Re: Radioactive Porcelain?

["William CTR Kolb"<William.CTR.Kolb@faa.gov>]

     Older Ceramic tile used in floors and walls sometimes contained small 
     amounts of uranium in the glaze. This would produce several times the 
     activity you reported, however. Most likely it is tramp thorium and 
     uranium found in kaolin or zirconia used in the porcelain. Depending 
     on where the zirconia or kaolin was mined, there can be a significant 
     amount of U/Th contaminant present. Two times background is rather 
     common for zirconia products.
     
     Uranium as never used to improve the strength of dentures. Teeth 
     fluoresce a blue color under any light source with a wavelength 
     component of 340-350 nanometers. This component is found in daylight 
     and in many fluorescent lamps, and combines with the yellowness of 
     teeth to produce a whiter appearance. In order for dental restoratives 
     to produce the same fluorescence as natural teeth, a fluorescing agent 
     such as a mixture of cerium oxide and uranium oxide or sodium uranate 
     was added to the ceramic in the manufacturing process. Dentures made 
     with these materials looked more natural in all types of artificial 
     lighting. Depending on the brightness required, the amount of uranium 
     varied from about 0.008 to 0.1 percent by weight with an average 
     content of about 0.02 percent. The practice of using uranium in 
     dentures has all but ceased in the last 10 years here in the U.S.
     
     bill
     william.ctr.kolb@faa.gov


______________________________ Reply Separator _________________________________
Subject: Radioactive Porcelain? 
Author:  <radsafe@romulus.ehs.uiuc.edu> at SMTPGate
Date:    04/13/2000 8:52 AM


What might be found in some batches of new porcelain, particularly near 
Eastern Europe?  The porcelain is not used, is fashioned into typical 
fixtures, and not all batches are > bkgd (~ 2x bkgd).  I KNOW that taking a 
sample or spec'ing a piece would give me the answer, that isn't an option 
at present.  
     
While I'm looking for answers, what is purpose for U to be in dentures? 
I've heard that it's for color, but recently heard that the U is to make 
the denture harder.  What is it really?  
     
Brian Rees
brees@lanl.gov
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