Re: radioactive beads

[Robert_A_Jones@RL.gov]

     These peaks likely came from Uranium (without knowing more about the 
     beads and glazes).  The lower energy peaks can be explained by the 
     daughter of U-238, which is Th-234.  About a 4% chance for a 63 keV 
     photon, and a 6% chance for a 92-93 keV photon (2 photons, 2.7% each). 
      This may explain the lower energy peaks.  The "bump" at 165 kev could 
     possibly be from the slight amount of U-235 found in natural uranium.  
     This has a 54% chance of a 184 keV photon and a 10% chance of a 144 
     keV photon, which may appear as a wide "bump" with an apparant peak at 
     the 165 keV.  I assume this because you are likely calibrated with 
     higher energy sources, and not with an x-ray or low energy gamma 
     source.  
     
     An interesting experiment would be X-ray fluorescence (one of my 
     favorites).  This is a great non-destructive technique.  Though it 
     will not tell you, to any degree of certainty, the quantity, it will 
     give you a good idea of what is in the material.  If you have a 
     doughnut shaped Co-60 source, put it on the detector (if it is a 
     vertical detector).  Place one of the beads (or a bunch of them) in 
     the middle (try not to allow any other metalics in this - like metal 
     wire).  Then count away on the MCA.  Ignore the Co peaks, and observe 
     the lower energy peaks.  Tell me what you find (besides the peaks 
     previously mentioned).  This may tell you more, without destroying the 
     beads.  This may also be wasted effort, so check the binding energies 
     of the electrons for Uranium to see if the data would just interfere 
     with the peaks already obtained (sorry, I don't have it on me).
     
     Good Luck,
     
     Robert A. Jones
     Health Physicist - PFP
     Hanford, WA


______________________________ Reply Separator _________________________________
Subject: radioactive beads
Author:  Marjorie Bartlett <bartlett@ohsu.edu> at -MailLink
Date:    11/27/96 2:23 PM


Hi all, 
     
Briefly, we have come across a string of glass beads that are painted with some 
sort of irridescent yellow and blue material.  The owner of the beads noticed 
that her survey meter responded to them and brought them to the RSO for 
analysis.  The gamma spectrometer showed two strong peaks at roughly 65 and 90 
keV and a smaller bump at approximately 165 keV.  The owner bough the beads from
a gem dealer and
thinks they came from czechoslovakia.  Any thoughts on what nuclide we are 
seeing here?  
     
Thanks,
     
Marjorie Bartlett
Al Castellane
Radiation Safety Office
Oregon Health Sciences University
Portland, OR  
     
<bartlett@ohsu.edu
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Subject: radioactive beads
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