Dirty Clocks. (radioactive).

[newlite4]

I had been concious of radioactive products in the home for some time and had an awareness of which items contained Radium (Ra226) paint. I borrowed a Mini 900 geiger counter from work this week and conducted a survey throughout my home.

Major emitters were Smiths and Metamec fifties mantle clocks which at 1 cm measured 100 counts per second, less so was a Goblin Teasmade which came in at 60 cps. Worst find was a pair of Ekco clock hands (not shielded by the glass face) that were lying in the bottom of a Raaco drawer, these measured 200 cps! Aircraft instruments only measured 10 to 20 cps. As a comparison, a battery smoke alarm (Americium 241) measured 50cps.

So, as collectors we are highly likely to have these sources in our homes, whether as a free standing clock, as part of a clock/radio, or as parts of military radios. The only way to deal with this is perhaps to just display them but never open them for repair and to stay aware.

Neil

[Nickthedentist]

Hello Neil,

Interesting stuff.

Could you post pictures of the Smiths and Metamecs, please? I assume these are alarm clocks rather than mantel clocks in the normal sense, as it's not usual for the latter to have luminous hands.

N.

[Brigham]

Did you chance to pass near any gas mantles with the Geiger set, or are you 'all-electric'?

[Gulliver]

What was the count rate, say, 20cm away from the sources?

As with any ionising radiation the damage done is cumulative. A few seconds or minutes exposure to relatively high doses is unlikely to do you any harm. People who work in areas of increased radiation have a safe "lifetime dose" which they must not go over - even people such as pilots and astronauts as the radiation up there is greater than down here.

If you cannot measure any increase in count rate a reasonable distance from your clocks etc. then it's safe to have them on display as long as nobody pokes around close to them for long periods.

If you're concerned it might be possible to obtain dose meters similar to those worn by people who work in nuclear power stations, to keep an eye on the cumulative dose over the years.

[paulsherwin]

Originally Posted by newlite4

Major emitters were Smiths and Metamec fifties mantle clocks which at 1 cm measured 100 counts per second, less so was a Goblin Teasmade which came in at 60 cps. Worst find was a pair of Ekco clock hands (not shielded by the glass face) that were lying in the bottom of a Raaco drawer, these measured 200 cps!

These are still very low readings, though such emissions wouldn't be acceptable today of course. The important thing is to avoid prolonged close contact with the paint for any reason, and to avoid ingesting it.

[newlite4]

Nick, the two clocks are typical fifties bakelite types. I will try to get some images of them tomorrow.
Brigham, gas mantles contain Thorium so I was tempted to try in the pub opposite, but ran out of loan time.
Gulliver, 20cm away the count was just background say between 2 and 3 counts per second so fairly radsafe. Main concern would be break up of the paint compound over time releasing particles.
Paul, quite right, important to avoid getting too hands-on with the dial parts, occasional brief contact probably OK.
Neil

[julie_m]

Unless you're going to carry the clock around such that the hands are in intimate contact with delicate parts of your body, it's really not worth worrying about those sorts of figures. Paper is enough to stop an alpha particle. Beta particles and gamma rays tend just to pass harmlessly straight through the empty space which constitutes most of every atom.

The factory workers who painted the clock hands used to lick their paintbrushes to get a fine point on them! That probably wasn't a good idea. But the health and safety people have to keep declaring stuff dangerous -- or more dangerous -- simply in order to keep their jobs from one year to the next.

And, of course, stuff that's really, really radioactive tends not to stay radioactive for very long.

Common sense springs to mind, sausages are more dangerous http://www.bbc.co.uk/news/health-21682779. When I was a kid I spent ages finding a radioactive clock hand to test a Wilson Cloud Chamber (http://en.wikipedia.org/wiki/Cloud_chamber) I made. Getting the dry ice proved even more difficult.

[newlite4]

Here are the affected items, Smiths, Metamec, Goblin teasmade and some aircraft instruments (minimal) just so you know what to look out for.
Neil

[cheerfulcharlie]

Green and yellow glass was coloured by uranium in the pre nuke age.

So if you have a pre 1940's house with some green or yellow stained window panels you could try waving your gig over it?
Does it mysteriously glow a bit in strong (UV) sunlight ?

However a vaseline glass jug I think might be quite useful in keeping the milk fresher longer ?

[dseymo1]

I've noticed the glowing glass phenomenon, but never knew the reason. Thanks!

[Bazz4CQJ]

Couldn't this problem be minimised, certainly in terms of alpha and betas, by spraying the hands with a thin (invisible) layer of aerosol lacquer of some kind?

I've used this approach on one or two items with brass parts which I didn't want to tarnish (or clean repeatedly) and had some quite pleasing results.

I'd guess that the worst hazard here is the risk of inhaling a fine particulate of the material?

[G6Tanuki]

The RadHaz issues associated with luminous dials are the reason that in the 1950s/1960s a lot of Government Surplus gear [19-sets etc] were sold with the meters removed.

Such stuff can turn up in all sorts of unexpected places:

http://www.bbc.co.uk/news/uk-scotlan...-fife-15306597

http://www.bbc.co.uk/news/uk-17921639

And don't mention the Tritium-powered "Betalights" used in the 1960s-era Trimphones....

[Anthony Thomas]

Thanks for this article Neil, have often wondered just how dangerous these things might be.

Anothe item that we might offer a thought about could be Voltage stabiliser tubes like for example 85A2 and so on. I was told they contain some form of radioactive substance but do not know for sure. It might be a question of not breaking them open or exposing ones self to the contents.

But what about diposal of these things, these and CRTs containing lead glass should not go into the bottle banks espite the temptation since they are glass.

I did find this article: http://www.orau.org/ptp/collection/c...ctrontubes.htm

Best wishes Tony

[newlite4]

Tony, good that you mention voltage stabiliser tubes. I did test some at work and found them to be clean. As far as I know, the only stabilisers that contained a source were the military types since they had to operate in complete darkness whereas the commercial types did not need a source because there was generally enough ambient light to ionise the filler gas to initiate conduction.
Neil

[Ed_Dinning]

Hi Gents, 0Z4 rectifier might be a candidate for radioactivity as no heater was fitted.

Ed

[Anthony Thomas]

I have an OZ4 and quite a few stabilisers myself in my collection. Shall see if I can borrow an instrument of measure

Tony

[ColinTheAmpMan1]

Guys,

I think that some are getting unduly worried here. It is not necessarily the presence of "radiation" that is important, but its energy. We all should remember from school that alpha particles are helium nuclei and that beta rays are electrons. A sheet of paper will stop most alpha particles and a sheet of aluminium will stop the electrons. The sources of these particles generally give low-energy emissions. The gamma rays are the most harmful, but you are unlikely to come across any significant source of that. The danger from all of this radiation is that it is ionising. If DNA within your body gets a sufficient dose to undergo mutation, then your body will either reject that molecule or molecules, or accept it as normal, which could cause various illnesses up to and including cancer.

I am surprised that a smoke-detector contains Americium 241. As I recall, Americium was an artificial element produced in the USA during the sixties. I suppose that the 241 isotope (with a half-life of 460 yrs, emitting alpha and gamma radiation with an energy of 5.48 MeV) might be more abundant, but it still remains artificial, as far as I am aware. The smoke-detectors that I am familiar with use a Nickel 63 (beta emitter of half-life 125 yrs, 0.063 MeV energy) source which emits slow beta particles. The gap between the emitter and detector (it just measures the tiny electron current, AFAIK) is small and the likelihood of radiation leakage is tiny.

The possible real danger is ingestion/absorption of any of the emitting material. This would result in you having a permanent source inside you. If you already have children or are over fifty, then passing on dud genes is not a big problem. Also, if you smoke, drink alcohol or indulge in dangerous activities like sky-diving or motor-sports (or maybe fiddling with high-voltage equipment while it is turned on) then you are probably more likely to expire from those activities than any radiation-caused malady.

Don't suck or eat the clock hands, or go to bed with the alarm-clocks under the blankets with you and you will probably live to a ripe old age (as you might have done already, if you have stuff left over from the fifties).

It is also worthwhile remembering that Cornwall stands on granite which is constantly emitting radiation. Now I can see how some of you might think that the Cornish are a bit weird, but I really can't recall seeing one with two heads or constantly vomiting, have you?

Regards, Colin.

smoke-detector contains Americium 241

Lots do...

https://www.google.co.uk/search?q=sm...-a&channel=rcs

[HamishBoxer]

Radion gas I believe you mean Colin. Pretty deadly.