RE: Portable NaI/MCA

["Lieskovsky, Miro" <MLieskovsky@nbpower.com>]

Brent,
We at PLGS use this method for screening large dimension objects, e.g. large
boxes, barrels, large pieces of equipment, etc., for a presence of
artificial gamma radioactivity.  Obviously, the larger the detector's size
is, the better results are obtained.  Normally we use 4x5", 4x4" or 3x3"
NaI. These "scans" are performed in low background areas and often require
more than one measurement, i.e. from different sides, directions. 
The energy resolution may cause some problems.  About 90% of gamma
contaminants at our station are activation products of 60Co and 95Zr/Nb and
they can be easily resolved.  Usual collection times are 100-300 seconds. 
  
I've derived many "standard" geometry photon transport formulas
[MathCad(tm)] that incorporate intrinsic photopeak efficiency.  The measured
net photopeak count rates are entered together with the geometry of
measurement and the attenuation coefficients.   The detection limits (in
order of kBq) depend on many factors.

Regards,

Miroslav Lieskovský
Health Physicist
NB POWER - PLGS - HP Dep't
PO BOX 10, Lepreau, NB, Canada, E0G 2H0
tel. (506) 659 7421, fax. (506) 659 6507
mlieskovsky@nbpower.com





-----Original Message-----
From: Brent_Robinson@fpl.com [mailto:Brent_Robinson@fpl.com]
Sent: August 26, 1999 5:26 PM
To: Multiple recipients of list
Subject: Portable NaI/MCA


Anyone have experience with portable NaI/MCAs for field use?    For the
benefit
of commercial nuclear power Radsafers, ANI has identified use of  these
units
(at RCA exits to "qualify" material as natural vs. licensed material) as a
good
practice.   I've got some vendor material, but want to know any "real"
experience with this type equipment.   Thanks in advance!


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