Re: "Puzzler"

["Neil, David M" <NEILDM@inel.gov>]

     Something like this happened to me some years ago.  I surveyed a "hose
     washer" for the INEL Fire Dept. prior to disposal to excess property.
     My results were similar to yours; no removable, but a contact reading
     indicating alpha. By vigorous rubbing with a cloth swipe, I removed
     enough for it to be identified as Po210.  It appeared that it had
     attached to the galvanized surface of the unit. since the items you
     mention are both galvanized, this looks like something you should
     check out.

     Dave Neil
     neildm@inel.gov


______________________________ Reply Separator _________________________________
Subject: "Puzzler"
Author:  RADSAFE (INELMAIL.RADSAFE) at _EMS
Date:    10/29/97 9:42 AM


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