Re: New license questions

[avest@magnus.acs.ohio-state.edu (Albert Lee Vest)]

Boston Robert asked:

>"a sealed source or detector cell received from another person shall
>not be put into use until tested". What is a 'detector cell'?

This most often refers to the Electron Capture Detector (ECD) cells found in 
some Gas Chromatographs.  Most contain Ni63 foil; Varian's have 8 mCi new, 
Hewlett-Packard's have 15 mCi new.  There are other brands, with other 
activities.  Most are generally licensed, so you just have to keep your eyes 
open for them.
Older models of ECD cell are made with tritium. These usually had 100 to 
1000 mCi when new.  Being H-3, they are leak-test exempt, but tend to leak 
copiously if run at too high a temperature.
Reliable sources assure me that Beckman ECD cells have no radioactive material.
 
>2.  Another license condition states "sealed sources designed to emit 
>alpha particles shall be tested for leakage at intervals not to 
>exceede 3 months".  Are all sources that contain an alpha emitting isotope 
>classified as alpha emitters, or do (only those) sources that have a thin 
>membrane which allows alphas to escape fall into that category?

The latter.  (Please forgive my sticking words in your mouth - parenthesized 
above - for clarity.)  Examples of non-alpha-emitting-alpha-emitting-nuclide 
sealed sources are neutron sources (Am-Be, Pu-Be, etc.  Neutrons get out but 
alphas don't) and gamma sources utilizing Am-241.  We've got a couple of 
annular Am-241 sources whose photon emissions were used for x-ray 
fluorescence, and one lab on campus has an Am-241 gamma standard (in an 
Amersham source set) that was just over 10 microcuries.  I learned a lot 
from the latter source about two years ago.
Albert Lee Vest    avest@magnus.acs.ohio-state.edu
Health Physicist        Office of Radiation Safety
(614)292-0122            The Ohio State University
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