent any unnecessary exposure, more so beyond the general public/student/worker safety limits.

I wouldn't trust or use a G-M tube for dose measurements. Unfortunately DIY people talk about mSv all the time, they have no idea what they're talking about. The sievert is the unit of dose equivalent, which is the product of the absorbed dose by a dimensionless quality factor Q. Q = 1 for gammas and electrons, but it can be as high as 20 for high LET radiation, for instance alphas. What they mean is absorbed dose, which is measured in grays, 1 Gy = 1J/1kg = 100 rad. But in order to measure this you need to measure the absorbed energy, for instance with a chamber where you can apply the Bragg-Gray principle.

G-Ms actually detect radiation as radiation monitors, they count ionizing particle events that get into their chamber (that means that you need a thin window and being really close to the source for alpha and beta particles, because of air attenuation: the range of alpha particles in air is just a few cm), but can't give you any information about their energy or type because they operate in a kind of saturation plateau, so there is no way to measure the absorbed energy. I think there are some variants that claim to use "energy compensation" (this one probably isn't), I haven't seen one myself. People use ionization chambers (often inside phantoms) for these things.

So what are you measuring here?

Decay scheme Ra 226

Decay scheme Rn 222

Well, let's consider the Rad 226. Besides the 186 keV gamma emission of the Rn 222 that happens 3.5% of the time, which you detect mostly through Compton scattering electrons from the walls of the chamber (the G-M efficiency for gammas is a few percents), most of the counts are delta rays (secondary electrons) coming from the 4.6-4.8 MeV alphas in air.

You have have the decay chain of the daughter nuclide as well, Rn 222, which is a dense inert gas that will diffuse around. Its progeny, while emitting more alphas (more delta rays for the counter) and now betas too, will deposit nearby resulting in a certain amount of Pb 210 contamination (that will turn slowly into awful Po 210).

Notice that you have this in a plastic bag, then air, the pic shows the detector next to, but not over the source (it could be closer as well) and we have no idea about the efficiency of the detector (its geometric efficiency is hard to figure), or its calibration (what about dead time?). Those 7000cpm are surely proportional to the activity of the source, but we can't really tell their relation to it.

About your G-M tube, I've found this info:

http://gstube.com/data/2398/

http://mightyohm.com/blog/2014/11/a-spot...nter-tube/

According to this, at 500V you're probably operating it beyond its VDC rating (350V-475V), recommended 400V (there is a 260V min, 320V max starting voltage there). Above the G-M plateau the gas-filled cylindrical ionization chamber is not a G-M any more and you might break it, specially if the quench compound is worn out.

I don't understand the "Gamma Sensitivity Ra226 (cps/mR/hr)" figure. It makes sense it being higher than the one for Co 60, as Co 60 is a >1 MeV gamma emitter but I really don't know how to use that number. If someone does, please give us a hint. On the other hand, I wouldn't trust the specs of a radiation detector hopefully calibrated some 40 years ago.

Please, check this:

https://www.orau.org/ptp/collection/radi...ntinfo.htm

Quote:"NCRP Report 56 indicated that the estimated average dose equivalent to the gonads of an individual wearing a radium-containing watch was approximately 3 mrem per year. The estimated dose from a watch containing 4.5 uCi of radium, a very large amount, would be 310 mrem per year to the gonads. Note that the associated risk here is much lower than if the dose had been the same over the entire body.

In the previously mentioned study of pocket watches by the National Center for Radiological Health, measurements using TLDs and a human phantom indicated that the annual dose to the gonads was 60 mrem (assuming that the watch was worn 16 hours per day)."

As 1 Sv = 100 rem, that high activity watch would yield a dose equivalent of roughly 3 mSv/year to gonads. For the entire body it would be less because the tissue weighting factors are higher for gonads (w_T=0.20) than for instance, lungs (w_T=0.12) or skin (w_T=0.01). The ICRP recommended exposure limit for members of public is 1 mSv/year for whole body exposure. I guess watches are relatively safe to wear (not to tinker with) but, as you might take planes frequently and maybe have an X-rays or CT scan every once in a while, I think there's just no need for that.

My advice would be: use disposable gloves, put that bag in a sealed thick-plastic food container, throw in the gloves before closing it and (assuming you are in Lisbon) contact these people (my educated guess, I really don't know how things go in Portugal, for instance in Spain we have a state-owned company -Enresa- for this) they can measure/dispose of it:

http://www.itn.pt/sec/psr/pt_psr_rrr.htm

Let me recommend you a book on this (I used its full of typos 2nd edition some years ago):

James E. Turner - Atoms, Radiation, and Radiation Protection

[jebem]

(01-19-2015 03:21 PM)Manolo Sobrino Wrote:  (...) I wouldn't trust or use a G-M tube for dose measurements. Unfortunately DIY people talk about mSv all the time, they have no idea what they're talking about.
(...)
About your G-M tube, I've found this info:
http://gstube.com/data/2398/
According to this, at 500V you're probably operating it beyond its VDC rating (350V-475V), recommended 400V (there is a 260V min, 320V max starting voltage there).

Excellent analysis and useful information, thank you!

This is just one more toy, and as you pointed out, one can not trust the readings as accurate - this is not a lab nor a professional field equipment.
But the readings are real and gives us enough information about the radiation around us. For instance, inside home the background radiation is about 8 to 10 CPM and this value seems to be the usual in many places around the world.

Concerning the high voltage power supply, it is adjustable - when I mentioned 500V is just the nominal initial value - It can be as low as 200V and as high as 900V in this circuit. I'm running it at 400VDC as recommended in the Russian datasheet.

Saludos Cordiales,
Jose

[Katie Wasserman]

(01-19-2015 07:22 PM)jebem Wrote:  But the readings are real and gives us enough information about the radiation around us. For instance, inside home the background radiation is about 8 to 10 CPM and this value seems to be the usual in many places around the world.

This is typical for sea level readings from the tube you're using. If you buy an LND-712 you'll see somewhat higher readings as it's more sensitive, I find about 12 to 14 CPM is typical. I also have a much better GM tube counter that uses a 2 inch pancake style tube (with a mica window) that gives background counts of around 35 CPM. This one is calibrated too so I have something to compare my DYI counters to. I also have a few small radiations sources to test with.

[John Galt]

Fascinating stuff Jose!

Radium chocolate, toothpaste, lipstick...? From our perspective half a century later, one has to wonder "what where they thinking".

However, that only makes me wonder what people will say about us a half century from now. Especially since the more I interact with people, the more it seems mankind has only grown stupider. Frightening.

Be careful with those bananaphones!

[Marcus von Cube]

It was only a few days ago that a so called "Radiumbecher" was detected by chance in a container with metal waste.

This thing was used to treat drinking water with radium. It's a piece of art if it weren't so dangerous.

[everettr]

(01-18-2015 11:19 AM)jebem Wrote:  At last, the watch hands radiation emitting testing...
Considering the current safety standards, what would be the risk level for someone using that watch for a full year, accepting the monitored value of 39uSv/h?

I don't think that there is currently any reason to wear a radium dial watch instead of a normal watch. My understanding is that the typical luminescent material, for example ZnS, breaks down over the years, so that the radium + phosphor mixture no longer glows, even though there is still plenty of radioactive decay. Do you observe any glow from your watch hands?

Here is a link to an interesting article about the Radium thumb rule, for estimating the activity and the amount of radium that you actually have.
Radium Thumb Rule

Note that your GM tube will overestimate the activity, especially if you choose a short (less than 15 cm) measurement distance. The article explains that if the source is too close to the detector, you start measuring beta particles in addition to gamma rays. The radium thumb rule assumes you are only measuring gamma rays.

It might be interesting for you to try and detect radiation from your source with a webcam. The CMOS sensor in a typical webcam responds to betas and gammas. See:
Photographing radioactivity with a webcam

[jebem]

(01-20-2015 09:43 PM)Marcus von Cube Wrote:  It was only a few days ago that a so called "Radiumbecher" was detected by chance in a container with metal waste.

This thing was used to treat drinking water with radium. It's a piece of art if it weren't so dangerous.

Nice vintage piece of art!
I remember from my first years in Africa (1960), people used to drink water that was first to boiled and then put in these large ceramic containers using ceramic filters where the water had to pass by gravity only.
I wonder how much radioactive materials they put in those ceramic filters and containers.

(01-20-2015 10:30 PM)everettr Wrote:  My understanding is that the typical luminescent material, for example ZnS, breaks down over the years, so that the radium + phosphor mixture no longer glows, even though there is still plenty of radioactive decay. Do you observe any glow from your watch hands?

It might be interesting for you to try and detect radiation from your source with a webcam.

Thanks for the information.

No, my watch hands are not emitting light any more, so the phosphorescent material is gone.

Concerning semiconductors working as gamma particles detectors, I have been reading a few articles about PIN diodes as well.
I remember my work for WANG Computers in the 80's, where the ECC (error correction code) used extra 6-bits to correct 1-bit in 16-bit words. WANG used to say that even cosmic radiation could cause memory "soft" errors on the dynamic RAM modules. Hence the need to make sure an hardware automatic algorithm to fix those errors.

[jebem]

(01-19-2015 09:06 PM)Katie Wasserman Wrote:  

(01-19-2015 07:22 PM)jebem Wrote:  For instance, inside home the background radiation is about 8 to 10 CPM and this value seems to be the usual in many places around the world.

This is typical for sea level readings from the tube you're using. If you buy an LND-712 you'll see somewhat higher readings as it's more sensitive, I find about 12 to 14 CPM is typical. I also have a much better GM tube counter that uses a 2 inch pancake style tube (with a mica window) that gives background counts of around 35 CPM. This one is calibrated too so I have something to compare my DYI counters to. I also have a few small radiations sources to test with.

My bad. On the other day I did some readings in a rush, like during 10 to 20 seconds only, and somehow I got lower readings than what is expected.

Today I let my GM counter run for 10 minutes and it come up with a total count of 220, so I got an average value of 22 CPM.

However my watch hands Radium radiation source still is nearby, about 60cm away (2 feet) from my workbench, stored in a plastic bag inside a glass bottle inside a plastic case inside a paper bag in a wooden drawer.
I guess the Gamma particles just pass thru all these materials like my knife cutting butter at breakfast, increasing the background radiation level readings a bit

I will have to repeat the readings once I put my Radium source away from my apartment and see if I get a lower count.

[walter b]

(01-21-2015 09:02 PM)jebem Wrote:  However my watch hands Radium radiation source still is nearby, about 60cm away (...) from my workbench, stored in a plastic bag inside a glass bottle inside a plastic case inside a paper bag in a wooden drawer.
I guess the Gamma particles just pass thru all these materials like my knife cutting butter at breakfast, increasing the background radiation level readings a bit :)

For sure. The only common material really working as a gamma shield is lead (Pb). Plastic and wood are mainly carbon - they don't shield gamma.

d:-/

[Manolo Sobrino]

(01-21-2015 09:43 PM)walter b Wrote:  For sure. The only common material really working as a gamma shield is lead (Pb). Plastic and wood are mainly carbon - they don't shield gamma.

Yes, the half-value layer for 186 keV gammas in lead is ~0.4 mm (you need a 1.35 mm thick lead shield to reduce it to 10%... or about 8 cm of concrete). The idea for gammas is to use high Z materials. You'd use plastic (low Z) for betas, so you can reduce Bremsstrahlung. Usually beta sources are kept in plastic boxes (e.g. PMMA), to avoid having an X-ray source around. Plastics are rich in hydrogen, that's an interesting point for using them to stop (heavy) particles.

(But the trouble with jebem's radium are not the gamma rays. After all, those watches aren't really dangerous to wear if we look at the measured doses. The trouble is having radium in a battered paint laying around!)

[Katie Wasserman]

(01-21-2015 09:02 PM)jebem Wrote:  I will have to repeat the readings once I put my Radium source away from my apartment and see if I get a lower count.

You might find other low-level sources of radiation around your home too. I found that some of the Nixie tube calculators I have have small amount of radioactive gas (krypton 85?) to help get the ionization started. Some ceramic glazes have uranium in them. I have an old Elgin alarm clock/radio with radium painted hands. Ionization-type smoke alarms have a strong , but tiny, alpha source in them. Old color TV tubes emitted radiation until they put lead in the glass, but even then you can still detect a slight increase in the background count at the edge of tube.

[Thomas Radtke]

Hi jeben,

as long as one isn't concerned by cancer personally or in his or her family, probability calculations for events causing cancer are interesting. If you are, you just want to get rid of any dangerous agents, viruses or radiation sources ;-(.

Be careful and lots of luck,

Thomas

@Manolo, are you a radiobiologist? Thanks for your nice summary on ionizing radiation and quality factors. It's been a long time (late 90th) since I worked at the University Clinics of Essen in this field. Spent the most interesting years there :-).