[ RadSafe ] Thorium in Welding Rods - Release of Thoron

John R Johnson idiasjrj at gmail.com
Tue Nov 6 20:54:32 CST 2012


I agree with you but (as you know) the major risk from Th bearing rods
is the gamma radiation.

How are thngs in TO?

John R Johnson

On Tue, Nov 6, 2012 at 2:26 PM, Leo M. Lowe <llowe at senes.ca> wrote:
> In the many recent comments on thorium in welding rods, a few  related to
> the release of thoron (Rn-220) from large quantities of the rods.  It was
> suggested that the short half-life of thoron (56 s) would result in
> insignificant emission rates.  However, that may not be the case.
> For thorium (actually Ra-224) - bearing sources, the surface flux of thoron
> is inversely proportional to the square root of the half-life of thoron.
> This also applies to radon (Rn-222) from uranium ( Ra-226)-bearing sources,
> with the result that the flux of thoron from soil containing equal
> concentrations of Ra-224 and Ra-226 is about 80 times that of the radon
> flux.  This is discussed in many publications, including those of UNSCEAR.
> Thus, the thoron flux from welding rods could be substantial (other factors
> are also important).  Of course, the resultant air concentrations of thoron
> would be greatly mediated by its short-half life and any local ventilation
> and air dispersion, as it is in the general environment.
> L. Lowe
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