[ RadSafe ] Fwd: Fwd: Which welding rods are hot?

Chris Alston achris1999 at gmail.com
Tue Nov 6 11:42:33 CST 2012

Hi Dan

Yes, that is my presumption too; i.e., because the Th is alloyed with
the other metal(s) in the rod, it's not going anywhere.  (I also
presumed no porosity of the rod, that would allow thoron to emanate.)
"Alpha creep" can, and does, most definitely cause problems in other
situations, though.

One imagines that some tiny amount of Th might be able to eject itself
from the surface of the rod, but simple friction would likely remove
much more, in the short term.  What does one see for removable
activity, on wiping testing such a rod (anyone? anyone?).


---------- Forwarded message ----------
From: Dan McCarn <hotgreenchile at gmail.com>
Date: Tue, Nov 6, 2012 at 12:03 PM
Subject: Re: [ RadSafe ] Fwd: Which welding rods are hot?
To: "The International Radiation Protection (Health Physics) Mailing
List" <radsafe at health.phys.iit.edu>

Hi Chris:

I'm going to take a wild guess here, since my "reference" is the behavior
of the progeny of U-238 in a mineral lattice.

That's what I thought about radon being emitted from mineral grains, that
it would be minimal. But I was wrong. For natural thorium, there are three
alpha decays with an energy in excess of 4 MeV in the decay chain to
Rn-220.  If these alphas behave in a similar way to U-238 decay, then the
recoil energy, perhaps 50-100 KeV, should have dislocated the
progeny significantly by the time that it becomes Rn-220, allowing more to

But then, the thorium is part of a metal and may behave differently.

See Figure 6 in the following hyperlink:
Fig. 6. Recoil range vs α- recoil energy of radionuclides of U–Th
radioactive series in water (*ρ*=1) and calcite (*ρ*=2.7).


Dan ii

Dan W McCarn, Geologist
108 Sherwood Blvd
Los Alamos, NM 87544-3425
+1-505-672-2014 (Home – New Mexico)
+1-505-670-8123 (Mobile - New Mexico)
HotGreenChile at gmail.com (Private email) HotGreenChile at gmail dot com

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