Uranium Surprise

[Bates.Estabrooks@rfets.gov (Bates Estabrooks)]

          Here's one for all you RADSAFERs with uranium experience.
          
          Rocky Flats recently began excavation of Trench 1, which was 
          used in the late 1950s (note the Y2K-compliant date) to bury 
          drums filled with depleted uranium machine turnings and chips 
          packed in a coolant called CimCool.  CimCool was primarily 
          water with some fatty acids.  Most of these turnings had been 
          "roasted" in a high-temp. furnance to oxidize them prior to 
          burial.
          
          After 40-some years, the drums we are finding run from 
          nominally intact (whole but with some holes) to rusted 
          carcasses.  We have found none with CimCool remaining.  The 
          material we are finding in the drums mostly is black, as we 
          expected.  BUT, some of the material is a rich yellow-green 
          color, which we did not expect.
          
          In some cases the material from a drum remnant is entirely 
          yellow-green.  In some cases, material from a better-condition 
          drum is black with a surface coating of yellow-green.
          
          These drums were shallow buried (~2-3 ft.) and the soils here 
          include a fair amount of caliche (calcium carbonate).
          
          Gamma spec. on a sample indicated that the material is 
          primarily U238 (as expected).
          
          We figure that this yellow-green stuff is some oxide of U, but 
          would be interested in knowing which form specifically, and 
          how it might have formed.
          
          Any help?
          
          Bates Estabrooks
          bates.estabrooks@rfets.gov