The “Activity” tab is designed to determine the absolute and specific activity of the Cs-137 isotope in various loose and watery materials (primarily in food) and the absolute activity of Cs-137 point sources. This isotope is one of the main pollutants after nuclear accidents and tests.


Measurement parameters

The upper part of the tab displays the parameters that shall be specified before starting the measurement:
Parameter name
The parameter is selected from the list and determines the geometry of the sample in which the activity of Cs-137 is evaluated.
If the sample dimensions are small (less than 5 mm), then the geometry should be selected “Point source 5 cm”. In this case, during the measurement, the sample is located at a distance of 5 cm from the “+” symbol on the back cover of the device and from the side of this symbol.
If the sample is large enough (does not fit the description of the point source above), then one of the containers in the list should be selected. Containers are not included in the device delivery set and should be purchased separately.
Name of the sample material, selected from the list. The parameter if not entered if geometry is selected “Point source 5 cm”.
Numerical value of the sample weight in grams with an accuracy of 0.1 g. The parameter if not entered if geometry is selected “Point source 5 cm”.
Displays the spectrum name of the sample taken from the spectrum library, or “Current” if a new spectrum is being accumulated during the measurement process.
Name of the background spectrum from the spectra library.
There are no rows in this table

Measurement results

The results are displayed below the measurement parameters and grouped into: Activity/Specific, MDA/Specific and MPC.
Result name
Absolute activity of the sample minus the background, in becquerels.
Relative activity
Specific activity of the sample, based on the injected mass, in becquerels per kilogram. The parameter is not calculated if geometry is selected “Point source 5 cm”.
Estimation of the random error of the current values of absolute and specific activity. The error decreases with increasing the measurement time. At error values greater than 30%, the measured activity values are considered unreliable and are displayed in gray. If it is impossible to estimate the error, dashes are displayed.
Estimate of the minimum detectable activity, in becquerels. Calculated from the background spectrum and the sample spectrum, taking into account their random errors.
Relative MDA
Estimate of the minimum detectable specific activity calculated based on the MDA and the sample mass, in becquerels per kilogram. The parameter is not calculated if geometry is selected “Point source 5 cm”.
Exceeding the MPC level, in times. MPC is maximum permissible concentration, tabular values are taken for Russia. The parameter is not calculated if geometry is selected “Point source 5 cm”.
There are no rows in this table


At the bottom of the “Activity” tab there is an area for displaying the histogram of the spectrum section, according to which the above estimates are calculated. In the center of the histogram, there is a region of the spectrum where the presence of a Cs-137 peak with an energy of 662 keV is assumed. The region with energies of 662 ±100 keV is displayed in brighter colors. The criterion for the availability of cesium in the sample is the bell-shaped peak on the spectrum, which stands out above the background level, with a maximum in the middle of the graph. If such peak is not visible, then the measured values may be unreliable.

Start/stop button (combined) serves to start/stop the measurement. When starting a measurement, you can either continue the current measurement (if any) or start a new one. During the measurement, the current data is saved once a minute, the measurement will automatically continue after reconnecting the device and after restarting the application.

“Diskette” button serves to save the obtained spectrum to the spectra library.

“i” button serves to display extended information about the measurement.

Measurement procedure

Use the following methods to assess the sample activity:

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