RE: thorium abundance? -Reply

[don@radpro.uchicago.edu]

You may also want to check "Radioactivity & Health - a history" by J.
Newell Stannard.  Chapter 4 is devoted to Th and Po.  Figure 4.7 (on 
p 237 in our 3 vol. edition) shows the re-growth of activity following
separation of Th from its decay products as a function of time since
initial isolation.  I can fax you a copy of this fig. if you want.  
The original source for the figure is cited as: F.L. Cuthbert 1958,
"Thorium Production Technology"  Addison-Wesley, Menlo Park, California.

Also of potential interest is the next Fig. in this chapter which shows 
the regrowth of many of the Th daughters in monazite ore containing both
U & Th.


Don