Re: check sources

["Mike Bohan" <mike.bohan@yale.edu>]

        Reply to:   RE>check sources

Mark and RadSafers:

The NRC requires Medical Licensees to perform an operation check of any survey meter used to demonstrate compliance with NRC survey requirements, on each day of use.  Consequently, we have attached an operational check source to each of our GM survey meters.  

When this rule first came out, I started attaching $25, ~ 8 uCi Cs-137 button sources to my meters with epoxy.  I finally got smart and went to my local sporting goods store and bought a bunch of Thorium (green top) lantern mantles.  You get two of them for a dollar.  I cut mine in half and fold them up to about 1.5 x 1.5 cm.  (Put gloves on and use disposable table covering to catch cuttings when you do this.  Oh, and follow the package warning and wash you hands after handling mantles or ash!) I then laminate the folded mantle using clear 3M type packing tape to seal them up.  I then take another piece of tape and tape the "sealed" check source to the side of the GM and write "Operational Check Source" on it.   

These operational sources usually deliver indicated  exposure rates of approx. 1 - 2 mR/hr at contact with a pancake GM.  They also don't cause too much operational background signals for LEG probes.  (If you use dual probe meters like my Cs-137 sourced meters do...This can sometimes cause inexperienced users to fool themselves into thinking they found something when they really are only getting the probe too close to the check source!)  

I place the detector over the operational check source and outline the "ideal" probe geometry on the side of the meter with a "Sharpie"  permanent marker.  Voilá!!!    An operational check source for every meter at a cost of 25 cents and a little time each!  And, if one falls off the meter, I don't have to loose any sleep over finding where the source went!  %^)

If the GM is intended for use by our intrepid resident physicians, I even circle the correct scale to put the multiposition switch at and draw a line on the meter face indicating the correct operational response point!  Works like a charm!   Every meter should have one, even if the NRC or State regs. don't require them.

Regards,

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Michael J. Bohan, RSO   |  e-mail: mike.bohan@yale.edu
Yale-New Haven Hospital |    Tele: (203) 688-2950
Radiological Physics    |     FAX: (203) 737-4252
20 York St. - WWW 204   |    As usual, everything I say may be plausibly
New Haven, CT    06504  |    denied at my employer's convenience ...
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--------------------------------------
Date: 02/26/1998 2:23 PM
To: Mike Bohan
From: radsafe@romulus.ehs.uiuc.edu

I have a question regarding  survey instruments and check sources.
Do you install a check source on every instrument that is in your facility
or institution?

If you do not install check sources how do you insure that the instrument
is functioning everytime a person picks the instrument up to use?
Thanks in advance for your comments,

Mark Dater
NeXstar Pharmaceuticals, Inc.
2860 Wilderness Place
Boulder, CO. 80301
Work phone: (303) 546-7703
Fax: (303) 444-0672
E-mail mdater@Nexstar.com