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RE: Floor monitors and a wish list
About 8 years ago, my hospital radiation safey office purchased a Berthold
LB-122 contamination monitoring instrument which employs a 12 x 18 cm
xenon-filled proportional detector (very good intrinsic detection efficiency
for betas, much less so for gammas). The detector is connected to
electonics featuring a microprocessor with a menu of 20 different
radionuclides. The microprocessor instantly converts raw count data -
factoring in automatic background subtract and correction for specific
radionuclide detection efficiency - and displays contamination levels in
Bq/cm.
(We Canadians have been using SI units for about 20 years, so I've been
bemused by all the fuss on the recent - hopefully dead, thread).
. The instrument works very well for workplace contamination surveys - but
I (like many others) find that careful and thorough direct monitoring for
floor contamination is certainly a physical challenge to back and thigh
muscles - a sustained deep squat is ergonomically difficult. I believe the
end result is that because of the discomfort factor, most people tend to do
a much more thorough monitoring of countertops than floors, so a lot of
trackable contamination is missed.
So I requested that Labserco (the since disbanded Canadian vendor) provide
me with a floor-sweeper assembly which would hold two of the Berthold
detectors (combined detector surface 24 x 18 cm) connected to a single set
of instrument electronics. They collaborated with me on the design and
built quite a spiffy custom unit featuring some Pb shielding of the top and
sides of the detector cradle (electronics are mounted on closed top surface
of the cradle) and a telescoping handle. Monitoring of floor contamination
is now a breeze.
My workload includes radiopharmacy, nuclear medicine and biomedical research
laboratories, so I am dealing with a full spectrum of beta emitters - from
150 KeV to over 2 MeV. The gamma energies we are dealing with mostly fall
between 25 and 400 KeV. Any proportional counter (because it is gas-filled
) has a relatively lousy intrinsic detection efficiency for gamma rays -
usually less than 1%. I would like to see a contamination monitoring
instrument that combined the same sort of microprocessor / electronics /
display features as the Berthold system with a similar large size detector
which has a much higher intrinsic detection efficiency for gammas in that
energy range, without losing detection efficiency for betas. One detector
comes to mind - the GP13A caesium iodide manufactured by Nuclear
Enterprises (recently taken over by Bicron) which has quite decent
detection efficiencies for betas and gammas in the energy ranges mentioned
above.
I should mention that in my experience the inspectors from the Canadian AECB
regulatory authority insist that licencee staff must be able to instantly
correlate instrument readout (CPS or CPM) to actual contamination level
(Bq/cm).
Any instrument manufacturer who can offer a combination of the slick
electronics (Berthold is just one, I know there are others) linked to a
detector sensitive to betas AND gammas in the medical environment will
certainly get a lot of business. And being able to put the hand-held
instrument into an optional floor sweeper assembly would make the product
even more appealing.
The Berthold LB122 has since been replaced by the LB-123 - more bells and
whistles in the electronics, and with more possibility of exchanging
detectors - I'm not sure if the LB-123 elecrtronics could be made to work
with the Nuclear Enterprises CsI detector, or whether one can enter into the
Berthold instrument microprocessor memory the detector efficiencies specific
to the radionuclides in use (crucial to calculation of surface contamination
level).
Are any of the vendors or manufacturers out there listening??
Karin Gordon
Radiation Safety Officer
Health Sciences Centre
GC-214, 820 Sherbrook Street
Winnipeg,
Manitoba
Canada R3A 1R9
phone: (204) 787-2903
fax: (204) 787-1313
e-mail: KGordon@hsc.mb.ca
> ----------
> From: GUILLEMOT Jean-Paul[SMTP:jpg@mgpi.com]
> Sent: Friday, September 10, 1999 8:03 AM
> To: Multiple recipients of list
> Subject: Floor monitors
>
> I am looking for some kind of floor monitor able to detect beta & gammas.
> I would like to have something mounted on wheels and if possible motorized
> (think about a lawnmower with detectors instead of the blade).
>
> Does any one out there know about a possible vendor.
>
>
> Thanks to anyone who can help.
>
>
> Jean Paul GUILLEMOT
> Customers Service Manager
> MGP Instruments
>
> tel: 33 (04) 90 59 60 41
> fax: 33 (04) 90 59 55 18
> e-mail:jpg@mgpi.com
>
>
>
> I possibly on wheels
>
>
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information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html