RE: Natural Thorium

[Craig Reed <CReed@novoste.com>]

Elizabeth,

Your answer is sufficiently accurate for a geologist in the mineral
extraction industry (See NRCP 118), but might not be adequate if he/she
is working on a radioactive waste repository or a thorium compound
processing facility that will accept thorium from all possible DOE/DOD
operations. 

As you indicate, natural thorium is the naturally occurring distribution
of thorium isotopes (essentially 100% Thorium by weight.)  For example,
Th-228 in near equilibrium Th-232.  However, it is possible to
accumulate inventories of thorium (compounds) from various fuel/weapon
cycle activities that yield Th-232/Th-232, Th-229 and Th-230 in
significantly different proportions.  Different proportions will yield
different specific activities depending upon the mixture and would
present a range of  "doses per mass of intake" (and a complex
radon/thoron release scenario).

Craig Reed
Novoste
creed@novoste.com
Tel 770 717 6098 

> -----Original Message-----
> From:	Elizabeth Algutifan
> [SMTP:elizabeth_algutifan@wssrap-host.wssrap.com]
> Sent:	Wednesday, May 26, 1999 9:46 AM
> To:	Multiple recipients of list
> Subject:	Natural Thorium 
> 
> This is a question of semantics: What does the term "natural thorium"
> really
> mean? A geologist colleague of mine came up to me this morning and
> asked me to
> tell him the specific activity of natural thorium. As I got to
> thinking about
> it, it occurred to me that if natural thorium is only referring to the
> thorium
> isotopes in the decay chain, I can calculate it based on assuming
> secular
> equilibrium between Th-232 and Th-228 (and say they both contribute
> half to the
> total nat Th activity). Is that an oversimplification? 
> 
> Elizabeth Algutifan
> Elizabeth_Algutifan@wssrap-host.wssrap.com
> 
> **********************************************************************
> **
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at
> http://www.ehs.uiuc.edu/~rad/radsafe.html
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html