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Measurement of low activities

For the measurement of low activities in the range of a few millibecquerel up to some kilobecquerel, the Working Group has a radiochemistry laboratory, various gamma and alpha-spectrometry measurement workplaces (figure 1)as well as beta-counter (figure 2) at its disposal.

Figure 1: Alpha-spectrometry measurement
set-up with PIPS detector and counting source

Figure 2: Beta-counter with strontium
counting source

Figure 3: Microwave digestion system for the total
dissolution of an environmental sample

Figure 4: Radiochemical separation

In the radiochemistry laboratory, most different environmental samples can be dissolved. (figure 3). The total dissolution is followed by radiochemical separation and purification of the radioelements (figure 4) and the preparation of plutonium, strontium, thorium or uranium counting sources. The measurement- and radiochemical procedures are outlined in a special edition of PTB-Mitteilungen (in German) "Spurensuche: Radioaktive Stoffe in der Luft" focusing on air dust samples.

Gamma-ray emitting radionuclides are determined directly in the respective materials without previous radiochemical separation. Depending on the quantity and specific activity, volumes of 1 ml to 1 L are investigated by gamma-spectrometry. In this non-destructive analysis method, the sample-specific absorption of the gamma radiation must be taken into account. These so-called self-absorption corrections as well as nuclide-specific coincidence summation correction factors are determined with the GESPECOR computer program which has been developed in a cooperation between the University of Bucharest and PTB.