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Re: GM Probe Efficiencies
A calibrated GM detector, alone, does not "know" its efficiency for monitoring
radiation. The detector's efficiency is determined during calibration and then
applied in the field by the operator (or a meter which can convert cpm to
activity). Calibration can be performed using known quantities of "pancake-probe
detectable" radioisotopes. Such a calibration will provide the operator with an
efficiency value for only the isotope(s)/geometry used in the calibration.
To state that it is impossible to determine a GM pancake probe's efficiency for
detecting P-32 activity is wrong. However, if a GM detector is calibrated with
P-32, it will not provide the user with an "efficiency measurement" for when
surveying C-14 activity. It will only give you a useless cpm reading.
I hope this answers your question.
Rodney Bauman, CHP, RRPT
rodney_bauman@wssrap-host.wssrap.com
____________________Reply Separator____________________
Subject: Re: RADSAFE digest 2723
Author: <radsafe@romulus.ehs.uiuc.edu>
Date: 10/22/99 11:23 AM
To all,
Yesterday I received a phone call from an RSO who was informed by the
manufacturer of their radiation monitoring instrument that it was impossible to
calibrate a GM tube to give the efficiencies for particular isotopes (C-14,
P-32, Pu-238, etc). This was an industry wide used GM tube with a pancake probe
(Model 44-x).
I feel that either the vendor misspoke, or the RSO miscommunicated, since we
routinely do this at the Reed Reactor Facility.
Is there something I am missing, or is this just a communications breakdown?
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