Re:: Thorium in lantern mantles

["Ron L. Kathren" <rkathren@beta.tricity.wsu.edu>]

Joel --

A possible answer to your question lies in the fact that Th-230, with a 
relatively short (at last compared to Th-232) half life is chemically 
inseparable from Th-232, and is also the daughter of the U-238 decay 
chain.  If the Th ore contained an appreciable amount of U, the 
separation would include the Th-230 as well.  If, of course, the Th ore 
was lacking in U, then it would be more or less free of the 230 isotope.  
As for the U-235, your guess is as to it being an artifactis probably 
correct.

Hope this helps.

Ron Kathren

PS  It is well known that Thorotrast preparation frequently contained 
appreciable amounts (on an activity basis) of Th-230.  See the July 1992 
Health Physics.

Ron

On Fri, 14 Jul 1995, Joel T. Baumbaugh wrote:

>      Bruce,
> 
>      Funny you should ask a Thorium question!  While I don't know
> the  answer  to your question (and excuse me, I don't mean to  go
> off  into  another direction, but) I did recently run  across  an
> interesting "phenomenon".
> 
>      I  was  doing a "show and tell" to someone using an EG&G  PC
> based  MCA  and  a  3" NaI(tl) detector and threw  in  a  thorium
> lantern  mantel  (of  unknown  age/manufacture)  and  found  some
> "interesting"  peaks.   I double checked my calibration and  they
> were  still  there in the same channels.  I had "assumed" (and  I
> know  what  words "ass- u-m-e" contain) that I was  dealing  with
> "natural  thorium"  (Th-232),  but much to my  surprise  I  found
> thorium(s)  and  their daughter(s) ("progeny" of course,  is  the
> politically  correct  word now-a-days) from OTHER decay series  -
> e.g.  U-238  and MAYBE some from U-235 although with a  Ni(tl)  I
> wouldn't bet money on it (I won't list all of the isotopes unless
> someone  is REALLY interested).  I tried a "newer" (I had  bought
> within 4 years or so) lantern mantel and found just Th-232 peaks.
> 
>      Hey what gives here, do I have a deviant lantern mantel?  Am
> I  having a religious experience?  Has anyone else had a  similar
> experience?  Enquiring minds want to know!
> 
>      Thanks,
> 
>      Joel Baumbaugh (Baumbaug@nosc.mil)
>      NRaD
>      San Diego, CA
> 
> STD  Disclaimer re: the Navy, the Fed.Gov., NRaD, my boss and  my
> co- workers.
> 
> 
>