Re: DU Gammas

["Oldewage, Hans D" <HDOLDEW@sandia.gov>]

In response to Joel Cehn - No offense, but the scientific geniuses (and the
rest of us) who wave a G-M pancake probe around in the air are right.  This
is not CRAP as you suggest.  The U-238 in DU is an alpha emitter like you
said, but there are also two beta emitting daughters (Th-234 and Pa-234m)
which are in secular equilibrium with the U-238 a short time after
processing (within about 6 months).  Pa-234m has a max beta energy around
2.3 MeV and the Th-234 has a max beta energy around 200 keV, making the
pancake probe just about ideal for exposed DU.  In fact, there are almost 3
betas to every alpha (when you take into account the U-234, U-235 and
assorted daughter products), so looking for alphas is probably the least
preferred method. Look for the gammas/x-rays (which are abundant enough from
the daughter products to be useful) with a NaI or Ge detector if your DU is
shielded by soil or whatever or if you're surveying in vegetated areas that
will destroy you pancake probes, but this will be less efficient than the
beta survey.  

=====================
Hans Oldewage, CHP
Sandia National Laboratories
505-845-7728
hdoldew@sandia.gov


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