Re: Thorium Mantles as Check Sources-Dating Age of Mantle

[RADPROJECT@aol.com]

In a message dated 9/21/98 10:32:15 PM !!!First Boot!!!, heinmillerb@aecl.ca
writes:

<< What you should see if you look over a period of
 even months (and if it's relatively freshly separated thorium) is decreasing
 activity as the Th-228 decays much faster than it's replaced from Th-232
 decay, as one of the intermediaries is 5.7-year Ra-228.  And then after a
 few years (I haven't run the equations) I would expect the activity to
 increase again as the Ra-228 builds up.  If you've got a 20-year-old mantle,
 you should have the whole chain pretty much back in equilibrium.  Also, you
 should be able to date a mantle (or at least the final separation before its
 manufacture, and if the separation's specific to thorium) by gamma
 spectroscopy, >>

Back in the 1980's I met a professor who published a paper on dating lantern
mantles from the time of manufacture. I remember obtaining a copy of a paper
he co-authored with a student but don't ask me to find it now. His name is Dr.
John Luetzelschwab of Dickenson College in PA. He is member of the HPS and
recently chair of the Public Education Committee. His email address is
luetzelj@dickinson.edu and phone number is (717) 245-1241

I also used to use lantern mantles to do a quick multipoint energy check for a
field gamma detector I was using based on a few of the major peaks of the
thorium decay series. Worked great and avoided any problems with getting
byproduct material sources on and off planes.


Stewart Farber, MS Public Health
Public Health Sciences
email: radproject@usa.net    (401) 727-4947
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