Berthold LB 134, User Manual

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LB 134 9. Basis of Calculation
120
9.5 Determination of Calibration Factors in the Event of Contamination
The explanation of the basic principles of the Becquerel calcula-
tion is not only of a documentary nature; rather, it is meant to
enable you to

determine calibration factors for other nuclides for contami-
nation measurements, which are not included in the nuclide
library of the LB 134. New nuclides can be added to the nu-
clide list.
To convert counts per second into decays per second per cm
2
,
the calibration factor K must be determined for each nuclide
and each detector type according to the formula
Contamination = C x cps [ Bq/cm 2 ]
Contamination = area activity in Bq/cm²
C
= calibration factor in Bq/cm 2 /cps
cps = measured net counts per second
For the determination of C according to the DIN standard, a cal-
ibration source with known activity per cm
2 is used (standard-
ized to 100 cm 2 ) and measured with the LB 134. The result of
the measurement is converted using the formula
𝑪 = 𝑨/𝒄𝒑𝒔
into Bq/cm 2 /cps.
A = calibration source activity in Bq/cm 2
Requirements for the
calibration source
Sources meeting the requirements of the international standard
ISO Nr. 8769 "Reference Sources for Calibration of Surface
Contamination Monitors" should be used to comply with the
ISO-7503 standard for the calibration for beta measurements.
This standard requires that the measured values must relate to
the surface emission rate, i.e. beta particles per second and
cm
2 being emitted from the test source surface.
Berthold Technologies offers two different selectable types of
calibration (on the
Nuclides menu) with the designations
"A100" and "ISO 7503". The A-100 calibration of Berthold
Technologies contamination monitors is done using the follow-
ing equations relative to the activity of the reference source and
the reference surface W of 100cm² (A is the activity of the cali-
bration source in Bq):