Source Checks vs. Calibration

["Carbaugh, Eugene H" <gene.carbaugh@pnl.gov>]

The discussion on use of thoriated lantern mantles was with regard to an
operational source check as opposed to a periodic (say, annual or semi-annual)
instrument calibration.  Source checks should be performed each time an
instrument is used to verify that major changes haven't occurred (i.e., broken
cable, bad connections, damaged detector, etc).  Source checks are rarely
quantitative and may only work for one range of the instrument (hopefully the
range most commonly used).  If instruments are used in a variety of critical
operations over many ranges, a sophisticated source check is appropriate using,
e.g. a Sr-90 fan source for a CP ion chamber.  For a simple contamination survey
meter, I see no problem using a lantern mantle as a qualitative check source.
Many instruments incorporate a built in check source - again, this is not to be
confused with a calibration.

Calibrations on the other hand are highly detailed quantitative determinations
and adjustment of response to well-defined (ideally NIST traceable or
relateable) sources.  I wouldn't use a lantern mantle for a true calibration.
Likewise, I wouldn't run a complete calibration check everytime I use a survey
meter.

Gene Carbaugh
Radiation Protection Services
Pacific Northwest National Laboratory
Richland, WA 

gene.carbaugh@pnl.gov

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