[R-390] meter luminescence

Wed Jan 15 20:43:06 EST 2014

The Radioluminescent paint in this era used Radium as the "active" agent.
Radium is an Alpha emitter when it decays. While it is possible some of the
daughter products give off a VERY slight amount of gamma or beta particles
as they decay, the VAST majority of all radiation from these meters is alpha
radiation. Alpha radiation is able to shielded by single layer of dead skin
so unless the meter face glass is broken there is NO chance of alpha
contamination.  Any concern about alpha radiation relates to if it is
ingested. Moral of the story.....don't eat the needles or meter faces. 

>From everyone's favorite source of info....Wikipedia :-)

In the second half of the 20th century, radium was progressively replaced
with promethium-147. Promethium is only a relatively low-energy
beta-emitter, which, unlike alpha emitters, does not degrade the phosphor
lattice and the luminosity of the material does not degrade so fast.
Promethium-based paints are significantly safer than radium; the Pm-147
half-life is however only 2.62 years, it is therefore not too suitable for
long-life applications.

Promethium-based paint was used to illuminate Apollo Lunar Module electrical
switch tips and painted on control panels of the Lunar Roving Vehicle.

"Radioluminescent paint was invented in 1908 and originally incorporated
radium-226. The toxicity of radium was not initially understood, and
radium-based paint saw widespread use in, for example, watches and aircraft
instruments. During the 1920s and 1930s, the harmful effects of this paint
became increasingly clear. A notorious case involved the "Radium Girls", a
group of women who painted watchfaces and later suffered adverse health
effects from ingestion. It is now recognized that radium paint requires
great care in application, maintenance and disposal to avoid creation of a
hazardous condition.

Radium dials were almost always painted by young women, who used to 'point'
their brushes by licking and shaping the bristles prior to painting the fine
lines and numbers on the dials. This practice resulted in the ingestion of
radium, which caused serious jaw-bone degeneration and malignancy and other
dental diseases reminiscent of phossy jaw. The disease, radium-induced
osteonecrosis, was recognized as an occupational disease in 1925 after a
group of radium painters, known as the Radium Girls, from the United States
Radium Corporation sued. By 1930, all dial painters stopped pointing their
brushes by mouth. Stopping this practice drastically reduced the amount of
radium ingested and therefore, the incidence of malignancy, to zero by 1950
among the workers who were studied.

Radium paint used silver-doped zinc sulfide phosphor, usually doped with
copper (for green light), silver (blue-green), and more rarely
copper-magnesium (for yellow-orange light). The phosphor degrades relatively
fast and the dials lose luminosity in several years to a few decades,
despite the long half-life of the Ra-226 isotope (1600 years); clocks and
other devices available from antique shops and other sources therefore are
not luminous anymore, though they are still radioactive and can be
identified with a Geiger counter. The dials can be renovated by application
of a very thin layer of fresh phosphor, without the radium content (with the
original material still acting as the energy source); the phosphor layer has
to be thin due to the light self-absorption in the material."

Duffy Floyd
N3JHA

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Jim Barrie
Sent: Wednesday, January 15, 2014 3:15 PM
To: Ted Breaux; rbethman; r-390 at mailman.qth.net
Subject: Re: [R-390] meter luminescence

I was at Fair Radio and stuck Geiger counter up to the meter face of an
R-390A and it definitely read up scale. Other that it was a yellow CD
counter, have no idea what it was accurately reading.
I bought that one. So far I have not. Glowed in the dark, lost any body hair
or had any body parts fall off. L O L.
Jim
WA8SDF
From: Ted Breaux
Sent: 1/15/2014 2:56 PM
To: rbethman; r-390 at mailman.qth.net
Subject: Re: [R-390] meter luminescence
The Plutonium comment was meant as a Joke.

----- Original Message -----
From: "rbethman" <rbethman at comcast.net>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, January 15, 2014 11:18 AM
Subject: Re: [R-390] meter luminescence

> The idea of Plutonium on dial faces is absolutely absurd!
>
> It takes a Uranium fissile process to create Plutonium - period.
>
> The radioactive material - Plutonium - is HIGHLY radioactive and WILL 
> remain so for some 24 ** (4) or longer.  IOW - 24000 years for the 
> half-life.
>
> The military has NEVER used such.  The only radioactive elements used, 
> have been Radium, and Tritium.
>
> Bob - N0DGN
>
>
> On 1/15/2014 11:20 AM, Ted Breaux wrote:
>> Plutonium is known to do that!
>>
>>
>> ----- Original Message ----- From: "KA9EGW" <ka9egw1 at britewerkz.com>
>> To: <r-390 at mailman.qth.net>
>> Sent: Wednesday, January 15, 2014 8:14 AM
>> Subject: [R-390] meter luminescence
>>
>>
>>> Seen plenty of blah brown meters that do nothing but move the 
>>> pointer, in '390's and '390A's, in my day.  Never before seen ones 
>>> where the markings glow a "Luna Moth green" after exposure to light, 
>>> like the hands on a Big Ben clock of some years back.  Were there 
>>> actually meters that had the strontium aluminum silicate [I'm 
>>> guessing at the composition here] rather than the radium?  73, Brian 
>>> KA9EGW
>
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