re "Puzzler"

[LIPTONW@detroitedison.com]

You wrote: 
	 
	Here's a "Puzzler" for the RADSAFE community.  Unlike Click  
          and Clack I don't know the answer, nor can I offer fuzzy dice  
          to the winner, but this may be of interest to all of you and  
          help us out a bit. 
           
          Here at Rocky Flats we have a long history of working with  
          "the most dangerous substance known to man."  As such, as we  
          tear this place down, we need to screen everything that leaves  
          the site for disposal, for "DOE radionuclides"; i.e.,  
          239/240Pu, 241Am, 233/234U, 235U, and 238U. 
           
          Recently we have surveyed several metallic items like trailer  
          roofs, and chain link fence posts, using smears, and direct  
          surveys with NE Electra instruments.  Often we have seen  
          effectively no removeable activity (<20 dpm/100 cm2 alpha) but  
          high direct alpha readings (~200 to 240 dpm/100cm2). 
           
          Subsequently, we have covered these high spots with plastic  
          and resurveyed days later to allow the short-lived activity to  
          decay away.  In one case, with chain link fence posts, we  
          covered eight spots, and allowed them to sit for 28 days (I'm  
          not sure why that particular duration). 
           
          The resultant surveys showed direct alpha activity still  
          running in the range of 60-150 dpm/100cm2. 
           
          In another similar instance (a trailer roof) we had a piece of  
          the metal lab analyzed by radiochem. and alpha spec. for DOE  
          nuclides and they all came back extremely low (Am: 0.0427  
          pCi/g, Pu: 0.0177 pCi/g, 234U: 0.0338, and 235U: 0.0216).  We  
          are having the fence posts analyzed now. 
           
          So, the question:  what alpha-emitters are we seeing? And,  
          what mechanism is fixing them to these metal surface so they  
          are not seen on smears? 
           
          Any ideas would be appreciated to help corraborate/refute our  
          own. 
           
          Bates Estabrooks 
          RFETS 
          bates.estabrooks@rfets.gov 
           
 One question you should answer is whether the alpha activity is surface 
contamination of is distributed throughout the metal.  There's a chance that 
it may be due to uranium or thorium in the metal. 
 
The opinions expressed are strictly mine. 
It's not about dose, it's about trust. 
 
Bill Lipton 
liptonw@detroitedison.com