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With the new technologies such as pixelated CZT detectors,
advanced signal processing, and automatic energy calibration, some of
these handheld gamma specs are truly point and shoot simple. They are designed
for customs, military, fire departments, where there is no site HP. The
systems include extensive nuclide libraries that display type of source
(industrial,medical, etc.,) and the nuclide and usually some confidence
factor. For gamma sources that are strong enough to set off portal alarms,
it will be fairly easy to determine what it is with these new handheld gamma
specs. Cost will be something that will have to be sacrificed for ease of
use but it should save in the long run on training, false alarms, expert help,
etc., The European community has been dealing with this type of
monitoring long before Sept. 11. The Germans have developed some very
good (but expensive) systems for this application. Maybe we can hear
experience from some of our easterly brothers.
I believe that the key factors
will turn out to be: ease of use by security
staff, portability and cost.
The ability to quantify activity, detect low
levels in a short period of
time, or differentiate uncommon nuclides are not
required and may not be
desirable. Certainly any system that requires a
trained spectroscopist or
substantial outlay of time and money to maintain
in the field will be
excluded.
I think this last sentence is where I have serious questions
about the proliferation of these devices. While I agree that the intent
of these proposals and use of these spectroscopy based survey instruments is
based on real concerns, I do not believe this can be implemented as easily as
implied. These instruments seem relatively easy to
use....similar to a point and shoot camera, however, understanding the
underlying theory and expertise in nuclide identification is still necessary
to properly interpret the data and implement such a screening program.
None of the devices that I have seen/reviewed can be properly
utilized with out a good background in gamma spectroscopy. The
alternative will be that the security staff and probably the site radiation
safety office will be spending a considerable amount of time chasing
ghosts. ...just my humble opinion, of
course.
Regards,
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Dave
Brown, CHP
National Institute of Standards and Technology
100 Bureau
Drive, Stop 3543
Bldg 235 Rm B104
Gaithersburg, MD
20899-3543
301-975-5810 - office
301-921-9847 -
fax
david.brown@nist.gov
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