Re[4]: 137Cs check sources -Reply

[Steven.Rima@DOEGJPO.COM (Steven Rima)]

     Ted de Castro wrote:
     
This particular tube and circuit would top out at about 100 mr/hr but to 
test its high field response I ran it to about 1 megaR/hr (a cm or so from 
a 2500 Ci Co-60 source.  It still read 100 mr/hr.
     
Any manufacturer who knows anything about GMs and instrumentation will use 
non paralyzing circuits.  For a while - and long after this problem was 
identified and solved - they would even advertise this as a spec.  It is so 
commonplace now that it is hardly even mentioned.
     
BUT many who remember how it used to be still bring it up as a problem.
     
     
     Okay, am I missing something here??? An old GM instrument would 
     saturate and essentially peg low if exposed to a very high radiation 
     level. Now, at least the one Ted "tested", will read about 100 mR/h 
     when exposed to MegaR/h levels. I guess I don't understand, why is 
     this any better than reading zero?!? It is still a potentially BIG 
     problem if this GM instrument is used in a very high radiation 
     environment. It doesn't seem to me that this problem is "solved" 
     whatsoever by the non-paralyzing circuit.
     
     Steven D. Rima, CHP, CSP
     Manager, Health Physics and Industrial Hygiene
     MACTEC-ERS, LLC
     steven.rima@doegjpo.com
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