5.2.3 Explanations on Raw Data and Calculated Units
In this chapter you will learn to choose the appropriate meas-
urement mode for each situation, and what differences there
are between the individual modes:
Net [cps] Net - counts per second
In this measurement mode, the net count rate coming from the
detector is displayed, provided that a stored background is
available. In addition, the gross count rate can also be dis-
played.
This measurement mode is always used to determine a general
change of the degree of contamination or the radiation level or if
you do not know which nuclide contains the contamination.
Bq/cm² Area activities
In this and the following measurement mode, the detector count
rates (cps) are converted into area activities using a calibration
factor stored in the device (Bq/cm²). The stored background
rate is automatically subtracted.
e.g. Beta sources (total) = β-tot
-tot means "Beta total". In this case, the conversion factor
does not refer to a specific radionuclide, e.g. iodine-131, but is
based on the average factor of a nuclide mix which can typically
be expected after a reactor accident.
This measurement mode is used
a) to check whether the limit values for surface contamination
stipulated in regulations or provisions have been exceeded,
and
b) the contamination has been caused by a recent power plant
accident and its composition is not known.
e.g. Cs-137 (or another nuclide)
In this measurement mode, the conversion factor is related to
the surface activity of a particular nuclide. The nuclide can be
retrieved from the built-in nuclide library.
This measurement mode is used
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