Vintage command TX radiation.

[mickm3for]

Hi just placed this item on the bench to remove some of the mods, IE the conversion to top band from 3 to 6 mhz, when for some reason i checked this for radiation and finding the meter gives a reading of 7614 cpm. The said meter is NOT luminous in any way, the camera would not focus, even with a 1/8 inch thick ally plate between i still get 1879cpm. The counter has to be around 20 inches away with nothing between to give a background reading. Should i be concerned, your thoughts please. Mick

[jamesinnewcastl]

Hi

So you are saying that you are getting a worrying radiation reading? I don't know about radiation levels but I'll assume it is high.

Dials on aircraft used radioactive materials to stimulate light from another material in the paint. The material that converts the radiation into light 'wears out' but the radioactive material doesn't (well, not for a while anyway).

I'm assuming here that when you say that the dial is 'not luminous in any way', you mean that it doesn't glow.

Cheers
James

[HamishBoxer]

It sounds like the meter even though it is not green paint.

[turretslug]

I think that the radioactive component actually degrades the phosphorescent component of the paint over time, so non-luminescence in no way means that an item is harmless- indeed, anything from that era with that often-seen dirty-yellow/pale-brown scale marking that doesn't glow should be regarded warily by now. It's opening meters up that is the big no-no- very small radioactive flakes may be breathed in, and it's in the body that the stuff can cause real harm as poor old Alexander Litvinenko found.

Whatever is present in that meter sounds quite fierce!

[G6Tanuki]

Yes, the glow fades quickly with time but the radioactive component has a somewhat longer half-life and remains actively emitting alpha-particles even though it's got nothing to glow against.

A lot of the ex-military radio/electronics stuff sold as surplus during the 50s and 60s had the meters removed before sale because they were a potential hazard; there's also this:

https://www.bbc.co.uk/news/uk-17921639
https://www.bbc.co.uk/news/uk-scotla...-fife-15635527
https://www.theguardian.com/environm...-world-war-two

Or search for stories about "The Radium Girls".

[Sparky67]

I'm not an expert but I guess you really need to know the conversion factor for the detector used in your instrument to be able to turn the counts-per-minute reading into micro- or milli-Sieverts, something which has defined exposure levels you can refer to.

This is a relevent chart...

Martin
G4NCE

[mickm3for]

Hi the usv/h is 30.2usv/h i cant work out if this is safe or not thanks for your help Mick

[Colinaps]

Not an expert either but I should keep it somewhere well ventilated, where the glass isn't going to get broken and avoid sitting too close to it for extended periods. If the radiation level is close to the normal background at a couple of feet, that's probably a sensible distance to keep!
I have a pocket watch a lot hotter that lived in a pocket for decades with no apparent ill-effects to the owner. Provided you don't get radium paint dust on or in your person (or house), or breathe in a noticeable amount of radon, you'll be fine.

A worthwhile test might be to put the meter in a ziploc bag for a couple of hours, then removing it to measure the half-life of whatever gas is left in the bag. There might not be anything detectable on your GC but things like altimeters and ASIs are open to the atmosphere and leak quite a bit.

If you're not seeing a difference when you put a sheet of aluminium in between the meter and the GM tube, there's probably a lot of beta radiation your meter can't detect. All the alpha particles, which stimulate and ultimately destroy the zinc sulphide phosphor will be comfortably contained behind the glass, but any leaking radon will also emit alpha particles so you don't want to be breathing the stuff unnecessarily. Polonium is a further decay product you don't want to be near.

https://www.ld-didactic.de/software/...a226Series.htm

Colin

[GMB]

The most radioactive meters do border on dangerous in my experience. The big danger is inhaling dust from the paint so ensure it stays sealed up.

By the way, a reverse way to check for radioactive paint that is not glowing is to shine UV light on it. If that gives a nice strong glow then it is probably not radioactive. Later aircraft instruments used the same phosphors with no active additive and used a UV lamp to light them.

[G3VKM_Roger]

Hi All,

I'm a bit confused about the risk of radiation from the meter. If Mick is restoring a Command Set transmitter then that British meter is not part of the Command Set system and will, presumably, be removed? He can then use a safe disposal method to get rid of it.

I have a small collection of Command gear and there isn't a PA current meter in the system, IIRC there is only an aerial current meter.

73

Roger/G3VKM

[Radio Wrangler]

If the counter is accurate, the radiation from the meter is at such a level that someone would have to stay close to it for a long period in order to reach one of the recommended max doses.

Though the linear theory says that there is no safe dose and that risk tapers off with reducing level only reaching zero risk at zero dose.

However, the radium in that paint will have released Radon, a gas at normal pressures and temperatures. Inhaling any is a far greater danger. Those meters have to stay sealed and are best disposed of properly.

Not far from me was an airfield, Donibristle, which specialised as a repair centre during WWII and did a lot of work on aircraft panel instruments. They burned their scrap and the residue got dumped on the beach of a nearby bay. Years passed and a large housing estate was buily around the bay. Strongly radioactive particles keep turning up on the beach and it is now cordoned off and the subject of arguments over when a serious clean-up job will be done. Just google Dalgety Bay and radiation to see the story. It's pretty serious. And it's all from instrument dials.

David

[Argus25]

Originally Posted by Radio Wrangler

If the counter is accurate, the radiation from the meter is at such a level that someone would have to stay close to it for a long period in order to reach one of the recommended max doses.


David

I agree.

There is far too much paranoia about low level radiation sources. Its like people running from the room when somebody drops a mercury thermometer when 50% of the fillings in their teeth are metallic mercury, or heaven forbid, someone actually touches a fisherman's lead sinker.

Firstly, zero radiation might not be healthy.

It was assumed for example that the graph of radiation dose (x axis) vs incidence of cancer (y axis on the graph), was a sloping upward line, the more radiation (x on the graph) the higher the risk. True, but what happens when the Y value = 0, guess what x is not 0. The graph does not intersect x = 0 and y=0. It crosses the x axis and y goes negative for a little before it hits 0.

So, it turns out that a small amount of radiation is protective. How could that be ? If you think about it, life on Earth evolved in the presence of a moderate amount of background radiation. We are designed/have evolved to deal with that and its part of our biology, just like some sunlight is good for us, too much is bad. Its a view known as Hormesis.

https://www.ajronline.org/doi/full/1....179.5.1791137


But, it still pays to be sensible. If you look at radioactive capsule smoke detectors for example, the amount of radiation you receive is ok, when they are in a hallway and you walk by from time to time. You might not want to install one over the baby's crib, in that case go for a photo-electric/optical type.

The instrument or clock with luminous paint won't harm you at all, unless you bolted it to your head 24/7, even then probably ok, or scraped off the paint and put it in your vegemite sandwich and its a heck of a lot less toxic than Litvineko's Polonium 210.

In the old days of clock making, year after year, the people who painted on the luminous paint did get sick, mind you they were licking the tips of the brushes every day for years.