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Trace analysis of radioactive materials in air close to the ground

09.08.2007

The 2nd intercomparison in the field of trace analysis of radioactive materials in air close to the ground was carried out by the Co-ordinating Office for Trace Analysis at the Federal Office for Radioprotection in cooperation with PTB. Offices for trace analysis from Germany, Austria and Switzerland took part in the intercomparison. This intercomparison allowed the participants to assess their procedures of analysis and measurement in the form of an external measure of quality assurance. Furthermore, it serves to check the measurement uncertainties taken into account.

For the intercomparison, each participant used air filters clogged with dust. In addition to the actual dust from the air which always contains radionuclides in measurable quantities, further gamma-radiating radionuclides (22Na, 88Y, 125Sb, 133Ba, 134Cs, 241Am), as well as 89Sr and 90Sr were added. The nuclide composition was chosen in such a way that coincidental summations and self-absorption became visible during gamma spectrometry.

Trace-measurement bodies from Germany, Austria and Switzerland took part in the intercomparison.

The results of the gamma-spectrometric measurements show that the mean activities determined by the participants are, for the largest part, in agreement with the reference activities within the measurement uncertainties. Greater deviations (from -27% to +23%) can be attributed to summation and absorption effects which were not fully corrected.

The deviations from the reference activities observed in the determination of the activities of the strontium isotopes are more important (from -33% to +8%, even including an Sr-89 outlier with 157%) than in the gamma-spectrometric measurements. This can be attributed to known difficulty in radio-chemical processing or to radiometric activity determination.