Accuracy and reliability of radiometric measurements – results of a laboratory proficiency test with labelled sediment

 In 1995, a laboratory proficiency test was carried out in Germany with labelled sediment which was analyzed by 40 participants (operators of nuclear power plants, officially authorized institutions of the German Federal States, and laboratories of research centers). Preparation and certification of the labelled material were described in detail. The deviations of the laboratory means from the corresponding certified reference values of ten radionuclides were determined. Outliers of type 2 were recognized by means of the Grubbs test and eliminated. The consistency of laboratory means and reference values was tested by a modified t test. To describe the reliability of the measurements performed, a radioanalytical quality index which has been defined elsewhere was used. By use of this index, the radioanalytical quality of laboratory means and the means of laboratory means could be evaluated and a very realistic picture of the "state-of-the-practice" of the participating laboratories obtained. In some cases, it was possible to identify systematic errors and to explain their causes by physical phenomena.