RE: Natural Thorium

["Karam, Andrew" <Andrew_Karam@URMC.Rochester.edu>]

Dear Elizabeth,

My guess would be that the specific activity of "natural" thorium could be
affected by the presence of U decay series Th isotopes and, therefore, would
be dependent on U concentrations in the rocks or soils of interest.  I
recall reading something once asking if there was any such thing as
"natural" thorium, but I don't remember much more than this.  I'll see if I
can dig it out and give you a reference.  The Chart of the Nuclides, of
course, lists Th-232 as being 100% abundance, but its half-life is
sufficiently long that even a little contribution from decay series Th could
be significant.

Andy
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