Re: Info on radium paint?

["Ron L. Kathren" <rkathren@beta.tricity.wsu.edu>]

The exposure rate measured at 'contact' depends on a number of factors, 
not the least of which are instrument related.  For example, size of the 
detector determines where the effective center is, and hence the 
magnitude of the measurement.  Similarly, detector wall thickness can 
play a significant role.  Thus, the 1 mR/h measurement cited may or may 
not be meaningful.  In my career I have run across radium dials and 
switches which produced levels of several hundred mR/h and even several 
R/h at an effective distance of 3-5 cm from the surface.  Hopefully, 
these are now all out of public circulation.

But to the point:  would you be kind enough to give a little more 
information on the instrument with the radium dial?  Would be interested 
in knowing such things as what it is, who made it, and when.

Many thanks.

Ron Kathren

On Fri, 27 Jan 1995, Chris Davey wrote:

> 
> 
> On Fri, 27 Jan 1995 CLEMENTC@crl.aecl.ca wrote:
> 
> > My office deals with the occasional radium painted dial.  The radionuclide
> > is Ra-226.  I've never worked out the concentrations, but the most active
> > dial I've seen reads about 1 mR/h on contact.  Interestingly, the dial
> > is on a radiation detection instrument (but the scale is in R/h, so
> > one mR/h would hardly show up).  As for manufacturing techniques, the
> > radium paint was simply painted on by hand.
> > 
> > Hope this info is useful.
> > 
> > Chris Clement
> > Low-Level Radioactive Waste Management Office
> > Atomic Energy of Canada Limited
> > CLEMENTC@CC4.CRL.AECL.CA
> 
> I used to be an inspector for the Atomic Energy Control Board (Canada's
> equivalent of the U.S. NRC) and surveyed a lot of aircraft with
> radium-painted dials.
> 
> Dose rates off one dial can be as much as 5 mR/h, with as many as 40 dials
> in DC-6, Convair, and other, similar vintage planes.  With a large number
> of dials facing the pilot, the dose rate in the pilot's seat can easily be
> 0.5 mR/h.  Some old signs, controls, and other components have radium
> paint on exposed surfaces (i.e. not behind glass).
> 
> But the biggest hazard from these dials is to the instrument repair
> companies, as it is not, repeat not possible to visually ascertain whether
> a particular dial is radioactive or not, and these people take the dials
> off during repairs.  Problem is, the activity has accelerated the aging of
> the paint, and it is flaking off and floating around in the air in the
> form of microscopic particles.
> 
> Of course, all things are relative, and the actual hazard in most cases is
> probably not too great.  If young children were exposed to someone's
> personal collection of antique instruments, and ate their lunch without
> washing their hands, then some radium would certainly be ingested.
> 
> I have a lot more information on locations of aircraft (museums, personal
> antique WW2 planes, short commercial routes, etc) and would be willing to
> provide same if it would be useful.
> 
> Chris Davey, RSO
> Cross Cancer Institute
> Edmonton, Alberta
> Canada, T6G 1Z2
> (403) 492-7477
> fax   492-8202
> 
> 
>